JP2009284299A - Image processors, image forming apparatus, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a more excellent ground color elimination amount by reducing the influence of recording images in a document, even if document positional deviation or the like occurs on a platen, in an image processor which performs document ground color elimination through real-time processing using a white backing member. <P>SOLUTION: The image processor includes: an LUT 51 for acquiring an image in real time from the lead-edge side of an image reading area in which a document is placed on a document platen and a white backing member is fitted; a background density detection section 53 for detecting background density from the image acquired in real time; and a ground color elimination section 54 for applying ground color elimination to the image in real time using the background density detected by the background density detection section 53. If the document is placed while being deviated with respect to the document platen, the background density detection section 53 sets a detection exclusion area in a main scanning direction and determines the starting position of a detection area in a sub scanning direction, thereby detecting the background density in the document. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that processes read image data, for example.

  For example, when a large document such as a newspaper is placed on a document table (platen) for copying, the document cannot be placed at the correct position, and the so-called platen cover (backing member) cover surface is placed in the reading area. In some cases, so-called platen back is exposed. Further, for example, even when a standard document of A4 size or the like is placed on an A3 size document placing table, the platen back may be exposed due to tilt or misalignment.

On the other hand, in the so-called ground color removal mechanism for removing the background of the document, the image level of the background of the read document is detected and the image signal is changed in the bright direction according to the detected value.
For example, in Patent Document 1, the lower surface of the backing plate is black, and the leading edge position of the document is detected from the level change of the acquired video signal. Then, a scanning line corresponding to the detected occurrence time is taken as a base point, and a ground color signal is generated immediately thereafter or after an appropriate time.

JP-A-62-230257

  Here, in general, the method of making the platen back black and removing the area from the detection area has a problem that a black frame is formed in the area outside the original of the copy output. Therefore, the platen back density is generally set to a density close to white, but the exposed part of the platen back may be detected as the background density, and the document area may not be specified. is there.

  The present invention is also applicable to an image processing apparatus that uses a low-density backing member to remove the background color of a document by so-called real-time processing, and when the document is misaligned on a document table (platen). An object of the present invention is to obtain a better ground color removal amount (usually the paper density of the original document) with reduced influence of the recorded image in the original document.

  According to the first aspect of the present invention, there is provided an area dividing means for dividing the read image into predetermined areas sequentially from the leading end side of the image reading area where the original is placed on the original table and the white backing member is applied. A density acquisition unit that acquires the density of an image included in the area divided by the division unit, and compares the density acquired by the density acquisition unit with the density of the backing member, An image comprising: determination means for determining whether or not a certain effective area; and area determination means for determining an area for detecting a background amount of the document using a result determined by the determination means It is a processing device.

According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, a detection exclusion area is determined in the main scanning direction of document reading, and a detection exclusion area is set in the sub-scanning direction of the document reading, so A detection start position for detecting the quantity is determined.
According to a third aspect of the present invention, in the image processing apparatus according to the second aspect, the area determining unit obtains a predetermined number of areas divided by the area dividing unit in the sub-scanning direction and the main scanning direction of document reading. When the number of determination results of the determination means for the acquired area as the effective area is equal to or greater than a threshold value, the area determined as the effective area among the acquired areas is set as the leading edge of the document. .
According to a fourth aspect of the present invention, in the image processing apparatus according to the second or third aspect, the area determining means performs a contraction process in the main scanning direction and / or the sub-scanning direction, and is effective for detecting a background value. A region is determined.

According to a fifth aspect of the present invention, in the image processing apparatus according to any one of the first to fourth aspects, the background amount is calculated from the leading edge of the document determined by the area determining unit, and the background removal is performed based on the calculated background amount. It is further characterized by further comprising a background removing means for performing the above.
According to a sixth aspect of the present invention, in the image processing apparatus according to the first aspect, the determining means sets all or a density range within which the density of the image acquired by the density acquiring means can be determined as the density of the backing member. It is characterized in that it is determined that it is not the effective area when it is included in the above ratio.
According to a seventh aspect of the present invention, in the image processing apparatus according to any one of the first to sixth aspects, the determination unit calculates a density of the backing member from a density obtained by actually reading the backing member. It is characterized by doing.

  The invention according to claim 8 is an acquisition unit that acquires an image in real time from a front end side of an image reading area where a document is placed on a document table and a white backing member is applied, and the acquisition unit acquires the image in real time. A background density detecting unit for detecting a background density from the image; and a background color removing unit for performing ground color removal on the image in real time using the background density detected by the background density detecting unit. The detection unit sets a detection exclusion area in the main scanning direction and moves the start position of the detection area in the sub-scanning direction when an original is shifted with respect to the original table, An image processing apparatus that detects the background density.

According to a ninth aspect of the present invention, in the image processing apparatus according to the eighth aspect, the background density detection unit divides the image into predetermined areas, and the area is determined to be a density area where the density of the backing member can be determined. The detection exclusion area is set in the main scanning direction when it is determined that it is included.
According to a tenth aspect of the present invention, in the image processing apparatus according to the eighth aspect, the background density detection unit counts the setting results of the detection exclusion area in the main scanning direction, and an effective area excluding the detection exclusion area The start position of the detection area is moved in the sub-scanning direction by determining that there are a predetermined number or more.
According to an eleventh aspect of the present invention, in the image processing apparatus according to the eighth aspect, the background density detection unit determines an end position determined from the start position of the detection area in the sub-scanning direction, and starts the start. The background density value is updated from the position to the end position, the background density value is fixed at the end position, and the ground color removal unit is updated or fixed by the background density detection unit. The background color is removed from the image using the background density.

  According to a twelfth aspect of the present invention, there is provided area dividing means for sequentially dividing the read image into predetermined areas from the leading end side of the image reading area on which the original is placed on the original table and the white backing member is applied, and the area A density acquisition unit that acquires the density of an image included in the area divided by the division unit, and compares the density acquired by the density acquisition unit with the density of the backing member, A determination unit that determines whether the effective region is present, a region determination unit that determines a region for detecting the background amount of the document using the result determined by the determination unit, and the region determination unit An image forming apparatus comprising: an image forming unit that forms an image on which a background removal process has been performed based on a background amount detected from an area on a recording material.

  The invention of claim 13 is a computer connected to an image reading device that reads an image from an image reading area in which an original is placed on a document table and a white backing member is applied, and sequentially from the leading end side of the image reading area. A function of dividing the read image into predetermined areas, a function of acquiring the density of an image included in the divided area, and whether the divided area is an effective area or an invalid area from the acquired density. This is a program that realizes a function of determining and storing from the density of the abutting member and a function of determining a region for detecting the background value of the document using the determined and stored result.

  According to a fourteenth aspect of the present invention, in the program according to the thirteenth aspect, the function of dividing the predetermined area divides the predetermined number of pixels into one block in the main scanning direction.

  According to the first aspect, the document area can be specified by so-called real-time processing using a white backing member (platen) having a low density, and this configuration can be realized even when the document is placed on the document table. The document area can be specified more accurately than in the invention that does not have the invention.

According to the second aspect, when the document is displaced in the sub-scanning direction, the starting point of background detection can be determined according to the amount of deviation, and the detection area can be adjusted to the document position.
According to the third aspect, the area other than the original can be excluded from the acquired image data in the sub-scanning direction and the main scanning direction, and the leading edge of the original can be specified as compared with the invention not having this configuration.
According to the fourth aspect of the present invention, when the divided area is at the boundary between the document and the backing member, even if pixels of the document and the backing member are mixed in the area, the present invention does not have this configuration. In comparison, the detection area can be more reliably limited within the document.
According to the fifth aspect of the present invention, it is possible to provide an image processing apparatus that can perform better background removal.
According to the sixth aspect of the present invention, the detection exclusion region can be determined better than the invention without this configuration based on the density of the backing member.
According to the seventh aspect, for example, even when the backing member is contaminated due to the operating state of the machine or the like, the detection accuracy can be increased as compared with the invention not having this configuration.

According to the eighth aspect, when detecting the background value in so-called real-time processing, it is possible to detect the background density in the original better even if the original is displaced as compared with the invention having no configuration.
According to the ninth aspect, by processing the area divided into the small areas in the main scanning direction, the platen back areas at both ends of the document can be excluded from the detection area, and the document is shifted in the main scanning direction. But it can detect the background in the document.
According to the tenth aspect, when the document is displaced in the sub-scanning direction, it is possible to move the starting point of the background detection according to the amount of deviation using the result determined in the main scanning direction. .
According to the eleventh aspect, by controlling the detection end position based on the detected front end position, it is possible to detect the document front end position by a predetermined area size better than the invention having no configuration.

  According to the twelfth aspect, it is possible to provide an image forming apparatus that can specify a document region by so-called real-time processing using a white backing member (platen) having a low density, and even when the document is placed on the document table, The document area can be specified more accurately than in the invention without this configuration.

According to the thirteenth aspect, it is possible to provide a program that can satisfactorily detect the background density in a document even when document misalignment occurs during the so-called real-time processing background value detection.
According to the fourteenth aspect, the background in the document can be detected well even when the region divided into the small regions is processed in the main scanning direction and the document is shifted in the main scanning direction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating an overall configuration of an image forming apparatus 1 to which the exemplary embodiment is applied. The image forming apparatus 1 functions as a multi-function device such as a printer, a scanner, and a facsimile, for example, and includes a printer device 10 and an image reading device 20 as image processing devices. The printer device 10 includes, for example, an image forming unit (not shown) that forms an image on a recording material by an electrophotographic method, an image processing unit (not shown) that performs various image processes, and the like.

  An image reading device 20 that functions as one of the image processing devices includes, for example, a device main body 21 that incorporates a CCD sensor or the like and reads an image, and a document table 22 that is provided on the upper surface of the device main body 21 and places a document. Have. The document table 22 is formed of a transparent glass member, for example, and has a glass surface on which a document of, for example, A3 size (297 mm × 420 mm) can be placed. Further, the image reading apparatus 20 has a document cover 23 that covers a document placed on the document placement table 22, and a backing member 24 that holds the document placed on the document placement table 22 is provided on the document cover 23. Is attached. The backing member 24 is formed of a white member. As the density of the backing member 24 (platen back (PB) density), for example, about 0.2D (D is an optical density) is adopted. Here, the optical density is a logarithm of the degree to which light is not transmitted / reflected with respect to a specific portion such as a photographic film or photographic paper, and the minimum value is 0.00 (all In transmission and reflection), the larger the value, the darker.

  FIG. 2 is a block diagram of the control / image processing unit 30 that controls the image reading device 20 shown in FIG. 1 and processes an image read by the image reading device 20. The control / image processing unit 30 is provided in the apparatus main body 21, and controls the overall operation of the image reading apparatus 20, and signal processing for processing read image data acquired in real time from the CCD image sensor. Part 50.

  The control unit 40 includes a reading controller 41 that performs various controls for reading an original, and a CCD driver 42 that controls an image data capturing operation by the CCD image sensor. Further, a light source driver 43 is provided that outputs a lighting signal and controls turning on / off of the light source in accordance with the reading timing of the document. Further, when the image reading apparatus 20 includes a scan driver 44 that controls operations of a full-rate carriage (not shown) and a half-rate carriage (not shown) and, for example, an automatic document feeding mechanism (not shown). Includes a transport mechanism driver 45 that controls various transport mechanisms for transporting documents.

  FIG. 3 is a functional block diagram showing the configuration of the signal processing unit 50 that performs signal processing on the read image data acquired in real time. The signal processing unit 50 functions as one of the image acquisition units together with the CCD sensor, and a look-up table (LUT) that replaces the logarithmic curve of the image data read from the CCD sensor with a linear space such as brightness and density. 51 is provided. In addition, a digital filter (DF) 52 that performs MTF correction and smoothing is provided. Further, a background density detection unit 53 that detects the background density of the document, and a ground color removal unit that removes the ground color from the actually read image data using the background value detected by the background density detection unit 53. 54. Furthermore, a tone conversion unit (TRC) 55 that performs tone correction to absorb the nonlinear characteristics of the image forming unit of the printer device 10 and the image data that has been subjected to tone conversion are converted into the number of dots in a certain area. An error diffusion (ED) dither 56 that reproduces the gradation at a ratio and binarizes it is provided. Image data from the ED dither 56 is output to the printer device 10.

  Next, the ground color removal method executed by the background density detection unit 53 and the ground color removal unit 54 described above will be described in detail. The present embodiment is characterized in that the background density is detected in so-called real time. This “real time” is a process that is performed using image data that is actually taken out as document information in sequence when the document image is actually read as necessary image data. By removing the ground color in real time, there is no need to accumulate a multi-value image for the removal process following the detection of the background value, and no page memory is required because an image of the entire page is not needed. In addition, it is not necessary to detect the background value while reading an image for one page in advance, the processing time is short, and productivity can be improved. In the present embodiment, the image of the surface (platen back) of the backing member 24 that may be exposed on the leading edge and both sides of the document for each line is removed from the background detection area in real time, for example. The background value used for ground color removal is detected from

FIG. 4 is a view showing a state where the document is placed on the document table 22 at an angle. As viewed from the apparatus main body 21 side (lower side) of the image reading apparatus 20, the surface of the backing member 24 and the document surface are shown. The backing member 24 is exposed in an area outside the document, and the exposed surface of the backing member 24 is also read by a sensor (an image reading sensor such as a CCD sensor).
In the present embodiment, the background density detection unit 53 divides the image data read from the leading edge (LE: Lead Edge) into small areas and measures the density to determine whether the background is present. As this small region, for example, a block of 64 pixels or 48 pixels on one line in the main scanning direction, or a block having a width of several lines in the sub scanning direction may be formed. is there.

  FIG. 5 shows a state in which the background detection area A is set as an area for distinguishing between the document and the platen back portion. In the example shown in FIG. 5, the area surrounded by the thick line is determined as a non-platen back area that is not a platen back. However, in the example shown in FIG. 5, the boundary portion indicated by diagonal lines is a portion where the document and the platen back are mixed. When the background is detected in this portion, not only the document density but also the platen back density is a judgment material for background detection. Therefore, depending on the detection method, an inappropriate value may be indicated as information for background detection.

  FIG. 6 is a diagram showing a state in which the original area shown in FIG. 5 is logically shifted by about 2 blocks by the shrinking process to reduce the area. In the example shown in FIG. 6, only the hatched area surrounded by the thick line, that is, the part that has entered the document area is subject to background detection. The detection start position is obtained by counting the blocks determined to be included in the document in the main scanning direction. If the determined block is 1 or more, for example, the row (main scanning line) is determined to contain valid information. First, a row satisfying the condition is set as a background value update start point (background detection start point). For example, in a system that ends background detection in a certain area, the number of lines and the number of blocks are counted from the start point detected in this way, and a background value update stop point (background detection end point) is determined. . Between the background value update start point and the background value update stop point is a detection area (described later) in the sub-scanning direction as a specified length.

  FIG. 7 is a diagram for explaining the density change state in the main scanning direction and the detection area in the sub-scanning direction. The density change in the section A in FIG. 7 is as shown on the right side of the figure. The portions on both sides where the document is not placed are platen back (PB) regions, and indicate the density of the backing member 24 (platen back (PB)). The density of the original can be obtained in the central portion excluding the PB areas at both ends. In the present embodiment, a detection area for detecting a background value (“specified length” shown in FIG. 6) is defined in an area in the sub-scanning direction where an original actually exists.

  FIG. 8 is a flowchart showing document area / platen back (PB) area determination processing mainly executed by the background density detection unit 53 shown in FIG. In the present embodiment, in the so-called real-time background color removal method, a detection exclusion region is set in the main scanning direction with respect to document deviation, and the detection region start position is moved in the sub-scanning direction, thereby determining the document region. To do. In the background density detection / background color removal by this “real-time method”, when detecting the background color amount from the document, the detection amount is sequentially determined from the leading edge of the read image, and the read image is sequentially detected according to the detected amount. Remove colors. The detected background amount is determined from the already read partial image.

  First, the background density detection unit 53 divides an image read from the front end in real time for each small region (block) (step 101). As this small area (block), for example, there is a method of making one block every several pixels (for example, 64 pixels, 48 pixels) in one line in the main scanning direction. Further, for example, it is possible to divide into small regions as rectangular regions of n pixels × m pixels (n and m are integers) by adding several pixels in the sub-scanning direction. As a method for determining one block, dividing an area every several pixels in the main scanning direction on one line leads to a reduction in memory capacity.

  Thereafter, the density is acquired for each pixel of each block (step 102). Then, each block is compared with the platen back (PB) density, and an invalid area that is not used for background value detection or an effective area (as an area excluding the invalid area) that is a target when determining an area for background value detection That is, the effective area / ineffective area is determined and stored in a predetermined memory (not shown) (step 103). Here, for example, whether or not the image (for example, each pixel) included in the small area (block) is included in the density range (for example, 0.2D ± α) that can be specified as the platen back density or more than the set ratio. Determine whether. When the platen back (PB) density is included in all the pixels or in pixels that are equal to or higher than the set ratio, it is determined as a platen back exposure area, and this small area (block) is set as an invalid area. . Then, it is determined whether or not this determination and storage processing has been performed until the end of the line in the main scanning direction (line end) (step 104). If it is not the line end, the process returns to step 102, and if it is the line end, the process proceeds to step 105. The leading end of the target area on the document reading side is defined as the leading end of the document.

  Next, the background density detection unit 53 performs a contraction process in the main scanning direction on the effective area determined by the above-described process (step 105). As a result, the mixed area at the end in the main scanning direction is deleted. As a method of excluding the invalid area in the main scanning direction, there is a method of processing directly from the excluded area stored in step 103 in addition to the method of processing after performing the contraction process on the effective area as described above. . Further, for example, there is a method in which an effective area is specified from both sides of a document and all the insides are made effective.

  Next, the effective areas after the contraction process are totaled in the main scanning direction (step 106). Then, an effective area in the sub-scanning direction is detected from the total result (step 107). In this method of detecting the effective area in the sub-scanning direction, the result obtained by summing up the results of the determination of the effective area / ineffective area in the main scanning direction in the main scanning direction is equal to or more than the set number. When the method of determining the background value in a certain area from the front end is adopted, the background value is determined by the image signal read from the platen back unless the front end exclusion area process is performed. However, the detection processing start position, which is the region start point in the sub-scanning direction, is aligned with the leading edge of the document by the processing of step 106 to step 107.

  Here, for example, when a newspaper is used as an original, the paper has a grayish density, and when a background value is correctly detected, a large removal value is detected. Since the removal is performed with the set value, the background color is largely removed, and the covering of the newspaper can be eliminated. On the other hand, if the original is displaced and detection is performed from the front end of the reading area even though the platen is exposed at the front end of the original placing table 22, it is affected by the density of the platen back, resulting in a low density. Is detected. In addition, when a technique is adopted in which only a specified area is detected from the tip and then the detection value is fixed, the entire target area is covered with a platen back, and an appropriate value may not be detected. In this case, the ground color removal hardly works, and the background (fogging) remains in the background of the output image. In the present embodiment, the background value is correctly detected by the above-described processing of Step 106 to Step 107, and this problem is solved.

  Thereafter, contraction processing in the sub-scanning direction is performed (step 108), and the mixed area at the end portion in the sub-scanning direction is deleted. Then, it is determined whether or not the processing so far is performed up to the page end which is the end position in the sub-scanning direction (step 109). If not, the process returns to step 101 and the same process is repeated. If the process is performed up to the page end, the document area / PB area determination process ends. For example, when a punch hole is opened in the original, it is possible to exclude the density close to the platen back in the main scanning direction process, and the original is not affected by these areas. The background value in can be detected.

  Note that the background detection area A as shown in FIG. 5 is converted into the background detection area B as shown in FIG. 6 by the contraction processing in steps 105 and 108. The determination as to whether the area is an effective area or an invalid area is made for each block. Therefore, the pixel value in the block determined to be an effective area includes a pixel representing the density of the platen back. This is especially true for blocks containing the border area of the document. In order to exclude an area representing the density of the platen in the effective area, the effective area is reduced and corrected. By reducing the effective area by the specified number of areas, inappropriate areas at the boundary are excluded.

  FIG. 9 is a flowchart showing processing for detecting a background value. The background value detection process is performed in parallel with the document area / platen back (PB) area determination process shown in FIG. First, the background density detection unit 53 detects and records the background value of a small area (block) (step 201). If the maximum density value in each block is detected as the background value, the calculation is facilitated. Instead of the maximum density, an average density can be extracted and used as a background value.

  Thereafter, it is multiplied by the determination of the document area shown in FIG. 8 to obtain an effective background value (step 202). Then, background values are totaled in the main scanning direction to determine a representative value (step 203). As representative values, for example, there are a method of adopting a maximum value and a method of taking an average value. Next, if the area is in the document, the ground color removal value is updated (step 204). In the update of the ground color removal value, for example, if it is larger than the previous line removal value, a certain amount (for example, 1/255) is increased, and if it is smaller than the previous line removal value, the certain amount (for example, 1/255) is decreased. Made. This constant amount can be approached as soon as possible to the true background value by applying, for example, a larger value (for example, 2/255) closer to the front end of the document, and a smaller amount (for example, 1/255) if it is far.

Thereafter, it is determined whether or not processing has been performed for the set area (step 205). As this setting area, for example, about 10 mm from the background value update start point is set. If only the set area has not been processed, the process returns to step 201 to repeat the process, and the ground color removal amount is updated and fluctuated up to this set area. When processing is performed for the set area, the removal value is fixed (step 206), and the process ends. That is, after processing for the set area, the removal amount as the background value does not change, and the ground color removal by the ground color removal unit 54 (see FIG. 3) is performed using a fixed value as the background value.
In this embodiment, the above-described performance is realized by performing background detection and background removal in this way.

  The processes shown in FIGS. 8 and 9 can be realized by a CPU (not shown) of a computer (image reading device 20), for example. When realized by a computer, these functions are installed in the memory of the computer in the form of a program. As a method of using the program, for example, when it is stored in a ROM or when a program stored in a CD-ROM is read and installed in a memory, it is downloaded from a remote computer via a network (not shown). And install it in memory.

  As described above in detail, in the present embodiment, when a document is shifted with respect to the document table 22, the detection exclusion region is set in the main scanning direction and the detection region is started in the sub scanning direction. By moving the position, the background density in the document is detected. At this time, the method of setting the detection exclusion area in the main scanning direction is to determine an effective width (area), divide the image into small areas (blocks), and make the area a density area that can be determined as the platen back density. Judging that it is in. Although the density range is detected as a platen back, since the platen back has a designed value, the density range is calculated using the value as a specified value. However, there is a problem that it fluctuates due to variations and dirt during use. Therefore, in order to avoid this, it is possible to improve the determination accuracy by periodically reading in the absence of a document before the operation, reading the values of the actual machine, and storing them one-dimensionally or two-dimensionally.

  And the method of setting a detection exclusion area | region in a subscanning direction totals the detection result of a main scanning direction, and determines that an effective area | region is more than a regulation number. Further, when determining the area of the document, a contraction process is performed to exclude a portion including erroneous boundary determination. In this manner, the platen back image that may be exposed at the leading edge and both sides of the document is removed from the background detection area, and the background value used for ground color removal is detected only from the background density of the document. Furthermore, in this embodiment, when the detection result is fixed in a predetermined length from the tip in the sub-scanning direction in real time, the end point of the detection region is determined as a certain amount from the tip of the determined effective region. To do. For example, in the method in which the background detection value is fixed within a predetermined length area from the leading edge of the document, it is necessary to move the start and end of detection in accordance with the document position. According to the present embodiment, by controlling the detection end position based on the detected front end position, it is possible to satisfactorily detect the specified area size of the document front end position.

  In order to specify the document area using the difference between the density of the white platen back and the document density, the attribute is not determined for each area from the real-time processing as described above. For example, the entire document is read. It is also possible to divide the area after completion and determine the attribute of the area.

1 is a diagram illustrating an overall configuration of an image forming apparatus to which the exemplary embodiment is applied. FIG. 2 is a block diagram of a control / image processing unit that controls the image reading apparatus shown in FIG. 1 and processes an image read by the image reading apparatus. It is the functional block diagram which showed the structure of the signal processing part which performs a signal process about the read image data acquired in real time. FIG. 6 is a diagram showing a state in which a document is placed obliquely on a document table. A state in which the background detection area A is set as an area for distinguishing between the original and the platen back portion is shown. FIG. 6 is a diagram showing a state in which the original area shown in FIG. 5 is logically shifted by about 2 blocks by shrinking processing to reduce the area. It is a figure for demonstrating the change state of the density | concentration of the main scanning direction, and the detection area of a subscanning direction. 6 is a flowchart showing a document area / platen back (PB) area determination process. It is a flowchart which shows the process for a background value detection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image formation apparatus, 20 ... Image reading apparatus, 21 ... Apparatus main body, 22 ... Original stand, 23 ... Original cover, 24 ... Backing member, 50 ... Signal processing part, 51 ... Look-up table (LUT), 53 ... background density detection unit, 54 ... ground color removal unit

Claims (14)

Area dividing means for dividing the read image into predetermined areas sequentially from the front end side of the image reading area where the original is placed on the original table and the white backing member is applied;
Density acquisition means for acquiring the density of an image included in the area divided by the area dividing means;
A determination unit that compares the density acquired by the density acquisition unit with the density of the backing member, and determines whether the effective region is a candidate for the document region;
An image processing apparatus comprising: an area determining unit that determines an area for detecting a background amount of the document using a result determined by the determining unit.   The area determination means determines a detection exclusion area in the main scanning direction of document reading, sets a detection exclusion area in the sub-scanning direction of the document reading, and determines a detection start position for detecting the background amount of the document. The image processing apparatus according to claim 1.   The area determination means acquires a predetermined number of areas divided by the area dividing means in the sub-scanning direction and main scanning direction of document reading, and the number of determination results as effective areas by the determination means for the acquired areas is The image processing apparatus according to claim 2, wherein an area that is determined to be an effective area among the acquired areas is set as a leading end portion of the document when the value is equal to or greater than the threshold value.   4. The image processing apparatus according to claim 2, wherein the area determination unit performs a contraction process in the main scanning direction and / or the sub-scanning direction to determine an effective area for detecting a background value.   5. The apparatus according to claim 1, further comprising a background removing unit that calculates a background amount from a leading end portion of the document determined by the area determining unit, and performs background removal based on the calculated background amount. Image processing apparatus.   The determination unit is not the effective region when the density of the image acquired by the density acquisition unit is included in the density range that can be determined as the density of the backing member or more than a set ratio. The image processing apparatus according to claim 1, wherein the determination is performed.   The image processing apparatus according to claim 1, wherein the determination unit calculates a density of the backing member from a density obtained by actually reading the backing member. An acquisition unit that acquires an image in real time from the front end side of the image reading area where the document is placed on the document table and the white backing member is applied;
A background density detection unit for detecting a background density from the image acquired in real time by the acquisition unit;
A ground color removal unit that performs ground color removal on the image in real time using the background density detected by the background density detection unit;
The background density detection unit sets a detection exclusion area in the main scanning direction and moves the start position of the detection area in the sub-scanning direction when the document is shifted with respect to the document table. An image processing apparatus for detecting the background density in a document.   The background density detection unit divides the image into predetermined areas, and when it is determined that the area is in a density area that can be determined as the density of the backing member, the detection exclusion area in the main scanning direction. The image processing apparatus according to claim 8, wherein: is set.   The background density detection unit totalizes the detection exclusion region setting results in the main scanning direction, and determines that the number of effective regions excluding the detection exclusion region is equal to or more than a specified number, thereby detecting the detection in the sub-scanning direction. The image processing apparatus according to claim 8, wherein the start position of the area is moved. The background density detection unit determines an end position determined from the start position of the detection area in the sub-scanning direction, updates the background density value from the start position to the end position, The background density value is fixed at the end position,
The image processing apparatus according to claim 8, wherein the ground color removal unit performs ground color removal on the image using the background density updated or fixed by the background density detection unit. Area dividing means for dividing the read image into predetermined areas sequentially from the front end side of the image reading area where the original is placed on the original table and the white backing member is applied;
Density acquisition means for acquiring the density of an image included in the area divided by the area dividing means;
A determination unit that compares the density acquired by the density acquisition unit with the density of the backing member, and determines whether the effective region is a candidate for the document region;
Area determining means for determining an area for detecting the background amount of the document using the result determined by the determining means;
An image forming apparatus comprising: an image forming unit configured to form an image on which a background removal process has been performed based on a background amount detected from an area determined by the area determination unit, on a recording material. To a computer connected to an image reading device that reads an image from an image reading area where a document is placed on a document table and a white backing member is applied,
A function of sequentially dividing the read image into predetermined areas from the front end side of the image reading area;
A function of acquiring the density of an image included in the divided area;
A function for determining and storing whether the divided area is an effective area or an invalid area from the acquired density from the density of the backing member;
And a function for determining a region for detecting a background value of the document using a result determined and stored.   14. The program according to claim 13, wherein the function of dividing into predetermined areas divides the predetermined number of pixels into one block in the main scanning direction.

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