JP4726228B2 - Color data conversion apparatus and method - Google Patents

Description

  The present invention relates to a color data conversion technique for drawing processing.

  In color conversion for converting an image signal (for example, R (red), G (green), B (blue)) obtained by an input device into an image signal for an output device, a look-up table (LUT) that stores conversion data. ) Is used. Here, in order to reduce the capacity, the LUT generally stores only representative point conversion data, and the data between the representative points is calculated by interpolation calculation and used for color conversion reference.

  Various interpolation methods have been proposed depending on how many pieces of data (hereinafter referred to as “grid point data”) read from the LUT are used.

  For example, Patent Document 1 discloses a configuration in which, for example, R, G, B, three color signals are divided into upper bits and lower bits, and an operation result for the upper bits is stored in the LUT. In this method, LUT addresses for accessing LUT grid point data are generated for each number of output colors, and grid point data (8 vertices, that is, a cube) for each color is acquired. In the interpolation calculation, the output signal for the upper bits acquired from the LUT and the image signal of the lower bits are processed by the interpolation circuit, and a final output result is obtained.

In a printer, there are a mode that emphasizes gradation (high accuracy mode) and a mode that emphasizes high speed (high speed mode), and the mode is switched depending on printing conditions.
JP-A-9-289593

  However, in the above color conversion technique, in order to cope with the high-speed mode and the high-accuracy mode, it is necessary to prepare a high-precision, multi-output color number LUT and an interpolation operation circuit, and there is a problem that the circuit scale increases. .

  In the conventional color conversion technology, the processing mode is switched for each page depending on the printing conditions. However, a page may have a plurality of areas (objects) such as a character area and a photo / graphics area. In this case, the conventional color conversion technology has a problem that it cannot perform effective processing suitable for the object by switching the character area to the high-speed mode and the photo / graphics area to the high-precision mode. .

  The present invention has been made in order to solve the above-described problems. An object of the present invention is to provide a color conversion processing technique capable of supporting a plurality of processing modes such as high accuracy and multiple output colors while suppressing an increase in circuit scale. And

  Alternatively, an object of the present invention is to provide a color conversion processing technique capable of switching a processing mode for each region (object) in one page.

In order to achieve the above object, the color data conversion apparatus according to the present invention, the color data conversion apparatus for converting color data of a first color space composed of a plurality of colors in the color data in the second color space There ,
Conversion to the first conversion mode number of output bits per color color data of the second color space is a first number of bits to be output, or the color of the second color space for converting setting means for the number of output bits per color data sets of the second conversion mode of the a first number second bits greater than the number of bits,
According to the setting by the setting means, the color data of the first color space is converted in the first conversion mode and the color data of the second color space is output for each first number of colors, and the second color space is output. the first variant換手stage color data of the converted color data second color space you output less the second for each color number the first number of colors of the color space in the conversion mode and It is characterized by providing.

  According to the present invention, it is possible to perform color conversion processing corresponding to a plurality of processing modes such as high accuracy and the number of output colors while suppressing an increase in circuit scale.

  Or according to this invention, the color conversion process which switches a processing mode for every area | region (object) in 1 page is attained.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

(First embodiment)
FIG. 1A is a block diagram illustrating a configuration example of an image forming apparatus 100 according to an embodiment of the present invention. In the image forming apparatus 100, the input I / F 102 receives drawing data from an external information processing apparatus 200 connected via the network 300. Based on the overall control of the CPU 101, the color data converter 104 can perform color conversion processing of drawing data.

  The CPU 101 divides the first color space data into upper bits and lower bits based on the input drawing data, and inputs the first color space data to the address generator 1 and the coefficient generator 6 of the color data converter 104. Here, the first color space data input to the color data converter 104 includes, for example, R, G, B, and three color signals. In the following description, the configuration and processing contents of the color data conversion apparatus 104 will be described by taking R, G, B, and three color signals as examples of the first color space data.

  The CPU 101 can determine whether to process the input first color space data with priority on processing speed or accuracy.

  The color data converter 104 can generate interpolation data for converting the input first color space data to the second color space data in accordance with the printing conditions. Here, the second color space data includes, for example, “cyan”, “magenta”, “yellow”, “black”, “light cyan”, and “light magenta”. In addition to the output color, the printing conditions include, for example, printing conditions with priority on processing speed, printing conditions with priority on print quality, and selection of print media (plain paper, photo-dedicated paper, etc.).

  The drawing processing unit 103 processes the drawing data based on the color conversion processing of the color data conversion device 104 to generate a bitmap image. The printer engine 105 forms a visible image on the print medium according to the received bitmap image.

  For the printer engine 105, any known recording method such as an electrostatic photographic method using a laser beam or an ink jet method can be applied.

  FIG. 1B is a block diagram illustrating the configuration of the color data conversion apparatus 104 according to the first embodiment of the present invention.

  The address generator 1 generates an address for reading data from the LUTs 2 and 3 from the upper bits of the input signal. LUTs 2 and 3 are supplied with addresses for reading grid point data from the address generator 1 and output grid point data necessary for interpolation. The coefficient generation unit 6 generates an interpolation coefficient for each grid point from the lower bits of the input signal.

  The interpolation calculation units 4 and 5 perform an interpolation calculation based on the grid point data output from the LUTs 2 and 3 and the interpolation coefficient generated by the coefficient generation unit 6. A register (not shown) for switching input data is connected to the data selection unit 12.

  The CPU 101 determines whether to process the input drawing data in the two-color output mode (processing speed priority) or the one-color output mode (accuracy priority). The CPU 101 can switch the input of the data selection unit 12 to the input data on the port a side or the input data on the port b side by setting a register based on this determination.

  The data shift unit 7 can add a bit shift amount that can be arbitrarily set to the output of the interpolation calculation unit 4. The addition calculation unit 8 adds the output of the data shift unit 7 and the output of the interpolation calculation unit 5. The rounding calculators 9 and 11 perform rounding operations on the outputs of the interpolation calculators 4 and 5. When it is not necessary to round the number of output bits, the outputs of the interpolation calculation units 4 and 5 can be output as they are. The rounding operation unit 10 performs a rounding operation on the output of the addition operation unit 8. When there is no need to round the number of output bits, the output of the addition operation unit 8 can be output as it is.

The input signal is 8 bits, the grid number of 3D-LUT (the number of grid point data of each axis) is 17 (= 2 ⁴ +1), the bit number of stored data is 8 bits, and the coefficient generated by the coefficient generator 6 is It is assumed to be 4 bits. In this case, the outputs of the interpolation calculation units 4 and 5 are each 12 bits.

  When the number of output bits in the two-color output mode is 8 bits (or an arbitrary number of bits of 11 or less), it is rounded to 8 bits (or an arbitrary number of bits of 11 or less) by the rounding calculators 9 and 11. Data is output. When outputting 12-bit data, it is not necessary to round the output bits of the interpolation calculation units 4 and 5, so that the rounding calculation units 9 and 11 output the data as it is without performing the rounding operation (output 1, output 1). Output 2).

  The data selection unit 12 selects the input data on the port a side in the two-color output mode, and the output of the rounding calculation unit 9 is output from the data selection unit 12 (output 1). Further, the output from the interpolation calculation unit 5 and the output from the rounding calculation unit 11 are output from the color data converter 104 (output 2). Accordingly, in the two-color output mode (processing speed priority), two-color interpolation data is output from the two output ports.

  On the other hand, in the one-color output mode (accuracy priority), the data selection unit 12 switches the input port so as to input the input data on the port b side. The data output from the interpolation calculation unit 4 is shifted by 8 bits by the data shift unit 7, the output data from the interpolation calculation unit 5 is added by the addition calculation unit 8, and rounded to 16 bits by the rounding calculation unit 10 and output ( Output 1).

  Selection of the two-color output mode or the one-color output mode can be executed as follows under the control of the CPU 101. For example, when the printing mode of the image forming apparatus 100 can be set to two modes of “fast” and “pretty”, the CPU 101 can select the two-color output mode with priority on the processing speed and the “pretty” mode in the “fast” mode. Then, it is possible to select a one-color output mode in which priority is given to accuracy.

  When two modes of “plain paper” and “photo paper” can be set as print media, the CPU 101 selects the two-color output mode in the “plain paper” mode and the one-color output mode in the “photo paper” mode. Is possible.

  In the case of six colors of cyan, magenta, yellow, black, light cyan, and light magenta as output colors of the second color space data, it is possible to select one color output mode for cyan, magenta, and black. In addition, the two-color output mode can be selected for yellow, light cyan, and light magenta.

  In determining the output color, the CPU 101 combines the output colors (inks) in descending order of brightness. For example, since high-lightness ink is less likely to cause visual interference, the CPU 101 controls the color data converter 104 to select the two-color output mode (processing speed priority).

  In addition, the CPU 101 processes the color data conversion device 104 so that ink with high brightness of dots on the print medium is processed in the two-color output mode, and ink with low brightness (high density) is processed in the high-precision one-color output mode. To control.

  According to the present embodiment, it is possible to perform color conversion processing corresponding to a plurality of processing modes such as high accuracy and multiple output colors while suppressing an increase in circuit scale.

(Second Embodiment)
FIG. 2 is a block diagram illustrating the configuration of the color data conversion apparatus 204 according to the second embodiment of the present invention. Portions common to the configuration of the color data conversion apparatus 104 described in the first embodiment are given the same reference numerals. In the following description, different components will be mainly described in order to avoid overlapping description.

  The CPU 101 determines whether the input drawing data is converted into the four-color output mode, the three-color output mode, the two-color output mode, or the one-color output mode. The CPU 101 can switch the input of the data selection units 12, 27, and 28 to the input data on the port a side or the input data on the port b side by setting a register based on this determination. Further, the CPU 101 can control the data selection units 17 and 18 based on the determination result.

  The LUTs 13 and 14 are supplied with addresses for reading grid point data from the address generation unit 1, and grid point data necessary for interpolation is output to these inputs. In the coefficient generation unit 6, an interpolation coefficient for each grid point is generated from the lower bits of the input signal. The interpolation calculation units 15 and 16 perform interpolation calculation from the grid point data output from the LUTs 13 and 14 and the interpolation coefficient generated from the coefficient generation unit 6.

Here, the input signal is 8 bits, the number of grids of 3D-LUT (the number of grid point data of each axis) is 17 (= 2 ⁴ +1), the number of bits of stored data is 8 bits, and the coefficient generation unit 6 generates The coefficient is 4 bits. In this case, the outputs of the interpolation calculation units 15 and 16 are each 12 bits.

(4-color output mode)
When the number of output bits in the 4-color output mode is 8 bits (or an arbitrary number of bits equal to or less than 11), the data is output after being rounded to 8 bits by the rounding calculators 9, 11, 23, and 25. In the case of 12-bit output, the rounding operation units 9, 11, 23, and 25 do not need to round the data, so the data is output as it is.

  Registers (not shown) for switching input data are connected to the data selection units 27 and 28. The CPU 101 determines whether to convert the input drawing data in the four-color output mode, the three-color output mode, the two-color output mode, or the one-color output mode. The CPU 101 can switch the input of the data selection units 27 and 28 to the input data on the port a side or the input data on the port b side by setting a register based on this determination.

  The data selection units 27 and 28 select the input data on the port a side in the four-color output mode, and select the input data on the port b side in other than the four-color output mode. In the four-color output mode, the data selection unit 27 outputs the data of the rounding operation unit 23 (output 1). Further, the data selection unit 28 outputs the data of the rounding operation unit 25 (output 2). Since the data selection unit 12 is similarly controlled, the data selection unit 12 outputs the data of the rounding calculation unit 9 (output 3).

  Then, it is output from the interpolation calculation unit 5, and the output of the rounding calculation unit 11 is output from the color data conversion device 204 (output 4). Accordingly, four colors of interpolation data are output from the four output ports.

(2-color output mode)
In the case of the two-color output mode, the data selection units 17 and 18 select the output data of the interpolation calculation units 15 and 4. The outputs of the data selection units 17 and 18 are shifted by 8 bits by the data shift units 19 and 7 and added to the output data of the interpolation calculation units 16 and 5 by the addition calculation units 21 and 8. The outputs of the addition calculation units 21 and 8 are input to the rounding calculation units 24 and 10, rounded to 16 bits by the rounding calculation units 24 and 10, and output.

  Since the data selection units 27 and 12 are controlled so as to select the input data on the port b side except in the 4-color output mode, 16-bit interpolation data of two colors is output from the data selection units 27 and 12 (output 1 , Output 3).

(3-color output mode)
In the case of the three-color output mode, the LUT 13 stores the interpolation data of the three colors by bit combination. FIG. 3 is a diagram exemplarily showing a data format stored in the LUT 13. FIG. 3A shows a state in which 2-bit data for each color (first color, second color, third color) is combined for three colors with 0 interposed therebetween. FIG. 3B shows a state in which the first color and the second color are stored as 3 bits and the third color is stored as 2 bits data.

  Here, by assigning a large number of bits to an output color with high visibility (a color in which tone jumping is conspicuous), it is possible to perform data conversion that is visually good (with less image quality interference). The example of bit combination is not limited to the combination shown in FIG. 3, and the CPU 101 can arbitrarily set the data format of each color.

  The interpolation calculation unit 15 interpolates the bit-combined grid point data for each color. In the case of FIG. 3A, since the number of bits of each grid point data is 2 bits, if the coefficient data is 4 bits, the interpolation output corresponding to each color data is 6 bits.

  Each color data interpolated by the interpolation calculation unit 15 is output from the output ports c, d, e of the interpolation calculation unit 15.

  The data selection units 17 and 18 select the output data of the output ports c and e of the interpolation calculation unit 15 and output the output data of the output ports c and e of the interpolation calculation unit 15 to the data shift units 19 and 7. The data shift units 19 and 7 shift the input data by 8 bits, and then input the addition units 21 and 8.

  The addition calculation units 21 and 8 add the data input from the data shift units 19 and 7 and the output data of the interpolation calculation units 16 and 5. The rounding calculators 24 and 10 round the data input from the addition calculators 21 and 8 to, for example, 10 bits or an arbitrary number of bits of 14 or less and output the data.

  Since the data selection units 27 and 12 select the input data on the port b side except in the four-color output mode, 10-bit (or any number of bits equal to or less than 14) interpolation data of two colors is output from the data selection units 27 and 12 (Output 1, output 3).

  On the other hand, the output data of the output port d of the interpolation calculation unit 15 is input to the data shift unit 20. The data shift unit 20 shifts the input data by 8 bits and inputs it to the addition operation unit 22. The addition operation unit 22 adds the data input from the data shift unit 20 and the output of the interpolation operation unit 4 and inputs the result to the rounding operation unit 26. The rounding calculator 26 rounds the input data to, for example, an arbitrary number of bits of 10 bits or 14 and outputs the result.

  Since the data selection unit 28 selects the input data on the port b side except in the 4-color mode, the remaining 10-bit (or any number of bits equal to or less than 14) interpolation data of one color is output from the data selection unit 28 ( Output 2).

  The selection of the multi-color output mode or the single-color output mode can be executed as follows under the control of the CPU 101. For example, when three modes of “fast”, “standard”, and “pretty” can be set as the print mode of the image forming apparatus 100, the CPU 101 selects the four-color output mode in the “fast” mode (processing speed priority). select. The CPU 101 can select the three-color output mode in the “standard” mode, and can select the two-color output in the “clean” mode (accuracy priority).

  When three modes of “plain paper”, “high quality exclusive paper”, and “photo paper” can be set as print media, the CPU 101 outputs four colors in the “plain paper” mode, and “high quality exclusive paper”. Three-color output can be selected in the mode, and two-color output can be selected in the “photo paper” mode.

  In the case of 7 colors of cyan, magenta, yellow, black, light cyan, light magenta and orange as the output colors of the second color space data, the 2-color output mode can be selected for cyan, magenta, black and orange. It is. In addition, the three-color output mode can be selected for yellow, light cyan, and light magenta.

  The combination of ink is not limited to this, and various combinations are conceivable. In general, the CPU 101 combines inks in descending order of brightness. Since ink with high lightness is less likely to cause visual interference, the CPU 101 controls the color data converter 104 to select the multicolor output mode. In addition, since ink with low lightness (high density) tends to cause visual interference, the CPU 101 selects a high-precision one-color output mode.

  In addition, in order to increase the accuracy of the color conversion process, it is possible to perform the process in two steps, the former stage and the latter stage. In this case, it is generally preferable to perform color matching in the pre-stage processing and to convert the device color space in the post-stage processing. At this time, since the pre-processing is RGB-RGB conversion, the three-color output mode is selected.

  According to the present embodiment, it is possible to perform color conversion processing corresponding to a plurality of processing modes such as high accuracy and multiple output colors while suppressing an increase in circuit scale.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 4 is a block diagram showing the configuration of the color data conversion apparatus 304 according to the third embodiment. In the figure, the same reference numerals are assigned to components common to FIG. In the one-color output mode, LUT2 is loaded with the lower bits of the grid point data, and LUT3 is loaded with the upper bits of the grid point data. In the case of the two-color output mode, LUTs 2 and 3 are loaded with the grid point data of the two-color output mode.

  The object determination unit 170 determines the two-color output mode (processing speed priority) or the one-color output mode (accuracy priority) from the result of the object area detection unit 160 under the control of the CPU 101. Based on this determination, the CPU 101 can control the setting of a register (not shown) connected to the data selection unit 12.

  The data selection unit 12 switches the inputs of the rounding operation units 9 and 10 based on the register settings controlled by the object determination unit 170. The data selection unit 12 can switch to input data on the port a side or input data on the port b side and output the data.

The input signal of the color data converter 304 is 12 bits, the number of grids of 3D-LUT (the number of grid point data of each axis) is 17 (= 2 ⁴ +1), the number of stored data bits of LUTs 2 and ³ is 8 bits, The interpolation coefficient generated by the coefficient generation unit 6 is assumed to be 8 bits. In this case, the outputs of the interpolation calculation units 4 and 5 are each 16 bits.

  When the number of output bits in the two-color output mode is, for example, 12 bits or an arbitrary number of bits of 16 or less, it is rounded to an arbitrary number of bits of 12 bits or 16 by the rounding calculators 9 and 11 Data is output. In the case of 16-bit output, since there is no need to round the data, the data output from the interpolation calculation units 4 and 5 is output as it is.

  The data selection unit 12 selects input data on the port a side in the two-color output mode, and selects input data on the port b side in the one-color output mode.

  In the two-color output mode, the data selection unit 12 outputs the data input from the rounding calculation unit 9 (output 1). Further, the data is output from the interpolation calculation unit 5 and the data of the rounding calculation unit 11 is output (output 2). Accordingly, two colors of interpolation data are output from the two output ports.

  On the other hand, in the one-color output mode, the interpolation calculation unit 4 outputs lower-order interpolation data based on the data of the LUT 2 that stores the lower-order bits of the grid point data. The interpolation calculation unit 5 outputs higher-order interpolation data based on the data in the LUT 3 that stores the higher-order bits of the grid point data.

  The lower-order interpolation data output by the interpolation calculation unit 4 is right-shifted by 8 bits by the data shift unit 7, the decimal point is aligned, and the addition calculation unit 8 adds the higher-order interpolation data output from the interpolation calculation unit 5. . The data added by the addition operation unit 8 is input to the rounding operation unit 10. The rounding operation unit 10 rounds the input data to 12 bits and outputs it (output 1).

  When the output mode is switched, the data conversion process is interrupted, and it is necessary to rewrite the LUTs 2 and 3 for storing the lower bits of the grid points (if the upper bits of the grid points are not changed, the LUT for storing the upper bits of the grid points) Can be left as is.)

  In order to prevent the processing speed from dropping if the output mode is frequently switched, the CPU 101 limits the number of output mode switching to a predetermined number or less, and determines a switching point by giving priority to an object having a large area. To do.

  For example, since there is almost no gentle gradation in a small image (high gradation is not required), an image area having a predetermined size or less is processed in the two-color output mode. On the other hand, an image area exceeding a predetermined size is processed in the one-color output mode, and the remaining area is processed in the two-color output mode. In this case, if it takes more time to rewrite the LUT than the processing time shortened by processing the remaining area in the two-color output mode, it is better to process in the two-color output mode.

  In order to perform such processing easily, a threshold for the size of the region is set so that the output mode is not switched unless the size of each region is equal to or larger than a predetermined value.

  Note that it is desirable that the threshold fluctuate depending on the number of output mode switching point candidates (the number of boundaries of the object area for switching the output mode) in one processing line (when the number of switching points increases, the threshold is set to increase). .

  The processing of the object area detection unit 160 according to the present embodiment will be specifically described with reference to the flowchart of FIG. The object area detection unit 160 performs pre-scanning of the image before starting the processing. At this time, a character area, a photograph area, and a graphics area in the pre-scanned data are detected, and the position of the area and the processing mode are set. Note that characters with gradation are handled as graphics.

  FIG. 5 is a flowchart for explaining the flow of processing performed by the object area detection unit 160 before the start of color data conversion processing.

  First, in step S501, the object area detection unit 160 performs pre-scanning of an image.

  In step S502, the object area detection unit 160 detects whether there is a character area (low gradation area) or a photo / graphics area (high gradation area) in the image of one page.

  In step S503, when a character area (low gradation area) or a photographic / graphics area (high gradation area) is detected in the previous step S502, the size of each area and the set threshold value (size) are set. , Compare.

  When each detected area is larger than the set threshold (size) (S503-YES), the process proceeds to step S504. On the other hand, if it is determined in step S503 that each detected area is smaller than the set threshold value (size) (S503-NO), the process proceeds to step S505.

  In step S504, when the detected size of the high gradation area is equal to or larger than the first threshold value (size), it is set as a switching (change) point (area boundary) for switching to the one-color output mode (accuracy priority). Switching (change) point (area boundary) for switching to the two-color output mode (processing speed priority) when the low gradation area (area divided by the high gradation area) is equal to or larger than the second threshold (size) Set as. When the size of each area is smaller than a preset threshold value, the output mode is not switched (changed).

  The threshold can be set in consideration of the rewrite time of LUT2 and LUT3, for example. For example, in one processing line for forming an image, the number of processing mode switching (changing) point candidates (the number of area boundaries) is set, and the output mode switching (changing) point within this range is set. Settings can be made.

In step S505, it is determined whether the pre-scan has been completed. If pre-scan has not been completed for all images (NO in step S505), the process returns to process step S502, and the same process is repeated. If it is determined in step S505 that prescanning for all images has been completed (S505—YES), the processing ends.
next,
Next, the processing of the object determination unit 170 will be described with reference to the flowchart of FIG.

  First, in step S601, the object determination unit 170 determines, for example, a change in an object in an image from a high gradation region to a low gradation region (or from a low gradation region to a high gradation region). If the area has changed (S601—YES), the object determination unit 170 executes the process.

  In step S <b> 602, the object determination unit 170 confirms the output mode set by the object region detection unit 160 for the detected object.

  If the output mode has not been changed by the object region detection unit 160 (S602—NO), the process proceeds to step S607 without switching the object output mode.

  In step S607, the object determination unit 170 determines whether the processing for all objects included in the image of one page has been completed. If not (S607-NO), the processing returns to step S601, and the same processing is performed. repeat. If it is determined in step S607 that the object determination unit 170 determines that the processing has been completed for all objects included in the image of one page (S607—YES), the processing ends.

  If it is determined in step S602 that the output mode has been changed (S602-YES), the process proceeds to step S603, and the object determination unit 170 notifies the CPU 101 that the output mode has been changed. Upon receiving this notification, the CPU 101 controls to interrupt the processing of the color data conversion device 304.

  In step S604, the CPU 101 loads the grid point data of the multi-output color mode into the LUT2 and LUT3. Then, under the control of the CPU 101, the object determination unit 170 switches the input of the data selection unit 12 to the port a side (S605).

  When the switching of the input port of the data selection unit 12 is completed, in step S606, the CPU 101 resumes the color conversion process in the changed output mode. In this manner, the number of output colors (output mode) can be efficiently switched and processed for each region.

  In addition, although the structure which performs an object area | region detection at the time of a pre-scan was demonstrated here, this invention is not limited to this.

  For example, when the area determination of each object is performed without pre-scanning by using image area separation processing, pre-scanning is unnecessary.

  Also, when two 4-bit LUTs are added in addition to LUTs 2 and 3, for example, it is possible to set output modes corresponding to objects in the high gradation region, medium gradation region, and low gradation region. is there.

  For example, it is possible to set a high gradation region (region such as CG where there is almost no noise and a smooth gradation) as a one-color output mode (high gradation mode: grid point 16 bits).

  Further, it is possible to set the middle gradation area (image read by a digital camera, a scanner, etc., graphic area without gradation) to be a two-color output mode (medium gradation mode: grid point 12 bits).

  In addition, it is possible to switch a plurality of modes such as a three-color output mode (low gradation mode: 8-bit grid point) for the low gradation area (the remaining area other than the high gradation area or the intermediate gradation area). is there.

  According to the present embodiment, it is possible to perform color conversion processing for switching the output mode for each region (object) in one page.

(Fourth embodiment)
FIG. 7 is a block diagram illustrating the configuration of a color data conversion apparatus 404 according to the fourth embodiment of the present invention. In the present embodiment, a configuration of a color data conversion device 404 capable of switching the output mode without interrupting the processing as described in the third embodiment will be described. Portions common to the configuration of the color data conversion device 304 described in the third embodiment are denoted by the same reference numerals. In the following description, different components will be mainly described in order to avoid overlapping description.

  The processing of the CPU 101 and the object determination unit 170 will be described by taking as an example a case where processing from a photo / graphics region (high gradation region) is switched to processing of a character region (low gradation region).

  The CPU 101 stores the lower bits of the grid point data in LUT2 and the upper bits of the grid point data in LUT3. Then, the lower bits of the grid points that are required when the output mode is switched are stored in the LUT 13. If there is no change in the upper bits of the lattice points, the LUT for storing the upper bits of the lattice points may be left as it is. When it is necessary to change the upper bits, for example, an LUT can be added to the configuration of FIG. 7 to store data corresponding to the upper bits that need to be changed.

  In the present embodiment, the CPU 101 determines the two-color output mode (processing speed priority) or the one-color output mode (accuracy priority) from the result of the object area detection unit 160. Based on this determination, the CPU 101 can change the combination of LUTs 2, 3, and 130.

  When processing a photo / graphics region (high gradation region), under the control of the CPU 101, the object determination unit 170 sets the output of the data selection unit 12 to input data input from the port b side.

  The lower-order interpolation data output by the interpolation calculation unit 4 is right-shifted by 8 bits by the data shift unit 7, the decimal point is aligned, and the addition calculation unit 8 adds the higher-order interpolation data output from the interpolation calculation unit 5. . The data added by the addition operation unit 8 is input to the rounding operation unit 10. The rounding operation unit 10 performs rounding operation on the input data and outputs it (output 1). When there is no need to round the number of output bits, the output of the addition operation unit 8 can be output as it is.

  When the object changes from the photo / graphics region (high gradation region) to the character region low gradation region, the object determination unit 170 receives the output of the data selection unit 12 from the port a side under the control of the CPU 101. Switch to input data.

  Then, instead of the LUTs 2 and 3 selected in the photo / graphics region (high gradation region), the CPU 101 switches to a combination of LUTs 3 and 130 in the character region low gradation region. The outputs of the interpolation calculation units 5 and 14 are input to the rounding calculation units 11 and 150, and the rounding calculation units 11 and 150 perform rounding calculation and output data (output 2 and output 3). When there is no need to round the number of output bits, the rounding calculators 11 and 150 can output the outputs of the interpolation calculators 5 and 14 as they are.

  According to the present embodiment, it is possible to perform color conversion processing for switching the output mode for each region (object) in one page without interrupting the processing of the color data conversion apparatus in order to load grid point data.

(Other embodiments)
Needless to say, the object of the present invention can also be achieved by supplying a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus. Needless to say, this can also be achieved by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a nonvolatile memory card, a ROM, or the like can be used.

  Further, the functions of the above-described embodiment are realized by executing the program code read by the computer. In addition, an OS (operating system) running on a computer performs part or all of actual processing based on an instruction of a program code, and the above-described embodiment is realized by the processing. Needless to say.

1 is a block diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. It is a block diagram explaining the structure of the color data converter which concerns on 1st Embodiment of this invention. It is a block diagram explaining the structure of the color data converter which concerns on 2nd Embodiment of this invention. It is a figure which shows the data format stored in LUT13 as an example. It is a block diagram which shows the structure of the color data converter which concerns on 3rd Embodiment of this invention. It is a flowchart explaining the flow of the process performed in the object area | region detection part before a color data conversion process start. It is a flowchart explaining the flow of a process of an object determination part. It is a block diagram explaining the structure of the color data converter which concerns on 4th Embodiment of this invention.

Claims (5)

A color data conversion device that converts color data of a first color space composed of a plurality of colors into color data of a second color space,
Conversion to the first conversion mode number of output bits per color color data of the second color space is a first number of bits to be output, or the color of the second color space for converting setting means for the number of output bits per color data sets of the second conversion mode of the a first number second bits greater than the number of bits,
According to the setting by the setting means, the color data of the first color space is converted in the first conversion mode and the color data of the second color space is output for each first number of colors, and the second color space is output. the first variant換手stage color data of the converted color data second color space you output less the second for each color number the first number of colors of the color space in the conversion mode and ,
A color data conversion apparatus comprising: The converting means includes
A first lookup table in which first grid point data and an address for reading the first grid point data are associated with each other;
A second lookup table in which the second grid point data is associated with the address for reading the second grid point data;
From the upper bits of the input signal of the color data of the first color space, for reading said first and said second grid point data from each of said first look-up table and said second look-up table and address generating means for generating the address,
Coefficient generation for generating a first interpolation coefficient for interpolating the first grid point data and a second interpolation coefficient for interpolating the second grid point data from the lower bits of the input signal Means,
Interpolating the first grid point data with the first grid point data and the first interpolation coefficient read out from the first lookup table by the address generated by the address generation means First interpolation calculation means for performing first interpolation calculation and outputting first interpolation data;
Interpolating the second grid point data with the second grid point data and the second interpolation coefficient read from the second lookup table by the address generated by the address generation means Second interpolation calculation means for performing second interpolation calculation and outputting second interpolation data;
Shift means for shifting the first interpolation data output by the first interpolation calculation means to a higher number of predetermined bits;
Adding means for adding the first interpolation data shifted by a predetermined number of bits higher by the shift means and the second interpolation data output by the second interpolation calculation means ;
The converting means includes
In the first conversion mode, the first interpolation data output by the first interpolation calculation means and the second interpolation data output by the second interpolation calculation means are converted into the second conversion data . 2. The output according to claim 1 , wherein the color data is output as color data of a color space, and the addition data added by the adding unit is output as color data of the second color space in the second conversion mode. Color data converter. In the first lookup table, data of upper bits of the grid point data of the second color space is stored as the first grid point data,
Wherein the second lookup table, the color data according to claim 2, characterized in that the data of the lower bits of the grid point data of the second color space is stored as the second grid point data Conversion device. Images representing the color data of the first color space includes a plurality of regions,
The setting means, the color data according to any one of claims 1 to 3, characterized in that to set one of the first conversion mode for each of the region and the second conversion mode Conversion device. A color data conversion method in the color data conversion apparatus color data that converts the color data of the second color space of the first color space composed of a plurality of colors,
The first conversion mode in which the number of output bits per color of the color data of the second color space to be converted and output is the first number of bits , or the color data of the second color space to be converted and output a setting step of number of output bits per color to set the second conversion mode the a first number second bits greater than the number of bits of,
Wherein in accordance with the settings in the setting step, and outputting the color data of said first converting the color data of the first color space in the conversion mode and the second color space to the first for each color number, the second An output step of converting the color data of the first color space and outputting the color data of the second color space for each second number of colors smaller than the first number of colors in the conversion mode of A color data conversion method characterized by the above.

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