JP2007096391A - Image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor for enhancing visibility or image quality of a printed matter where importance is attached to appearance than to reproducibility or visibility. <P>SOLUTION: The image processor comprises a means for acquiring color image data, a means for generating a frequency distribution of hue by counting the pixel data of each pixel constituting the acquired image data for every hue, a means for judging whether importance is attached to visibility or not in the image data based on the generated frequency distribution, a means for converting at least one of the gray level, saturation and hue of the pixel data if importance is attached to visibility in the image data, and a means for printing the image data where the pixel data is converted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus such as a printer, a copier, or a multifunction peripheral.

With the spread of color copiers in recent years, there are increasing opportunities to use materials printed with pie charts, etc., in which sales amounts by product are color-coded in meetings in offices and the like.
JP 2001-43369 A

  The visibility of the color of printed matter with the naked eye is greatly influenced by the hue. For example, a yellow color has a very low visibility compared to colors such as red and blue. For this reason, if yellow is used in a color-coded pie chart, a portion printed in yellow becomes difficult to recognize with the naked eye.

  In addition, when a pie chart color-coded in color is used as a meeting material, if this graph has uneven density, it does not look good as a meeting material.

  SUMMARY An advantage of some aspects of the invention is that it provides an image processing apparatus that improves the visibility and image quality of printed matter in which visibility and appearance are more important than reproducibility.

  Since the image processing apparatus according to the present invention is intended to improve the visibility and image quality, it is a printed matter in which the visibility and appearance are more important than the reproducibility, so that the image data to be processed has the visibility and appearance. A generation unit and a type determination unit are provided in order to determine whether or not the value is important. The generation unit generates a frequency distribution of hues that serves as a reference for determining whether or not the image data emphasizes visibility. The frequency distribution of the hue is generated by counting pixel data of each pixel constituting the image data for each hue. The type discriminating unit discriminates whether or not the image data is image data that places importance on visibility based on the hue frequency distribution generated by the generating unit.

  The determination performed by the type determination unit may be performed based on, for example, the peak form of the hue frequency distribution. Since materials used in meetings and the like use fewer colors than landscape images, for example, if the number of peaks is equal to or less than a predetermined number, the type determination means uses image data that places importance on visibility. You may make it discriminate | determine.

  In addition, for materials used in meetings and the like, colors with completely different hues are usually used in order to improve visibility, and the amount of use varies greatly depending on the hue. Therefore, for example, the hue frequency distribution of a material printed with a color-coded graph such as red or yellow has a high frequency of hues such as red and yellow, but a low frequency of other hues. Therefore, the peak width of the frequency distribution of hues of materials used in meetings and the like is narrow. Therefore, if the skirt width is equal to or less than a predetermined value, the type determination unit may determine that the image data is important for visibility.

The image processing apparatus according to the present invention includes conversion means for converting at least one of density, saturation, and hue of pixel data constituting image data when it is determined that the image data emphasizes visibility.
The conversion performed by the conversion means is performed in order to improve visibility. For example, the conversion is performed by increasing the density, increasing the saturation, or changing the hue from yellow, which is difficult to visually recognize, to another hue. It is.

  Moreover, since the cause of lowering visibility is the use of a hue with low visibility, the conversion means may perform the above conversion only on pixel data indicating a hue with low visibility. For example, the hue having low visibility is stored in advance in the hue storage unit, and the conversion unit can determine pixel data to be converted based on the hue stored in the hue storage unit.

  Further, the conversion performed by the conversion unit may be performed only on pixel data indicating a hue forming a peak. The hue that forms the peak is likely to be the hue that was intended and used by the document creator, so if the hue that forms the peak is converted, the hue that was intended by the document creator and so on There is a high possibility that the visibility can be improved.

  Further, the conversion means may convert pixel data indicating hues forming the same peak into the same density, saturation, and hue. By converting to the same density, saturation, and hue in this way, an image in which density unevenness has occurred due to, for example, a printing defect can be made an image without density unevenness.

  The image data for which the generation means generates the hue frequency distribution may be, for example, image data created by a terminal such as a personal computer, or image data generated by reading a document. The document reading means for reading the document and generating image data may be provided in the image processing apparatus of the present invention, or may be a device such as a scanner connected to the image processing apparatus of the present invention via a network.

  When color image data is copied in black and white, it may be difficult to distinguish colors with the naked eye. This is because when color image data is copied in black and white, the hue and saturation are removed from the color image data and the color image data becomes only density data (monochrome data), and this monochrome data is printed. is there. Therefore, even if the colors have different hues and saturations, if the density is the same, when a monochrome copy is made, the same color (density) is printed, making it difficult to distinguish the colors. Thus, when colors with different hues are printed in monochrome, the color density of the image data is converted to a density based on the hue when printing color image data in monochrome so that the color can be distinguished with the naked eye. Then, monochrome printing is performed using image data whose density has been converted based on the hue. Since colors having different hues are printed at different densities by converting the density based on the hue as described above, it is easy to distinguish the colors having different hues with the naked eye.

  According to the image processing apparatus of the present invention, it is possible to improve the visibility and image quality of a printed matter in which visibility and appearance are more important than reproducibility.

  In the present embodiment, the image processing apparatus of the present invention functions as a multi-function machine having a printing, scanner, copying function, and the like. As shown in FIG. 1, the image processing apparatus 100 according to the present embodiment includes a main body 101 and a plan cover 102 attached above the main body 101. A document table 103 is provided on the upper surface of the main body 101, and the document table 103 is opened and closed by a platen cover 102. The platen cover 102 is provided with an automatic document feeder 104, a placing table 105, and a sheet discharging table 109.

  The automatic document feeder 104 includes a document conveyance path 108 formed inside the platen cover 102, a pickup roller 106 and a conveyance roller 107 provided inside the platen cover 102, and the like. The document conveyance path 108 is a document conveyance path that leads from the placement table 105 to the sheet discharge table 109 via a reading position P where reading is performed by the reading unit 110 provided in the main body 101.

  The automatic document feeder 104 draws each document placed on the placing table 105 into the conveyance path 108 by the pickup roller 107, and passes the drawn document through the reading position P by the conveyance roller 106 and the like. The paper is discharged onto the table 109. When the document passes the reading position P, the document is read by the reading unit 110.

  The reading unit 110 is provided below the document table 103. The reading unit 110 includes a light source 111 that illuminates the document table 103 in the main scanning direction, mirrors 112, 113, and 114 that guide light from the document table 103, and an image sensor 115 that captures light guided by the mirror. It is configured.

  When the automatic document feeder 104 conveys a document, the light source 111 moves to a position where the reading position P can be irradiated and emits light. Light from the light source 111 is reflected by a document that passes through the document table 103 and passes through the reading position P, and is guided to the image sensor 115 by mirrors 112, 113, and 114. The image sensor 115 is composed of an image sensor 115 of each color in which RGB filters are provided in the light receiving unit, and the image sensor 115 of each color captures the received light to obtain the color of each pixel in three colors of RGB. Is generated (hereinafter referred to as “pixel data”).

  The reading unit 110 can read not only the document conveyed by the automatic document feeder 104 but also the document placed on the document table 103. When reading a document placed on the document table 103, the reading unit 110 moves the light source 111 in the sub-scanning direction while emitting light, and irradiates the entire document table 103. In order to guide the reflected light from the document table 103 to the image sensor 115, the mirror 112 moves together with the light source 111, and in order to make the optical path length from the light source 111 to the image sensor 115 constant, the mirrors 113 and 114 The mirror 112 moves at half the speed.

  The image sensor 115 generates pixel data based on the light guided to the mirrors 112, 113, and 114 as in the case of the document conveyed to the automatic document feeder 104.

  A printing unit 120 that prints image data composed of pixel data is provided below the reading unit 110 of the main body 101. Image data that can be printed by the printing unit 120 includes pixel data generated in the image sensor 115 as described above, and data transmitted from a terminal such as a personal computer connected to the image forming apparatus 100 and a network such as a LAN. It is.

  The printing unit 120 is configured to perform both monochrome printing and color printing. In the printing unit 120, in order to enable both monochrome printing and color printing, four color developing devices 124C, 124M, and 124Y of C (cyan), M (magenta), Y (yellow), and K (black) are provided. , 124K.

  When performing monochrome printing, the printing unit 120 prints the image data converted into monochrome in the following procedure. First, the printing unit 120 uniformly charges the photosensitive drum 121 with the charger 122 and then irradiates the photosensitive drum 121 with the laser 123 to form a latent image corresponding to monochrome image data on the photosensitive drum 121. The latent image is made a visible image by the developing device 124K, the visible image is transferred to a sheet by the transfer roller 125, and the sheet is discharged to the sheet discharge tray 130 as described below.

  In the case of color printing, the printing unit 120 uniformly charges the photosensitive drum 121 with the charger 122, and then irradiates the photosensitive drum 121 with the laser 123 to convert the image data into CMYK image data. A latent image corresponding to the component is formed on the photosensitive drum 121, and the latent image is made visible by the cyan developing device 124C. The printing unit 120 uniformly charges the photosensitive drum 121 on which the cyan visible image is formed again with the charger 121, and forms a latent image corresponding to the magenta component of the image data on the photosensitive drum 121 with the laser 123. The latent image is made a visible image by the magenta developer 124M, and the magenta visible image is superimposed on the cyan visible image. When the magenta visible image is formed, the printing unit 120 forms the yellow and black visible images on the photosensitive drum 121 in the same procedure as the magenta visible image formation, and the CMYK four-color visible images are formed. Overlay on the photosensitive drum 121. When the printing unit 120 forms a CMYK four-color visible image, the transfer roller 125 transfers the visible image onto the sheet, and discharges the sheet onto the sheet discharge tray 130 as described below.

  The paper on which the visible image is printed is placed on a paper feed tray such as the manual feed tray 131 and the paper feed cassettes 132, 133, and 134.

  When performing printing, the printing unit 120 draws one sheet from any one of the paper feed trays using the pickup roller 135, and the pulled-in sheet is conveyed by the conveyance roller 136 or the registration roller 137 to the photosensitive drum 121 and the transfer roller 125. Send in between.

  When the printing unit 120 transfers the visible image onto the paper fed between the photosensitive drum 121 and the transfer roller 125, the printing unit 120 sends the paper to the fixing device 127 by the conveyance belt 126 in order to fix the visible image. The fixing device 127 includes a fixing roller 128 having a built-in heater and a pressure roller 129 pressed against the fixing roller 128 with a predetermined pressure. When the sheet passes between the fixing roller 128 and the pressure roller 129, the visible image is fixed to the sheet by heat and a pressing force to the sheet. The printing unit 120 discharges the sheet that has passed through the fixing device 127 to the discharge tray 130.

  The image forming apparatus 100 includes an operation unit 140 provided with an operation panel 141 and a start key 142 on the upper portion of the main body 101. When printing, scanning, copying, or the like, the user operates the operation panel 141 or the start key 142 to instruct the image forming apparatus 100 to print, read a document, or copy.

  For example, when the conference processing document 201 shown in FIG. 2 is color-copied by the image processing apparatus 100 to create a plurality of conference materials, the user places the document 201 on the mounting table 105 and presses the start key 142. Press. When the start key 142 is pressed, the document reading unit 301 provided in the image processing apparatus 100 shown in FIG. 3 determines on which of the mounting table 105 and the document table 103 the document is placed. The mounting table 105 is provided with a contact-type sensor (not shown) that comes into contact with the placed document. The document reading unit 301 determines that the document is placed on the placing table 105 by this sensor. When the document reading unit 301 determines that the document is placed on the mounting table 105, the document reading unit 301 conveys the document 201 using the automatic document feeder 104, reads the document 201 using the reading unit 110, and outputs pixel data. Is generated (FIG. 4, S401 → S402). The image reading unit 301 sequentially stores the generated pixel data in the memory 302, and generates document image data based on all the pixel data of the document 201.

  When the image data is stored in the memory 302, the generation unit 303 acquires the image data from the memory 302. The generation unit 303 converts each pixel data constituting the acquired image data into pixel data representing a color by L * a * b * (a color system standardized by the International Commission on Illumination and adopted in JISZ8729). Convert. The generation unit 303 generates the frequency distribution of the hue by counting the pixel data for each hue based on each pixel data represented by L * a * b * (FIG. 4, S403). The generation method is performed, for example, by counting pixel data for each hue determined by the a * value and b * value of the pixel data represented by L * a * b *.

  As shown in FIG. 2, the original 201 read as described above is composed of a character portion on which a sentence 202 is printed and an image portion on which a pie chart 203 is printed. The text 202 is printed in black, and the pie chart 203 is composed of a red area 204, a yellow area 205, and a blue area 206, and the paper is white.

  Since white and black are achromatic colors, the frequency portion of the text 202 and the background of the document 201 do not affect the hue frequency distribution, and the generated hue frequency distribution indicates the color of each area of the pie chart 203. It will be reflected. Therefore, as shown in FIG. 5, the hue frequency distribution has peaks in the hues of red, yellow, and blue, and in other hues, the frequency is almost zero.

  When the frequency distribution of the hue is generated, the generation unit 303 notifies the peak identification unit 304 of the fact, and inputs the image data converted into the pixel data representing the color by L * a * b * to the conversion unit 306. .

  When notified that the frequency distribution of hue has been generated, the peak specifying unit 304 specifies the number of peaks and the skirt width of each peak (S404 in FIG. 4). For example, the peak is identified based on whether or not the frequency is greater than a predetermined amount (threshold 500 shown in FIG. 5), and hues whose frequencies exceed the threshold 500 in the hue frequency distribution are continuous. In this case, it is assumed that one peak is formed with continuous hues exceeding the threshold 500. In FIG. 5, there are three places where the frequency exceeds the threshold 500, and the identification unit 304 identifies the number of peaks as three in the present embodiment. The skirt width of the peak is, for example, a number in which a hue having a frequency exceeding the half of the maximum frequency is continued from a hue having the highest frequency (maximum frequency) in each peak.

  After specifying the number of peaks and the skirt width of each peak, the peak specifying unit 304 inputs the number of peaks and the skirt width of each peak to the type determining unit 305.

  The type discriminating unit 305 discriminates whether or not the image data stored in the memory 302 is image data that places importance on visibility based on the input number of peaks and the skirt width (FIG. 4, S405). Image data that emphasizes visibility, for example, does not require color reproducibility of copied materials, such as landscapes, but it does not require manuscripts and colors such as conference materials and educational materials used at examination institutions. Even if they are different, the contents can be grasped.

  Since materials used in meetings and the like use fewer colors than landscape images, for example, the number of peaks tends to be smaller than landscape images. In addition, for materials such as those used in meetings, in order to improve visibility, colors with completely different hues are often used for color coding of graphs, and the amount used varies greatly depending on the hue. Therefore, the type discriminating unit 305 discriminates that the image data emphasizes visibility when the number of peaks is small and the skirt width of each peak is small.

  As the number of peaks and the skirt width, which are used as criteria for determining the type of image data, for example, those stored in advance in the type determining means 305 can be used.

  Here, it is assumed that the type determination unit 305 determines that the image data emphasizes visibility.

  When the type discriminating unit 305 discriminates that the image data emphasizes visibility, the converting unit 306 performs a conversion process on the image data input from the generating unit 303 (S406 in FIG. 4).

  In the present embodiment, this conversion processing is processing for uniformly increasing the density (L value) of all pixel data of the input image data by a predetermined gradation. However, if the density is increased uniformly, the color (white) of the background portion of the document 201 becomes dark and the appearance of the document deteriorates. Therefore, it is preferable to remove the white pixel data from the conversion processing target. When the white pixel data is excluded from the conversion target, the density of the pixel data corresponding to the text 202 and the pie chart 203 among the pixel data constituting the image data of the document 201 is increased. If the sentence 202 is black and the density cannot be increased any more, the pixel data corresponding to the document 202 does not need to be subjected to a process for increasing the density in the conversion process.

  When excluding the white pixel data from the conversion target, the conversion unit 306 recognizes the white pixel data with reference to all the pixel data input from the generation unit 303, and converts the pixel data into pixel data other than the white pixel data. On the other hand, the conversion process is performed.

  When the conversion unit 306 performs the conversion process, the conversion unit 306 inputs the image data subjected to the conversion process to the printing unit 307. When the image data is input, the printing unit 307 converts the pixel data constituting the input image data into pixel data representing colors in CMYK (hereinafter referred to as “CMYK data”), and uses the printing unit 120. Then, color printing is performed (FIG. 4, S407).

  Since the original image data has been subjected to processing for increasing the density of the text 202 and the pie chart 203 in the conversion process, the density of the pie chart 203 printed by the printing unit 307 is high. Therefore, since the density of the yellow region 205 that is difficult to visually recognize increases, the user can easily visually recognize the yellow region 205.

  When it is determined in step 405 that the image data does not place importance on visibility, the type determination unit 305 issues a print instruction to the printing unit 307. When the printing instruction is issued from the type determining unit 305, the printing unit 307 converts the image data stored in the memory 302 into CMYK data, and performs color printing using the printing unit 120 (S407 in FIG. 4).

(Embodiment 2)
In the first embodiment, all the pixel data is subjected to conversion processing performed by the conversion unit 306. However, in order to make a printed matter easily visible, it is sufficient to improve the visibility of only a color that is difficult to visually recognize. . In this embodiment, a case will be described in which only pixel data indicating a color that is difficult to visually recognize is subjected to conversion processing.

  When the type discriminating unit 305 discriminates that the image data emphasizes visibility as in the first embodiment, in the present embodiment, the converting unit 306 acquires the hue that needs to be converted from the hue storing unit 308 (FIG. 6, FIG. 6). S601). The hue that requires conversion is, for example, a yellow hue that is difficult to visually recognize and a hue close to yellow. The hue stored in the hue storage unit 308 is expressed using the a * value and b * value of the L * a * b * color system. When the conversion unit 306 acquires the hue, the conversion unit 306 determines whether there is pixel data indicating the same hue as the acquired hue in the L * a * b * pixel data input from the generation unit 303 (FIG. 6). S602).

  When there is pixel data that shows the same hue as the acquired hue, the conversion unit 306 uses only pixel data that represents the same hue as the acquired hue as the target of the conversion process. The conversion unit 306 uniformly increases the density of the pixel data to be converted (step S603 in FIG. 6).

  When the conversion unit 306 performs the conversion process, the conversion unit 306 inputs the image data subjected to the conversion process to the printing unit 307. When the image data is input, the printing unit 307 converts the pixel data represented by L * a * b * of the input image data into CMYK data, and performs color printing using the printing unit 120 ( FIG. 6, S604).

  As described above, by setting only the hue color stored in the hue storage unit 308 as the target of the conversion process, for example, the density of only a color having a hue close to yellow or yellow is increased. Therefore, the density of only the yellow area 205 of the pie chart 203 of the original 201 is high, and the density of the other areas of the original 201, that is, the sentence 201, the red area 204, the blue area 206, and the background area of the original does not increase.

  In step 602, if there is no pixel data indicating the same hue as the acquired hue, the conversion unit 306 issues a print instruction to the printing unit 307. When a printing instruction is issued, the printing unit 307 converts the image data stored in the memory 302 into CMYK data, and performs color printing using the printing unit 120 (FIG. 6, S604).

(Embodiment 3)
If the visibility of the red area 204, the yellow area 205, and the blue area 206 is improved in the original 201, the color classification of the pie chart 203 becomes easier to see. Only the pixel data indicating yellow, blue) may be subject to conversion processing.

  When only pixel data having a hue that forms a peak is to be subjected to conversion processing, the peak specifying unit 304 inputs the number of peaks and the skirt width of each peak to the type determining unit 305, and in the frequency distribution of hues A hue whose frequency exceeds the threshold value 500 is notified to the conversion means 306 (FIG. 7, S404 → FIG. 7, S701). In the hue frequency distribution, when there is no hue whose frequency exceeds the threshold value 500 and the peak cannot be specified, the peak specifying unit 304 notifies the conversion unit 306 that the peak cannot be specified instead of the hue.

  When the type determining unit 305 determines that the image data emphasizes visibility, the converting unit 306 determines whether or not the hue is notified from the peak specifying unit 304 in this embodiment (FIG. 7, S405 → FIG. 7, S702).

  If it is determined that the hue is notified, the conversion unit 306 performs a conversion process for uniformly increasing the density only for the pixel data having the notified hue (FIG. 7, S703).

  When the conversion unit 306 performs the conversion process, the conversion unit 306 inputs the image data subjected to the conversion process to the printing unit 307. When the image data is input, the printing unit 307 converts the pixel data represented by L * a * b * of the input image data into CMYK data, and performs color printing using the printing unit 120 ( FIG. 7, S704).

  If it is determined in step 702 that the hue has not been notified, the conversion unit 306 issues a print instruction to the printing unit 307. When a printing instruction is issued, the printing unit 307 converts the image data stored in the memory 302 into CMYK data, and performs color printing using the printing unit 120 (S704 in FIG. 7).

As described above, in the first to third embodiments, the conversion process is a process for increasing the density, but it may be a process for increasing the saturation or changing the hue.
(Embodiment 4)
The conversion processing according to the first to third embodiments is processing for uniformly increasing the density of target pixel data by a predetermined gradation. However, if the density is uniformly increased by a predetermined gradation, for example, the red region 204 of the document 201 is displayed. If there is density unevenness in the yellow area 205 and the blue area 206, the density unevenness in the red area 204, yellow area 205, and blue area 206 remains even if the conversion process is performed. In order to eliminate density unevenness in each region, the object of the conversion process is limited to the hue that forms the peak, and the hue that forms the same peak is converted to the same color, that is, the same density, saturation, and hue. May be.

  When the pixel data indicating the hue forming the peak in the conversion process is converted to the same color, the peak specifying unit 304 specifies the peak number and the skirt width of each peak after specifying the peak number and the skirt width of each peak. In addition to notifying the type discriminating means 305, the conversion means 306 is notified of the hue that forms a peak and the hue that has the highest frequency (hereinafter referred to as a mode value) in the hue that forms each peak (FIG. 4 S404 → FIG. 8). , S801). If the peak cannot be specified, the peak specifying unit 304 notifies the conversion unit 306 that the peak cannot be specified instead of notifying the hue forming the peak and the mode value of each peak.

  When the type determining unit 305 determines that the image data emphasizes visibility, the converting unit 306 determines whether or not the hue that forms a peak and the mode value of each peak are notified from the peak specifying unit 304 in this embodiment. Is determined (FIG. 8, S405 → FIG. 8, S802).

  If it is determined that the notification has been made, the conversion unit 306 converts the hue of the pixel data indicating the hue forming each peak into a hue corresponding to the mode value of each peak (the highest frequency hue at each peak). Next, the conversion unit 306 converts the density and saturation of the pixel data obtained by converting the hue component into a hue corresponding to the mode value of each peak into a predetermined gradation (FIG. 8, S803).

  When the conversion unit 306 performs the conversion process, the conversion unit 306 inputs the image data subjected to the conversion process to the printing unit 307. When the image data is input, the printing unit 307 converts the pixel data represented by L * a * b * of the input image data into CMYK data, and performs color printing using the printing unit 120 ( FIG. 8, S804).

  In this way, by converting pixels having hues that form the same peak into the same color, for example, even if there is uneven density in the red area 204, yellow area 205, and blue area 206 of the original 201, The red area 204, yellow area 205, and blue area 206 without density unevenness are printed on the copy.

  If it is determined in step 802 that the hue forming the peak and the mode value of each peak are not notified, the conversion unit 306 issues a print instruction to the printing unit 307. When a printing instruction is issued, the printing unit 307 converts the image data stored in the memory 302 into CMYK data and performs color printing using the printing unit 120 (S804 in FIG. 8).

(Embodiment 5)
Even a color original as shown in FIG. 2 may be copied in monochrome. When color image data is copied in black and white, it may be difficult to distinguish colors with the naked eye. For example, if the red area 204 and the blue area 206 of the original 201 have the same density, the red area 204 and the blue area 206 cannot be distinguished when the original 201 is copied in monochrome.

  This is because when color image data is copied in black and white, the hue and saturation are removed from the color image data and the color image data becomes only density data (monochrome data), and this monochrome data is printed. is there. Therefore, even if the colors are different in hue and saturation, if the monochrome density is the same, when the monochrome copy is made, the same color (density) is printed, making it difficult to distinguish the colors. Therefore, when colors with different hues are printed in monochrome, the density is determined based on the hue of each color when converting color image data into monochrome image data so that the color can be distinguished with the naked eye. It may be.

  First, when making a monochrome copy, the user places an original on the mounting table 105, presses a monochrome copy key (not shown) displayed on the operation panel 141, and presses a start key 142. In the present embodiment, the monochrome copy key functions as the monochrome instruction means 309 shown in FIG.

  When the monochrome copy key is pressed and the start key 142 is pressed, the document reading unit 301 and the conversion unit 306 are notified that the monochrome copy key is pressed, and the document is read as in the first embodiment. The image data of the document is stored in the memory 302. When the image data is stored in the memory 302, the generation unit 303 generates a hue frequency distribution and notifies the peak identification unit 304 that the hue frequency distribution has been generated, as in the first embodiment. Each pixel data of the image data stored in 302 is converted into pixel data represented by L * a * b * used for generation of the frequency distribution of the hue and input to the conversion means 306.

  When notified that the hue frequency distribution has been generated, the peak specifying unit 304 specifies the number of peaks and the skirt width of each peak, and the type determining unit 305 determines the number of specified peaks and the skirt width of each peak. input.

  The type discriminating unit 305 discriminates whether or not the image data stored in the memory 302 is image data that places importance on visibility based on the input number of peaks and the skirt width.

  When the type determining unit 305 determines that the image data emphasizes visibility, the converting unit 306, in this embodiment, the density component (L *) of each L * a * b * pixel data input from the generating unit 303. Value), hue / saturation component (a * value), and (b * value) are converted into densities based on the hue component indicated by the a * value and b * value, and each pixel data is converted into monochrome data. Convert. For example, as shown in the color system chromaticity diagram shown in FIG. 9, the hue conversion based on the hue component is performed by converting the hue having a * of +60 and b * of 0 to the highest density. This can be done by converting to a lower density as it goes in the counterclockwise direction. Since the original paper is often white, conversion to an extremely low density may be avoided during conversion.

  In the color system chromaticity diagram shown in FIG. 9, since the hues of red and blue are greatly different, the densities when red and blue are converted to monochrome are also greatly different.

  The conversion unit 306 inputs the image data in which each pixel data is converted into monochrome data to the printing unit 307 after conversion into monochrome data. When the image data is input, the printing unit 307 prints the input image data using the printing unit 120.

  When converting color data to monochrome data, instead of using the density component of the color data as the density component of the monochrome data, the density value based on the hue component of the color data is used as the density component of the monochrome data. Even if the colors are similar in density, if the hue is different, when printed in monochrome, it is printed at a different density, so that it is easy to distinguish with the naked eye.

  The conversion unit 306 notifies the printing unit 307 of a monochrome printing instruction if the type determination unit 305 does not determine that the image data emphasizes visibility. When the monochrome printing instruction is notified, the printing unit 307 converts each pixel data of the image data stored in the memory 302 into monochrome data and prints it using the printing unit 120.

  In the above description, the L * a * b * color system is used to generate the hue frequency distribution. However, the color system used to generate the hue frequency distribution is not limited to L * a * b *. You may carry out using another color system.

1 is a schematic diagram of an image processing apparatus. Schematic diagram of the manuscript. The functional block diagram of an image processing apparatus. The flowchart which shows the procedure in which a conversion process is performed. The figure which shows the frequency distribution of a hue. The flowchart which shows the procedure in which a conversion process is performed. The flowchart which shows the procedure in which a conversion process is performed. The flowchart which shows the procedure in which a conversion process is performed. The figure which shows a color system chromaticity diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image processing apparatus 301 Document reading means 302 Memory 303 Generation means 304 Peak identification means 305 Type determination means 306 Conversion means 307 Printing means 308 Hue storage means 309 Monochrome printing instruction means

Claims (9)

Acquisition means for acquiring color image data;
Generating means for counting the pixel data of each pixel constituting the acquired image data for each hue and generating a frequency distribution of the hue;
Type discriminating means for discriminating whether or not the image data is image data placing importance on visibility based on the generated frequency distribution;
When it is determined that the image data emphasizes visibility, conversion means for converting at least one of density, saturation, and hue of the pixel data;
An image processing apparatus comprising printing means for printing the image data converted from pixel data. Hue storage means for storing hues that require conversion,
The image processing apparatus according to claim 1, wherein the conversion unit performs the conversion only on the pixel data indicating the same hue as the hue stored in the hue storage unit. A peak specifying means for specifying the peak of the frequency distribution,
The image processing apparatus according to claim 1, wherein the conversion unit performs the conversion only on pixel data indicating a hue forming a peak. A peak specifying means for specifying the peak of the frequency distribution,
The image processing apparatus according to claim 1, wherein the type determination unit performs the determination based on the identified peak form. The peak specifying means specifies the number of the peaks,
The image processing apparatus according to claim 4, wherein the type determination unit performs the determination based on the number of specified peaks. The peak specifying means specifies the skirt width of the peak,
The image processing apparatus according to claim 4, wherein the type determination unit performs the determination based on the specified skirt width.   The image processing apparatus according to claim 4, wherein the conversion unit converts pixel data indicating a hue forming the same peak into the same density, saturation, and hue.   The image processing apparatus according to claim 1, wherein the acquisition unit includes a document reading unit that reads a document and generates image data. Monochrome printing instruction means for inputting a monochrome printing instruction;
The image forming apparatus according to claim 1, wherein the conversion unit converts the density of the image data into a density based on a hue of the image data when an instruction for monochrome printing is given.

Images