JP3546629B2 - Image processing device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing device that converts original image data generated by a computer or transmitted from an external computer into output image data for output to a connected output device.
[0002]
[Prior art]
Conventionally, when converting original image data generated by a computer or transmitted from an external computer into output image data adapted to an output range and resolution to an output device, the image size of the original image data is changed to an output image data. If the original image data is larger than the image size of the data, the original image data is subjected to a data reduction process such as a thinning process of thinning out one pixel for every several pixels so that the image size of the original image data becomes equal to the image size of the output image data. I was
[0003]
An example is shown, where the image size is the capacity of the image data. For example, assuming that the output resolution is 300 dpi, the output range is 30 inches × 30 inches, the number of gradations per pixel is 2 (1 bit / 1 pixel), and there are four colors, the capacity of output image data is about 40 MB (megabytes). ). Here, assuming that the capacity of the original image data is 60 MB, first, the thinning processing of the original image data is performed, and the image data capacity is made equal to the output image data capacity, and is temporarily stored in the storage device. Further, an area occupied on the storage device by each pixel as a pixel of the output image data (hereinafter referred to as a filled area) is obtained, and the output image data is obtained by writing a numerical value corresponding to the pixel value of the original image data into the filled area. .
[0004]
As a result, even if original image data larger than the image size of the output image data is received as input, the conversion to the output image data has been normally performed.
[0005]
In addition, when a wide range of output is performed by a large output device, a defect in a small portion of the output result is inconspicuous to human eyes. Is performed, there is a fact that even if jaggies exist in the original image data, it seems that little jaggies and the like hardly occur.
[0006]
An example of the above-mentioned fact will be described with reference to FIGS. 1 and 2 in a case where binarization is performed by halftone dither. FIG. 1A is an example of a dither matrix used for the binarization processing. This is a 3 × 3 dither matrix. Each element value 11 of the dither matrix 10 is compared with a pixel value 21 overlapping the element value. If the pixel value 21 is equal to or greater than the element value 11, the pixel is output. Otherwise, the binarization process is performed by performing an operation of not outputting the data for all the pixels. As shown in FIG. 1B, it is possible to express ten gradations including 3 × 3 pixels that do not output all the pixels.
[0007]
FIG. 2 shows how the actual original image data 20 is binarized using the dither matrix 10. It is assumed that the pixel values 21 of the original image data 20 handled here are all 128. Since the resolution of the original image data 20 in FIG. 2B is smaller than that in FIG. 2A, the image of FIG. It is. However, if the original image data 20 is binarized using the dither matrix 10 of FIG. 1, the binarized image 22 is almost the same in FIGS. 2A and 2B. From this result, it is understood that when the binarization processing is performed by the halftone dither processing or the like, even if jaggies exist in the original image data 20, little jaggies or the like hardly occur.
[0008]
[Problems to be solved by the invention]
However, in recent years, large color output devices exceeding A0 in paper size have been increasing, and when the resolution of the output device is high and the output range is wide as in the above example, the image size of the output image data is large. In other words, there is a problem that the conversion process from the original image data takes a considerable time.
[0009]
Further, the example of the binarization processing using the halftone dither described above suggests that in order to obtain the output image data, the original image data equal to the image size of the output image data is not necessarily required. There is also a problem that unnecessary processing is performed on such unnecessary data.
[0010]
Further, there is also a problem that a large-capacity storage device is required when temporarily storing the reduced original image data in the storage device.
[0011]
As a method for reducing the amount of data to be stored, there is a method using a compression technique. However, there is a problem that the entire processing speed is reduced by performing the compression processing, and the conversion processing from the original image data to the output image data is problematic. The processing speed is only adversely affected.
[0012]
SUMMARY An advantage of some aspects of the invention is to solve the above-described problem by setting an image size smaller than the image size of output image data as a minimum image size, and making the image size of the original image data larger than the minimum image size. In this case, the conversion process from the original image data to the output image data is performed at high speed by forcibly reducing the image size of the original image data to the minimum image size and obtaining the output image data from the data of the minimum image size. It is an object of the present invention to provide an image processing apparatus capable of performing the above.
[0013]
[Means for Solving the Problems]
In order to achieve this object, an image processing apparatus according to claim 1 of the present invention is arranged such that an image size of the output image data is determined based on a resolution of an output device and an image print size for outputting the original image data. Output image size calculation means for calculating the image size of the output image data, minimum image size setting means for setting an image size smaller than the image size of the output image data as a minimum image size, and an image size of the original image data larger than the minimum image size In the case, an image data reduction unit that performs conversion to intermediate image data in which the image size of the original image data is reduced to the minimum image size,
Storage means for storing the intermediate image data; gradation conversion means for converting the number of gradations of each pixel of the original image data to a number of gradations smaller than the number of gradations of the original image data; Image data drawing means for obtaining the output image data by determining a writing area to the storage means for each pixel, and writing a numerical value after gradation conversion processing corresponding to the value of the pixel to the storage means; Have.
[0014]
The output image size calculating means calculates the image size of the output image data based on the resolution of the output device and the image print size for outputting the original image data, and the minimum image size setting means calculates the image size of the output image data based on the image size of the output image data. If the image size of the original image data is larger than the minimum image size, the image data reduction unit reduces the image size of the original image data to the minimum image size. And the intermediate image data is stored in the storage unit, and the gradation conversion unit converts the gradation number of each pixel of the original image data into a gradation number smaller than the gradation number of the original image data. and, the image data drawing unit determines a write area to the storage means for each pixel of the intermediate image data, after the tone conversion process corresponding to the value of the pixel numerical Obtain the output image data by writing to the storage means.
[0015]
By forcibly reducing the image size of the original image data to the minimum image size and obtaining the output image data from the data of the minimum image size, the writing area to the storage device in the conversion process from the original image data to the output image data Is determined, and the number of pixels of the original image data to be subjected to the operation of writing the numerical value after gradation conversion processing corresponding to the pixel value is reduced, so that high-speed processing can be performed. Further, since the processing is performed after the original image data is converted into image data of the minimum image size, the processing can be performed with a small-capacity storage device. In addition, the output image data generated from the intermediate image data has substantially the same output result as the output image data generated from the original image data having the output image data size.
[0016]
An image processing apparatus according to a second aspect is characterized in that the image size is defined by the number of pixels of the height or width of the image.
[0017]
The output image size calculation means calculates the image size of the output image data, the minimum image size setting means sets an image size smaller than the image size of the output image data as the minimum image size, and sets the image size of the original image data and the minimum image size. When comparing the size, the number of pixels of the height or width of the image is used as a reference for the image size.
[0018]
Thus, the image size of the output image data can be calculated by (multiplication of height or width) × (resolution) by one multiplication. Also, referring directly to the height or width of the image as the image size and not performing complicated calculations means that the image size itself is represented by a small numerical value. Can be handled without exceeding the range.
[0019]
An image processing apparatus according to a third aspect is characterized in that the minimum image size is a size in which the height and width of the output image data are each halved.
[0020]
The minimum image size setting means sets the image size obtained by halving the height and width of the output image data as the minimum image size.
[0021]
As a result, the original image data can be reduced to an optimum image size that hardly affects the image quality of the output image data.
[0022]
[0023]
[0024]
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the image processing apparatus according to the present invention will be described with reference to the drawings.
[0026]
FIG. 3 is a block diagram of an embodiment in which the image processing apparatus of the present invention is embodied as a print control apparatus 100. This block diagram will be described with reference to FIGS. The CPU 30 , ROM 31, RAM 32, input interface 34, and output interface 37 are connected via a bus 33. The PC 36 and the input interface 34 are connected via an input cable 35, and the printing device 39 and the output interface 37 are connected via an output cable 38.
[0027]
The PC 36 is a computer for transmitting the original image data 50. The original image data 50 is data created by the PC 36 or created by another computer and transmitted to the PC 36 via a network and a storage medium.
[0028]
Original image data 50 transmitted by the PC36 is received via the input cable 35 with input interface 34. The received original image data 50 is temporarily stored in the RAM 32 as intermediate image data 60 as shown in the flowchart of FIG. 6 (FIG. 6: S20). The RAM 32 corresponds to the storage unit of the present invention. At the time of storage, after the size of the original image data is obtained (FIG. 6: S10), the output image size calculation procedure 110 (FIG. 6: S12) stored in advance in the ROM 31 and the minimum image size setting procedure 120 (FIG. 6). 6: S16), if the image size of the original image data 50 exceeds the image size of the output image data 70 by the image data reduction procedure 130 (FIG. 6: S18), the original image data 50 is reduced to image data of the minimum image size. These procedures will be described later in detail. Next, output image data 70 is created by the image data drawing means 140 while reading the intermediate image data 60 stored in the RAM 32 (FIG. 6: S22).
[0029]
The created output image data 70 is sent to the output interface 37, and further sent to the printing device 39 via the output cable 38 to perform printing.
[0030]
Next, the output image size calculation procedure 110 will be described with reference to FIG. First, a resolution R (dpi) is obtained (S30). If the resolution of the printing device 39 connected to the printing control device 100 is known, the value is used. However, the CPU 30 can inquire the printing device 39 via the output interface 37. In this case, it is premised that the printing device 39 has means for responding to a request from the print control device 100. Next, the height H (inch) of the output image is obtained (S32). H is a numerical value indicating the height of a desired image print size in inches. Of course, the unit is not limited to inches but may be millimeters or the like. The height h '(dot) of the output image data 70 is obtained by multiplying the obtained R and H (S34). In this embodiment, the image data size is based on the number of pixels at the height of the image data.
[0031]
Next, the minimum image size setting procedure 120 will be described with reference to FIGS. First, the height h '(dot) of the output image data 70 obtained in the output image size calculation procedure 110 is obtained (S40). Next, half the size of h '(dot) is set as the minimum image size height hmin (S42). Here, half of the height of the output image data is set as the minimum image size, but this ratio may be changed according to the capacity of the RAM 32 and the image size of the output image data. For example, as shown in FIG. 9, when the output image data is small (100 dots or less in FIG. 9), the minimum image size is set to be the same as the output image data. Can be set to half the height of the output image data. When the unused capacity of the RAM 32 is small, it is possible to set the minimum image size to 1/4, 1/8 instead of 1/2. However, as the minimum image size is set smaller than the image size of the output image data, the image quality of the output image deteriorates more conspicuously. Therefore, the height of the minimum image size is about の of the height of the output image data. It is appropriate to keep it.
[0032]
Next, the image data reduction procedure 130 will be described with reference to FIG. The image data reduction procedure 130 described in the present embodiment employs a thinning process of reading and discarding surplus pixels as a reduction method. First, a value obtained by dividing the height h of the original image data 50 by the height hmin of the minimum image size is set to f (S50). f is a real number. f is a numerical value serving as a reference for storing the read pixel as the intermediate image data 60 or discarding the read pixel. Next, the row counter Y is initialized to 0 (S51). When 1 is added to Y (S52), and the value of Y is smaller than f (S53: No), after all the pixels in this row are read and discarded (S54), if the original image data 50 to be read still remains, The pixel data of the next row is read (S63: No). If the value of Y is greater than or equal to f (S53: Yes), the column counter X is initialized to 0 (S55), and 1 is added to X (S56). If the value of X is smaller than f (S57: No), one pixel is read and discarded (S58). If the value of X is greater than or equal to f (S57: Yes), one pixel of the original image data 50 is read and stored in the RAM 32 as the intermediate image data 60 (S59).
[0033]
Furthermore, by subtracting the f from the value of X (S60), if the original image data 5 0 loading of one line is not completed (S61: No) flow returns to S56. When the reading of the original image data 60 for one line is completed (S61: Yes), f is subtracted from the value of Y (S62), and if the original image data 50 to be read still remains, the process returns to S52 (S63: No), if the reading of all the pixels of the original image data 50 is completed (S63: Yes), the image data reduction processing ends (S64). As a result of this processing, the thinned image data is stored in the RAM 32 as the intermediate image data 60.
[0034]
Next, the image data drawing procedure 140 will be described with reference to FIGS. First, H is initialized to the number of pixels of the height of the intermediate image data 60 (S70), and W is initialized to the number of pixels of the width of the intermediate image data 60 (S71). Next, the value of one pixel 80 is read from the intermediate image data 60 (S72), and the writing area 81 is determined (S73). The writing area 81 is an area where one pixel 80 of the intermediate image data 60 occupies the output image data 70. The binarization process is performed on each pixel 82 of the writing area 81 by the halftone dither described with reference to FIG. 1 (S74). This binarization processing corresponds to the gradation conversion means of the present invention. Each binarized pixel 82 is written to the write area 81 on the RAM 32 (S75). Next, 1 is subtracted from W (S76). If W is not 0 (S77: No), the process returns to S72. If W is 0 (S77: Yes), it means that the processing for one row is completed, and 1 is subtracted from H (S78). If H is not 0 (S79: No), the process returns to S71 and returns to 0. If there is (S79: Yes), the drawing of the image data ends.
[0035]
In the present embodiment, a method using halftone dither is employed for the binarization processing as the gradation conversion means, but a generally known method such as an error diffusion method may be employed. If a printing device 39 capable of expressing multi-values such as ternary and quaternary values instead of binary values is connected, techniques such as a multi-value error diffusion method and a multi-value halftone dither method have been proposed. And it is also possible to adopt these.
[0036]
Although the present embodiment has been described in detail with reference to the drawings, the present invention is not limited to the above-described embodiment. For example, there is a case where the print range is not similar to the original image data 50 (the aspect ratio changes) by limiting the view range of the output image by clipping or the like. In this case as well, it is possible to perform the processing assuming that the output image data 70 is a rectangle similar to the original image data 50 as in the present embodiment. Considering this, the area of the output range may be used as a reference value to determine whether to reduce the image data.
[0037]
In addition, it is needless to say that the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.
[0038]
【The invention's effect】
As is apparent from the above description, in the image processing apparatus according to the first aspect of the present invention, the output image size calculation unit determines the output image size based on the resolution of the output device and the image print size for outputting the original image data. Calculating the image size of the output image data, the minimum image size setting means sets an image size smaller than the image size of the output image data as the minimum image size, and when the image size of the original image data is larger than the minimum image size, The image data reduction means converts the image size of the original image data to intermediate image data reduced to the minimum image size , stores the intermediate image data in the storage means, and the gradation conversion means converts the gradation number of each pixel in the gradation number smaller than the number of gradations of the original image data, the image data drawing means, stores hand for each pixel of the intermediate image data It determines the write area to, Ru obtain the output image data by writing the value of the gradation conversion processing corresponding to the value of the pixel to the memory means. In this way, by storing the intermediate image data converted into the output image data by the storage means , the image size of the original image data is forcibly reduced to the minimum image size, and the output image data is converted from the minimum image size data. Obtainable.
[0039]
Therefore, in the conversion processing from the original image data to the output image data, the number of pixels of the original image data to be subjected to the operation of determining the writing area to the storage device and writing the numerical value after the gradation conversion processing corresponding to the pixel value , And high-speed processing can be performed. Further, since the processing is performed after the original image data is converted into image data of the minimum image size, the processing can be performed with a small-capacity storage device. Further, the gradation conversion means converts the gradation number of each pixel of the original image data to a gradation number smaller than the gradation number of the original image data, so that the output image data generated from the intermediate image data is converted to the output image data. The output result is almost the same as the output image data generated from the original image data having the data size.
[0040]
Further, in the image processing apparatus according to the second aspect, the output image size calculating means calculates the image size of the output image data, and the minimum image size setting means sets the image size smaller than the image size of the output image data to the minimum image size. When comparing the image size of the original image data with the minimum image size, the image size of the output image data is set to (height or Calculation can be performed by multiplying (length of width) × (resolution) by one multiplication. In addition, referring directly to the height or width of an image as an image size and not performing a complicated operation means that the image size itself is represented by a small numerical value. There is also an effect that it can be handled without exceeding the range.
[0041]
In the image processing apparatus according to the third aspect, the minimum image size setting means sets an image size obtained by halving each of the height and width of the output image data as the minimum image size, thereby providing image quality of the output image data. The original image data can be reduced to an optimal image size that hardly affects the image quality.
[0042]
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a halftone dither matrix.
FIG. 2 is a diagram for comparing processing results when binarization processing is performed;
FIG. 3 is a block diagram of a print control device.
FIG. 4 is a diagram showing a state in which a plurality of procedures are stored in a ROM in advance.
FIG. 5 is a diagram illustrating a flow of image data from a PC to a printing apparatus.
FIG. 6 is a flowchart illustrating a processing procedure in the print control apparatus.
FIG. 7 is a flowchart illustrating an output image size calculation procedure.
FIG. 8 is a flowchart illustrating a minimum image size setting procedure.
FIG. 9 is a flowchart illustrating another minimum image size setting procedure.
FIG. 10 is a flowchart illustrating an image data reduction procedure.
FIG. 11 is a flowchart illustrating an image data drawing procedure.
FIG. 12 is a diagram illustrating a state in which one pixel is drawn by an image data drawing procedure.
[Explanation of symbols]
30 CPU
31 ROM
32 RAM
36 PC
39 printing device 50 original image data 70 output image data 81 writing area

Claims (3)

An image processing device that converts original image data generated by a computer or transmitted from an external computer into output image data for output to a connected output device,
Output image size calculating means for calculating an image size of the output image data based on a resolution of the output device and an image print size for outputting the original image data,
Minimum image size setting means for setting an image size smaller than the image size of the output image data as a minimum image size,
When the image size of the original image data is larger than the minimum image size, image data reduction means for converting the image size of the original image data to intermediate image data reduced to the minimum image size,
Storage means for storing the intermediate image data;
Tone conversion means for converting the number of tones of each pixel of the original image data to a number of tones smaller than the number of tones of the original image data;
An image in which the output image data is obtained by determining a writing area to the storage unit for each pixel of the intermediate image data and writing a value after gradation conversion processing corresponding to the value of the pixel to the storage unit An image processing apparatus comprising: a data drawing unit. The image processing apparatus according to claim 1, wherein the image size is defined by the number of pixels of a height or a width of the image. The image processing apparatus according to claim 1, wherein the minimum image size is a size obtained by halving a height and a width of the output image data.

Images