JP2013042449A - Image compression method, image decompression method, and image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image quality deterioration in at least one of a completely transparent area and a completely opaque area during decompression reproduction even if image information including transparency information is irreversibly compressed including the transparency information.
Rectangle image data, which is a processing unit, is input (step S1). Next, a completely transparent area and a completely opaque area are extracted for the input rectangular pixel data (step S2). Next, the rectangular image data is subjected to irreversible compression processing including transparency information, that is, an α value (step S3). Here, as a lossy compression algorithm for still images, for example, JPEG (Joint Photographic Experts Group) and JPEG2000 are typical. Then, the compressed image data obtained in step S3 and the area data obtained in step S2 are output together (step S4).
[Selection] Figure 1

Description

  The present invention relates to an image compression method, an image decompression method, and an image processing apparatus for an image displayed on a game machine or the like, and in particular, an image compression method and an image whose image quality is not relatively lowered even by high compression by irreversible compression. The present invention relates to a decompression method and an image processing apparatus.

  A gaming machine such as a pachinko machine or a game machine changes to an image display device (typically, a liquid crystal display (LCD)) as a still image or a high speed as the game progresses. Displaying video is now common sense.

  Here, for example, for a color image represented by a bitmap, each pixel typically has a so-called R (red), G (green), and B (blue) value.

  In addition, various large and small images are displayed on a single display device, but recently, even when images are superimposed, it is possible to display such that the image can be seen through the image. ing. At this time, in addition to the R, G, and B information, each pixel has information related to transparency (for example, referred to as α).

  The transparency α is defined by, for example, 0 to 255. In this case, the case where α = 0 is referred to as “completely transparent”, the case where α = 255 is referred to as “completely opaque”, and otherwise, that is, 1 ≦ The case where α ≦ 254 is referred to as “translucent”. However, the value of 0 to 255 is an example, and can be arbitrarily set according to the definition. For example, Patent Literature 1 discloses an encoding device and a decoding device that process image data including such transparency information.

  Incidentally, in order to realize efficient storage and transmission of image information, it is common to perform processing for compressing image information in view of the redundancy. Here, the image compression method has no loss due to the compression process, and there is a lossless compression method that can completely restore the same image as the original image, and there is a loss due to the compression process, which represents the same image as the original image. However, there is a “lossy compression method” that is different from the original image. The “lossless compression method” has an advantage that the same image as the original image can be completely restored, but the compression rate is low. On the other hand, the “lossy compression method” cannot completely restore the same image as the original image, but has an advantage of a higher compression rate than the “lossless compression method”. Therefore, the “reversible compression method” and the “irreversible compression method” are selected and used according to necessity or purpose.

  On the other hand, in the compression coding processing of moving images, it is established as one of standardization methods to perform so-called “motion prediction” and “motion compensation”. For example, Patent Document 2 discloses such a technique.

JP 2000-324501 A JP 2001-112009 A

  By the way, when image information including a pixel to which “completely transparent” is assigned is compressed by an irreversible compression method, after decompression, the pixel is completely transparent in the vicinity of the boundary between the completely transparent region and the semitransparent or completely opaque region. There arises a problem that the image quality deteriorates due to coloration. In addition, even in the “completely opaque” region, there is a problem that after expansion, there is a portion that is not completely opaque but lightly transparent.

  The present invention has been made for the above-mentioned circumstances, and the object of the present invention is to completely complete image information including transparency information at the time of decompression and reproduction even if it is irreversibly compressed including the transparency information. An object of the present invention is to provide an image compression method, an image expansion method, and an image processing apparatus in which image quality does not deteriorate in at least one of a transparent region and a completely opaque region.

  In order to achieve the above object, an image compression method of the present invention is a method for compressing image information including transparency information, and is based on the image information including the transparency information. Region information of a region including at least one of the completely transparent region and the completely opaque region, the image information including the transparency information is irreversibly compressed. The gist is to output together. Preferably, both the completely transparent area and the completely opaque area are extracted, and the area data of the area including them is also output.

  In addition, the image information is an image related to a moving image, and the gist is that motion compensation processing is performed in the lossy compression processing. Typically, this moving image is an animated image.

  The gist of the invention is that the region data is also compressed and output.

  In order to achieve the above object, the image decompression method of the present invention includes compressed image information obtained by irreversible compression of an original image including transparency information, a completely transparent region and a completely opaque image of the original image. Region data including at least one of the regions, the decompression processing corresponding to the lossy compression is performed on the compressed image information, and the region indicated by the region data in the decompressed image information by decompression The gist of the present invention is to perform mask processing with information relating to at least one of completely transparent and completely opaque.

  Preferably, the region data of the region including both the completely transparent region and the completely opaque region of the original image is input, and the region indicated by the region data of the restored image information by decompression is completely transparent and completely opaque. Mask processing is performed using information relating to both of the above.

  The area data is also input as compressed data. After decompressing the compressed area data to restore the area data, the mask process is performed.

  In order to achieve the above object, the image processing apparatus according to the present invention includes compressed image information obtained by irreversible compression of an original image including transparency information, a completely transparent region of the original image, and a completely opaque image. A storage unit that stores region data including a region including at least one of the regions, and the compressed image information is input from the storage unit based on an external command, and decompression processing corresponding to the lossy compression is performed. A decoder, and a mask processing unit that inputs the region data from the storage unit and performs mask processing with information relating to at least one of completely transparent and completely opaque in the region indicated by the region data of decompressed image information by decompression; The gist is to provide.

  According to the image compression method, the image expansion method, and the image processing apparatus of the present invention, even if the image information including the transparency information is irreversibly compressed including the transparency information, the completely transparent region or the Image quality does not deteriorate in imperfectly transparent areas.

It is a flowchart which shows the process sequence of one Embodiment of the image compression method of this invention. It is a figure for demonstrating the process sequence of one Embodiment of the image compression method of this invention. It is a flowchart which shows the process sequence of one Embodiment of the image expansion | extension method of this invention. 1 is a block diagram illustrating a schematic configuration of an image processing apparatus in which an embodiment of an image expansion method of the present invention is realized. 1 is a block diagram illustrating a schematic configuration of an image processing apparatus in which an embodiment of an image compression method of the present invention is realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart showing a processing procedure of an embodiment of an image compression method of the present invention. The processing shown in the figure can be realized by a so-called general-purpose personal computer. FIG. 2 is a diagram for explaining the processing procedure of an embodiment of the image compression method of the present invention.

  Therefore, first, rectangular image data (for example, 1024 × 768 pixels) as a processing unit as shown in FIG. 2A is input from the entire stored image data (step S1). Next, a completely transparent area and a completely opaque area are extracted for the input rectangular pixel data (step S2). FIG. 2B shows a case where a completely transparent area CTA is extracted from the image data as the specific example shown in FIG. 2A, and FIG. 2C shows a completely opaque area COA extracted. Shows the case.

  Next, the rectangular image data is subjected to irreversible compression processing including transparency information, that is, an α value (step S3). Here, as a lossy compression algorithm for a still image, for example, JPEG (Joint Photographic Experts Group) and JPEG2000 are typical, but not limited thereto.

  Then, the compressed image data obtained in step S3 and the area data obtained in step S2 are output together (step S4). The output data is stored in a CGROM (Character Generator Read Only Memory) of an image processing apparatus that performs drawing processing by decompressing compressed image data, for example.

  In the above description, in step S2, the completely opaque area data is extracted together with the completely transparent area data. However, the image quality deterioration between the completely opaque area and the translucent area is a problem. If not, only the completely transparent area data may be extracted. In the above description, the area data is output as it is, but the compression encoding process may be performed on the area data. However, in this case, it is a reversible compression process.

  Next, decompression processing in the image processing apparatus that decompresses the compressed image data obtained as described above and performs drawing processing will be described. FIG. 3 is a flowchart showing the procedure of the image decompression method in the image processing apparatus. FIG. 4 is a block diagram showing a schematic configuration of an image processing apparatus in which an embodiment of the image decompression method of the present invention is realized.

  4 includes a central processing unit (hereinafter referred to as a CPU (Central Processing Unit)) 1, an image display processor (hereinafter referred to as a VDP (Video Display Processor)) 2, a program ROM 3, A CGROM 4 and a display unit 5 are provided. The VDP 2 includes at least a decoder 21, a mask processing unit 22, and a drawing circuit 23. Here, as described above, the CGROM 4 stores compressed image data relating to the cut-out rectangle compressed by the above-described method, and completely transparent / opaque region data corresponding to the cut-out rectangle data.

  Therefore, first, the decoder 21 in the image processing apparatus inputs compressed image data relating to the cut-out rectangle from the CGROM 4 based on a command from the CPU 1 (step S11), and decompresses it (step S12). The expanded image data is sent to the mask processing unit 22. On the other hand, the mask processing unit 22 inputs completely transparent / opaque area data corresponding to the input decompressed image data from the CGROM 4 (step S13). Then, the mask processing unit 22 performs a mask process on the input decompressed image data based on the input completely transparent / opaque region data (step S14). For example, for a completely transparent area, mask processing is performed on the decompressed image data using the area data shown in FIG. 2B as mask data. For a completely transparent area, it is forcibly completely transparent, that is, α = 0. On the other hand, for an area designated as a completely opaque area, the expanded image data is masked using the area data shown in FIG. 2C as mask data, and designated as a completely opaque area. For the region, it is forced to be completely opaque, that is, α = 255. As a result, even if the image data is obtained through irreversible compression / decompression, the phenomenon that the completely transparent part is colored or the completely opaque part is slightly transparent is avoided. For transparent and completely opaque parts, exactly the same as the original image is guaranteed.

  The decompressed image data after the mask processing is sent to the drawing circuit 23 (step S15). The drawing circuit 23 displays the decompressed image data after the mask processing at a predetermined position on the display unit 5.

  If the completely transparent / opaque area data is also compressed and stored in the CGROM 4, the mask processing unit 22 performs the decompression process and then performs the mask process described above. In the image processing apparatus shown in FIG. 4, the mask processing unit 22 is logically independent from the decoder 21, but the function of performing the mask processing is not only logical but physically also the decoder 21. May be included.

  Next, a compression method when the image is a moving image (for example, an animation image) will be described. FIG. 5 is a block diagram showing a schematic configuration of an image processing apparatus in which an embodiment of the image compression method according to the moving image of the present invention is realized.

  The encoder 6 serving as the image processing apparatus shown in the figure includes a completely transparent / opaque region extracting unit 601, a motion predicting unit 602, a motion compensating unit 603, a subtracting unit 604, an orthogonal transform unit 605, and a quantizing unit 606. A variable length coding unit 607, an inverse quantization unit 608, an inverse orthogonal transform unit 609, an addition unit 610, a picture storage unit 611, and a multiplexing unit 612. Note that the picture data of each frame of the moving image input to the encoder 6 has transparency information (for example, α = 0 to 255) for each pixel as described above.

  The completely transparent / opaque area extracting unit 601 extracts a completely transparent area and a completely opaque area from the picture data of each input frame, and multiplexes it as area data AD, as described with reference to FIG. The picture data is sent to the subsequent stage as it is. Therefore, the following moving image compression encoding process is performed including transparency information.

  The motion prediction unit 602 searches for the macroblock with the highest correlation from the macroblocks of the picture related to the immediately preceding frame stored in the picture storage unit 611 for each macroblock obtained by dividing the picture as the input encoding target frame. Then, these macro blocks are sent to the motion compensation unit 603. When there is a part that moves integrally as a fixed area between two macroblocks, the motion compensation unit 603 sends the amount of movement to the multiplexing unit 612 as a motion vector MV, and from the picture storage unit 611. Are supplied to the subtracting unit 604.

  The subtraction unit 604 subtracts the macro block picture information sent from the motion compensation unit 603 from the encoding target macroblock of the picture as the encoding target frame, and supplies the sub information to the orthogonal transformation unit 605 as a residual prediction signal. To do. Note that, in the motion prediction unit 602, a threshold value of correlation is set, and when a correlation of a certain level or more is not recognized, without performing predictive coding, that is, without performing subtraction in the subtraction unit 604, The picture information may be sent to the orthogonal transform unit 605 as it is. A so-called I picture is sent as it is.

  The orthogonal transform unit 605 divides the residual prediction signal of the target macroblock sent from the subtraction unit 604 into unit blocks of n × n dots (n is 4 for example), and performs discrete cosine transform on each unit block. An orthogonal transformation process such as (DCT: Discrete Cosine Transform) is performed. In addition, as an orthogonal transformation process, there exists Hadamard transformation (Hadamard Transform).

  When the orthogonal transform processing in the orthogonal transform unit 605 is, for example, DCT processing, the quantization unit 606 divides the DCT coefficient of each unit block by a predetermined divisor (quantization step), rounds the remainder, and encodes (quantization). )I do. The quantized DCT coefficient of each unit block obtained by the quantization unit 606 is sent to the variable length coding unit 607 and the inverse quantization unit 608.

  The inverse quantization unit 608 performs inverse quantization processing by multiplying the DCT coefficient of each quantized unit block output from the quantization unit 606 by the predetermined divisor. Also, the inverse orthogonal transform unit 609 performs inverse orthogonal transform processing opposite to that corresponding to the orthogonal transform in the orthogonal transform unit 605, reconstructs a macro block from the decoded block, and sends the macro block to the adder 610. send. The adding unit 610 adds the information related to the macroblock output from the inverse orthogonal transform unit 609 to the information related to the macroblock having the highest correlation output from the motion compensation unit 603, thereby performing the macro before prediction. The block is restored and stored in the picture storage unit 611 for comparison with the subsequent (at least a macroblock related to the I picture) as necessary.

  On the other hand, the variable length coding unit 607 performs lossless compression on the quantized DCT coefficient output from the quantization unit 606 by variable length coding such as Huffman coding or arithmetic coding for each block. The multiplexing unit 612 receives the encoded image data from the variable length encoding unit 607, the motion vector MV from the motion compensation unit 603, and the region data AD from the complete transparent / opaque region extraction unit 601 and inputs them. Multiplex and output. Although the area data AD is output as it is, the encoder 6 may perform the compression encoding process on the area data as well.

  The processing device that decompresses the compressed data obtained by the encoder 6 and reproduces it as moving image data has the same conceptual configuration as the processing device shown in FIG. That is, decompression is performed by the reverse process to the above process performed on the moving image data, and then the mask process is performed based on the area data AD. As a result, even if the image data is obtained through irreversible compression / decompression, the phenomenon that the completely transparent part is colored or the completely opaque part is slightly transparent is avoided. For transparent and completely opaque parts, exactly the same as the original image is guaranteed.

  In the above-described embodiment, only the completely transparent portion and the completely opaque portion, that is, only the region of α = 0 and the region of α = 255 are guaranteed, but a desired width is given (for example, α = 0 to 0). 2 and α = 253-255).

  According to one embodiment of the image compression method, the image expansion method, and the image processing apparatus of the present invention, the image information including the transparency information can be subjected to the decompression reproduction even if irreversibly compressed including the transparency information. In particular, the image quality does not deteriorate in a completely transparent region and completely opaque.

  The image compression method, image decompression method, and image processing apparatus of the present invention can be applied to image data displayed on a gaming machine such as a pachinko machine.

1 CPU
2 Image display processor 21 Decoder 22 Mask processing unit 23 Drawing circuit 3 Program ROM
4 CGROM
5 Display Unit 6 Encoder 601 Completely Transparent / Opaque Extraction Unit 602 Motion Prediction Unit 603 Motion Compensation Unit 604 Subtraction Unit 605 Orthogonal Transform Unit 606 Quantization Unit 607 Variable Length Coding Unit 608 Inverse Quantization Unit 609 Inverse Orthogonal Transform Unit 610 Addition Unit 611 Picture storage unit 612 Multiplexing unit

Claims (9)

A method for compressing image information including transparency information,
Based on the image information including the transparency information, extract at least one of a completely transparent region and a completely opaque region,
Irreversibly compresses the image information including the transparency information;
The compressed image information is output together with region data of a region including at least one of the completely transparent region and the completely opaque region.   2. The image compression method according to claim 1, wherein both the completely transparent area and the completely opaque area are extracted, and area data of the area including them is also output.   The image compression method according to claim 1, wherein the image information is an image related to a moving image, and motion compensation processing is performed in the lossy compression processing.   The image compression method according to claim 3, wherein the moving image is an animation image.   The image compression method according to claim 1, wherein the region data is also compressed and output. Input compressed image information obtained by irreversible compression of an original image including transparency information, and region data of a region including at least one of a completely transparent region and a completely opaque region of the original image,
The compressed image information is subjected to decompression processing corresponding to the lossy compression,
An image decompression method characterized by masking a region indicated by the region data of decompressed image information by decompression with information relating to at least one of completely transparent and completely opaque. Input region data of a region including both a completely transparent region and a completely opaque region of the original image;
The image decompression method according to claim 6, wherein the region indicated by the region data of the restored image information by decompression is masked with information relating to both complete transparency and complete opaqueness.   8. The image decompression method according to claim 6, wherein the area data is also input as compressed data, the decompression process is performed on the compressed area data to restore the area data, and then the mask process is performed. . A storage unit for storing compressed image information obtained by irreversibly compressing an original image including transparency information, and region data of a region including at least one of a completely transparent region and a completely opaque region of the original image When,
Based on an external command, the decoder inputs the compressed image information from the storage unit, and performs a decompression process corresponding to the lossy compression,
A mask processing unit that inputs the region data from the storage unit and performs mask processing with information related to at least one of completely transparent and completely opaque in the region indicated by the region data of decompressed restored image information,
An image processing apparatus comprising:

Images