JP2007158902A - Image processor and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor which can always compress again with high compression rate even after compressed multilayer image data are extended and editing is given, and to provide an image processing method. <P>SOLUTION: After extending and editing the compressed multilayer image data which consist of a layer of base image and at least one-layer of foreground image (E), stopgap processing is performed so that a region in the edited multilayer image data which corresponds to the foreground image of the base image is filled with picture data in which compression rate becomes high when compressing of the whole picture data is performed again which data shows the base image (F), the edited multilayer image data which include the base image to which the stopgap processing has been performed is compressed for each layer, and they are saved in a storage means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method for editing image data having a compressed multilayer structure including a background image layer and at least one non-underground image layer.

  In a multifunction device equipped with multiple functions such as a scanner and printer, when handling images read by a scanner or images input from an external computer inside the multifunction device, the data transfer speed can be improved, In order to reduce the capacity, the image is compressed and transferred and stored.

  In general, an irreversible compression method such as Joint Photographic Experts Group Format (JPEG) is widely known and frequently used as an image compression method. The lossy compression method is a very suitable method for compressing a natural image such as a photograph, and achieves both a high compression rate and high image quality. However, if the compression ratio is prioritized in this compression method, the image quality deteriorates. Therefore, in the case of a character image, there is a problem that the reproducibility of the character is remarkably lowered when the compressed image is decompressed and output. .

  Therefore, conventionally, a method has been employed in which an original image is divided into a foreground image layer such as characters and a background image layer such as a background, and compressed by a compression method suitable for each layer. In general, the background image cannot be completely restored even if the compressed data is decompressed, but is compressed by an irreversible compression method that can be compressed at a high compression rate, and the foreground image is compressed at a low compression rate. In many cases, compression is performed by a reversible compression method that can be completely restored (see, for example, Patent Document 1).

  Note that when the image is separated into multiple layers, the area corresponding to the foreground image in the background image is a state in which the foreground image is removed, and no significant image data remains. The background image layer is compressed after the hole filling process is completed (see, for example, Patent Documents 2 and 3). At this time, hole filling processing is performed so as to obtain a high compression rate in consideration of the characteristics (for example, direction dependency) of the compression method when compressing the background image.

For example, in the case of a compression method using a predictive coding method, the value of the pixel of interest to be coded from the already coded pixels is used by utilizing the fact that the correlation between adjacent pixels (neighboring pixels) is high. And the difference between the predicted value and the actual pixel value is encoded. Therefore, in order to obtain a high compression rate by such encoding, it is necessary to reduce the amount of change between adjacent pixels. Therefore, for example, when encoding is performed from the left pixel to the right direction, a filling process is performed so as to fill the region with the pixel value on the left side of the region.
JP 2003-219187 A JP 2003-244447 A JP 2003-271979 A

  In many cases, after the image is compressed and stored, the image is read and expanded again, and editing processing such as rotation processing for rotating the image and additional processing for adding characters or the like (foreground image) is often performed. After the editing process, the area is compressed and saved again. However, the area that has been subjected to the hole filling process is an area that has been filled with pixel values (images) so that a high compression rate can be obtained in the state before the editing process. Even in the state after processing, a high compression rate is not always obtained. Depending on the content of the editing process, the compression ratio of the background image layer may be significantly reduced.

  In the techniques described in Patent Documents 1 to 3, no consideration is given to the problem of a reduction in compression rate after editing processing.

  The present invention has been made in order to solve the above-described problem. Even when the compressed multilayer image data is expanded and edited, the image processing can always be compressed again at a high compression rate. An object is to provide an apparatus and an image processing method.

  In order to achieve the above object, an image processing apparatus according to the present invention includes an editing unit that decompresses and edits compressed multilayered image data including a background image layer and at least one non-underground image layer. The region corresponding to the non-background image of the background image in the edited multi-layered image data is filled with image data that has a high compression ratio when the entire image data representing the background image is compressed again. Processing means for performing image processing, and compression storage means for compressing the image data of the edited multilayer structure including the image-processed background image for each layer and storing the compressed image data in a storage means. Yes.

  Even if the image data has a multilayer structure in which the area corresponding to the non-background image of the background image is processed so that a high compression ratio can be obtained in the state before the editing process, the image processing is high even after the editing process. It is not always effective in realizing the compression rate.

  In the present invention, after decompressing and editing image data having a compressed multilayer structure composed of a background image layer and a non-background image layer, an area corresponding to the non-background image of the background image Image processing is performed so that the entire image data shown is filled with image data that increases the compression rate when the image data is compressed again, and the multilayered image data including the image-processed base image is compressed and stored for each layer. Thus, even after the editing process, it is always possible to compress again at a high compression rate.

  The processing means performs the image processing when the editing content performed by the editing means is at least one of rotation processing for rotating the multilayer image and addition processing for adding the non-background image. be able to.

  The image processing method of the present invention also includes an editing step of expanding and editing image data having a compressed multilayer structure composed of a background image layer and at least one non-underground image layer, and the edited multilayer image Processing that performs image processing so that an area corresponding to the non-background image of the background image in the image data of the structure is filled with image data that has a high compression ratio when the entire image data representing the background image is compressed again And a compressing and storing step of compressing the edited multi-layered image data including the image-processed base image for each layer and storing the compressed image data in a storage means.

  Since the image processing method of the present invention also operates in the same manner as the image processing apparatus of the present invention, it can always be compressed again at a high compression rate even after editing processing.

  As described above, according to the present invention, even when editing processing is performed on compressed image data having a multilayer structure, it is possible to always perform compression again at a high compression rate.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of a network system 1 including a multifunction machine 10 as an image processing apparatus.

  The network system 1 includes a plurality of multifunction peripherals 10 having both a print function and a scanner function, and a personal computer (hereinafter referred to as a PC) 30. The multifunction peripheral 10 and the PC 30 are mutually connected via a network 5 such as a LAN. It is connected to the.

  FIG. 2 is a block diagram illustrating a main configuration of the multifunction machine 10.

  The multifunction machine 10 records an electrostatic latent image on a photoconductor based on the input image data and a scanner unit 11 that reads an image recorded on a document, and the electrostatic latent image is printed using color toner or monochrome toner. A hard disk drive (HDD) that stores the developed image data, image data of the original image read by the scanner unit 11, image data received via the network 5, and the like. 15 is provided. The printer unit 12 may output an image by an ink jet method.

  The HDD 15 stores image data and the like. The image data is stored in a state of a multilayer structure including a foreground image layer such as a character image and a background image layer such as a background. The foreground image layer may be a single layer or a plurality of layers. For example, when there are a plurality of character strings, the character strings can be stored in a plurality of layers by separating the layers for each character string.

  In addition, the image data is usually compressed for each layer by a compression method according to the attribute of each layer before being stored in the HDD 15. For example, a foreground image layer such as a character image is compressed by a lossless compression method, and a background image layer such as a background image is compressed by an irreversible compression method. The compressed image data stored in the HDD 15 is appropriately read out and transferred to the printer unit 12 and the like via the bus. During this transfer, the compressed image data is expanded and supplied to the printer unit 12 and the like.

  Further, the multifunction machine 10 includes a layer separation unit 20, a hole filling unit 22, and an editing unit 24.

  The layer separation unit 20 receives image data of a document image read by the scanner unit 11 and image data output from the PC 30. The layer separation unit 20 separates the input image data into a foreground image layer such as a character image and a background image layer such as a background. This separation can be performed using known techniques. For example, it is possible to use a technique based on edge detection that detects discontinuous portions of image features, and obtains and separates regions by closed edges, or obtains and separates a uniform connected pixel set of features as regions. A technique by division may be used. Specifically, for example, as shown in FIG. 4, the image data (A) of the original image is separated into a layer (B) of a foreground image such as a character image and a layer (C) of a background image such as a background image. To do.

  The layer separation unit 20 outputs the layered image data of the multilayer structure to the hole filling unit 22. Note that if the image data input from the PC 30 is already multi-layer image data, the layer separation unit 20 outputs the image data as it is without performing layer separation processing.

  The hole filling unit 22 performs hole filling processing on the layer of the base image of the image data having the multilayer structure input from the layer separation unit 20. Since the area corresponding to the foreground image in the background image is in a state in which the foreground image is removed, no significant image data remains, and therefore, normally, a filling process for filling the area with the color of the surrounding pixels is performed. Here, hole filling processing is performed so as to obtain a high compression rate in consideration of the characteristics (for example, direction dependency) of the compression method when compressing the image data indicating the background image.

  For example, in the case of a compression method using a predictive coding method, the value of the pixel of interest to be coded from the already coded pixels is used by utilizing the fact that the correlation between adjacent pixels (neighboring pixels) is high. And the difference between the predicted value and the actual pixel value is encoded. Therefore, in order to obtain a high compression rate by such encoding, the amount of change between adjacent pixels may be reduced. When encoding from the left pixel in the right direction, as shown in FIG. 4D, a filling process is performed to fill the area with the pixel value on the left side of the area to be filled in the background image. .

  The hole filling unit 22 may receive multi-layered image data after editing processing from the editing unit 24. In this case, the filling process is performed again on the base image layer of the multi-layered image data after the editing process input from the editing unit 24 as necessary. This process will be described later.

  The editing unit 24 performs editing processing on the image data having a multilayer structure. Specifically, in accordance with an instruction from the user input via a display panel (not shown), the image writing / reading unit 26 described later reads out and decompresses the multi-layered image data from the HDD 15 and performs the decompression. The processed image data is subjected to a rotation process for rotating the image, an additional process for adding characters or the like (foreground image), an editing process such as a color correction process for correcting the color tone, and the like. The image data after the editing process is output to the hole filling unit 22.

  The image writing / reading unit 26 writes / reads image data to / from the HDD 15. The image writing / reading unit 26 includes a compression unit 26a and an expansion unit 26b. The compression unit 26a compresses the multilayered image data output from the hole filling unit 22 for each layer by a compression method according to the attribute of each layer. Here, as described above, the foreground image layer such as the character image is compressed by the lossless compression method, and the background image layer such as the background image is compressed by the lossy compression method. The image data compressed by the compression unit 26a is stored in the HDD 15. The decompressing unit 26b decompresses the multi-layered image data read from the HDD 15 by the decompressing method corresponding to the compression method for each layer, and outputs the decompressed data to the editing unit 24 and the printer unit 12.

  Next, a filling process performed by the filling unit 22 of the multifunction machine 10 according to the present embodiment will be described.

  FIG. 3 is a flowchart showing the flow of the hole filling process executed by the hole filling unit 22.

  In step 100, it is determined whether image data has been input. If it is determined that the image data has been input, the process proceeds to step 102 to determine whether the input source of the input image data is the layer separation unit 20 or the editing unit 24.

  When it is determined in step 102 that the input source is the layer separation unit 20, image data is newly input from the scanner unit 11 or the PC 30, and the layer of the foreground image such as a character image and the background are input by the layer separation unit 20. In step 106, as shown in FIG. 4D, an area corresponding to the foreground image in the background image is separated from the background image layer (or already separated at the time of input). Considering the characteristics (for example, direction dependency) of the compression method when compressing the image data of the background image, the image data of the background image is subjected to hole filling processing so that the image is filled with a high compression rate.

  If it is determined in step 102 that the input source is the editing unit 24, it is determined in step 104 whether or not the hole filling process needs to be executed again.

  Specifically, the determination is made from the content of the editing process performed on the image data input by the editing unit 24. If the editing process is a rotation process for rotating the image or an additional process for adding characters or the like (foreground image), it is determined that the hole filling process is executed again, and other editing processes, for example, the color tone is corrected. In the case of color correction processing or the like, it is determined that it is not necessary to execute hole filling processing. This is due to the following reason.

  The editing unit 24 edits the image data that has been already filled. The area corresponding to the foreground image of the background image is filled with pixel values (images) that can obtain a high compression rate according to the characteristics of the compression method when compressing the layer of the background image before the editing process. Therefore, at the time when an affirmative determination is made in step 104 (the state after editing processing such as rotation processing), a high compression rate may not be obtained during compression.

  For example, as described above, in the case of a direction-dependent compression method in which predictive encoding is performed from the left pixel to the right side, as shown in FIG. 4D, the pixel value on the left side of the area to be filled is used. A hole filling process for filling a region to be filled is performed. However, if the editing unit 24 performs a rotation process that rotates the image by 90 degrees, as shown in FIG. 4E, the image that fills the area to be filled becomes an image that is contrary to the direction dependency of the compression method. , The compression rate decreases. Therefore, it is determined that the hole filling process needs to be executed again.

  Also, when an additional process for adding a foreground image such as a character is performed, it is determined that it is necessary to perform a hole filling process on a region corresponding to the added foreground image of the background image. A pixel value that, when a foreground image is added, does not leave the area corresponding to the added foreground image in the background image as it is, but can compress the area at a higher compression rate when compressing the background image By replacing with, a higher compression ratio can be realized. Therefore, also in this case, it is determined that it is necessary to execute the hole filling process.

  In the case of an editing process that hardly affects the compression such as a color correction process, it is determined that it is not necessary to execute the hole filling process.

  When an affirmative determination is made at step 104, the routine proceeds to step 106, where hole filling processing is executed.

  FIG. 4F illustrates a state in which the hole filling process is performed again on the base image that has been in the state of FIG. 4E after the editing process. As shown in the figure, the area to be filled in the background image is subjected to a filling process in which the area to be filled is filled with the pixel values on the left side after the rotation process. Thereby, the compression rate when the whole image data which shows a base image is compressed by the compression part 26a can be made high.

  After the process of step 106 or after a negative determination is made in step 104, the process proceeds to step 108.

  In step 108, the image data of the multilayer structure after the hole filling process or the image data of the multilayer structure that has not been subjected to the hole filling process because the hole filling process is not necessary (as input to the hole filling unit 22) is written and read out. To the unit 26. The compression unit 26 a of the image writing / reading unit 26 compresses the multilayered image data for each layer and stores the compressed data in the HDD 15.

  As described above, after decompressing and editing the compressed multi-layered image data composed of the background image layer and the foreground image layer, the area corresponding to the foreground image of the background image The entire image data shown is filled with image data that has a high compression ratio when it is compressed again, and the multilayered image data including the underlying image subjected to the filling processing is compressed for each layer and stored in the HDD 15. Since the image data having the multilayer structure after the compression processing is decompressed and edited, the image data can always be compressed again at a high compression rate.

  Thereby, the storage capacity of the HDD 15 can be reduced, and data can be transferred to the printer unit 12 or the like at high speed.

  In the above embodiment, the multifunction machine 10 has been described as an example. However, an image processing apparatus that does not include a scanner or a printer function may be used.

It is a figure which shows the schematic structure of the network system which concerns on this Embodiment. 1 is a block diagram illustrating a main configuration of a multifunction machine. It is a flowchart which shows the flow of the hole-filling process performed in a hole-filling part. It is explanatory drawing explaining a hole-filling process.

Explanation of symbols

10 MFP 11 Scanner Unit 12 Printer Unit 15 HDD
20 layer separation unit 22 hole filling unit 24 editing unit 26 image writing / reading unit 26a compression unit 26b expansion unit

Claims (3)

Editing means for decompressing and editing compressed multilayered image data composed of a background image layer and at least one non-underground image layer;
An area corresponding to the non-background image of the background image in the edited multilayered image data is filled with image data that has a high compression ratio when the entire image data representing the background image is compressed again. Processing means for image processing;
Compression storage means for compressing the image data of the edited multilayer structure including the image-processed background image for each layer and storing the compressed image data in a storage means;
An image processing apparatus.   The processing unit performs the image processing when the editing content performed by the editing unit is at least one of a rotation process of rotating the multilayer image and an additional process of adding the non-background image. The image processing apparatus according to 1. An editing step for decompressing and editing the compressed multi-layered image data composed of a background image layer and at least one non-underground image layer;
An area corresponding to the non-background image of the background image in the edited multilayered image data is filled with image data that has a high compression ratio when the entire image data representing the background image is compressed again. Processing steps for image processing;
A compression storing step of compressing the image data of the edited multilayer structure including the image-processed base image for each layer and storing the compressed image data in a storage unit;
An image processing method including: