JP4172399B2 - Image processing apparatus and program - Google Patents

Description

  The present invention relates to an image processing apparatus that converts a multi-value image into a binary image and outputs the binary image.

  In recent years, in the plate making process, a method called CTP (computer to plate) has been adopted in which digitized printing original data is used and a printing plate for printing is directly produced by a digital plate making apparatus. When creating a printing plate for printing by CTP, document data described in a page description language is converted into binary image data having a halftone dot component by RIP (Raster Image Processing) processing, and this binary image data Make a plate from

  Now, when a printing plate is created by CTP, when proofing a document, image data binarized by RIP processing is usually output to a color proofing system called DDCP (direct digital color proof). In recent years, a method and apparatus has been developed to obtain proof prints without using expensive equipment such as DDCP by outputting image data binarized by RIP processing to a color printer. (For example, refer to Patent Document 1).

  FIG. 26 is a block diagram showing the configuration of the color output device described in Patent Document 1. In FIG. In the color output device described in Patent Document 1, first, image data D binarized by RIP processing is supplied to the multi-value conversion means 11. This image data has a halftone dot component. Next, the multi-value conversion means 11 artificially converts the supplied binary image data into multi-value image data Do, and the descreening means 12 performs a descreening process on the image data Do. . Thereby, the halftone dot component is removed from the image data Do, and the image data Dd having a halftone is generated. Next, color correction data Dc for performing color correction on the image data Dd is read from the color correction table 13. The color correction unit 14 adds the color correction data Dc and the multivalued image data Do having a halftone component, and the image data Dx obtained by the addition is input to the error diffusion processing unit 15. The error diffusion processing unit 15 converts the multi-valued image data into binary image data by performing error diffusion processing on the input image data, and outputs the converted image data Dz to the output unit 2. The image data Dz output in this way has the original halftone dot component and is image data that has been subjected to color matching, so that a highly accurate proof can be obtained.

For example, a technique described in Patent Document 2 is known as a technique for performing color correction processing suitable for the characteristics of a color printer on binary image data. In the image data processing method described in Patent Document 2, first, after binary image data is converted into multi-value image data, color correction processing is performed so as to match the characteristics of the color printer. The multi-valued image data that has been subjected to the color correction processing is binarized, and the number of print pixels corresponding to the multi-valued data is determined. When the number of print pixels is determined, the print pixels are arranged by referring to the pixel arrangement of the binary image data, and when there is an increase / decrease in the print pixels, which position of the pixel is increased / decreased by referring to the table Is determined. Errors that occur when pixels are arranged, particularly errors that occur in conversion from multivalue to binary, are diffused to other pixels. In the image data processing method described in Patent Document 2, binary image data that is optimal for a color printer is generated by such processing, and an image close to an image of a document can be obtained.
Japanese Patent Laid-Open No. 2001-144799 Japanese Patent No. 2877356

  In the color output device described in Patent Document 1, when the pixel value of multi-valued image data takes a value of, for example, 0 to 255, the pixel value range of the multi-valued image data after color correction is also 0 to 0. It was 255. Therefore, for example, when the pixel value of the multivalued image data Do before color correction is “0” and the pixel value of the color correction data Dc is “−5”, the pixel value of the image data after color correction is Therefore, the lower limit is “0”, and the content does not reflect the color correction data.

  Color correction must be accurately performed to obtain an accurate proof. However, when the color output device described in Patent Document 1 adds the result of color correction to multi-valued image data, as described above, the amount exceeding the range of values taken by the multi-valued image data. May be omitted, and the corrected color information may be lost. For this reason, in the color output device disclosed in Patent Document 1, the color correction performed at the corner is not applied accurately, and there is a problem that it is not possible to obtain a proof printed with the color correction performed accurately. In addition, in the output image data Dz, although the halftone dot component that the image data D binarized by the RIP process has is basically retained, black pixels and white pixels generated by error diffusion are There has been a problem that it occurs regardless of the halftone dot component that the binarized image data D had.

  On the other hand, in the method described in Patent Document 2, unlike the color output method described in Patent Document 1, data at the time of color correction is not discarded, and the color characteristics of the printer are met. Images can be output. However, in the method described in Patent Document 2, when converting multi-valued image data to binary image data, it is determined which pixel to increase or decrease by referring to a previously provided table. The In such a method, if the period of the halftone dot component included in the input binary image data does not match the period of the pixels that are increased or decreased by the table, a beat occurs in the output image. Problems arise.

  The present invention has been made in view of the above-described circumstances, and outputs a binary image that accurately reflects the correction result of color correction while retaining the halftone dot component of the input binary image data. The purpose is to provide.

In order to solve the above-described problem, the present invention provides binary image input means for receiving binary image data, multi-valued image data obtained by multi-leveling the binary image data and subjected to predetermined processing, or the binary value. Multi-value image input means for receiving multi- value image data obtained by performing predetermined processing on multi-value image data representing the same image as the image of the image data , supplied error data, and pixels from the multi-value image input means An image correction unit that adds pixel values of multi-valued image data supplied in units to generate error addition data, and binarizes the error addition data generated by the image correction unit by using a threshold value. Detecting whether the pixel of interest in the binary image data received by the binary image data received by the comparison unit that generates the binarized image data is a pixel of an edge portion of the image indicated by the binary image data; The binary image When the pixel of interest in the data is a pixel of an edge portion of the image, and outputs the pixel value selection signal instructing to select the re-binarized image data the comparison means has generated, the binary image data A pixel determination unit that outputs a pixel value selection signal instructing to select binary image data received by the binary image input unit when the pixel of interest is not a pixel at an edge portion of the image; and the pixel determination according pixel value selection signal is output means, and selector means for the binary image input means binary image data or the comparison means received selects re binary image data generated as the output binary data Binarization error data indicating an error caused by binarization using the error addition data generated by the image correction unit and the output binary data output by the selector unit. And error calculating means for determining, the error data is added to the pixel values of the multivalued image data in the image correction means, determined using the binarization error data obtained by the error calculating means calculates error There is provided an image processing apparatus comprising correction calculation means for supplying data to the image correction means .

According to another aspect of the present invention, there is provided a computer apparatus comprising: binary image input means for receiving binary image data; multivalued image data obtained by converting the binary image data into multivalued data and subjected to predetermined processing ; Multi-value image input means for receiving multi- value image data obtained by performing predetermined processing on multi-value image data representing the same image as the image , supplied error data, and supplied from the multi-value image input means in pixel units an image correcting unit that the pixel value of the multivalued image data by adding in pixel units to generate the error addition data, binarized and re binarized image error added data by the image correcting means is generated by the threshold A comparison unit for generating data, and detecting whether the pixel of interest in the binary image data received by the binary image input unit is a pixel at an edge portion of the image indicated by the binary image data; Image When the pixel of interest in the data is a pixel of an edge portion of the image, and outputs the pixel value selection signal instructing to select the re-binarized image data the comparison means has generated, the binary image data A pixel determination unit that outputs a pixel value selection signal instructing to select binary image data received by the binary image input unit when the pixel of interest is not a pixel at an edge portion of the image; and the pixel determination according pixel value selection signal is output means, and selector means for the binary image input means binary image data or the comparison means received selects re binary image data generated as the output binary data Binarization error data indicating an error caused by binarization using the error addition data generated by the image correction unit and the output binary data output by the selector unit. And Mel error calculation means, the error data is added to the pixel values of the multivalued image data in the image correction means, determined using the binarization error data obtained by the error calculating means calculates error A program is provided for causing data to function as correction calculation means for supplying data to the image correction means .

  According to the present invention, the image processing apparatus receives binary image data and multi-value image data. The image processing apparatus adds the multi-value image data and the error data in units of pixels, generates error addition data indicating the addition result, and binarizes the error addition data with a threshold value. Further, the image processing apparatus may be configured to receive the binary image data received by the binary image input unit based on the pixel value of the pixel of interest in the binary image data and the pixel value of the pixel adjacent to the pixel of interest, or the second image data. A pixel value selection signal that indicates which of the re-binarized image data generated by the binarization means is output is output, and the output pixel value selection signal is the binary image data received by the binary image input means. When the signal is an instruction to output, the binary image data received by the binary image input unit is output as output binary data, and the signal output by the selection signal output unit is converted to the re-binarized signal. When the signal is an instruction to output the re-binarized image data generated by the means, the re-binarized image data generated by the re-binarization means is output as output binary data. Then, the image processing apparatus uses the pixel value of the error addition data and the pixel value of the output binary data to obtain error data to be added to the pixel value of the multivalued image data.

  According to the present invention, it is possible to output a binary image that accurately reflects the correction result of color correction while retaining the halftone dot component of the input binary image data.

[1. First Embodiment]
[1-1. Configuration of First Embodiment]
First, the configuration of the image processing apparatus according to the first embodiment of the present invention will be described with reference to FIG. The image input unit 100 functions as an interface for receiving image data (hereinafter referred to as input binary image data D10) of a document converted into binary image data having a halftone dot component by RIP processing. The obtained image data is supplied to the multi-value quantization unit 200 and the error diffusion unit 500. In the input binary image data D10, the value of each pixel is represented by 1 bit. That is, the value of the black pixel is “1”, and the value of the white pixel is “0”.

  The multi-value conversion unit 200 converts the input binary image data D10 into multi-value image data. When the input binary image data D10 is received, each of the binary pixel values represented by the binary image data is converted. Data represented by a plurality of bits is generated for each pixel. For example, when the pixel value is “0”, simple conversion is performed with “0” as the new pixel value and “255” as the new pixel value. That is, the image data is converted so that the pixel value represented by 1 bit is represented by 8 bits (hereinafter, the image data generated by the multi-value conversion unit 200 is referred to as simple multi-value image data D20). ). The multi-value conversion unit 200 supplies the simple multi-value image data D20 to the halftone dot removal unit 300.

  The halftone dot removing unit 300 is, for example, data obtained by removing the halftone dot component of the simple multilevel image data D20 by performing a smoothing filter process on the input simple multilevel image data D20, and Then, image data having intermediate gradation (hereinafter, this image data is referred to as smoothed image data D30) is generated. The halftone dot removal unit 300 supplies the smoothed image data D30 to the color conversion unit 400. In the smoothed image data D30, the pixel value of each pixel is represented by 8 bits.

  The color conversion unit 400 performs color correction on the smoothed image data D30 supplied from the halftone removal unit 300, and the color of the printed material printed by the image processing apparatus and the printed material printed by the printing machine. Are subjected to color correction on the smoothed image data D30. The color conversion unit 400 supplies the multi-value image data subjected to the color correction (hereinafter, this image data is referred to as color correction image data D40) to the error diffusion unit 500. In this color corrected image data D40, the pixel value of each pixel is represented by 8 bits.

  The error diffusion unit 500 performs error diffusion processing on the color-corrected image data D40 supplied from the color conversion unit 400 using the average error minimum method, and binary image data that represents each pixel as 1-bit digital data. (Hereinafter, this image data is referred to as output binary image data D60). The error diffusion unit 500 supplies the generated image data to the image output unit 600. Details of the error diffusion unit 500 will be described later.

  The image output unit 600 has a printing function, receives the output binary image data D60 supplied from the error diffusion unit 500, and performs printing based on the received image data.

[1-2. Configuration of error diffusion unit]
FIG. 2 is a block diagram illustrating the configuration of the error diffusion unit 500. The binary image input unit 570 functions as an interface that receives the input binary image data D10 supplied from the image input unit 100. When the binary image input unit 570 receives the input binary image data D10, the binary image input unit 570 generates 1-bit data (hereinafter referred to as binary pixel data D50b) indicating the value of each pixel from the inversion unit 511 of the threshold value calculation unit 510. This is sequentially supplied to the adjacent pixel determination unit 522 and the selector unit 523 of the binarization unit 520.

The threshold calculation unit 510 generates threshold data using the binary pixel data D50b supplied from the binary image input unit 570, and includes an inversion unit 511, a coefficient generation unit 512, and a multiplication unit 513. is doing.
The inversion unit 511 inverts the pixel value of the binary pixel data D50b supplied from the binary image input unit 570. When the binary pixel data D50b is supplied, the inversion unit 511 converts the pixel value to “1” when the pixel value of the binary pixel data D50b is “0”, and the pixel of the binary pixel data D50b When the value is “1”, the pixel value is converted to “0”, and the converted binary pixel data D50b is supplied to the multiplication unit 513 as inverted data D50g.
The coefficient generation unit 512 generates a coefficient to be multiplied by the inverted data D50g supplied from the inversion unit 511. For example, the coefficient is a maximum pixel value that the color correction image data D40 can take, and a coefficient indicating the coefficient The data D50h is supplied to the multiplication unit 513. The coefficient is not limited to the maximum pixel value that the color correction image data D40 can take, and may be an arbitrary value.
The multiplier 513 multiplies the pixel value of the inverted data D50g supplied from the inverter 511 by the coefficient indicated by the coefficient data D50h supplied from the coefficient generator 512, and binary threshold data D50i indicating the value obtained by this multiplication. To the conversion unit 520.

The binarization unit 520 binarizes the error addition data D50c supplied from the image correction unit 530 using the threshold value data D50i supplied from the threshold value calculation unit 510. A determination unit 522 and a selector unit 523 are provided.
The comparison unit 521 binarizes the error addition data D50c supplied from the image correction unit 530 with the threshold data D50i supplied from the threshold calculation unit 510. When the value indicated by the error addition data D50c is equal to or greater than the value indicated by the threshold data D50i, the comparison unit 521 supplies re-binarized data D50j with the pixel value “1” to the selector unit 523, and adds the error. When the value indicated by the data D50c is less than the value indicated by the threshold data D50i, the re-binarized data D50j with the pixel value “0” is supplied to the selector unit 523.

The adjacent pixel determination unit 522 uses the binary pixel data D50b supplied from the binary image input unit 570 and uses “Disable” or “Enable” according to the value of the target pixel and the value of the pixel adjacent to the target pixel. The pixel value changeable signal D50k taking the value "" is supplied to the selector 523.
3 and 4 are diagrams showing the relationship between the value of the target pixel and the value taken by the pixel value changeable signal D50k. When the value indicated by the focused binary pixel data D50b is “0”, the adjacent pixel determination unit 522 calculates a logical sum of the values of the upper, lower, left, and right binary pixel data adjacent to the focused pixel, and performs this logical operation. And the exclusive OR of the pixel value of the target pixel. As shown in FIG. 3, the adjacent pixel determination unit 522 outputs “Disable” as the pixel value changeable signal D50k when the value of the pixel of interest and the logical sum of the pixel values of the adjacent pixels are the same. If the value of the logical sum of the pixel value of the target pixel and the pixel value of the adjacent pixel is different, “Enable” is output as the pixel value changeable signal D50k.
In addition, when the value indicated by the focused binary pixel data D50b is “1”, the adjacent pixel determination unit 522 calculates a logical product of the values of the upper, lower, left, and right binary pixel data adjacent to the target pixel. An exclusive OR is calculated between the result of the logical operation and the pixel value of the target pixel. As shown in FIG. 4, the adjacent pixel determination unit 522 sets “Disable” as the pixel value changeable signal D50k when the value of the pixel of interest and the logical product of the pixel values of the adjacent pixels are the same. If the value of the pixel of interest differs from the logical product of the pixel values of adjacent pixels, “Enable” is output as the pixel value changeable signal D50k.

  The selector unit 523 uses the binary pixel data D50b supplied from the binary image input unit 570 or the re-binary supplied from the comparison unit 521 based on the pixel value changeable signal D50k supplied from the adjacent pixel determination unit 522. One of the digitized data D50j is output. When the pixel value changeable signal D50k supplied from the adjacent pixel determination unit 522 is “Enable”, the selector unit 523 uses the re-binarized data D50j supplied from the comparison unit 521 as the output binary data D50m and is binary. When the pixel value changeable signal D50k is “Disable” supplied to the image output unit 590, the binary image output unit 590 uses the binary pixel data D50b supplied from the binary image input unit 570 as output binary data D50m. To supply.

  The binary image output unit 590 has a function as an interface for supplying the data supplied from the selector unit 523 to the image output unit 600, and the data supplied from the selector unit 523 is used as output binary image data D60. The image is supplied to the image output unit 600.

  On the other hand, the multi-value image input unit 580 functions as an interface that receives the color correction image data D40 supplied from the color conversion unit 400. When the color correction image data D40 is received, 8-bit data indicating the value of each pixel. (Hereinafter, referred to as multi-value pixel data D50a) is sequentially supplied to the image correction unit 530.

  The error calculation unit 540 generates binarization error data D50d using the error addition data D50c supplied from the image correction unit 530 and the output binary data D50m supplied from the binarization unit 520. is there. For example, when the output binary data D50m supplied from the binarization unit 520 indicates “0”, the error calculation unit 540 uses the difference between the value indicated by the error addition data D50c and “0” as a difference value. When the data supplied from the binarization unit 520 indicates “1”, a value obtained by subtracting “255” from the value indicated by the error addition data D50c is obtained as a difference value, and the obtained difference value is indicated. The data is supplied to the error storage unit 550 as binarized error data D50d. The binarized error data D50d is stored in the error storage unit 550.

  The correction calculation unit 560 obtains error data D50f from errors generated in pixels around the target pixel. The correction calculation unit 560 multiplies the binarization error data D50d of the pixels around the pixel of interest among the binarization error data D50d stored in the error storage unit 550 by multiplying the error data D50f by a predetermined coefficient. Ask for. Then, the correction calculation unit 560 supplies error data D50f to be added to the value indicated by the multi-value pixel data D50a supplied to the image correction unit 530 to the image correction unit 530.

  The image correction unit 530 adds the value indicated by the error data D50f supplied from the correction calculation unit 560 to the pixel value indicated by the multi-value pixel data D50a supplied from the multi-value image input unit 580. Error addition data D50c indicating the obtained value is supplied to the comparison unit 521 and the error calculation unit 540.

  That is, the image correction unit 530 supplies the multi-valued pixel data with the error added by error diffusion to the comparison unit 521, and the comparison unit 521 calculates the threshold value for the multi-valued pixel data with the error added by the error diffusion. Binarization is performed using the threshold data supplied from the unit 510, and rebinarized data D50j is generated. Then, in accordance with the pixel value changeable signal, the selector unit 523 outputs the data input to the binary image input unit 570 as it is as output binary data D50m in the portion where black pixels or white pixels are continuous, In the portion where the value changes, rebinarized data obtained by binarizing the data with the error added is output as output binary data D50m.

[1-3. Operation of First Embodiment]
Next, the operation of the first embodiment will be described. In the following description, first, an operation until the input binary image data D10 and the color correction image data D40 are input to the error diffusion unit 500 will be described. Next, the input binary image data D10 and the color correction image data will be described. The operation of the error diffusion unit 500 that has received D40 will be described.

[1-3-1. Operation until the color correction image data D40 is input to the error diffusion unit 500]
When the input binary image data D10 is input to the image input unit 100, the input binary image data D10 is supplied from the image input unit 100 to the multilevel conversion unit 200 and the error diffusion unit 500. When the input binary image data D10 is input to the multilevel conversion unit 200, the input binary image data D10 is converted into a simple multilevel image in which each pixel is represented by 8-bit digital data in the multilevel conversion unit 200. Converted to data D20. This simple multi-value image data D20 is supplied from the multi-value conversion unit 200 to the halftone dot removal unit 300.

  The simple multi-valued image data D20 supplied to the halftone dot removing unit 300 is subjected to smoothing filter processing in the halftone dot removing unit 300 to remove halftone dot components and converted to smoothed image data D30 having an intermediate gradation. The smoothed image data D30 is supplied from the halftone dot removal unit 300 to the color conversion unit 400. In the color conversion unit 400 to which the smoothed image data D30 is supplied, color correction is performed on the smoothed image data D30 to generate color corrected image data D40. This color correction data is supplied from the color conversion unit 400 to the error diffusion unit 500.

  The binary image data output from the image input unit 100 is supplied to the binary image input unit 570 of the error diffusion unit 500, and the color correction image data D40 supplied from the color conversion unit 400 is the multi-value image of the error diffusion unit 500. When supplied to the input unit 580, the error diffusion unit 500 performs error diffusion using these data.

[1-3-2. Operation of error diffusion unit 500]
Next, the operation of the error diffusion unit 500 will be described. From the binary image input unit 570 to which the input binary image data D10 is input, the binary pixel data D50b includes the inversion unit 511 of the threshold value calculation unit 510, the adjacent pixel determination unit 522 and the selector unit of the binarization unit 520. 523.

  The binary pixel data D50b supplied to the inversion unit 511 is supplied from the inversion unit 511 to the multiplication unit 513 as inverted data D50g after the pixel value is inverted by the inversion unit 511. The multiplier 513 multiplies the value indicated by the inverted data D50g supplied from the inverter 511 by the value indicated by the coefficient data D50h supplied from the coefficient generator 512, and the value obtained by this multiplication is 2 as the threshold data D50i. The value is supplied to the comparison unit 521 of the value conversion unit 520.

  When the threshold value data D50i is supplied to the comparison unit 521, the comparison unit 521 compares the value indicated by the error addition data D50c supplied from the image correction unit 530 with the value indicated by the threshold value data D50i. Re-binarized data D50j obtained by binarizing D50c is generated. For example, when the value indicated by the error added data D50c is “255” and the value indicated by the threshold data D50i is “0”, the value indicated by the multi-valued image data is equal to or greater than the value of the threshold data D50i. The re-binarized data D50j with the pixel value “1” is supplied from the comparison unit 521 to the selector unit 523, the value indicated by the error addition data D50c is “0”, and the value indicated by the threshold data D50i is “255”. As described above, when the value indicated by the multi-valued image data is less than the value of the threshold data D50i, the re-binarized data D50j with the pixel value “0” is supplied from the comparison unit 521 to the selector unit 523. .

  On the other hand, in the adjacent pixel determination unit 522, the pixel value changeable signal D50k is generated based on the binary pixel data D50b supplied from the binary image input unit 570. The operation of the adjacent pixel determination unit 522 will be described with reference to FIG. FIG. 5 is a diagram for explaining the relationship between the image indicated by the input binary image data D10 and the pixel value changeable signal D50k output based on the binary pixel data D50b. In FIG. 5, a 13 × 13 matrix is used to represent the pixels, codes A to M in the horizontal direction and codes 1 to 13 in the vertical direction, and the pixels are represented by a combination of these codes. To do.

  When the input binary image data D10 is scanned in the X to Y direction and the pixel B7 is set as the target pixel, the value of the target pixel is “0”. Therefore, the adjacent pixel determination unit 522 is vertically and horizontally adjacent to the pixel B7. The logical sum of the pixel values of these pixels is obtained. Since the logical sum of the pixel values of the upper, lower, left and right pixels adjacent to the pixel B7 is “0” and the value of the target pixel is “0”, the pixel value changeable signal is output from the adjacent pixel determination unit 522 according to FIG. “Disable” is output as D50k (FIG. 5: period a).

  Next, when the pixel C7 is the target pixel, the adjacent pixel determination unit 522 calculates the logical sum of the pixel values of the upper, lower, left, and right pixels adjacent to the pixel C7. Since the value of the right pixel D7 of the pixel C7 is “1” and the values of the upper, lower, and left pixels of the pixel C7 are all “0”, the logic of the pixel values of the upper, lower, left, and right pixels adjacent to the pixel B7 The sum is “1”. Since the value of the target pixel is “0” and the logical sum of the pixel values of adjacent pixels is “1”, according to the table of FIG. 3, the adjacent pixel determination unit 522 generates “Enable” as the pixel value changeable signal D50k. Is output (FIG. 5: period b).

  Next, when the pixel D7 is the pixel of interest, since the value of the pixel of interest is “1”, the adjacent pixel determination unit 522 calculates the logical product of the pixel values of the upper, lower, left, and right pixels adjacent to the pixel D7. Since the value of the left pixel C7 of the pixel D7 is “0” and the values of the upper, lower, and right pixels of the pixel D7 are all “1”, the logic of the pixel values of the upper, lower, left, and right pixels adjacent to the pixel D7 The product is “0”. Since the value of the target pixel is “1” and the logical product of the pixel values of adjacent pixels is “0”, according to the table of FIG. 4, the adjacent pixel determination unit 522 generates “Enable” as the pixel value changeable signal D50k. Is output (FIG. 5: period c).

  Next, when the pixel E7 is the pixel of interest, the adjacent pixel determination unit 522 calculates the logical product of the pixel values of the upper, lower, left, and right pixels adjacent to the pixel E7. Since the upper, lower, left, and right pixels of the pixel E7 are all “1”, the logical product of the pixel values of the upper, lower, left, and right pixels adjacent to the pixel E7 is “1”. Since the value of the target pixel is “1” and the logical product of the pixel values of adjacent pixels is “1”, according to the table of FIG. 4, the adjacent pixel determination unit 522 generates “Disable” as the pixel value changeable signal D50k. Is output (FIG. 5: period d).

  As described above, in the adjacent pixel determination unit 522, the result of the logical sum of the pixel value of the target pixel and the pixel value of the pixel adjacent to the target pixel, or the result of the logical product of the pixel value of the pixel adjacent to the target pixel. Is taken as the pixel of interest, that is, only at the edge portion of the image, the pixel value changeable signal D50k having the value of “Enable” is output. .

  The pixel value changeable signal D50k output from the adjacent pixel determination unit 522 is supplied to the selector unit 523. When “Enable” is input as the pixel value changeable signal D50k to the selector unit 523, the re-binarized data D50j supplied from the comparison unit 521 is output from the selector unit 523 (FIG. 5: period (A)). . As described above, when “Enable” is output as the pixel value changeable signal D50k, that is, the period in which the pixel value change portion (the edge portion of the image) is the target pixel is supplied from the comparison unit 521. The re-binarized data D50j, that is, the color-corrected image data D40 is subjected to error diffusion, and the re-binarized data D50j obtained by binarizing the error-diffused data is output from the selector unit 523 as binary data. D50m is output.

  When “Disable” is input as the pixel value changeable signal D50k to the selector unit 523, the binary pixel data D50b supplied from the binary image input unit 570 is output as it is from the selector unit 523 (FIG. 5: period ( B)). As described above, when “Disable” is output as the pixel value changeable signal D50k, that is, in a period in which a portion in which black pixels forming an image are continuous is a target pixel, the pixel value is supplied from the binary image input unit 570. The binary pixel data D50b thus output is output from the selector unit 523 as it is.

  The data output from the selector unit 523 is supplied to the binary image output unit 590 and the error calculation unit 540. The data supplied to the binary image output unit 590 is supplied to the image output unit 600 as output binary image data D60. In the image output unit 600 supplied with the output binary image data D60, printing is performed based on the supplied output binary image data D60.

  The error calculation unit 540 uses the output binary data D50m supplied from the selector unit 523 and the error addition data D50c supplied from the image correction unit 530, and generates binarized error data D50d. In the correction calculation unit 560, error data D50f for the target pixel is calculated using the binarized error data D50d stored in the error storage unit 550. The error data D50f is supplied to the image correction unit 530, and the value indicated by the error data D50f is added to the value indicated by the multi-value pixel data D50a supplied to the image correction unit 530 next.

  As described above, according to the present embodiment, in accordance with the pixel value changeable signal D50k, in the portion where black pixels or white pixels are continuous, the data subjected to error diffusion is not output, but the input binary value is output. The image data D10 is output as it is. When multi-valued image data is binarized by error diffusion, pixels that the original binary image data has may be lost due to error accumulation in a portion where pixels forming an image are continuous. However, as described above, the binarization unit 520 of the present embodiment does not output error-diffused data in a portion where black pixels or white pixels are continuous, but uses the input binary image data D10 as it is. Since the data is output, it is possible to output image data in which the halftone dot component included in the input binary image data D10 input to the image processing apparatus is accurately stored.

In the present embodiment, the color correction result is added to the simple multi-valued image data D20 as in the color output device described in Patent Document 1, and the multi-valued image data obtained by this addition has an error. Rather than performing binary diffusion to obtain binary image data, color correction is performed on the smoothed image data D30, and error diffusion is performed on the corrected image data to obtain binary image data. . The color output device described in Patent Document 1 adds the result of color correction to the simple multivalued image data D20. However, in a simple multivalued image having a halftone dot structure, there are many pixels having a value of “0”. Therefore, there are many cases where the addition result exceeds the range of values that the pixel can take. The color output device described in Patent Literature 1 corrects the pixel value so that the pixel value falls within the range that the pixel value can take when the addition result exceeds the range of the value that the pixel can take. In the image data obtained by adding the results, there are many pixels that have not been accurately subjected to color correction.
On the other hand, in the present embodiment, the binary image data reflecting the accuracy of color correction is obtained by directly error-diffusing the color-corrected image data D40 obtained by performing color correction on the smoothed image data D30. It becomes possible to output.

[2. Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, in 2nd Embodiment demonstrated below, the same code | symbol as 1st Embodiment is attached | subjected about the part which has the same structure as 1st Embodiment, and the description is abbreviate | omitted.

[2-1. Configuration of Second Embodiment]
FIG. 6 is a block diagram illustrating the configuration of the error diffusion unit 500 according to the second embodiment of the invention. The second embodiment of the present invention differs from the first embodiment in that the error diffusion unit 500 includes an image correction unit 595.

The image correction unit 595 corrects the output binary data D50m supplied from the selector unit 523, and is supplied from the output binary data D50m supplied from the selector unit 523 and the binary image input unit 570. A memory (not shown) for storing the binary pixel data D50b and the pixel value changeable signal D50k supplied from the adjacent pixel determination unit 522 is provided.
When the pixel value changeable signal D50k changes from “Disable” to “Enable”, the image correction unit 595 differs in the value of the binary pixel data D50b and the value of the output binary data D50m in the pixel immediately after this, Even when the value changeable signal D50k changes from “Disable” to “Enable”, if the value of the binary pixel data D50b is different from the value of the output binary data D50m in the immediately following pixel, the pixel value changeable signal changes. The value of the output binary data D50m at that time is inverted. In addition, when the pixel value changeable signal D50k changes from “Enable” to “Disable”, the image correction unit 595 differs in the value of the binary pixel data D50b and the value of the output binary data D50m for the immediately preceding pixel. Even when the pixel value changeable signal D50k changes from “Enable” to “Disable”, if the value of the binary pixel data D50b and the value of the output binary data D50m are different in the immediately preceding pixel, this pixel value changeable signal The value of the output binary data D50m at the time when is changed is inverted. When the confirmation of the change in the stored pixel value changeable signal D50k is completed, the image correction unit 595 supplies the corrected output binary data D50m to the binary image output unit 590.

[2-2. Operation of Second Embodiment]
Next, the operation of the second embodiment of the present invention will be described. Note that, in the operation described below, the operation of the other parts excluding the image correction unit 595 is the same as the operation of the first embodiment, so the description thereof will be omitted, and only the operation of the image correction unit 595 will be described. . In the operation of the image correction unit 595 described below, as shown in FIG. 7, when the pixel value changeable signal D50k changes from “Disable” to “Enable”, the output from the binary image input unit 570 is performed. The operation will be described assuming that the output binary data D50m having a value different from the value of the binary pixel data D50b is output from the selector unit 523.

  FIG. 7 shows the image indicated by the input binary image data D10, the value of the binary pixel data D50b output from the binary image input unit, the pixel value changeable signal D50k, and the output 2 output from the selector unit 523. It is a figure for demonstrating the relationship between value data D50m and the output binary data D50m output from the image correction part 595. FIG. In FIG. 7, pixels are represented by combinations of symbols as in FIG. 5.

In the image correction unit 595, the stored pixel value changeable signal D50k is sequentially read, and as shown in FIG. 7, the read pixel value changeable signal D50k changes from “Disable” to “Enable” at the time point e. Then, among the data supplied from the selector unit 523, the pixel value indicated by the output binary data D50m corresponding to the pixel C7 and the binary pixel data D50b supplied from the binary image input unit 570 are equivalent to the pixel C7. The pixel value indicated by the binary pixel data D50b to be compared is compared.
As shown in FIG. 7, the pixel value “1” indicated by the output binary data D50m supplied from the selector unit 523 and the pixel value “0” indicated by the binary image data supplied from the binary image input unit. Therefore, the image correcting unit 595 finds a point where the pixel value changeable signal D50k changes from “Disable” to “Enable”.
In the image correction unit 595, the pixel value changeable signal D50k is sequentially read, and when the pixel value changeable signal D50k changes from “Disable” to “Enable” at the time point g, the output binary value supplied from the selector unit 523 is output. Among the data D50m, the pixel value indicated by the output binary data D50m corresponding to the pixel J7 and the pixel value indicated by the binary pixel data D50b corresponding to the pixel J7 among the binary pixel data D50b supplied from the binary image input unit. And compare.
As shown in FIG. 7, the pixel value “0” indicated by the output binary data D50m supplied from the selector unit 523 and the pixel value “1” indicated by the binary image data supplied from the binary image input unit. Therefore, the image correcting unit 595 corrects the pixel value of the output binary data D50m in the pixel C7 to “0” and corrects the pixel value of the output binary data D50m in the pixel J7 to “1”. The output binary pixel data D50b corrected in this way is supplied from the image correction unit 595 to the image output unit 600.

  As described above, according to the present embodiment, when the pixel value of the output binary data D50m output from the selector unit 523 is different from the pixel value of the input binary image data D10 at the edge portion of the image, the image correction unit 595 is used. Thus, the pixel value is corrected to the pixel value of the original input binary image data D10. According to this embodiment, even when an image obtained by binarizing error diffusion data is shifted by one pixel from the image of the input binary image data D10, the image correction unit 595 corrects the image. Therefore, it is possible to output an image that accurately holds the shape of the image indicated by the input binary image data D10.

[3. Third Embodiment]
Next, a third embodiment of the present invention will be described. Note that in the third embodiment described below, the same reference numerals as those in the first embodiment are given to portions having the same configurations as those in the first embodiment, and description thereof is omitted.

[3-1. Configuration of Third Embodiment]
FIG. 8 is a block diagram illustrating the configuration of an image processing apparatus according to the third embodiment of the present invention. The third embodiment of the present invention differs from the first embodiment in that it includes a difference calculation unit 700 and image data output from the difference calculation unit 700 (hereinafter, this image data is referred to as difference image data D70). The error diffusion unit 500 performs error diffusion to generate binary image data.

  As shown in FIG. 8, the difference calculation unit 700 receives the smoothed image data D30 generated by the halftone dot removal unit 300 and the color correction image data D40 generated by the color conversion unit 400. . The difference calculation unit 700 calculates the difference between the pixel value indicated by the smoothed image data D30 from which the halftone dot component has been removed and the pixel value indicated by the color corrected image data D40 obtained by performing color correction on the smoothed image data D30. Ask for. Thus, by taking the difference between the pixel value indicated by the smoothed image data D30 and the pixel value indicated by the color correction image data D40, the portion of the image data from which the halftone dot component has been removed is subjected to color correction. Only appears as a difference. The difference calculation unit 700 supplies difference image data D70 indicating this difference to the multi-value image input unit 580 of the error diffusion unit 500.

  In the third embodiment of the present invention, the error diffusion unit 500 performs error diffusion on the difference image data D70 output from the difference calculation unit 700. As in the first embodiment, the error diffusion unit 500 generates a pixel value changeable signal D50k from the binary pixel data D50b. When the pixel value changeable signal D50k is “Disable”, the input binary image When the data D10 is output as it is and the pixel value changeable signal D50k is “Enable”, rebinarized data D50j obtained by binarizing the difference image data D70 subjected to error diffusion is output.

  As described above, in the third embodiment of the present invention, since error diffusion is performed on the difference image data D70, the pixel value can be taken by the pixel as in the technique described in Patent Document 1. The problem that the range of values often occurs is solved, and the accuracy of color correction can be improved. Further, as in the first embodiment, the value of the pixel included in the input binary image data D10 is output in a portion where black pixels and white pixels are continuous, and the difference subjected to error diffusion is applied to the edge portion of the image. By outputting the image data obtained by binarizing the image data D70, it is possible to output an image that accurately holds the shape of the image indicated by the input binary image data D10.

[4. Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment of the present invention, a series of processes such as generation of simple multi-value image data, generation of smoothed image data, color correction and error diffusion for the smoothed image data are realized by software.

  FIG. 9 is a block diagram illustrating a hardware configuration of an image processing apparatus that implements these processes using software. As shown in FIG. 9, this image processing apparatus includes a ROM (Read Only Memory) 902, a RAM (Random Access Memory) 903, a CPU (Central Processing Unit) 904, a nonvolatile memory 905, and input binary image data D10. An interface unit 906 for receiving and an output unit 907 for printing are provided, and these units are connected by a bus 901. The ROM 902 stores a control program for causing the CPU 904 to control each unit of the image processing apparatus, and the nonvolatile memory 905 stores an error diffusion program for causing the CPU 904 to execute the above-described processing. When the image processing apparatus is turned on, the CPU 904 reads the control program from the ROM 902 and activates it. The CPU 904 that has activated the control program reads the error diffusion program from the nonvolatile memory 905 and executes the read program using the RAM 903 as a work area. Thus, it can be said that the image processing apparatus has a hardware configuration similar to that of a general computer apparatus in that the CPU 904 controls each unit according to a program and performs processing.

  FIG. 10 is a flowchart illustrating the flow of processing performed by the program that executed the error diffusion program. When the error diffusion program is activated, the CPU 904 waits for input binary image data D10 to be input to the interface unit 906 (step SA1). When the input binary image data D10 is input to the interface unit 906, the CPU 904 generates simple multi-value image data from the input binary image data D10 input to the interface unit 906 (step SA2), and the generated simple multi-value data. Smoothing processing is performed on the value image data (step SA3). When the CPU 904 performs smoothing processing to generate smoothed image data, the CPU 904 performs color correction on the smoothed image data to generate color corrected image data (step SA4). After performing the color correction processing, the CPU 904 performs error diffusion processing using the input binary image data D10 and the color correction image data to generate binary image data (step SA5). When the CPU 904 supplies the image data to the output unit 907 and controls the output unit 907, printing is performed based on the binary image data. As described above, when software performs simple multi-value image data generation, smoothed image data generation, color correction and error diffusion for the smoothed image data, these processes are realized by hardware. In comparison, it is possible to easily change parameters when color conversion is performed. Needless to say, when processing is performed by software, other embodiments can also perform processing by software.

[5. Other Embodiments]
The present invention is not limited to the above-described embodiments, and various modifications can be made.
<5-1>
For example, as shown in FIG. 11, instead of the input binary image data D10, simple multilevel image data D20 is input to the error diffusion unit 500, and the error diffusion unit 500 uses the simple multilevel image data D20. Then, a threshold value or pixel value changeable signal D50k may be generated, and the color corrected image data D40 subjected to color correction may be converted into binary image data.

<5-2>
The threshold value calculation unit 510 does not generate a threshold value from the input binary image data D10 input to the binary image input unit 570, but a binarization unit 520 using a predetermined value as a threshold value as shown in FIG. It is good also as a structure supplied to. Also in the error diffusion unit 500 of the second embodiment and the third embodiment, instead of generating a threshold value from the input binary image data D10 input to the binary image input unit 570, a predetermined value is used as the threshold value. May be supplied to the binarization unit 520.

<5-3>
The threshold calculation unit 510 may generate a threshold using an LUT (Look Up Table). FIG. 13 is a block diagram illustrating a configuration of the threshold value calculation unit 510 when a threshold value is generated using an LUT. The LUT unit 514 illustrated in FIG. 13 stores a table in the format illustrated in FIG. 14, and threshold values to be output according to input binary image data are stored in this table. In the table of FIG. 14, Lmax indicates the maximum value that the pixel can take when performing color correction, and Lmin indicates the minimum value that the pixel can take when performing color correction. Based on this table, the LUT unit 514 outputs Lmax as the threshold when the pixel value indicated by the input binary pixel data D50b is “0”, and when the pixel value is “1”. May output Lmin as a threshold value.

<5-4>
The configuration of the threshold value calculation unit 510 may include a reversing unit 511 and a filter unit 515 as illustrated in FIG. The inversion unit 511 performs the same operation as that of the inversion unit 511 of the above-described embodiment. For example, as illustrated in FIG. 16, the filter unit 515 generates threshold data D50i by performing a filtering process on binary image data whose values are inverted. According to such an aspect, the value of the threshold data D50i becomes a different value for each adjacent pixel. Therefore, the probability that the value of the target pixel changes as the number of pixels having different values from the target pixel increases around the target pixel. Get higher.

<5-5>
In addition to the above-described aspect, the adjacent pixel determination unit 522 compares the image indicated by the input binary image with a specific image pattern such as a character or a figure, and if pattern matching occurs, the adjacent pixel determination unit 522 “Disable” may be output even when the output of the pixel value changeable signal D50k is determined as “Enable” from the relationship with the pixel to be changed. According to such an aspect, since the input binary image data D10 is output as it is for a pattern such as a character, it is possible to output an image that maintains the shape of the character with high accuracy.

<5-6>
When the configuration of the error diffusion unit 500 is the configuration described in the first embodiment, the image processing apparatus may have the error diffusion units 500 in columns as illustrated in FIG. According to such an aspect, even when the change of the pixel value in the color conversion unit 400 is large, the error is sufficiently diffused.

<5-7>
Further, the configuration of the image processing apparatus may be as illustrated in FIG. In the configuration illustrated in FIG. 18, multi-value image data is input to the first image input unit 100A, and multi-value image data input to the first image input unit 100A is input to the second image input unit 100B. Then, image data subjected to screen processing, that is, binary image data having a halftone dot component is input. The color conversion unit 400 performs color conversion on the multivalued image data supplied from the first image input unit 100A, and supplies the color correction image data D40 to the error diffusion unit 500. The error diffusion unit 500 generates binary image data using the color correction image data D40 and binary image data, and supplies the generated binary image data to the image output unit 600, as in the above-described embodiment. Even in such an aspect, it is possible to output image data obtained by accurately storing original image data as binary image data for output.

<5-8>
In the fourth embodiment of the present invention, error diffusion processing is realized by software. In this aspect, the maximum value of the value indicated by the binarized error data is stored, and this value is larger than a predetermined value. The error diffusion process may be performed again, and if this value is greater than a predetermined value, the error diffusion process may be terminated.

<5-9>
In the fourth embodiment of the present invention, an image processing apparatus receives image data binarized by RIP processing, and the image processing apparatus performs color conversion and binarization on the image data to perform printing. However, the image processing apparatus is connected to a LAN (Local Area Network), receives image data binarized by RIP processing and data for specifying a color printer via the LAN, and outputs the color printer. It is also possible to generate binary image data converted in such a manner and transmit the generated image data to a device that has transmitted image data binarized by RIP processing.

<5-10>
Further, as illustrated in FIG. 19, the image processing apparatus is connected to a wide area network such as the Internet, and the image processing apparatus is binarized by data specifying a color printer and RIP processing transmitted from the client apparatus. Image data is received via a wide area network, and using these data, binary image data converted to match the output characteristics of the color printer is generated, and the generated binary image data is converted by RIP processing. You may make it transmit to the transmission source of the binarized image data, and the destination designated by this transmission source.
Further, as described above, in the aspect in which the image processing apparatus is connected to the Internet, binary image data converted to meet the output characteristics of the color printer is generated after receiving the binary image data by RIP processing. Among the processes up to, for example, the data transmission source performs the process until the smoothed image data is generated, and the image processing apparatus performs the rest of the processes, for example, the transmission source of the image data binarized by the RIP process And the image processing apparatus may communicate with each other to generate binary image data converted to match the output characteristics of the color printer.

<5-11>
When the adjacent pixel determination unit 522 performs a logical operation on a pixel value of a pixel adjacent to the pixel of interest, the embodiment is not limited to a mode in which a logical operation is performed on the pixel values of upper, lower, left, and right pixels adjacent to the target pixel. A logical operation may be performed on the pixel values of the two pixels. Even in such an aspect, the adjacent pixel determination unit 522 can output the pixel value changeable signal D50k at the edge portion of the image. The adjacent pixel determination unit 522 may output the pixel value changeable signal D50k when any pixel value of the pixel adjacent to the target pixel is different from the pixel value of the target pixel. According to such an aspect, for example, the pixel at the end, such as the pixel A1 to pixel A13, the pixel A1 to pixel M1, the pixel M1 to pixel M13, and the pixel A13 to pixel M13 illustrated in FIG. Also, the pixel value changeable signal D50k can be output.

<5-12>
In the error diffusion unit 500 of the third embodiment described above, the difference image data D70 is input to the multi-value image input unit 580, and error diffusion is performed on the difference image data D70. In this case, as shown in FIG. 20, the error diffusion unit 500 may be configured such that the binary pixel data D50b output from the binary image input unit 570 is supplied to the error calculation unit 540.

In this aspect, the error calculation unit 540 indicates that the error addition data D50c indicates that the pixel value indicated by the binary pixel data D50b is “0” and the pixel value indicated by the output binary data D50m is “1”. A value obtained by subtracting “255” from the value is supplied to the error storage unit 550 as binarized error data D50d.
The error calculation unit 540 sets the value indicated by the error addition data D50c when the pixel value indicated by the binary pixel data D50b is “1” and the pixel value indicated by the output binary data D50m is “0”. A value obtained by adding “255” or a value obtained by subtracting “−255” is supplied to the error storage unit 550 as binarized error data D50d.
When the pixel value indicated by the binary pixel data D50b and the pixel value indicated by the output binary data D50m are the same, the error calculation unit 540 directly uses the error addition data D50c as the binarized error data D50d to the error storage unit 550. Supply.

  The conventional error diffusion method assumes that all pixel values of an image subjected to error diffusion have a positive value. However, according to this aspect, error diffusion is performed on image data having both positive pixel value data and negative pixel value data, such as difference image data D70, and error diffusion is performed. Can be supplied to the binarization unit 520 and superimposed on the input binary image data D10, so that the result of color conversion can be reflected more accurately and the halftone dot shape can be stored more accurately. In particular, when the pixel values of all the pixels of the difference image data D70 are 0, the pixel values of all the pixels of the input binary image data D10 and the output binary image data D60 can be made the same.

<5-13>
In the error diffusion unit 500 of the third embodiment described above, the difference image data D70 is input to the multi-value image input unit 580, and error diffusion is performed on the difference image data D70. In this case, the error diffusion unit 500 may be configured such that the binary pixel data D50b is supplied to the image correction unit 530 as shown in FIG.

  In this aspect, the image correction unit 530 first adds the error data D50f and the multi-value pixel data D50a. Next, when the pixel value of the supplied binary pixel data D50b is “0”, the image correction unit 530 sets the value obtained by adding “0” to the previous addition result as error addition data D50c and supplies the supplied 2 When the pixel value of the value pixel data D50b is “1”, a value obtained by adding “255” to the previous addition result is set as error addition data D50c. The image correction unit 530 supplies the generated error addition data D50c to the binarization unit 520 and the error calculation unit 540.

  Even in this mode, it is possible to apply error diffusion to image data having both positive pixel value data and negative pixel value data, such as difference image data D70, and to superimpose it on input binary image data D10. Therefore, the result of color conversion can be reflected more accurately, and the halftone dot shape can be stored more accurately. Further, when the pixel values of all the pixels of the difference image data D70 are 0, the pixel values of all the pixels of the input binary image data D10 and the output binary image data D60 can be made the same.

<5-14>
Even when the configuration of the error diffusion unit 500 is the configuration described in <5-12> or <5-13>, as described in <5-6>, the error diffusion units may be arranged in columns. Good. The configuration of the image processing apparatus 500 in this case is shown in FIG. As shown in FIG. 2 2, the image processing apparatus, multi-value conversion unit, the halftone removal unit, the difference calculation section, and each 2 by one comprises an error diffusion unit.

  In the image processing apparatus according to this aspect, the input binary image data D10 is supplied to the first multi-value quantization unit 200A and the first error diffusion unit 500A. The first multi-value conversion unit 200A multi-values the supplied binary image data D10 to generate simple multi-value image data D20, and supplies this simple multi-value image data D20 to the first halftone dot removal unit 300A. . The first halftone dot removing unit 300A generates smoothed image data D30 from which halftone dot components included in the simple multi-valued image data D20 are removed, and the smoothed image data D30 is converted into the color conversion unit 400 and the first difference calculation unit. 700A. The color conversion unit 400 performs color correction on the smoothed image data D30 to generate color correction image data D40, and the color correction image data D40 is transferred to the first difference calculation unit 700A and the second difference calculation unit 700B. Supply. The first difference calculation unit 700A obtains a difference between the supplied smoothed image data D30 and the color-corrected image data D40, generates difference image data D70, and supplies the difference image data D70 to the first error diffusion unit 500A. To do.

The first error diffusion unit 500A performs error diffusion using the supplied binary image data D10 and difference image data D70, generates output binary image data D60, and generates second output binarization unit 200B and second image data D70. This is supplied to the error diffusion unit 500B. The second multi-value conversion unit 200B multi-values the supplied output binary image data D60 to generate simple multi-value image data D20, and supplies this simple multi-value image data D20 to the second halftone dot removal unit 300B. To do. The second halftone dot removing unit 300B generates smoothed image data D30 from which halftone dot components included in the simple multivalued image data D20 are removed, and supplies the smoothed image data D30 to the second difference calculation unit 700B. The second difference calculation unit 700B obtains a difference between the supplied smoothed image data D30 and the color-corrected image data D40, generates difference image data D70, and supplies the difference image data D70 to the second error diffusion unit 500B. To do.
The second error diffusion unit 500B performs error diffusion using the supplied output binary image data D60 and difference image data D70, generates output binary image data D60, and supplies it to the image output unit 600.
According to such an aspect, even when the change of the pixel value in the color conversion unit 400 is large, the error is sufficiently diffused.

<5-15>
Even when the configuration of the error diffusion unit 500 is the configuration described in <5-12> or <5-13>, as described in <5-7>, the multi-value image data and the binary image data are You may make it input separately. The configuration of the image processing apparatus 500 in this case is shown in FIG. In this aspect, the multi-value image data input to the first image input unit 100A is supplied to the color conversion unit 400 and the difference calculation unit 700. The color conversion unit 400 generates image data obtained by performing color correction on the input multi-value image data, and supplies the image data to the difference calculation unit 700. The difference calculation unit 700 obtains a difference between the supplied multi-value image data and the color-corrected image data, generates difference image data, and supplies the difference image data to the error diffusion unit 500. The error diffusion unit 500 performs error diffusion using the difference image data and the binary image data, and generates output binary image data. Even in such an aspect, it is possible to output image data obtained by accurately storing original image data as binary image data for output.

<5-16>
The error diffusion unit 500 may be configured to binarize the error addition data using two threshold values. FIG. 24 is a block diagram showing a configuration of the error diffusion unit 500 when binarizing the error addition data using two threshold values. In the following description, the same parts as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted.

  The threshold value calculation unit 510 supplies a predetermined value as a threshold value to the binarization unit 520, and includes first threshold value data D50i-1 indicating a first threshold value and second threshold value data D50i- indicating a second threshold value. 2 is output. The value indicated by the first threshold data D50i-1 is larger than the value indicated by the second threshold data D50i-2.

  The first comparison unit 521a binarizes the error addition data D50c supplied from the image correction unit 530 with the first threshold data D50i-1 supplied from the threshold calculation unit 510. When the value indicated by the error addition data D50c is equal to or greater than the value indicated by the threshold data D50i-1, the first comparison unit 521a excludes the first re-binarized data D50j-1 whose pixel value is “1”. If the value indicated by the error addition data D50c is less than the value indicated by the threshold data D50i-1, the first re-binarized data D50j-1 with the pixel value set to “0” is supplied to the logical OR operation unit 524a. Is supplied to the exclusive OR operation unit 524a.

  The second comparison unit 521b binarizes the error addition data D50c supplied from the image correction unit 530 with the second threshold data D50i-2 supplied from the threshold calculation unit 510. When the value indicated by the error addition data D50c is equal to or greater than the value indicated by the threshold data D50i-2, the second comparison unit 521b excludes the second re-binarized data D50j-2 having the pixel value “1”. When the value indicated by the error addition data D50c is less than the value indicated by the second threshold data D50i-2, the pixel value is set to “0”. The value data D50j-2 is supplied to the exclusive OR operation unit 524a and the selector unit 523.

The exclusive OR operation unit 524a obtains an exclusive OR of the value of the first rebinarized data D50j-1 and the value of the second rebinarized data D50j-2. Data D50n indicating the result is supplied to the negative operation unit 524b.
Specifically, when the first rebinarized data D50j-1 is “1” and the second rebinarized data D50j-2 is “1”, that is, the value indicated by the error addition data D50c is If it is larger than the first threshold data D50i-1, data D50n indicating "0", which is the result of the logical operation, is output. Further, when the first re-binarized data D50j-1 is “0” and the second re-binarized data D50j-2 is “1”, that is, the value indicated by the error addition data D50c is the first value. When it is smaller than the threshold data D50i-1 and equal to or larger than the second threshold data D50i-2, data D50n indicating “1” as a result of the logical operation is output. Further, when the first re-binarized data D50j-1 is “0” and the second re-binarized data D50j-2 is “0”, that is, the value indicated by the error addition data D50c is the second value. When it is smaller than the threshold data D50i-2, data D50n indicating "0" as a result of the logical operation is output.

The negative operation unit 524b obtains negation of the data D50n by a logical operation, and supplies data D50p indicating the result of the logical operation to the logical product operation unit 524c.
The AND operation unit 524c obtains a logical product of the pixel value changeable signal D50k and the data D50p. When the result of this logical operation is “1”, “Enable” is output to the selector unit 523 as the second pixel value changeable signal D50r, and when the result of this logical operation is “0”, the pixel “Disable” is output to the selector unit 523 as the value changeable signal D50r.
Specifically, the AND operation unit 524c indicates that the pixel value changeable signal is “Enable”, the data D50p is “0”, that is, the value of the error addition data D50c is “first threshold data> error addition data”. If ≧ second threshold data ”,“ Disable ”is output as the pixel value changeable signal D50r. Further, the AND operation unit 524c determines that the pixel value changeable signal is “Enable” and the data D50p is “1”, that is, the value of the error addition data D50c is “error addition data> first threshold data”, Alternatively, when “second threshold data> error addition data”, “Enable” is output as the pixel value changeable signal D50r. Further, when the pixel value changeable signal is “Disable”, the logical product operation unit 524c outputs “Disable” as the pixel value changeable signal D50r regardless of the value of the data D50p.

  When the second pixel value changeable signal D50r is “Enable”, the selector unit 523 outputs the second re-binarized data D50j-2 as output binary data D50m, and the second pixel value changeable signal. When D50r is “Disable”, the binary pixel data D50b is output as output binary data D50m.

Next, the operation of the error diffusion unit 500 employing this configuration will be described using FIG. 25 in comparison with the operation of the error diffusion unit 500 of the first embodiment. In FIG. 25, in order to express a pixel, the code | symbol of 1-15 is attached to the horizontal direction, and it shall represent a pixel by this.
Further, it is assumed that the pixel value of the multi-value pixel data in the section 1 to 15 in FIG. 25 is “80”, and the value of the error data D50f is “0” at the start of error diffusion. Further, it is assumed that the value of the first threshold data D50i-1 is “128” and the value of the second threshold data D50i-2 is “−128”. For convenience of explanation, calculation of the error data D50f by the correction calculation unit 560 uses only the binarization error data D50d of the pixel to the left of the target pixel, and the adjacent pixel determination unit 522 Assume that the pixel value changeable signal is generated not in terms of left and right but in relation to the left and right pixels of the target pixel.

  First, the operation of the error diffusion unit 500 of the first embodiment will be described. When the pixel 1 of the binary pixel data D50b is the target pixel, the value of the multivalued pixel data D50a input to the image correction unit 530 is “80”, and the value of the error data D50f is “0”. The value of the error addition data D50c is “80”. In the adjacent pixel determination unit 522, since the pixel value of the pixel 1 is “0” and the logical sum with the adjacent pixel is “0”, the pixel value changeable signal D50k indicating “Disable” is output. . Since the pixel value changeable signal D50r is “Disable”, the selector unit 523 outputs the value “0” indicated by the binary pixel data D50b as output binary data. In the error calculation unit 540, a difference value “80” between the value “0” of the output binary data D50m and the error addition data D50c is obtained.

  Next, when the pixel 2 of the binary pixel data D50b is the target pixel, the value of the multi-value pixel data D50a input to the image correction unit 530 is “80”, and the value of the error data D50f is “80”. Therefore, the value of the error addition data D50c is “160”. In the adjacent pixel determination unit 522, the pixel value changeable signal D50k becomes “Disable” in the same manner as the pixel 1. Since the pixel value changeable signal D50k is “Disable”, the selector unit 523 outputs the value “0” indicated by the binary pixel data D50b as output binary data. In the error calculation unit 540, a difference value “160” between the value “0” of the output binary data D50m and the error addition data D50c is obtained.

  Next, when the pixel 3 of the binary pixel data D50b is the target pixel, the value of the multi-value pixel data D50a input to the image correction unit 530 is “80”, and the value of the error data D50f is “160”. Therefore, the value of the error addition data D50c is “240”. In the adjacent pixel determination unit 522, since the pixel value of the pixel 3 is “0” and the pixel value of the pixel 4 is “1”, the logical sum with the adjacent pixel is “1”. As a result, the pixel value changeable signal D50k becomes “Enalbe”. The comparison unit 521 supplies the re-binarized data D50j having the pixel value “1” to the selector unit 523 because the value “240” of the error addition data D50c is greater than the value “128” of the threshold data D50i. To do. Since the pixel value changeable signal D50k is “Enable”, the selector unit 523 outputs the value “1” of the re-binarized data D50j as the output binary data D50m. Since the output binary data D50m supplied from the binarization unit 520 is “1”, the error calculation unit 540 subtracts “255” from the value “240” indicated by the error addition data D50c as a difference value. The data indicating the obtained difference value “−15” is supplied to the error storage unit 550 as binarized error data D50d.

  Next, when the pixel 4 of the binary pixel data D50b is the target pixel, the value of the multivalued pixel data D50a input to the image correction unit 530 is “80”, and the value of the error data D50f is “−15”. Therefore, the value of the error addition data D50c is “65”. In the adjacent pixel determination unit 522, since the pixel value of the pixel 4 is “1” and the pixel value of the pixel 3 is “0”, the logical product with the adjacent pixel is “0”. As a result, the pixel value changeable signal D50k becomes “Enalbe”. The comparison unit 521 supplies the re-binarized data D50j whose pixel value is “0” to the selector unit 523 because the value “65” of the error addition data D50c is smaller than the value “128” of the threshold data D50i. To do. Since the pixel value changeable signal D50k is “Enable”, the selector unit 523 outputs the value “0” of the rebinarized data D50j as the output binary data D50m. Since the output binary data D50m supplied from the binarization unit 520 is “0”, the error calculation unit 540 has a difference between the value “65” indicated by the error addition data D50c and the output binary data D50m “0”. Data indicating the value “65” is supplied to the error storage unit 550 as binarized error data D50d. As described above, in the configuration of the error diffusion unit 500 according to the first embodiment, a portion that is a black pixel in the original image may be a white pixel in the edge portion of the image.

  Next, an operation of an aspect in which error diffusion is performed using two threshold signals will be described. Note that the operation when the pixel 1 is the target pixel and the operation when the pixel 2 is the target pixel are the same as the operation of the first embodiment described above, and thus description thereof is omitted.

  When the pixel 3 of the binary pixel data D50b is the target pixel, the value of the multi-value pixel data D50a input to the image correction unit 530 is “80”, and the value of the error data D50f is “160”. The value of the error addition data D50c is “240”. In the adjacent pixel determination unit 522, since the pixel value of the pixel 3 is “0” and the pixel value of the pixel 4 is “1”, the logical sum with the adjacent pixel is “1”. As a result, the pixel value changeable signal D50k becomes “Enalbe”.

  Since the value “240” of the error addition data D50c is larger than the value “128” of the first threshold data D50i-1, the first comparison unit 521a performs the first re-binarization with the pixel value “1”. The data D50j-1 is supplied to the exclusive OR operation unit 524a. On the other hand, since the value “240” of the error addition data D50c is larger than the value “−128” of the second threshold data D50i-2, the second comparison unit 521b performs the second re-creation with the pixel value “1”. The binarized data D50j-2 is supplied to the exclusive OR operation unit 524a and the selector unit 523.

  Since the supplied first re-binarized data D50j-1 is “1” and the second re-binarized data D50j-2 is “1”, the exclusive OR operation unit 524a Data D50n indicating “0” as the result of the sum operation is output. Since the value of the data D50n is “0”, the negative operation unit 524b supplies the data D50p indicating “1”, which is the result of the logical operation, to the logical product operation unit 524c.

  Since the pixel value changeable signal is “Enable” and the data D50p is “1”, the AND operation unit 524c sets “Enable” as the second pixel value changeable signal D50r. Output. Since the second pixel value changeable signal D50r is “Enable”, the selector unit 523 outputs the value “1” of the second rebinarized data D50j-2 as the output binary data D50m. Since the output binary data D50m supplied from the binarization unit 520 is “1”, the error calculation unit 540 subtracts “255” from the value “240” indicated by the error addition data D50c as a difference value. The data indicating the obtained difference value “−15” is supplied to the error storage unit 550 as binarized error data D50d.

  Next, when the pixel 4 of the binary pixel data D50b is the target pixel, the value of the multivalued pixel data D50a input to the image correction unit 530 is “80”, and the value of the error data D50f is “−15”. Therefore, the value of the error addition data D50c is “65”. In the adjacent pixel determination unit 522, since the pixel value of the pixel 4 is “1” and the pixel value of the pixel 3 is “0”, the logical product with the adjacent pixel is “0”. As a result, the pixel value changeable signal D50k becomes “Enalbe”.

  Since the value “65” of the error addition data D50c is smaller than the value “128” of the first threshold data D50i-1, the first comparison unit 521a performs the first re-binarization in which the pixel value is “0”. The data D50j-1 is supplied to the exclusive OR operation unit 524a. On the other hand, since the value “65” of the error addition data D50c is larger than the value “−128” of the second threshold data D50i-2, the second comparison unit 521b performs the second re-creation with the pixel value “1”. The binarized data D50j-2 is supplied to the exclusive OR operation unit 524a and the selector unit 523.

  Since the supplied first re-binarized data D50j-1 is “0” and the second re-binarized data D50j-2 is “1”, the exclusive OR operation unit 524a Data D50n indicating “1” which is the result of the sum operation is output. Since the value of the data D50n is “1”, the negative operation unit 524b supplies the data D50p indicating “0”, which is the result of the logical operation, to the logical product operation unit 524c.

  Since the pixel value changeable signal is “Enable” and the data D50p is “0”, the AND operation unit 524c sets “Disable” as the second pixel value changeable signal D50r. Output. Since the second pixel value changeable signal D50r is “Disable”, the selector unit 523 outputs the value “1” of the binary pixel data D50b as the output binary data D50m. Since the output binary data D50m supplied from the binarization unit 520 is “1”, the error calculation unit 540 subtracts “255” from the value “65” indicated by the error addition data D50c as a difference value. The data indicating the obtained difference value “−190” is supplied to the error storage unit 550 as binarized error data D50d.

As described above, according to this aspect, in the edge portion of the image, the black pixel portion in the original image is directly used as the black pixel. When the number of pixels is increased / decreased, for example, an isolated white pixel is generated in a portion where black pixels are continuous, and the problem that the halftone dots are not one cluster can be prevented.
In this aspect, the configuration of error diffusion section 500 may be the configuration described in <5-12> or <5-13>.
When the configuration of the error diffusion unit 500 is the configuration described in <5-12> or <5-13>,
When binary pixel data is input as shown in FIG. 25, the same processing as in this aspect is performed on the pixel portion before pixel 1. Since the error data D50f value at the pixel 1 is offset instead of “0” due to the characteristics of the error diffusion process, the section where the output binary data D50m is “1” is almost the section from the pixel 4 to the pixel 10. Become. Even in the case where the section where the output binary data D50m is “1” is the section from the pixel 3 to the pixel 9 as in this aspect, and is shifted by one pixel from the binary pixel data D50b, the second embodiment of the present invention By combining them, output binary image data in which the original input binary image data is stored with high accuracy can be output.

1 is a block diagram illustrating a configuration of an image processing apparatus according to a first embodiment of the present invention. 2 is a block diagram illustrating a configuration of an error diffusion unit included in the image processing apparatus according to the first embodiment. FIG. It is a figure which shows the relationship between the pixel value of an attention pixel and the pixel value changeable signal output from the adjacent pixel determination part 522 in the said 1st Embodiment. It is a figure which shows the relationship between the pixel value of an attention pixel and the pixel value changeable signal output from the adjacent pixel determination part 522 in the said 1st Embodiment. It is a figure for demonstrating operation | movement of the adjacent pixel determination part 522 of the 1st embodiment. It is a block diagram which illustrates the composition of the image processing device concerning a 2nd embodiment of the present invention. It is a figure for demonstrating the operation example of the 2nd Embodiment. It is a block diagram which illustrates the composition of the image processing device concerning a 3rd embodiment of the present invention. It is a block diagram which illustrates the composition of the image processing device concerning a 4th embodiment of the present invention. It is a flowchart which illustrates the flow of the process which CPU of the image processing apparatus concerning the 4th Embodiment performs. It is a block diagram which illustrates the composition of the modification of the image processing device concerning the present invention. It is a block diagram which illustrates the composition of the modification of error diffusion part 500 concerning the present invention. It is a block diagram which illustrates the composition of the modification of threshold calculation part 510 concerning the present invention. It is a figure which illustrates the format of LUT which the LUT part 514 of the threshold value calculation part 510 has memorize | stored. It is a block diagram which illustrates the composition of the modification of threshold calculation part 510 concerning the present invention. It is a figure which illustrates the threshold value data output from the threshold value calculation part 510. It is a block diagram which illustrates the composition of the modification of the image processing device concerning the present invention. It is a block diagram which illustrates the composition of the modification of the image processing device concerning the present invention. It is a figure for demonstrating the modification of the image processing apparatus concerning this invention. It is a block diagram which shows the structure of the modification of the image processing apparatus concerning this invention. It is a block diagram which shows the structure of the modification of the image processing apparatus concerning this invention. It is a block diagram which shows the structure of the modification of the image processing apparatus concerning this invention. It is a block diagram which shows the structure of the modification of the image processing apparatus concerning this invention. It is a block diagram which shows the structure of the modification of the image processing apparatus concerning this invention. It is a figure for demonstrating operation | movement of the modification of the image processing apparatus concerning this invention. It is a figure for demonstrating the prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Image input part, 200 ... Multi-value conversion part, 300 ... Halftone dot removal part, 400 ... Color conversion part, 500 ... Error diffusion part, 600 ... Image output part, 700: Difference calculation unit, 510 ... Threshold calculation unit, 511 ... Inversion unit, 512 ... Coefficient generation unit, 513 ... Multiplication unit, 514 ... LUT unit, 515 ... Filter , 520..., Binarization unit, 521... Comparison unit, 521a... First comparison unit, 521b... Second comparison unit, 522. , 524a ... logical sum operation unit, 524b ... negation operation unit, 524c ... logical product operation unit, 530 ... image correction unit, 540 ... error calculation unit, 550 ... error storage 560... Correction calculation unit 570... Binary image input unit 580. Image input unit, 590 ... binary image output unit, 595 ... image correction unit, 901 ... bus, 902 ... ROM, 903 ... RAM, 904 ... CPU, 905 ... Non-volatile memory, 906... Interface unit, 907.

Claims (22)

Binary image input means for receiving binary image data;
Multi-valued image data obtained by subjecting the binary image data to multi-valued data and subjected to predetermined processing, or multi-valued image data representing the same image as the image of the binary image data. Multi-value image input means for receiving data ;
And error data supplied, and image correcting means for generating an error added data by adding the pixel values of the multivalued image data supplied by the multi-valued image input unit pixels from a pixel unit,
A comparison unit that binarizes the error addition data generated by the image correction unit using a threshold value to generate re-binarized image data;
It is detected whether the pixel of interest in the binary image data received by the binary image input means is a pixel at the edge portion of the image indicated by the binary image data, and the pixel of interest in the binary image data is the image. A pixel value selection signal instructing to select the re-binarized image data generated by the comparison means , and the target pixel in the binary image data is the pixel of the image. A pixel determination unit that outputs a pixel value selection signal instructing to select the binary image data received by the binary image input unit when the pixel is not an edge portion pixel;
According to the pixel value selection signal output from the pixel determination means, the binary image data received by the binary image input means or the re-binarized image data generated by the comparison means is selected and output as output binary data. Selector means;
Error calculating means for obtaining binarized error data indicating an error caused by binarization using the error addition data generated by the image correcting means and the output binary data output by the selector means;
The error data to be added to the pixel value of the multi-value image data in the image correction means is obtained using the binarized error data obtained by the error calculation means, and the obtained error data is stored in the image correction means. Correction calculation means to be supplied ;
An image processing apparatus. When the pixel value of the pixel of interest in the binary image data received by the binary image input unit indicates a white pixel, the pixel determination unit is a pixel value of a pixel adjacent to the pixel of interest in the binary image data When the exclusive OR of the logical sum and the pixel value of the target pixel in the binary image data is true, the re-binarized image data generated by the comparison unit is selected. A pixel value selection signal for instructing selection of binary image data received by the binary image input means when the exclusive OR is false,
When the pixel value of the pixel of interest in the binary image data received by the binary image input means indicates a black pixel, obtain the logical product of the pixel values of the pixels adjacent to the pixel of interest in the binary image data, If the exclusive OR of the logical product and the pixel value of the pixel of interest in the binary image data is true, the pixel value selection instructing the selection of the re-binarized image data generated by the comparison unit A signal is output, and when the exclusive OR is false, a pixel value selection signal instructing selection of binary image data received by the binary image input means is output. The image processing apparatus according to 1. The pixel determination means compares the image indicated by the binary image data received by the binary image input means with a predetermined image pattern. If the image patterns match, the binary image input means The image processing apparatus according to claim 2, wherein a pixel value selection signal instructing to output the received binarized image data as output binary data is output. Comprising multi-value image data generating means for generating multi-value image data from the binary image data received by the binary image input means;
The image processing apparatus according to claim 1, wherein the multi-value image data received by the multi-value image input unit is multi-value image data generated by the multi-value image data generation unit. The multi-value image data generating means
Multi-value conversion means for generating simple multi-value image data in which each of the binary pixel values represented by the binary image data received by the binary image input means is represented by a plurality of bits for each pixel;
Smoothing means for smoothing simple multi-value image data generated by the multi-value conversion means to generate smoothed image data;
Color correction image data generation means for generating color correction image data obtained by performing color correction on the smoothed image data generated by the smoothing means;
The image processing apparatus according to claim 4, wherein the color correction image data is supplied to the multi-value image input unit as multi-value image data. The multi-value image data generating means
A difference image that obtains a difference between the smoothed image data generated by the smoothing unit and the color correction image data generated by the color correction image data generation unit in units of pixels and generates difference image data indicating the difference Comprising data generation means,
The image processing apparatus according to claim 5, wherein the difference image data is supplied to the multi-value image input unit as multi-value image data. The binary image data received by the binary image input means is data obtained by performing screen processing on multi-value image data in which each pixel is represented by a plurality of bits.
Color correction data generation means for generating color correction image data by performing color correction on multi-value image data in which each pixel is represented by a plurality of bits,
The image processing apparatus according to claim 1, wherein the multi-value image data received by the multi-value image input unit is color correction image data generated by the color correction data generation unit. The difference between the multi-valued image data received by the color correction data generation unit and each pixel represented by a plurality of bits and the color correction image data generated by the color correction data generation unit is obtained in units of pixels. , Comprising difference image data generation means for generating difference image data indicating the difference,
The image processing apparatus according to claim 7, wherein the difference image data is supplied to the multi-value image input unit as multi-value image data. The image correction unit receives the binary image data received by the binary image input unit, and when the pixel value of the target pixel in the binary image data indicates a black pixel, the color correction image data The image processing apparatus according to claim 6, wherein a maximum value that can be taken by a pixel value is added to the error addition data. The error calculation means receives the error addition data generated by the image correction means, the output binary data generated by the selector means, and the binary image data received by the binary image input means. When the pixel value of the pixel of interest in the data indicates a white pixel and the output binary data indicates a black pixel, the maximum pixel value that can be taken by the color correction image data is set as the error addition data. When the value subtracted from is output as binarization error data, the pixel value of the pixel of interest in the binary image data indicates a black pixel, and the output binary data indicates a white pixel, A value obtained by adding the maximum pixel value that can be taken by the color-corrected image data to the error addition data is output as binarization error data, and the pixel value of the pixel of interest in the binary image data and the output If the pixel value of the value data is the same, the image processing apparatus according to claim 6 or claim 8 and outputs the error-added data as the binarization error data. The error calculation means receives the error addition data generated by the image correction means, the output binary data generated by the selector means, and the binary image data received by the binary image input means. If the pixel value of the pixel of interest in the data indicates a white pixel and the output binary data indicates a black pixel, the pixel value that can be taken by the multi-value image data received by the multi-value image input means A value obtained by subtracting the maximum value of the error added data from the error addition data is output as binarized error data, the pixel value of the pixel of interest in the binary image data indicates a black pixel, and the output binary data is a white pixel if it represents outputs a value obtained by adding the error addition data the maximum value of the pixel values multivalued image data can take as the binarization error data, note in the binary image data The image processing apparatus according to claim 6 or 8, wherein when the pixel value of a pixel and the pixel value of the output binary data are the same, the error addition data is output as binarized error data. . The image processing apparatus according to claim 1, further comprising a threshold generation unit configured to generate a threshold used by the comparison unit using binary image data received by the binary image input unit. Threshold generating means for generating a first threshold and a second threshold having a value smaller than the first threshold;
The comparison unit binarizes the error addition data generated by the image correction unit using the second threshold generated by the threshold generation unit to generate re-binarized image data,
The pixel determination unit is configured such that the target pixel in the binary image data received by the binary image input unit is a pixel at an edge portion of an image indicated by the binary image data, and the error generated by the image correction unit When the value indicated by the addition data is less than the first threshold value and greater than or equal to the second threshold value, a pixel value selection signal instructing selection of the binary image data received by the binary image input means is output. The target pixel in the binary image data received by the binary image input means is a pixel at the edge portion of the image indicated by the binary image data, and the error addition data generated by the image correction means indicates When the value is greater than or equal to the first threshold value or less than the second threshold value, a pixel value selection signal instructing selection of the re-binarized image data generated by the comparison unit is output. The image processing apparatus according to claim 1. Storage means for storing, in time series, a pixel value selection signal output by the pixel determination means, binary image data received by the binary image input means, and output binary data output by the selector unit;
The pixel value selection signals stored in the storage unit are sequentially read out in time series, and the contents of the pixel value selection signals are reproduced by the comparison unit generated from the binary image data output instruction received by the binary image input unit. When changing to the output instruction of binarized image data, the pixel value of the output binary data output by the selector unit at the pixel immediately after this becomes the pixel value of the binary image data received by the binary image input unit. Differently
And, when the content of the pixel value selection signal is changed from the output instruction of the binary image data received by the binary image input means to the output instruction of the re-binarized image data generated by the comparison means , When the pixel value of the output binary data output by the selector unit at the pixel immediately after this is different from the pixel value of the binary image data received by the binary image input unit,
The image processing according to claim 1, further comprising: image data correction means for generating and outputting corrected image data obtained by inverting the pixel value of the output binary data at the time when the pixel value selection signal changes. apparatus. The image data correction means includes
When the content of the pixel value selection signal changes from an output instruction for re-binarized image data generated by the comparison means to an output instruction for binary image data received by the binary image input means, the immediately preceding pixel The pixel value of the output binary data output by the selector unit is different from the pixel value of the binary image data received by the binary image input unit,
And then, when the content of the pixel value selection signal changes from the output instruction of the re-binarized image data generated by the comparison means to the output instruction of the binary image data received by the binary image input means, When the pixel value of the output binary data output by the selector unit at the immediately preceding pixel is different from the pixel value of the binary image data received by the binary image input unit,
The image processing apparatus according to claim 14, wherein the image processing apparatus generates and outputs corrected image data obtained by inverting the pixel value of the output binary data when the pixel value selection signal changes. Binary image input means for receiving binary image data;
Multi-valued image data obtained by subjecting the binary image data to multi-valued data and subjected to predetermined processing, or multi-valued image data representing the same image as the image of the binary image data. Multi-value image input means for receiving data ;
And error data supplied, and image correcting means for generating an error added data by adding the pixel values of the multivalued image data supplied by the multi-valued image input unit pixels from a pixel unit,
A comparison unit that binarizes the error addition data generated by the image correction unit using a threshold value to generate re-binarized image data;
It is detected whether the pixel of interest in the binary image data received by the binary image input means is a pixel at the edge portion of the image indicated by the binary image data, and the pixel of interest in the binary image data is the image. A pixel value selection signal instructing to select the re-binarized image data generated by the comparison means, and the target pixel in the binary image data is the pixel of the image. A pixel determination unit that outputs a pixel value selection signal instructing to select the binary image data received by the binary image input unit when the pixel is not an edge portion pixel;
According to the pixel value selection signal output from the pixel determination means, the binary image data received by the binary image input means or the re-binarized image data generated by the comparison means is selected and output as output binary data. Selector means;
The error addition data generated by the image correction unit, the output binary data output by the selector unit, and the binary image data received by the binary image input unit are received, and the pixel of the target pixel in the binary image data When the value indicates a white pixel and the output binary data indicates a black pixel, the maximum value of the pixel values that can be taken by the multi-value image data received by the multi-value image input means is set as the error. When the value subtracted from the addition data is output as binarization error data, the pixel value of the pixel of interest in the binary image data indicates a black pixel, and the output binary data indicates a white pixel outputs a value obtained by adding the error addition data the maximum value of the pixel values multivalued image data can take as the binarization error data, wherein the pixel value of the target pixel in the binary image data If the pixel value of the force binary data are the same, the error calculation means for outputting the error-added data as the binarization error data,
The error data to be added to the pixel value of the multi-value image data in the image correction means is obtained using the binarized error data obtained by the error calculation means, and the obtained error data is stored in the image correction means. Correction calculation means to be supplied ;
An image processing apparatus. Comprising multi-value image data generating means for generating multi-value image data from the binary image data received by the binary image input means;
The image processing apparatus according to claim 16, wherein the multi-value image data received by the multi-value image input means is multi-value image data generated by the multi-value image data generation means. The multi-value image data generating means
Multi-value conversion means for generating simple multi-value image data in which each of the binary pixel values represented by the binary image data received by the binary image input means is represented by a plurality of bits for each pixel;
Smoothing means for smoothing simple multi-value image data generated by the multi-value conversion means to generate smoothed image data;
Color correction image data generation means for generating color correction image data obtained by performing color correction on the smoothed image data generated by the smoothing means;
The image processing apparatus according to claim 17, wherein the color correction image data is supplied to the multi-value image input unit as multi-value image data. The multi-value image data generating means
Difference image data for obtaining a difference between the smoothed image data generated by the smoothing unit and the color correction image data generated by the color correction image data unit in units of pixels and generating difference image data indicating the difference Comprising generating means,
The image processing apparatus according to claim 18, wherein the difference image data is supplied to the multi-value image input unit as multi-value image data. The binary image data received by the binary image input means is data obtained by performing screen processing on multi-value image data in which each pixel is represented by a plurality of bits.
Color correction data generation means for generating color correction image data by performing color correction on multi-value image data in which each pixel is represented by a plurality of bits,
The image processing apparatus according to claim 16, wherein the multi-value image data received by the multi-value image input unit is color correction image data generated by the color correction data generation unit. The difference between the multi-valued image data received by the color correction data generation unit and each pixel represented by a plurality of bits and the color correction image data generated by the color correction data generation unit is obtained in units of pixels. , Comprising difference image data generation means for generating difference image data indicating the difference,
The image processing apparatus according to claim 20, wherein the difference image data is supplied to the multi-value image input means as multi-value image data. Computer equipment,
Binary image input means for receiving binary image data;
Multi-valued image data obtained by subjecting the binary image data to multi-valued data and subjected to predetermined processing, or multi-valued image data representing the same image as the image of the binary image data. Multi-value image input means for receiving data ;
And error data supplied, and image correcting means for generating an error added data by adding the pixel values of the multivalued image data supplied by the multi-valued image input unit pixels from a pixel unit,
A comparison unit that binarizes the error addition data generated by the image correction unit using a threshold value to generate re-binarized image data;
It is detected whether the pixel of interest in the binary image data received by the binary image input means is a pixel at the edge portion of the image indicated by the binary image data, and the pixel of interest in the binary image data is the image. A pixel value selection signal instructing to select the re-binarized image data generated by the comparison means , and the target pixel in the binary image data is the pixel of the image. A pixel determination unit that outputs a pixel value selection signal instructing to select the binary image data received by the binary image input unit when the pixel is not an edge portion pixel;
According to the pixel value selection signal output from the pixel determination means, the binary image data received by the binary image input means or the re-binarized image data generated by the comparison means is selected and output as output binary data. Selector means;
Error calculating means for obtaining binarized error data indicating an error caused by binarization using the error addition data generated by the image correcting means and the output binary data output by the selector means;
The error data to be added to the pixel value of the multi-value image data in the image correction means is obtained using the binarized error data obtained by the error calculation means, and the obtained error data is stored in the image correction means. A program for functioning as a correction calculation means to be supplied .

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