JP2006050300A - Image processing device, and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that, when quantization is performed by changing error diffusion processing and dither processing for each drawing instruction, results of the dither processing and the error diffusion processing must output to different memory areas, and a binary valued result of the dither processing must expand in bits and be composed with the result of the error diffusion processing, since there is the restriction that the dither processing can perform only binary processing. <P>SOLUTION: It becomes possible to directly write out a result of multiple valued error diffusion processing and a binary valued result of the dither processing, without bit expansion for a memory area, by binarizing the output of the dither processing as 0 and the maximum output value of the error diffusion processing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and method, and more particularly to an image processing apparatus and method for switching an image processing method according to object information in rasterized document data.

  Generally, in order to connect a printer to a host computer, a printer driver is mounted on the host computer in order to configure a print control apparatus that controls the printer. Application software running on the host computer creates image data including graphics such as characters and graphics and image images such as photographic images. The application software supplies image data to be printed out to the printer driver as a drawing command via the operating system (OS). The printer driver analyzes a drawing command based on the supplied image data, creates RGB multi-gradation image data on the memory, and converts it into CMYK multi-value information representing each color of the printer ink. Further, the printer driver converts the CMYK multi-value information into CMYK binary data indicating whether or not to eject ink, and then generates output data that can be analyzed by the printer and transfers it to the printer.

  When a printer outputs an image based on image data satisfactorily, brightness / density conversion processing, masking processing, and gamma processing, which are color processing according to the type of drawing command, for each of a plurality of drawing commands constituting the output image And a color reduction process, a quantization process, and the like are required. Therefore, the printer driver is a type of drawing command issued for each element constituting the output image, for example, an image drawing command for a photographic image part, a text drawing command for a text part, and a graphics drawing command for a graphics part such as a chart. Appropriate color processing and quantization processing are performed for each time.

  General color processing used for print information processing is “color processing with priority on vividness” for graphics drawing commands, “colorimetric match” for text drawing commands, and “color with priority on color” for photo drawing commands. Processing "is performed. Thus, by switching the color processing for each drawing command, it is possible to obtain a good image output for all the drawing commands.

  Also, general quantization means used for print information processing include a dither method and an error diffusion method. The dither method is a quantization method that reads a threshold value corresponding to the coordinates of the pixel of interest from a dither matrix, compares the threshold value with an input pixel value, and determines whether dots are turned on or off. Yes, it is suitable for quantizing images such as text and graphics.

  In contrast, the error diffusion method is a quantization method in which an output value is determined by comparing a predetermined threshold value with an input pixel value, and an error between the output value and the input pixel value is diffused to surrounding pixels. Although it requires more processing time than the method, it can express subtle gradations and is suitable for quantization of images classified as photographic images.

  It should be noted that the number of output levels of the quantization process is such that the multi-value quantization has a plurality of indexes of the printer body rather than the binarization that determines whether or not to eject ink for one pixel of the input image data. Since the pattern can be switched and the dot size can be switched, the gradation expression is excellent, and it is often used for printing image images such as photographs.

  However, when printing image data such as photographs and data such as text mixed in a page, in order to perform appropriate color processing and quantization processing for each rendering command, all the drawing in the page is temporarily performed. After analyzing the command, the processing is optimized for each drawing command based on the analysis content, so it takes a lot of time for the analysis process, and the analysis result of the drawing command for one page is saved in the memory. There was a problem that required.

Therefore, Patent Document 1 proposes a method of switching color processing / quantization processing for each region when printing data in which an image region such as a photograph or a region such as text is mixed in a page.
JP 2001-144939 A

  However, in the above-mentioned patent document 1, only the binarization is described, and the gradation expression power of the image area is low.

  In addition to the above-mentioned patent document 1, there is a means in which the image area is multi-valued by error diffusion processing, the other areas are binarized by dither processing, and the results are synthesized and output. 12 and 13 are diagrams for explaining this prior art. The input raster data 1201 has a width of 32 pixels, and there are two image areas 1202 and 1203 and areas outside the images 1204, 1205, and 1206. Here, the dither will be described by taking a 1-bit binary output and the error diffusion by taking a 2-bit 4-level output as an example. In accordance with the number of output bits, the dither output buffer 1308 is prepared in advance with 4 bytes, and the error diffusion output buffer 1301 is prepared with 8 bytes in advance.

  First, the image areas 1202 and 1203 are binarized into 2 bits per pixel into corresponding areas 1302 and 1303 of the error diffusion output buffer 1301. Similarly, the areas 1204, 1205, and 1206 other than the image are binarized into 1 bit into corresponding areas 1309, 1310, and 1311 of the dither output buffer 1308, respectively.

  Next, the 1-bit binarization results 1309, 1310, and 1311 recorded in the dither output buffer 1308 are bit-expanded in accordance with the number of output bits / level of the image area, and the error diffusion output buffer Data is written in the corresponding areas 1304, 1305, 1306 of 1301, and data 1308 is sent to the printer.

  The bit expansion method will be described specifically by taking the first pixel 1312 of the dither output buffer 1308 as an example. When the value of the first pixel 1312 is “0 (binary number)”, “00 (binary number)” is changed to “1”. In the case of “(binary number)”, “11 (binary number)” which is the maximum error diffusion output value is written to the first pixel 1307 of the error diffusion output buffer 1301.

  In the above-described prior art, two output buffers must be prepared, and there is a problem that it takes time to bit-extend the dither output result.

  Therefore, there is a means to perform quantization processing by combining the number of multi-value levels in the image area and other areas by multi-valued areas other than the image by multi-value dither method instead of dither method. Since these areas are areas such as characters and backgrounds, high-speed processing is often required rather than gradation reproducibility.

  The present invention is for solving the above-mentioned problem, and multi-valued an image area by an error diffusion method excellent in gradation reproducibility, and binarized by a dither method while wasteful output buffer. Another object is to provide an image processing apparatus and method that do not require bit extension.

  The present invention has the following configuration as one means for achieving the above object.

An image processing apparatus according to the present invention includes: a discriminating unit that analyzes a drawing command input in units of bands obtained by dividing one page into a plurality of units to determine a specific drawing command; and a number of drawing regions based on the specific drawing command Extraction means for extracting information indicating the position, extraction means for extracting the number of drawing areas based on the specific drawing command and information indicating the start point and end point for each band line unit, Image processing means for performing image processing based on the extracted information on the image drawn based on the input drawing command in units of lines;
The quantization means in the image processing means has a dither means and an error diffusion means, the number of output bits of the dither means and the error diffusion means is the same, and the number of output levels of the error diffusion means is three or more. The number of output levels of the dither means is binary, and the output value is either 0 or the maximum output value of the error diffusion means.

  According to the present invention, it is possible to improve the disadvantage that the gray scale reproducibility is poor because both error diffusion and dither in the prior art are made to be binary output, and the dither and error diffusion output buffers are provided separately. It was possible to remedy the disadvantages of memory wasting and processing time that were caused by bit expansion of the output.

  Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Constitution]
FIG. 1 is a block diagram showing a schematic configuration example of a system in the present embodiment. For example, a printer 102 such as an ink jet printer is connected to the computer 101. The computer 101 includes application software 104 such as a word processor, spreadsheet, and Internet browser, and various drawing command groups (image drawing commands, text drawing commands, and the like) for drawing output images issued from the application software 104 to the OS 103. A printer driver 105 that processes the graphics rendering command and generates print data. As an embodiment shown in FIG. 1, for example, a Windows (registered trademark) XP of Microsoft Corporation and any application software having a printing function are installed as an OS 103 in a widely used IBM AT compatible personal computer. Thus, a form in which the printer 102 is connected can be considered.

  Next, the hardware configuration of the computer 101 and the printer 102 will be described with reference to FIG.

  The computer 301 includes a processing unit 303, a display device 313 (CRT in this example) for displaying graphic information and the like to an operator, an HDD (hard disk drive) 314 that is a mass storage device storing programs and data, and a keyboard 315. Including the entire computer. The printer 302 includes a drive unit such as a recording head 325, a carrier (CR) motor 326 that drives a carrier that conveys the recording head 325, a conveyance (LF) motor 327 that conveys paper, and a control circuit unit 304. Has been.

  The processing unit 303 of the computer 301 includes an MPU 305 that controls the entire host device according to a control program, a bus 308 that connects system components to each other, a DRAM 307 that temporarily stores programs and data executed by the MPU 305, a system bus and a memory bus, A bridge 306 for connecting the MPU 305 is included.

  Further, the processing unit 303 communicates between the graphic adapter 309 that controls the interface with the display device 313, the HDD controller 310 that controls the interface with the HDD 314, the keyboard controller 311 that controls the interface with the keyboard 315, and the printer 302 according to the USB 1.1 standard. A communication I / F 312 that controls communication is provided.

  On the other hand, the printer 302 is an inkjet serial printer in this embodiment. The control circuit unit 304 of the printer 302 has a control program execution function and a peripheral device control function, which controls the overall control of the printer 302, a system bus 316 that connects each component in the control circuit unit, and a recording data A gate array (GA) 317 is provided in which supply to the recording head 325, memory address decoding, a control pulse generation mechanism for a carrier motor, and the like are housed as a control circuit.

  In addition, the control circuit unit 304 conforms to a ROM 320 that stores a control program executed by the MCU 318, host print information, and the like, a DRAM 321 that stores various data (image recording information, recording data supplied to the head, and the like), and a USB 1.1 standard. A communication I / F 319 that controls communication with the host device 301 and a head driver 322 that converts the head recording signal output from the gate array 317 into an electric signal for driving the recording head 325 are provided.

  Further, the control circuit unit 304 converts the carrier motor control pulse output from the gate array 317 into an electric signal for actually driving the carrier (CR) motor 326, and the carrier motor control pulse output from the MCU 318. Is converted to an electric signal for actually driving the transport motor.

  Each block of the system shown in FIG. 1 is realized by executing a program including a program in the procedure of FIG. 2 described later in the computer of FIG.

[Example]
FIG. 2 is a diagram illustrating a processing example of the banding type printer driver 105 and the OS 103. The application software 104 creates text data classified into text such as characters, graphics data classified into graphics such as graphics, image image data classified into photographic images, and the like as output image data. When the created output image data is printed out, the application software 104 requests the OS 103 to print out, the text data portion is a text drawing command, the graphics data portion is a graphics drawing command, and the image image data portion is an image drawing. A drawing command group indicating an output image composed of commands is issued to the OS 103.

  The OS 103 that has received the print output request from the application software 104 issues a print start command to the printer driver 105 corresponding to the printer 102. When the printer driver 105 receives a print start command from the OS 103, the printer driver 105 secures a work area for banding processing (hereinafter also referred to as “band memory”) on the DRAM 307, and coordinates data (band size of the secured work area). Data) to the OS 103. The OS 103 issues a drawing command group existing in the band represented by the received coordinate data to the printer driver 105.

  In a raster printer that does not have a function for rendering an image by developing a page description language as shown in the present embodiment, image rendering processing is performed by the printer driver 105 on the computer 101. However, in many cases, the computer 101 is not equipped with sufficient memory necessary for developing all drawing commands for one page and drawing an image. Therefore, a work area for banding processing is secured in order to develop a drawing command and draw an image on a memory for each unit called a band obtained by dividing one page vertically.

  The printer driver 105 sequentially rasterizes (draws) the drawing commands supplied from the OS 103 in the band memory in RGB 24-bit format, and after rasterizing all the supplied drawing commands, converts the contents of the band memory into CMYK data. Then, the data is converted into a data format printable by the printer 102 and sent to the printer 102.

  The OS 103 causes the printer driver 105 and the printer 102 to execute printing for one page by repeating issuance of all drawing command groups existing in the page supplied from the application software 104 for each band.

[Print processing]
FIG. 4 is a flowchart illustrating an example of print processing by the printer driver 105.

  As shown in FIG. 2, the overall processing flow of the banding printer driver 105 is to secure a band memory (S401), perform all printing processes for each band (S402 to S409), and perform all band processing. After the process is finished, the band memory is released (S410). The print processing for each band by the printer driver 105 is roughly divided into three steps.

  In the first step, the printer driver 105 receives drawing commands to be drawn in the band memory one by one from the OS 103, and performs image drawing information analysis processing (to be described later) at the time of executing the drawing command, and the image area information table 1001 shown in FIG. (AreaInfoTBL) is created (S402), and RGB image data is generated by sequentially rasterizing the image in an RGB 24-bit band memory secured in advance according to the resolution of the printer 102 (S403).

  In the second step, the printer driver 105 initializes a counter ScanLine indicating a scan line in the band to zero (S404), and an image to be described later based on the AreaInfoTBL 1001 for each scan line of the RGB image data generated in the band memory. The area generation process is executed to form the image position information table 1101 (ImageAreaTBL) shown in FIG. 11 (S405).

  In the third step, the printer driver 105 sets the characteristics of each area in the image area and other areas from the leading edge to the trailing edge of the scan line for each scan line in the band based on the generated ImageAreaTBL 1101. After performing corresponding color processing (brightness / density conversion, masking, gamma correction, color reduction) and quantization processing, image processing within the band is converted into print data and output to the printer 102 is executed. (S406).

  Next, ScanLine is compared with the band height Hy to determine whether or not the image processing for all the scan lines in the band has been completed (S407). If ScanLine <Hy, the process returns to S405 to execute the next scan line, and if ScanLine = Hy, the memory area of AreaInfoTBL 1001 is released (S408).

  Next, it is determined whether or not the processing for all the bands has been completed (S409). If the processing has been completed, the band memory is released and the printing process is terminated (S410). If there is a band that has not been processed, the process returns to S402.

  Hereinafter, the three steps described above will be described in detail.

[Drawing command analysis processing]
FIG. 5 is a flowchart showing an example of the drawing command analysis process in S402. The drawing command analysis process analyzes information (ImageCount) indicating the number of image areas existing in the band and a rectangular area circumscribing the image existing in the band by analyzing the drawing command passed from the OS 103. AreaInfoTBL1001 which is information indicating the above is generated on the DRAM 307. Hereinafter, the flow of the drawing command analysis process will be described with reference to FIG.

  First, ImageCount is initialized to zero (S501), a drawing command is acquired from the OS 103 (S502), and it is determined whether or not the acquired drawing command is an image drawing command (S503). If it is an image drawing command, it is determined whether or not the object indicated by the drawing command is a photographic image (S504). In general, image data such as a photographic image is often a 24-bit RGB or 8-bit palette, and image data having a bit depth smaller than that is often not a photographic image. Referring to, for example, when the bit depth of image data is 24 bits or more or an 8-bit palette, it may be determined as a photographic image.

  When the object indicated by the drawing command is a photographic image, one entry is created in the AreaInfoTBL 1001 assigned to the DRAM 307, and the upper left coordinate (Left, Top) of the rectangular area, which is the drawing position information included in the image drawing command, is set in the entry. The lower right coordinates (Right, Bottom) are saved (S505), and ImageCount is incremented (S506).

  Since this drawing command analysis processing is executed for all drawing commands executed in the band, if there is an unprocessed drawing command in the band based on the determination in S507, the processing returns to S502.

  When AreaInfoTBL 1001 is created after all drawing commands have been analyzed, the record order is determined by the sorting priority of the leftmost (Left) value, the uppermost (Top) value, the rightmost (Right) value, and the lowermost (Bottom) value. Sort in ascending order and end processing.

[Image area generation processing]
FIG. 6 is a flowchart showing an example of the image area generation processing in S405. The image area generation processing is based on position information in the sub-scanning direction (Y direction) of one scan line in the band, information indicating the number of image areas existing on the scan line (ImageCountPerLine), and on the scan line ImageAreaTBL 1101 indicating the start point and end point of each image area in the main scanning direction (X direction) is generated on the DRAM 307. Hereinafter, the flow of the image area generation processing will be described with reference to FIG.

  The counter Count and ImageCountPerLine are initialized to zero (S601). Subsequently, the image count indicating the number of image areas existing in the band is compared with the counter count (S602). If Count = ImageCount, all the image areas in the band have been generated, and the process is terminated. Of course, the process is also terminated when there is no image area in the band (ImageCount = 0).

  Next, with reference to the record AreaInfoTBL [Count] of the AreaInfoTBL 1001 (S603), it is determined from the upper end (Top) value and the lower end (Bottom) value whether an image area exists on the current scan line (ScanLine). (S604). If the image area exists, the values of the left end (Left) and the right end (Right) are extracted from the record AreaInfoTBL [Count] corresponding to the image area (S605). If there is no image area on the scan line, the process advances to step S611.

  Next, when the ImageArea TBL 1101 has not been created, the ImageArea TBL 1101 and one entry are created (S607). Then, the values of the left end (Left) and the right end (Right) taken out in the created entry are saved as the start point and the end point, respectively, ImageCountPerLine is incremented (S608), and the process proceeds to S611.

  On the other hand, if the ImageArea TBL 1101 has been created, the end point (PreRight) value stored in the last entry is compared with the left end (Left) value extracted in S605 to determine whether the image areas overlap. (S606). If the image areas do not overlap (PreRight <Left), one entry is added to the ImageArea TBL 1101 (S607). Then, the values of the left end (Left) and the right end (Right) extracted in the entry are stored as the start point and the end point, respectively, and ImageCountPerLine is incremented (S608), and the process proceeds to S611.

  If it is determined in S606 that the image areas overlap, the value of the end point (PreRight) is compared with the value of the right end (Right) extracted in S605 (S609). If PreRight <Right, The end point (PreRight) value of the last record is updated to the right end (Right) value (S610), and the process proceeds to S611. Note that if the image areas overlap, the image count per line is not incremented because it is regarded as one image area. In addition, regarding the start point (PreLeft) and the left end (Left), since the records of the image area information are sorted in the rendering command analysis process so that PreLeft ≦ Left is always satisfied, there is no need to compare them.

  In S611, after the counter Count is incremented, the process returns to S602.

  As a result of such processing, the image position information in the generated ImageArea TBL 1101 is automatically sorted in order from the front end position (left end) of the scan line. Then, after the above-described processing is repeated for all the image area information existing in the band, the image area generation processing ends.

[Image processing]
FIG. 7 is a flowchart illustrating an example of the image processing in S406. In this embodiment, the image area is subjected to color processing with priority on color and quantization processing by error diffusion, and the other areas are subjected to color processing with priority on vividness and quantization with dither.

  First, image processing is initialized (S701). For error diffusion processing and dither processing, 2 is specified as the number of output bits and 4 is specified as the number of output levels.

  Here, the outline of the error diffusion processing / dither processing in the present embodiment will be briefly described.

  In the error diffusion process, the target pixel value inVal is corrected with an error from surrounding pixels, and an output value outHt and an error errHt are obtained from the following formulas using the obtained value lValue.

When lValue <43, outHt = 0, errHt = lValue ・ ・ ・ Equation 1
43 <= lValue <128, outHt = 1, errHt = lValue-85 ・ ・ ・ Equation 2
When 128 <= lValue <213, outHt = 2, errHt = lValue-170 Equation 3
When 213 <= lValue, outHt = 3, errHt = lValue-255 Equation 4
The error errHt obtained here is diffused to the peripheral pixels, and the process moves to the next pixel.

On the other hand, in the dither processing, assuming that the threshold value of the dither matrix (width m × height n) is D (x, y) (0 <= x <m, 0 <= y <n), the coordinates (X, Y) The relationship between the pixel of interest (pixel value inVal) and the output value outHt is as follows.
When inVal <D (X% m, Y% n), outHt = 0 ... Formula 5
When D (X% m, Y% n) <= inVal, outHt = 3 Equation 6
The outHt in Expression 6 is determined by “number of output levels−1”.

  Initial settings for performing such error diffusion processing and dither processing are performed in S701. At the same time, color processing with priority on color in the image area and color processing with priority on vividness in other areas are initialized.

  Next, the counter Count is initialized to zero, and information indicating the front end position and the rear end position of the scan line 805 is set in the variables StartPos and EndPos, respectively (S702).

  Subsequently, with reference to ImageCountPerLine indicating the number of image areas of the scan line 805 set in the image area generation process, it is determined whether or not there is an image area in the scan line 805 (S703).

  Here, color processing / quantization processing of the image region and other regions will be described. In the image area, first, the RGB color 8-bit image data in the corresponding area of the scan line 805 is converted to 8-bit CMYK color image data by performing color-priority color processing. Output to each corresponding area. Subsequently, the 8-bit image data of CMYK colors in the corresponding area of the color processing output buffer 901 for each color of CMYK is binarized into 4 bits by the error diffusion process initialized in S701, and is output to the quantization output buffer 902 for each color of CMYK. . On the other hand, for the area other than the image, first, 8-bit image data for each RGB color in the corresponding area of the scan line 805 is converted to 8-bit image data for each color of CMYK by performing color processing with priority on vividness, and color processing for each color of CMYK. The data is output to the corresponding area of the output buffer 901. Subsequently, the 8-bit image data of each CMYK color in the corresponding area of the color processing output buffer 901 for each color of CMYK is binarized into 2 bits by the dither processing initialized in S701, and is output to the quantization output buffer 902 for each color of CMYK.

  If ImageCountPerLine = 0, the entire scan line 805 is regarded as an area other than an image, vividness priority color processing is performed (S704), and quantization is performed by dither processing (S705). Next, the quantized image data is converted into print data and transmitted to the printer 102 (S706). Then, ScanLine is incremented (S707), the memory area of the image position information table (ImageAreaTBL) is released, and the image processing is ended (S708).

  On the other hand, if ImageCountPerLine> 0 and an image area exists on the scan line 805, the start point (X1) and end point (X2) of the image area from the record ImageAreaTBL [Count] of the image position information table generated by the image area generation process. Get the value. Then, color processing with priority on vividness is performed with the region from StartPos to X1 (start point) on the scan line 805 as a region other than an image (S709), and quantization is performed by dither processing (S710).

  Subsequently, color processing with priority on color is performed on the image area from X1 (start point) to X2 (end point) (S711), and quantization is performed by error diffusion processing (S712). Next, the value of X2 (end point) is set in StartPos, ImageCountPerLine is decremented, Count is incremented (S713), and the process returns to S703.

  Therefore, S709 to S713 are repeated until ImageCountPerLine becomes zero, that is, until all of the ImageAreaTBL 1101 on the scan line 805 are referenced. When the reference to ImageAreaTBL1101 is completed, the end point of the last image area on the scan line is set in StartPos. Therefore, in steps S704 to S706, the text or graphics area from StartPos to EndPos has priority for vividness. Color processing and dither quantization processing are performed, ScanLine is incremented (S707), the memory area of ImageAreaTBL1101 is released, and image processing ends (S708).

8 and 9 are diagrams for explaining in detail the processing results of the drawing command analysis process, the image area generation process, and the image process. In the band 801, there are three image regions 802, 803, and 804. As a result of the drawing command analysis process, ImageCount indicating the number of image areas existing in the band is “3”. In AreaInfoTBL 1001,
AreaInfoTBL [0] = {5, 12, 11, 16}
AreaInfoTBL [1] = {8, 10, 16, 16}
AreaInfoTBL [2] = {20, 8, 24, 15}
Is registered.

Next, when the image area generation processing is executed on the scan line 805 in the band, ImageCountPerLine indicating the number of image areas existing on the scan line 805 becomes “2”, and ImageAreaTBL has ImageAreaTBL [0] = {5, 16 }
ImageAreaTBL [1] = {20, 24}
Is registered.

  Next, details of the image processing will be described with reference to the flowchart of FIG. First, color processing / quantization processing is initialized (S701), and 0, 31, 0 are set in StartPos, EndPos, and Count, respectively (S702).

  Since ImageCountPerLine is 2, S703 is Yes, and referring to ImageAreaTBL [0 (= Count)], color processing of areas other than the image for the area from 0 (= StartPos) to 5 (= X1) of the scan line 805 Quantization is performed (S709, S710). The vividness priority color processing result of 8-bit data of each color of CMYK is written in the area 903 from 0 to the 4th byte of the color processing output buffer 901 for each color of CMYK (S709). Subsequently, the color processing result of each color of CMYK is quantized with 2 bits and 2 values per pixel, and is written in the entire 0th byte and the upper 2 bits area 904 of the first byte of the quantization output buffer 902 for each color of CMYK (S710). ). In the dither processing, either 00 (binary number) or 11 (binary number) is output according to Equations 5 and 6. Next, color processing / quantization of the image area is performed on the area from 5 (= X1) to 16 (= X2) (S711, S712). The color priority color processing result of 8-bit data for each color of CMYK is written in the area 905 from the 5th byte to the 15th byte of the color processing output buffer 901 for each color of CMYK (S711). Subsequently, the color processing result of each color of CMYK is quantized with 2 bits and 4 values per pixel, and the lower 6 bits of the first byte and the upper 6 bits of the second byte of the quantized output buffer 902 of each color of CMYK 906 are obtained. Each is written (S712). Subsequently, Count is incremented (= 1), ImageCountPerLine is decremented (= 1), X2 (= 16) is set in StartPos (S713), and the process returns to S703.

  Since ImageCountPerLine is 1, S703 is Yes, and referring to ImageAreaTBL [1 (= Count)], color processing / quantum of regions other than the image from 16 (= StartPos) to 20 (= X1) of scan line 805 is performed. (S709, S710), and color processing / quantization of the image area from 20 (= X1) to 24 (= X2) is performed (S711, S712). Similarly, the increment of Count (= 2), the decrement of ImageCountPerLine (= 0), and StartPos is set to 24 (= X2) (S713), and the process returns to S703.

  At this time, since ImageCountPerLine becomes 0, S703 becomes No, color processing / quantization of regions other than the image is performed from 24 (= StartPos) to 31 (= EndPos) (S704, S705), and the quantization output buffer 902 Is transmitted to the printer (S706), and the process proceeds to the next raster.

  As described above, according to the present embodiment, based on the information of the image area obtained as a result of analyzing the raster data by the rendering command analysis process, the image process for switching the quantization method between the image area and other areas by error diffusion and dithering The dither output was set to 0 and the error diffusion maximum output value. As a result, the problem of poor gradation reproducibility that occurred because both error diffusion and dither of the prior art were made to be binary output was improved, and dither output was separately provided with dither and error diffusion output buffers. Improved the shortage of memory and processing time that occurred due to bit expansion.

The block diagram which shows the schematic structural example of the system in this embodiment A diagram showing a processing example of a banding printer driver and OS Block diagram of computer and printer in this embodiment A flowchart showing an example of printing processing by a printer driver Flow chart showing an example of drawing command analysis processing Flow chart showing an example of image area generation processing Flow chart showing an example of image processing Diagram explaining drawing command analysis processing and image area generation processing The figure explaining image area generation processing and image processing Image area information table Image position information table The figure which shows the input raster data of the prior art Figure showing a prior art output buffer

Explanation of symbols

101, 301 Computer 102, 302 Printer 103 Operating system 104 Application software 105 Printer driver 303 Processing unit 304 Control circuit unit 308 Bus 316 System bus 801 Band 802, 803, 804 Image area 805 Scan line 901 Color processing output buffer 902 Quantization output Buffer 1001 Image area information table 1101 Image position information table 1201 Input raster data 1301 Error diffusion output buffer 1308 Dither output buffer

Claims (5)

A discriminating means for discriminating a specific drawing command by analyzing a drawing command inputted in a band unit obtained by dividing a page into a plurality of pieces, and a detection for detecting information indicating the number and position of drawing regions based on the specific drawing command Means for extracting information indicating the number of drawing areas based on the specific drawing command and the start point and end point for the line unit of the band, and based on the input drawing command for the line unit of the band. Image processing means for performing image processing on the drawn image based on the extracted information;
The quantization means in the image processing means has a dither means and an error diffusion means, the number of output bits of the dither means and the error diffusion means is the same, and the number of output levels of the error diffusion means is three or more. The number of output levels of the dither means is binary, and the output value is either 0 or the maximum output value of the error diffusion means. The image processing apparatus according to claim 1, wherein the specific drawing command is an image drawing command.   3. The quantization process is performed by the error diffusion unit for a region rendered by the image rendering command and by the dither unit for a region rendered by another rendering command. The image processing apparatus described.   The image processing apparatus according to claim 1, wherein the number of output bits is different for each color. A drawing command input in units of bands obtained by dividing one page into a plurality of pieces is determined, information indicating the number and position of drawing regions based on the specific drawing command is detected, and the line of the band is detected based on the detected information. Information extracted in the unit of the drawing area number based on the specific drawing command, and information indicating the start point and the end point, and extracted in the image drawn based on the input drawing command in the line unit of the band Image processing based on
The quantization processing in the image processing includes dither processing and error diffusion processing, the number of output bits of the dither processing and the error diffusion processing is the same, and the number of output levels of the error diffusion processing is three or more. The number of output levels of the dither processing is binary, and the output value is either 0 or the maximum output value of the error diffusion processing.