JP6228522B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus, and is suitable for application to an image processing apparatus such as a copying machine that performs image processing on image data obtained by reading (scanning) a document.

  When the image data obtained by pre-scanning the document is input from the document reading device, the conventional image processing device performs image processing for preliminary evaluation such as image area separation on the image data, and then When image data obtained by performing a main scan on a document is input from the document reading device, the image data is stored in a memory. Then, the image processing apparatus reads the image data from the memory, performs image processing based on the result of the pre-scan process on the image data, and outputs the image data (for example, Patent Document 1). reference).

  In such a conventional image processing apparatus, in order to reduce the capacity of the memory for storing the image data as much as possible, the image data is compressed and stored in the memory, and is expanded after being read out. The compression in this case is irreversible compression.

JP 2001-69345 A

  By the way, when image data is compressed as in a conventional image processing apparatus, a part of the image data is discarded at the time of compression. Therefore, even before decompression, the image data before compression cannot be completely restored. For this reason, the conventional image processing apparatus can reduce the capacity of the memory for storing the image data, but has a problem that the image quality of the output image data is deteriorated as compared with the non-compressed one.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose an image processing apparatus capable of preventing the image quality of image data from being deteriorated while reducing the capacity of a storage unit for storing image data.

  In order to solve such a problem, in the present invention, a pre-scan process using image data obtained by scanning a part of a document, and a whole part of the document is scanned based on the result of the pre-scan process. An image processing unit for performing a main scan process using image data, a buffer having a capacity capable of storing image data obtained by scanning a part of a document required for the pre-scan process, and an image to the buffer A control unit that controls writing and reading of data in units of lines of the image data, and the control unit writes image data obtained by scanning a part of a document to the buffer during the prescan process. The image data stored in the buffer is read without erasing from the buffer and sent to the image processing unit, During the scan process, the image data stored in the buffer during the pre-scan process is read from the buffer in the line order, sent to the image processing unit, and erased from the buffer to secure a free space in the buffer, and While writing the image data obtained by scanning the remaining part in the empty area of the buffer in line order, the image data of the previously written line is read from the buffer in order and sent to the image processing unit and the buffer. It was made to erase from.

  In this way, in the present invention, the capacity of the buffer that stores the image data can be suppressed to a capacity that can store the image data obtained by scanning a part of the document necessary for the pre-scan process. The capacity of the buffer can be significantly reduced as compared with a case where the capacity of the image data obtained by scanning the entire part of the original can be saved. Further, in the present invention, when performing the main scan processing, the image data is written in the buffer in the line order, while the image data of the previously written line is sequentially read from the buffer and erased from the buffer. While using a buffer with a capacity smaller than the capacity for storing image data obtained by scanning minutes, the image data of all lines obtained by scanning the original is buffered without being compressed and the main scanning process is performed. It can be carried out.

  According to the present invention, the capacity of the buffer can be significantly reduced as compared with the case where the capacity of the image data obtained by scanning all parts of the document can be stored, and such a small capacity buffer. However, it is possible to perform the main scanning process by buffering the image data of all the lines obtained by scanning the document without compressing it. Thus, it is possible to realize an image processing apparatus capable of preventing the image quality of image data from being deteriorated while reducing the capacity of a storage unit used as a buffer.

It is a block diagram which shows the function structure of an image processing apparatus. It is a basic diagram which shows the structure of an image data buffer. It is a flowchart which shows the procedure of a scanning process. It is an approximate line figure used for explanation of reading and writing to an image data buffer at the time of prescan processing. It is an approximate line figure used for explanation of reading and writing to an image data buffer at the time of this scan processing.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.

[1. Functional configuration of image processing apparatus]
FIG. 1 shows a functional configuration of an image processing apparatus 1 according to this embodiment. FIG. 1 is a diagram showing blocks for each function of the image processing apparatus 1. The image processing apparatus 1 includes an image input I / F (Interface) 2, an image processing unit 3, a write DMA (Direct Memory Access) controller 4, an image data buffer control unit 5, a read DMA controller 6, and a background removal. Unit 7, image processing unit 8, write DMA controller 9, read DMA controller 10, image output I / F 11, common bus 12, memory 13, and CPU 14.

  The CPU 14 controls the entire image processing apparatus 1. The write DMA controller 4, the read DMA controller 6, the write DMA controller 9, and the read DMA controller 10 can access the memory 13 via the common bus 12, and write (write) and read (read) data to the memory 13. To do. The image input I / F 2 is an interface connected to the image reading device 20 configured by a scanner or the like, and the image output I / F 11 is an interface connected to an image output device 21 such as a printer.

  The image input I / F 2 sends image data obtained by scanning a document from the image reading device 20 to the image processing unit 3. The image processing unit 3 performs correction processing such as shading correction, color correction, and gamma correction related to the characteristics of the image reading device 20 on the image data. Note that this correction processing does not include compression processing for reducing the amount of image data. Then, the image processing unit 3 sends the corrected image data to the write DMA controller 4.

  The write DMA controller 4 writes the image data to the memory 13 via the common bus 12. Note that image data obtained by line scanning the document from the image reading device 20 is input to the image input I / F 2 for each line, and the write DMA controller 4 receives the image data for each line. The data is written to the memory 13 in line order. The write DMA controller 4 receives the memory management information Md from the image data buffer control unit 5 and sends the write information Wd to the image data buffer control unit 5. Details of the memory management information Md and the write information Wd will be described later.

  The read DMA controller 6 reads the image data written in the memory 13 by the write DMA controller 4 from the memory 13 in the line order for each line via the common bus 12 and sends the read image data to the background removal unit 7. The read DMA controller 6 receives the memory management information Md from the image data buffer control unit 5, and sends the read information Rd to the image data buffer control unit 5. The read information Rd will be described later in detail.

  The background removal unit 7 performs background removal processing on the image data. Background removal processing is image processing that detects the background color (paper color) of a document from image data and removes it. By performing background removal processing, an image obtained by removing background dirt or show-through from the document. Data can be obtained. As an algorithm for such background removal processing, for example, the most frequent lightness is set as the background removal level from the lightness histogram of the pixel group constituting the image data obtained by scanning a part of the document, and this background removal level is set. A technique for removing pixels having the above brightness as a background color is known. The background removal unit 7 also performs background removal processing of such an algorithm, and sends the image data after the background removal processing to the image processing unit 8. Further, the background removal unit 7 sends the buffer configuration information Bd to the image data buffer control unit 5. The buffer configuration information Bd will be described later in detail.

  For example, the image processing unit 8 performs image processing such as image area separation, resolution conversion, and color conversion on the image data. In this image processing, for example, when conversion to low resolution is set by the user, the amount of image data may be reduced. The image processing unit 8 sends the image data after the image processing to the write DMA controller 9. The write DMA controller 9 writes the image data to the memory 13 via the common bus 12. The read DMA controller 10 reads the image data written to the memory 13 by the write DMA controller 9 from the memory 13 via the common bus 12 and sends it to the image output I / F 11. The image output I / F 11 outputs image data subjected to a series of image processing to the image output device 21.

  The functional configuration of the image processing apparatus 1 is such a configuration. Actually, the image processing apparatus 1 executes a pre-scan process using image data obtained by scanning a part of a document input from the image reading device 20, and then performs a process for the document input from the image reading device 20. The main scan process is executed using the image data obtained by scanning the entire part, and the image data after the main scan process is output to the image output device 21. Although the details of the pre-scan process and the main scan process will be described later, in brief explanation, the main scan process is a process for obtaining image data of all parts of a document and performing a background removal process on the image data. The prescan process is a process for obtaining image data of a part of a document and performing a preliminary evaluation necessary for performing background removal processing based on the image data.

  In the memory 13, an image data buffer which is an area accessed by the write DMA controller 4 and the read DMA controller 6 and an image data buffer which is an area accessed by the write DMA controller 9 and the read DMA controller 10 are separately secured. The write DMA controller 4 and the read DMA controller 6, and the write DMA controller 9 and the read DMA controller 6 access the respective image data buffers according to the control of the image data buffer control unit 5.

  Here, the image data buffer 100 accessed by the write DMA controller 4 and the read DMA controller 6 will be described with reference to FIG. The image data buffer 100 includes a plurality of continuous line storage areas 101, and each line storage area 101 has a size capable of storing image data for one line. The image data buffer 100 shown in FIG. 2 includes, for example, 16 continuous line storage areas 101 from 0 to 15, and has a buffer size (capacity) for 16 lines.

  The image data buffer 100 is managed as a so-called ring buffer so that the line storage area 101 next to the last (15th) line storage area 101 becomes the first (0th) line storage area 101.

  The buffer size of the image data buffer 100 is determined by the background removal unit 7. Specifically, the background removal unit 7 sets the number of lines necessary for detecting the background color based on the resolution of the image data input from the image reading device 20 during the prescan process. . Actually, when one page of a document is scanned with a resolution of, for example, vertical 70 pixels × horizontal 70 pixels, the image data obtained by scanning is image data for 70 lines in which the horizontal 70 pixels are one line. In order to detect the background color, for example, about 1/10 of the total lines are required. In this case, the number of lines necessary for detecting the background color is, for example, “7”. In this way, the background removing unit 7 sets the number of lines necessary for detecting the background color.

  In the image processing apparatus 1, the image data of the number of lines set in this way (for example, for 7 lines) is written to the memory 13 during the pre-scan process and stored until the main scan process. For this reason, the buffer size of the image data buffer 100 needs to be larger than the number of lines (for example, 7 lines) necessary for detecting the background color. The size of the image data necessary for detecting the background color (that is, the size of the image data necessary for the prescan process) is called a prescan data size, and the buffer size of the image data buffer 100 is larger than the prescan data size. There is a need to.

  Further, the image processing apparatus 1 writes image data in a so-called first-in first-out method in which image data is written to the image data buffer 100 line by line while reading from the image data buffer 100 line by line in order from the previously written image data. Lead is to be implemented. In this case, in order to prevent the write position on the image data buffer 100 from colliding with the read position, the time required to write the image data to the image data buffer 100 (this is called the write time) and the image data A line storage area 101 for absorbing a difference in the time required to read image data from the buffer 100 (referred to as a read time) is required separately from the line storage area 101 corresponding to the prescan data size.

  Actually, in the case of the image processing apparatus 1, the write time is, for example, the speed at which image data is input from the image reading apparatus 20 to the image input I / F 2 (referred to as input speed) and the data of the input image data. Depends on the amount. The read time depends on, for example, the speed at which image data is output from the image output I / F 11 to the image output device 21 (this is referred to as output speed) and the data amount of the output image data.

  Therefore, the background removal unit 7 obtains the write time from the input speed and the data amount of the input image data, and obtains the read time from the output speed and the data amount of the output image data. The number of areas 101 is set to a number corresponding to the difference between the write time and the read time. Specifically, for example, data describing the difference between the write time and the read time and the number of line storage areas 101 required separately corresponding to this difference is held in the background removal unit 7. Thus, the background removal unit 7 may refer to this data to set the number of line storage areas 101 required separately to a number corresponding to the difference between the write time and the read time. Since the image processing apparatus 1 operates so that the difference between the input speed and the output speed is not too large in the first place, the number of line storage areas 101 required separately is at most three or four times the prescan data size. To fit in.

  In this way, the background removal unit 7 sets the number of separately required line storage areas 101 to “9”, for example, and finally sets the buffer size of the image data buffer 100 to a pre-scan for 7 lines. The size is determined to be 16 lines by adding 9 lines to the data size. Since the buffer size necessary for storing the image data of all lines of one page of the document is, for example, 70 lines, the buffer size (16 lines) of the image data buffer 100 determined by the background removal unit 7 is the document size. Compared to storing image data of all lines of one page, the size is about 1/4.

  The background removal unit 7 sends the buffer size of the image data buffer 100 determined in this way to the image data buffer control unit 5 as buffer configuration information Bd. It is assumed that the pre-scan data size is also written in the buffer configuration information Bd. Then, the image data buffer control unit 5 secures the image data buffer 100 having the buffer size described in the buffer configuration information Bd on the memory 13. At this time, of the 16 line storage areas 101, 7 line storage areas 101 from No. 0 to No. 6 have the pre-scan data size, and these 7 line storage areas 101 are used for detection of the background color. This is an area for storing the required image data for seven lines.

  The image data buffer control unit 5 uses the status bit Sb indicating the presence / absence of data for each line storage area 101, the write pointer Wp indicating the current write position, and the read pointer Rp indicating the current read position to generate an image data buffer. 100 is managed. The status bit Sb, the write pointer Wp, and the read pointer Rp are held inside the image data buffer control unit 5.

  If the status bit Sb is “0”, it indicates that image data is not stored in the line storage area 101, and if it is “1”, it indicates that image data is stored in the line storage area 101. . Since no image data is stored in the line storage area 101 in which the status bit Sb is “0”, the write DMA controller 4 can write the image data in this line storage area 101. On the other hand, the read DMA controller 6 cannot read image data from the line storage area 101. When the write DMA controller 4 writes image data to the line storage area 101 whose status bit Sb is “0”, the status bit of this line storage area 101 is updated from “0” to “1”.

  Since the image data is stored in the line storage area 101 whose status bit Sb is “1”, the write DMA controller 4 cannot write the image data in this line storage area 101. On the other hand, the read DMA controller 6 can read image data from the line storage area 101. When the write DMA controller 4 reads image data from the line storage area 101 whose status bit Sb is “1”, the status bit of this line storage area 101 is updated from “1” to “0”. The image data is deleted from.

  The image processing apparatus 1 writes 7 lines of image data necessary for background color detection to the 7 line storage areas 101 from No. 0 to No. 6 during the pre-scan process, and reads them. The image data for 7 lines must be stored until the main scanning process. For this reason, in the image processing apparatus 1, during pre-scan processing, even if image data is read from the line storage area 101 whose status bit Sb is “1”, the status bit is not erased from the line storage area 101. Is maintained as “1”.

  The write pointer Wp points to the line storage area 101 that the write DMA controller 4 should write next. The write pointer Wp moves to the next line storage area 101 when the write by the write DMA controller 4 to the indicated line storage area 101 is completed, and when writing to the final (15th) line storage area is completed. Return to the first (0th) line storage area 101. The write DMA controller 4 sends write information Wd indicating the line storage area 101 for which writing has been completed to the image data buffer control unit 5 every time writing to the line storage area 101 is completed. . Accordingly, the image data buffer control unit 5 can know from the write information Wd to which line storage area 101 of the image data buffer 100 the image data has been written.

  The read pointer Rp indicates the line storage area 101 to be read next by the read DMA controller 6. The read pointer Rp moves to the next line storage area 101 when reading from the indicated line storage area 101 by the read DMA controller 6 is completed, and when reading from the final (15th) line storage area is completed. Return to the first (0th) line storage area 101. Each time the read from the line storage area 101 is completed, the read DMA controller 6 sends read information Rd indicating the completed line storage area 101 to the image data buffer control unit 5. . Thereby, the image data buffer control unit 5 can know from the read information Rd to which line storage area 101 of the image data buffer 100 the image data has been read.

  The image data buffer control unit 5 updates the status bit Sb of each line storage area 101 of the image data buffer 100, the write pointer Wp, and the read pointer Rp based on the write information Wd and the read information Rd. The status bit Sb and the write pointer Wp are sent from the image data buffer control unit 5 to the write DMA controller 4 as memory management information Md. The write DMA controller 4 determines which line storage area 101 of the image data buffer 100 should be written based on the memory management information Md. The status bit Sb and the read pointer Rp are sent from the image data buffer control unit 5 to the read DMA controller 6 as memory management information Md. The read DMA controller 6 determines which line storage area 101 of the image data buffer 100 should be read based on the memory management information Md.

[2. Scan processing by image processing apparatus]
Next, a procedure of scan processing including pre-scan processing and main scan processing will be described with reference to the flowchart shown in FIG. This scanning process is a process performed by the CPU 14 in cooperation with each functional unit of the image processing apparatus 1, and the processes in steps SP1 to SP4 shown in FIG. 3 are the pre-scan process, and the processes in steps SP5 to SP7 are the main processes. Scan processing.

  When the scanning process is started, first, in step SP1, the background removal unit 7 determines the pre-scan data size and the buffer size of the image data buffer 100. Here, as an example, the background removal unit 7 determines the prescan data size as a size corresponding to 7 lines, and further increases the image data buffer size to a size corresponding to a total of 16 lines corresponding to the prescan data size + 9 lines. decide. Then, the background removal unit 7 sends buffer configuration information Bd indicating the prescan data size determined in this way and the buffer size of the image data buffer 100 to the image data buffer control unit 5. Based on this buffer configuration information Bd, the image data buffer control unit 5 secures an image data buffer 100 on the memory 13 having a prescan data size for 7 lines + a total of 16 lines for 9 lines. .

  FIG. 4A shows the image data buffer 100 and the value of the status bit Sb of each line storage area 101 and the positions of the write pointer Wp and the read pointer Rp at this time. At this time, since the image data has not yet been written to the image data buffer 100, the value of the status bit Sb of all the line storage areas 101 is “0”, and both the write pointer Wp and the read pointer Rp are at the head ( No. 0) line storage area 101 is indicated.

  In subsequent step SP2, input of image data from the image reading device 20 to the image input I / F 2 is started. At this time, image data obtained by scanning the document is input to the image input I / F 2 in order from the first line, and after correction processing is performed by the image processing unit 3, the image data buffer is written by the write DMA controller 4. 100 is written for each line in order from the first line. Further, the image data written in the image data buffer 100 in this way is read for each line in order from the first line by the read DMA controller 6 and sent to the background removal unit 7.

  Here, the writing of the image data from the 0th to the 6th line storage areas 101 of the image data buffer 100 is completed, and the reading of the image data from the 0th to the 2nd line storage areas 101 is completed to the 3rd. It is assumed that image data is being read from the line storage area 101. The reading of the image data is not started at the same time as the writing of the image data, but is started after the writing for several lines is completed.

  At this time, as shown in FIG. 4B, the write pointer Wp points to the 7th line storage area 101 next to the 6th write, and the read pointer Rp is the 3rd line storage area 101 being read. Pointing. In addition, during the pre-scan process, even if the written image data is read, it is not erased from the image data buffer 100. Therefore, lines 0 to 6 where writing has been completed regardless of the read position. The status bit Sb of the storage area 101 is “1”, and the status bits Sb from No. 7 to No. 15 are “0”. At this time, the image data buffer 100 has been written with the image data for the pre-scan data size obtained by scanning a part of the document.

  In subsequent step SP3, the image data buffer control unit 5 causes the write DMA controller 4 and the read DMA controller 6 to continue writing and reading the image data until reading of the image data corresponding to the pre-scan data size is completed.

  Assume that reading of image data is completed up to the sixth line storage area 101 of the image data buffer 100, and reading of image data corresponding to the prescan data size is completed. At this time, the image data for the prescan data size, that is, the image data for 7 lines necessary for detecting the background color is sent to the background removal unit 7. At this time, it is assumed that the writing of the image data has been completed up to, for example, the tenth line storage area 101.

  At this time, as shown in FIG. 4C, the write pointer Wp points to the eleventh line storage area 101 next to the tenth when the write is completed, and the read pointer Rp is the next 7th after the sixth when the read is completed. No. line storage area 101 is indicated. Further, the status bits Sb of the line storage areas 101 from No. 0 to No. 10 where the writing is completed are “1”, and the status bits Sb from No. 11 to No. 15 are “0”.

  In this way, when reading of the image data for the pre-scan data size is completed and image data for 7 lines necessary for detecting the background color is sent to the background removal unit 7, background removal is performed in step SP4. The unit 7 detects the background color of the document from the image data for the seven lines, and determines background removal processing parameters required when performing background removal processing in the main scanning processing based on the background color.

  As described above, in the pre-scan process from step SP1 to step SP4, the image data buffer 100 is stored without compressing the image data corresponding to the pre-scan data size (7 lines) obtained by scanning a part of the document. The background removal unit 7 determines the background removal processing parameters.

  In subsequent step SP5, as shown in FIG. 5A, the image data buffer control unit 5 returns the read pointer Rp to the first (0th) line storage area 101 to write to the image data buffer 100. The read image data is again read from the first line by the read DMA controller 6.

  On the other hand, the writing of the image data to the image data buffer 100 is continued from the pre-scan process. Actually, the image data from the first line to the eleventh line obtained by scanning the document during the pre-scan process has already been written in the 0th to 10th line storage areas 101. The image data from the 1st line to the last line is written in order from the 11th line storage area 101.

  In the main scanning process, unlike the pre-scan process, the image data written during the pre-scan process (that is, image data from the first line to the eleventh line obtained by scanning a part of one page of the document). And reading the remaining image data (that is, the image data from the 12th line to the last line obtained by scanning the remaining portion of one page of the original) while sequentially writing to the image data buffer 100. Therefore, when the image data is read from the line storage area 101 to which the image data has been written, the status bit of the line storage area 101 is updated from “1” to “0” and sequentially the line storage area 101 The image data stored in is deleted. The image data read from the image data buffer 100 by the read DMA controller 6 is sequentially sent to the background removal unit 7.

  Here, it is assumed that the writing of the image data from the 0th to the 12th line storage area 101 of the image data buffer 100 is completed and the reading of the image data from the 0th to the 1st line storage area 101 is completed.

  At this time, as shown in FIG. 5B, the write pointer Wp points to the 13th line storage area 101 next to the 12th when the writing is completed, and the read pointer Rp is the 2nd next to the 1st after the reading is completed. No. line storage area 101 is indicated. In addition, among the state bits Sb of the line storage areas 101 from No. 13 to No. 15 that have not been written and the line storage areas 101 from No. 0 to No. 12 where writing has been completed, No. 0 to No. 1 from which reading has been completed The status bits Sb of the line storage area 101 until “0” are “0”, and the status bits Sb from No. 2 to No. 12 that have not been read yet are “1”.

  After that, as shown in FIG. 5C, when the writing of the image data is completed up to the final (15th) line storage area 101 of the image data buffer 100, the image data buffer control unit 5 sets the write pointer Wp to the image pointer. Move to the first (0th) line storage area 101 of the data buffer 100. Although not shown, the image data buffer controller 5 also reads the image data buffer 100 when the read of the read pointer Rp is completed up to the last (15th) line storage area 101 of the image data buffer 100. The (0th) line storage area 101 is moved.

  As described above, the image data buffer control unit 5 causes the image data buffer 100 to function as a ring buffer, and the write DMA controller until reading of the image data of all lines obtained by scanning all parts of one page of the original is completed. 4 and the read DMA controller 6 continue to write and read image data.

  In subsequent step SP6, the background removal unit 7 performs background removal processing on the image data sequentially sent in units of lines based on the background removal processing parameters determined during the prescan processing. The image data after the background removal processing is sent to the image processing unit 8, subjected to predetermined image processing, and then sent to the write DMA controller 9. The write DMA controller 9 writes the image data sent from the image processing unit 8 to the image data buffer secured separately from the image data buffer 100 of the memory 13 for each line.

  In the next step SP7, the read DMA controller 10 reads the image data written to the memory 13 by the write DMA controller 9 line by line, sends it to the image output I / F 11, and via the image output I / F 11 The image is output to the image output device 21.

  Note that the processes of steps SP5, SP6, and SP7 are performed in parallel. In other words, while performing writing and reading of image data to / from the image data buffer 100 in units of lines in step SP5, background removal processing is performed in units of lines on the image data read from the image data buffer 100 in step SP6. Further, in step SP7, the image data after the background removal processing is output line by line via the memory 13. Then, the image processing apparatus 1 continues the processing from step SP5 to step SP7 until the output of the image data of all lines for one page of the document is completed.

  As described above, in the main scanning process from step SP5 to step SP7, the image data of all lines for one page of the document is buffered in the image data buffer 100 and sent to the background removal unit 7, and the background removal unit 7 removes the background. After background processing based on the processing parameters is performed, this is output to the image output device 21.

  In the above-described main scan processing, the image data after the background removal processing is written to an image data buffer different from the image data buffer 100 secured in the memory 13, but the buffer size of this image data buffer Is, for example, a size capable of storing image data of all lines (for example, 70 lines) for one page of a document. This is because, for example, when output fails, the image data can be read again from the image data buffer and re-outputted.

[3. Summary and Effect]
As described above, when the image processing apparatus 1 starts the pre-scan process, first, the buffer size of the image data buffer 100 for storing the image data is set to a part of the document required for detecting the background color of the document. Is set to a size that can store image data obtained by scanning.

  Then, the image processing apparatus 1 writes the image data obtained by scanning a part of the document input from the image reading apparatus 20 to the image data buffer 100, and reads the image data while remaining in the image data buffer 100. The image is sent to the background removal unit 7 to detect the background color of the document based on the image data and set the background removal processing parameter.

  Thereafter, the image processing apparatus 1 starts a main scan. At this time, the image processing apparatus 1 reads the image data for several lines written at the time of the pre-scan processing stored in the image data buffer 100 for each line from the first line and sends it to the background removal unit 7. In order to secure a free space in the image data buffer 100, the read image data is deleted from the image data buffer 100. Furthermore, the image processing apparatus 1 writes the image data of the remaining lines following the lines written during the prescan process, which are input from the image reading apparatus 20, into the empty area of the image data buffer 100 for each line, and write The read image data is read from the image data buffer 100 and sent to the background removal unit 7.

  Then, the image processing apparatus 1 performs a background removal process using the background removal process parameters set in the prescan process on the image data sent to the background removal unit 7, and obtains the image data after the background removal process. The image is output to the image output device 21.

  As described above, in the image processing apparatus 1, the buffer size of the image data buffer 100 can be suppressed to a size necessary for the pre-scan process, that is, a size capable of storing image data obtained by scanning a part of a document. The buffer size of the image data buffer 100 can be reduced as compared with a case where a size capable of storing image data obtained by scanning the entire part of the document is secured.

  In addition, in the image processing apparatus 1, during the main scanning process, the image data obtained by scanning all parts of the document is written to the image data buffer 100 line by line, and the image data of the previously written line is sequentially read from the image data buffer 100. By reading and erasing from the image data buffer 100, the image data buffer 100 having a smaller capacity than the size capable of storing the image data of all lines obtained by scanning all parts of the document is used. The main scanning process can be performed by buffering the image data obtained by scanning the entire part without compressing the image data.

  Thus, in the image processing apparatus 1, the buffer size of the image data buffer 100 is significantly reduced as compared with the case where the image data buffer 100 having a size capable of storing the image data obtained by scanning all parts of the document is prepared. Since this small-capacity image data buffer 100 can be used to buffer the image data obtained by scanning the entire portion of the document without compression and send it to the background removal unit 7. Image quality deterioration of image data can be prevented while reducing the capacity of an image data buffer for storing data.

  Note that the fact that the buffer size of the image data buffer 100 can be reduced means that the capacity of the memory 13 used as the image data buffer 100 can also be reduced.

  In addition, in the image processing apparatus 1, the image data written to the image data buffer 100 during the prescan process (that is, image data necessary for the prescan process) is erased even if read from the image data buffer 100 during the prescan process. Without re-reading, this read process was re-read.

  In this way, for example, during the main scan process, the image data of the line written during the pre-scan process is read from the image data buffer 100, and the image data from the image data of the line following the line written during the pre-scan process is read out. Since the data can be written to the buffer 100, the time required for the main scanning process can be shortened in the main scanning process as compared with the case where the image data of all lines is written to the image data buffer 100 from the first line again and read.

[4. Other Embodiments]
[4-1. Other Embodiment 1]
In the above-described embodiment, the image data subjected to the background removal processing by the background removal unit 7 and the image processing by the image processing unit 8 is output to the image output device 21 such as a printer via the image output I / F 11. I did it. Not limited to this, for example, an external storage device such as a USB (Universal Sirial Bus) memory is connected to the image output I / F 11 of the image processing device 1 so that the background removal processing and the image processing unit are performed by the background removal unit 7. The image data that has undergone the image processing according to 8 may be output and stored in the external storage device via the image output I / F 11. Moreover, you may make it output to apparatuses other than these.

  Furthermore, in the above-described embodiment, the image data subjected to the image processing by the image processing unit 8 is buffered and output to the image data buffer secured on the memory 13 separately from the image data buffer 100. However, the present invention is not limited to this. For example, the image data that has been subjected to image processing by the image processing unit 8 may be output to the image output device 21 via the image output I / F 11 as it is. Further, an external storage device is connected to the image output I / F 11 so that the image data subjected to the image processing by the image processing unit 8 is directly output to the external storage device via the image output I / F 11 and stored. You may do it. Further, it may be output as it is to other devices.

[4-2. Other Embodiment 2]
In the above-described embodiment, the image data obtained by scanning from the document is written to the image data buffer 100 for each line and read from the image data buffer 100 for each line. However, the present invention is not limited to this, and image data may be written and read for each of a plurality of lines. Further, the unit of writing and the unit of reading may be changed such that writing is performed for each line and reading is performed for every two lines. In this case as well, the background removal unit 7 may determine the buffer size of the image data buffer 100 so that the read position for the image data buffer 100 does not catch up with the write position.

[4-3. Other Embodiment 3]
Further, in the above-described embodiment, the background removal process is performed in the main scan process, and the background color is detected as a preliminary evaluation necessary for performing the background removal process in the pre-scan process. The present invention is not limited to this, and image processing and preliminary evaluation different from image processing related to background removal may be performed in the main scan processing and the prescan processing.

  As described above, even when image processing and preliminary evaluation different from image processing related to background removal are performed in the main scan processing and the prescan processing, the number of lines required for the prescan processing is the same as in the above-described embodiment. The buffer size of the image data buffer 100 may be set to a size that can store data. Note that the pre-scan process in this case does not require image data obtained by scanning the entire part of the document, but requires image data obtained by scanning a part of the document. To do.

[4-4. Other Embodiment 4]
Further, in the above-described embodiment, the image data buffer 100 accessed by the write DMA controller 4 and the read DMA controller 6 and the image data buffer accessed by the write DMA controller 9 and the read DMA controller 10 are stored on one memory 13. However, the present invention is not limited to this. For example, the image processing apparatus 1 is provided with a memory different from the memory 13, and the memory 13 is an image data buffer accessed by the write DMA controller 4 and the read DMA controller 6. The memory provided separately as 100 may be used as an image data buffer accessed by the write DMA controller 9 and the read DMA controller 10.

[4-5. Other Embodiment 5]
Furthermore, in the above-described embodiment, image data obtained by scanning a document by the image reading device 20 is input to the image processing device 1, and the image processing device 1 performs a series of image processing on the image data. Then, the image is output to the image output device 21. For example, the image processing apparatus 1 may be provided with the function of the image reading apparatus 20, and the image processing apparatus 1 can be applied to, for example, a scanner. Further, the image processing apparatus 1 may be provided with the function of the image output apparatus 21. Such an image processing apparatus 1 can be applied to, for example, a printer. Further, the image processing apparatus 1 may be provided with both the function of the image reading apparatus 20 and the function of the image output apparatus 21. Such an image processing apparatus 1 is provided in, for example, an MFP (Multi Function Product). Applicable.

[4-6. Other Embodiment 6]
Further, in the above-described embodiment, the buffer size of the image data buffer accessed by the write DMA controller 9 and the read DMA controller 10 is set to a size that can store the image data of all lines for one page of the document. Not limited to this, the image data buffer may function as a first-in first-out ring buffer in the same manner as the image data buffer 100, so that the size of the image data for one page of the original can be made smaller than the size capable of storing the image data. .

[4-7. Other Embodiment 7]
Further, in the above-described embodiment, the buffer size of the image data buffer 100 is added to the pre-scan data size and the buffer size necessary for absorbing the difference between the read time and the write time to the image data buffer 100. The size is not limited to this. For example, when there is almost no difference between the read time and the write time to the image data buffer 100, the buffer size of the image data buffer 100 is made equal to the prescan data size. Also good.

[4-8. Other Embodiment 8]
Furthermore, in the above-described embodiment, the background removal unit 7 is used as a specific example of the image processing unit that performs the pre-scan process and the main scan process. For example, an image processing unit that performs prescan processing and main scan processing different from the background removal unit 7 may be used as long as it has a function of performing prescan processing and main scan processing. .

  Further, in the above-described embodiment, the image data buffer control unit 5, the write DMA controller 4, and the read DMA controller 6 are used as specific examples of the control unit that controls writing and reading of image data to the image data buffer 100. I made it. However, the present invention is not limited to this, and a control unit different from these may be used as long as it has a function of controlling writing to and reading from the image data buffer 100. The write DMA controller 4 and the read DMA controller 6 may be incorporated.

[4-9. Other Embodiment 9]
Furthermore, the present invention is not limited to the above-described embodiment and other embodiments. That is, the scope of application of the present invention extends to embodiments in which some or all of the above-described embodiments and other embodiments are arbitrarily combined, and embodiments in which some are extracted.

  The present invention can be widely used in image processing apparatuses that perform image processing by buffering image data obtained by scanning a document.

  DESCRIPTION OF SYMBOLS 1 ... Image processing device, 3, 8 ... Image processing part, 4, 9 ... Write DMA controller, 6, 10 ... Read DMA controller, 7 ... Background removal part, 13 ... Memory, 14 ... CPU , 20... Image reading device, 21... Image output device, 100... Image data buffer, 101.

Claims (6)

An image for performing a pre-scan process using image data obtained by scanning a part of a document and a main scan process using image data obtained by scanning all parts of the document based on the result of the pre-scan process. A processing unit;
A buffer having a capacity capable of storing image data obtained by scanning a part of a document required for pre-scan processing;
A controller that controls writing and reading of image data to and from the buffer in units of lines of the image data,
The controller is
During the pre-scan process, the image data obtained by scanning a part of the document is written and stored in the buffer, and the image data stored in the buffer is read from the buffer without being erased and sent to the image processing unit. Send,
During the main scan process, the image data stored in the buffer during the pre-scan process is read from the buffer in line order and sent to the image processing unit and erased from the buffer to secure a free space in the buffer; While writing the image data obtained by scanning the remaining portion of the document in the buffer empty area in line order, the image data of the previously written line is read from the buffer in order and sent to the image processing unit. An image processing apparatus characterized by being erased from the buffer. The capacity of the buffer is
Capacity required to absorb the difference between the time required to write image data to the buffer and the time required to read image data from the buffer to the data size of the image data required for the prescan process The image processing apparatus according to claim 1, wherein the image processing apparatus has a size obtained by adding The controller is
The pointer indicating the reading position of the image data in the buffer is updated each time the image data is read from the buffer line by line, and when the reading of the image data stored in the buffer is completed in the pre-scan process, the pointer The image processing apparatus according to claim 1, wherein the position is returned to a position indicating the first line of the image data stored in the buffer. The image processing unit
Determining the capacity of the buffer based on the image processing performed in the pre-scan process, the difference between the time required to write image data to the buffer and the time required to read image data from the buffer,
The controller is
The image processing apparatus according to claim 1, wherein the buffer having a capacity determined by the image processing unit is secured in a predetermined memory. For the pre-scan process,
The image processing apparatus according to claim 1, further comprising image processing for performing preliminary evaluation of a document for performing the main scanning processing. The main scanning process includes a background color removal process for removing the background color of the document,
The image processing apparatus according to claim 5, wherein the prescan process detects a background color of a document for performing the background color removal process.

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