JP2006080831A - Coding apparatus, coding method, and image processing system and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coding apparatus capable of effectively coding image data belonging to the scRGB space. <P>SOLUTION: The coding apparatus 6 includes a control unit 12 having a CPU 14 and a memory 16 or the like. A coding program 30 is fed to the control unit 12, wherein the program 30 is executed. The coding program 30 includes: a data receiving part 32 for receiving image data expressed in RGB colors in each 16 bits; an analysis part 34 for analyzing pixel values of the image data respectively and storing the result to a tag; a coding control part 36 for controlling coding of the pixel values on the basis of the analysis result; coding parts 38a, 38b, 38c with coding ranges from -0.5 to 0.0, from 0.0 to 1.0, and from 1.0 to 7.5 for respectively coding the pixel values in 8 bits; and a data output part 40 for outputting coded data comprising the tag and the coded pixel values. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an encoding device that encodes image data represented by a plurality of pixel values.

In this type of encoding device, it is known to encode each pixel value of image data expressed in red (R), green (G), and blue (B).
Non-Patent Document 1 discloses an scRGB space represented by 16 bits for each color as an extended color space. The scRGB color space has a real expression range in which pixel values are in the range from 0 to 1.0 and a virtual expression range in which the pixel value is less than 0 or exceeds 1.0.
For example, Patent Document 1 discloses a method that allows a user to select either 8-bit accuracy or 16-bit accuracy when performing color processing.
For example, Non-Patent Document 1 discloses a method of reducing the number of bits from 16 bits to 12 bits after compressing the range by performing nonlinear gamma conversion on the entire region of the scRGB color space.

  However, in view of the range that can be reproduced by the printer and its quantization accuracy, expressing the scRGB color space as it is has the disadvantage of increasing the amount of data.

IEC TC100 TA2 (61966-2-2, Ed. 1), "Multimedia systems and equipment-Color measurement management-Part 2-2: Color management-Extended RGB color space-scRGB", International Electrotechnical Commission (IEC), 2003 January, p. 2-15 JP 2001-292331 A

  The present invention has been made from the above-described background, and an object thereof is to provide an encoding device that can effectively encode image data belonging to the scRGB space.

  In order to achieve the above object, the first feature of the present invention is that an accepting unit that accepts image data that exceeds the actual expression range, and a pixel value of the image data received by the accepting unit is an actual expression range. The encoding device includes an analysis unit that analyzes whether or not the image data belongs, and an encoding unit that encodes image data according to the analysis result of the analysis unit.

Preferably, the encoding unit encodes the pixel value of the image data and adds the analysis result by the analysis unit as a tag.
Preferably, the encoding unit sets an encoding range according to an analysis result of the analysis unit, and encodes a pixel value based on the encoding range.
Preferably, the encoding means encodes each pixel value or at least one of the analysis results with a different number of bits.

Preferably, when the pixel value exceeds the actual expression range, the encoding unit encodes the pixel value as a predetermined value.
Preferably, the analysis unit is either a real expression range in which a pixel value of an image received by the reception unit is 0 or more and 1.0 or less, or a virtual expression range less than 0 or more than 1.0. It is analyzed whether it belongs to.

Preferably, when the analyzing unit analyzes that the pixel value belongs to the actual expression range, the encoding unit sets the encoding range to the actual expression range, encodes the pixel value, and the analyzing unit When it is analyzed that the pixel value belongs to the virtual expression range, the encoding range is set to a virtual expression range including the pixel value, and the pixel value is encoded.
Preferably, the reception unit receives image data expressed in an scRGB color space.

  A second feature of the present invention is an image processing system including an encoding device and a decoding device, wherein the encoding device includes an accepting unit that accepts image data that exceeds the actual expression range, and the accepting unit. Analysis means for analyzing whether the pixel value of the image data received by the means belongs to the actual expression range, and encoding means for encoding the image data according to the analysis result of the analysis means. The decoding apparatus is in an image processing system having decoding means for decoding encoded data encoded by the encoding apparatus.

  The third feature of the present invention is that it accepts image data that exceeds the actual expression range, analyzes whether the pixel value of the accepted image belongs to the actual expression range, and according to the analysis result. There is an encoding method for encoding image data.

  The fourth feature of the present invention is that, in an encoding device including a computer, an accepting step for accepting image data that exceeds the actual representation range, and whether or not the pixel value of the accepted image belongs to the actual representation range. There is a program for causing the encoding device to execute an analysis step for analyzing the above and an encoding step for encoding image data in accordance with the analysis result.

  The encoding apparatus according to the present invention can effectively encode image data belonging to the scRGB space.

Next, a first embodiment of the present invention will be described.
FIG. 1 is a diagram for explaining the outline of an image processing system 2 according to the present invention.
As shown in FIG. 1, the image processing system 2 is configured by connecting an encoding device 6, decoding devices 8 a and 8 b, and an image forming device 10 to a network 4. The encoding device 6 or the decoding device 8 is a computer terminal, and is connected to the image forming apparatus 10 via the network 4 constituted by a LAN or the like. In the case where any one of a plurality of components such as the decoding devices 8a and 8b is indicated without being specified, it may be simply abbreviated as “decoding device 8” or the like.

The encoding device 6 encodes image data and transmits the encoded image data to the decoding devices 8a and 8b, or transmits the image data to the image forming device 10 to request printing. The encoding device 6 encodes image data using an encoding program 30 described later.
The decoding device 8 and the image forming device 10 receive the encoded data and decodes the image data by a decoding program 50 described later.
Note that the encoding device 6 and the decoding device 8 may be in the same casing, and the encoding program 30 and the decoding program 50 may operate on the same casing.

FIG. 2 is a diagram illustrating a hardware configuration of the encoding device 6 according to the present invention.
2, the encoding device 6 includes a control device 12 including a CPU 14 and a memory 16, a display / input device 18 including an LCD display device or a CRT display device, a keyboard / touch panel, a communication device 20, an HDD It comprises a recording device 22 such as a CD device. For example, the encoding device 6 is a personal computer or the like.
Note that the decoding device 8 and the image forming device 10 have the same hardware configuration as the encoding device 6.

FIG. 3 is a diagram illustrating a data format for representing a pixel, where (a) is a sRGB data format, (b) is a scRGB data format, and (c) is a diagram according to the present invention. This is a data format encoded by the encoding device 6.
As shown in FIG. 3A, in the sRGB space, one pixel is encoded with 8 bits for each color of RGB. A pixel is included in an actual expression range that is a range from 0.0 to 1.0, and is expressed in 256 levels.
As shown in FIG. 3B, in the scRGB space, one pixel is encoded with 16 bits for each color of RGB. Pixels are expressed in 65,536 levels from −0.5 to 7.5, and can be included not only in the actual expression range but also in a virtual expression range that is less than 0.0 or more than 1.0. In quantization accuracy, in the sRGB space, for example, an actual expression range from 0.0 to 1.0 is expressed in 256 levels, whereas in the scRGB space, this range is expanded to 8,192 levels. It is expressed.

  As shown in FIG. 3C, the encoding device 6 according to the present invention encodes one pixel with 32 bits. One pixel includes RGB colors encoded in 8 bits and an 8-bit tag. This tag belongs to the actual expression range where each pixel value of RGB is 0.0 to 1.0, belongs to the virtual expression range less than 0.0, or belongs to the virtual expression range exceeding 1.0. Remember me.

When the pixel value belongs to the actual expression range from 0.0 to 1.0, the pixel value is stored in the tag to belong to the actual expression range, and the pixel value is any of 0 to 255 Is encoded. The encoding range is set to an actual expression range from 0.0 to 1.0, and this range is encoded in 256 stages.
When the pixel value belongs to the virtual representation range less than 0.0, the pixel value is stored in the tag that the pixel value belongs to the virtual representation range less than 0.0, and the pixel value is from 0 to 255. Either is encoded. The encoding range is set to a virtual representation range from −0.5 to 0.0, and this range is encoded in 256 stages.
Similarly, when the pixel value belongs to a virtual expression range exceeding 1.0, it is stored in the tag that the pixel value belongs to a virtual expression range exceeding 1.0. It is encoded to any one of up to 255. The encoding range is set to a virtual representation range from 1.0 to 7.5, and this range is encoded in 256 stages.

A tag is expressed by 8 bits from bit0 to bit7. In the present embodiment, bit 7 and bit 6 are empty bits.
Bit 5 represents whether or not the R component is smaller than 0.0. The bit 5 is 1 when the R component is smaller than 0.0, and is 0 when the R component is 0.0 or larger. When this bit is 1, encoding is performed so that a virtual expression range from −0.5 to 0.0 is expressed by R8 bits.
Bit 4 represents whether or not the R component is greater than 1.0, and is 1 when the R component is greater than 1.0, and 0 when it is less than or equal to 1.0. When this bit is 1, encoding is performed so that a virtual expression range from 1.0 to 7.5 is expressed by R8 bits.
When the R component belongs to the actual expression range from 0.0 to 1.0, both bit5 and bit4 are 0. In this case, encoding is performed so that the actual expression range from 0.0 to 1.0 is expressed by R8 bits.

Similarly, bit3 represents whether or not the G component is smaller than 0.0, and is 1 when the G component is smaller than 0.0 and 0 when it is equal to or larger than 0.0. When this bit is 1, encoding is performed so that a virtual expression range from −0.5 to 0.0 is expressed in G8 bits.
Bit 2 represents whether or not the G component is greater than 1.0, and is 1 when the G component is greater than 1.0, and 0 when it is less than or equal to 1.0. When this bit is 1, encoding is performed so that a virtual expression range from 1.0 to 7.5 is expressed in G8 bits.
When the G component belongs to the actual expression range from 0.0 to 1.0, both bit3 and bit2 are 0. In this case, encoding is performed so that the actual expression range from 0.0 to 1.0 is expressed in G8 bits.

Further, bit1 expresses whether or not the B component is smaller than 0.0, and is 1 when the B component is smaller than 0.0 and 0 when it is equal to or larger than 0.0. When this bit is 1, encoding is performed so that a virtual representation range from −0.5 to 0.0 is represented by B8 bits.
Bit 0 expresses whether or not the B component is greater than 1.0, and is 1 when the B component is greater than 1.0 and 0 when it is less than or equal to 1.0. When this bit is 1, encoding is performed so that a virtual representation range from 1.0 to 7.5 is represented by B8 bits.
When the B component belongs to the actual expression range from 0.0 to 1.0, both bit1 and bit0 are 0. In this case, encoding is performed so that the actual expression range from 0.0 to 1.0 is expressed in B8 bits.
In this way, the encoding device 6 adds an 8-bit tag and encodes each component of RGB with 8 bits.

FIG. 4 is a diagram illustrating the configuration of an encoding program 30 that is executed by the control device 12 (FIG. 2) of the encoding device 6 and implements the encoding method according to the present invention.
As shown in FIG. 4, the encoding program 30 includes a data reception unit 32, an analysis unit 34, an encoding control unit 36, a first encoding unit 38a, a second encoding unit 38b, and a third encoding unit. 38c and the data output part 40 are included.
The encoding program 30 is supplied, for example, as a printer driver to the control device 12 of the encoding device 6 via the recording medium 24 (FIG. 2) or the network, loaded into the memory 16 and executed.
It should be noted that in the case where any one of a plurality of components such as the first encoding unit 38a, the second encoding unit 38b, and the third encoding unit 38c is not specified, the “encoding unit 38” is simply indicated. Alternatively, it may be abbreviated as “encoding units 38a, 38b, 38c” or the like.

In the encoding program 30, the data receiving unit 32 receives image data to be encoded via the communication device 20 (FIG. 2) or the recording device 22, and analyzes a pixel value representing a pixel of the received image data. 34 for output. The data receiving unit 32 receives, for example, image data belonging to the scRGB color space.
The analysis unit 34 analyzes whether each pixel value of the pixel belongs to the actual expression range, and stores the analysis result in the tag (FIG. 3). Specifically, the analysis unit 34 analyzes whether the pixel value is smaller than 0.0 and whether the pixel value is larger than 1.0. Further, the analysis unit 34 outputs the pixel value to any of encoding units 38a, 38b, and 38c described later under the control of the encoding control unit 36.

  Based on the tag stored by the analysis unit 34, the encoding control unit 36 controls whether the pixel value is encoded by any of the encoding units 38a, 38b, and 38c. Specifically, when the analyzed pixel value is smaller than 0.0, the encoding control unit 36 sets the analysis unit 34 so that the pixel value is encoded by the first encoding unit 38a. Control the output destination. Also, the encoding control unit 36 analyzes the pixel value so that the pixel value is encoded by the second encoding unit 38b when the analyzed pixel value belongs to a range from 0.0 to 1.0. The output destination of the unit 34 is controlled, and when the analyzed pixel value is larger than 1.0, the output destination of the analysis unit 34 is controlled so that the pixel value is encoded by the third encoding unit 38c. To do.

The first encoding unit 38a, the second encoding unit 38b, and the third encoding unit 38c encode the pixel value input from the analysis unit 34, and the encoded pixel value is input to the data output unit 40. Output.
The encoding unit 38 has a DLUT (Direct LookUp Table), and encodes the pixel value input from the analysis unit 34 with 8 bits based on the DLUT. The encoding units 38a, 38b, and 38c have different DLUTs. The first encoding unit 38a uses the DLUT included in the first encoding unit 38a to set a 16-bit pixel value that can represent a range from −0.5 to 7.5 based on the tag to −0. Encode into 8-bit pixel values that can represent a range from .5 to 0.0. The second encoding unit 38b uses a DLUT included in the second encoding unit 38b to represent a 16-bit pixel value and an 8-bit pixel that can represent a range from 0.0 to 1.0 based on the tag. Encode to value. The third encoding unit 38c uses the DLUT included in the third encoding unit 38c to represent a 16-bit pixel value and an 8-bit pixel that can represent a range from 1.0 to 7.5 based on the tag. Encode to value. The pixel value output from the analysis unit 34 is sent to the corresponding encoding unit 38 under the control of the encoding control unit 36, and is encoded into 8 bits by the encoding unit 38.

  The data output unit 40 uses each of the encoded pixel values input from the encoding units 38a, 38b, and 38c and the 8-bit tag as encoded data in a data format as shown in FIG. The data is output to the communication device 20 or the recording device 22.

FIG. 5 is a diagram illustrating the configuration of the decoding program 50 executed by the decoding device 8 or the control device 12 of the image forming apparatus 10.
As shown in FIG. 5, the decoding program 50 includes a data receiving unit 52, a decoding control unit 54, a first decoding unit 56a, a second decoding unit 56b, a third decoding unit 56c, and a data output. Part 58. The decryption program 50 is supplied to the decryption device 8 or the control device 12 of the image forming apparatus 10 via the recording medium 24 (FIG. 2) or the network, and is loaded into the memory 16 and executed.

In the decoding program 50, the data receiving unit 32 receives the encoded data encoded by the encoding device 6 via the communication device 20 or the recording device 22, and decodes the received encoded data. 54 is output.
The decoding control unit 54 analyzes the tag included in the encoded data (FIG. 3C), and based on the analysis result, the decoded pixel value is one of the decoding units 56a, 56b, and 56c. Output for. Specifically, when the pixel value is smaller than 0.0, the decoding control unit 54 outputs the pixel value of the component stored in the tag to the first decoding unit 56a. Further, the decoding control unit 54 outputs the pixel value of the component stored in the tag to the second decoding unit 56b when the pixel value belongs to the range from 0.0 to 1.0. Furthermore, when the pixel value is larger than 1.0, the decoding control unit 54 outputs the pixel value of the component stored in the tag to the third decoding unit 56c.

The first decoding unit 56a, the second decoding unit 56b, and the third decoding unit 56c decode the pixel value input from the decoding control unit 54, and use the decoded pixel value as a data output unit. 58 for output.
Each of the decoding units 56a, 56b, and 56c has a different DLUT, and decodes the pixel value to 16 bits based on the DLUT. The first decoding unit 56a converts an 8-bit pixel value that can represent a range from −0.5 to 0.0 into a 16-bit pixel value that can represent a range from −0.5 to 7.5. Decrypt. The second decoding unit 56b decodes an 8-bit pixel value that can represent a range from 0.0 to 1.0 into a similar 16-bit pixel value. The third decoding unit 56c decodes an 8-bit pixel value that can represent a range from 1.0 to 7.5 into a similar 16-bit pixel value.

  The data output unit 58 records each of the 16-bit decoded pixel values input from the decoding units 56a, 56b, and 56c as image data having a data format as shown in FIG. Output to the device 22.

Next, the overall operation of the encoding device 6 will be described.
FIG. 6 is a flowchart showing the operation (S10) of the encoding device 6 (encoding program 30).
As shown in FIG. 6, in step 100 (S100), the data receiving unit 32 acquires image data to be encoded via the communication device 20 or the recording device 22, and this image data is obtained for each pixel. The data is output to the analysis unit 34.
In step 102 (S102), the analysis unit 34 acquires each pixel value (16 bits for each of RGB) of the pixel input from the data reception unit 32.

In step 104 (S104), the analysis unit 34 analyzes whether or not the pixel value belongs to the virtual expression range less than 0.0, and stores the analysis result in the tag. The encoding program 30 proceeds to the process of S106 when the pixel value belongs to the virtual expression range of less than 0.0, and proceeds to the process of S108 otherwise.
In step 106 (S106), the encoding control unit 36 controls the analysis unit 34 to output the encoding target pixel value (16 bits) to the first encoding unit 38a based on the tag. The first encoding unit 38a encodes the pixel value with 8 bits that can represent a range from −0.5 to 0.0 based on the DLUT. The first encoding unit 38 a outputs the encoded pixel value (8 bits) to the data output unit 40.

In step 108 (S108), the analysis unit 34 analyzes whether the pixel value belongs to the actual expression range from 0.0 to 1.0, and stores the analysis result in the tag. The encoding program 30 proceeds to the processing of S110 when the pixel value belongs to the actual expression range from 0.0 to 1.0, and proceeds to the processing of S112 otherwise.
In step S110 (S110), the encoding control unit 36 controls the analysis unit 34 to output the encoding target pixel value (16 bits) to the second encoding unit 38b based on the tag. The second encoding unit 38b encodes the pixel value with 8 bits that can represent a range from 0.0 to 1.0 based on the DLUT. Further, the second encoding unit 38 b outputs the encoded pixel value (8 bits) to the data output unit 40.

In step S112 (S112), the encoding control unit 36 controls the analysis unit 34 to output the encoding target pixel value (16 bits) to the third encoding unit 38c based on the tag. The third encoding unit 38c encodes the pixel value with 8 bits that can represent a virtual expression range from 1.0 to 7.5 based on the DLUT. The third encoding unit 38 c outputs the encoded pixel value (8 bits) to the data output unit 40.
In step S114 (S114), the encoding control unit 36 determines whether or not the encoding of all the pixel values of the pixel has been completed. If the encoding has been completed, the encoding program 30 performs the process of S116. If not, the process returns to S102.

In step S116 (S116), the data output unit 40 encodes the encoded pixel value (8 bits) and the tag input from each of the encoding units 38 into a data format as shown in FIG. Encode to data.
In step 118 (S118), the encoding control unit 36 determines whether or not encoding of all the pixels of the input image data has been completed. If the encoding has been completed, the encoding program 30 executes S120. If the process has not ended, the process returns to S102.
In step 120 (S120), the data output unit 40 outputs the encoded data to the communication device 20 or the recording device 22. This encoded data is composed of 8 bits representing each RGB component and 8 bits representing a tag.

  As described above, according to the encoding device 6 in the present embodiment, the image data expressed in 16 bits for RGB (48 bits in total) is set to an encoding range, and then 8 bits for RGB and 8 bits for tags are calculated. Since encoding is performed with 32 bits, image data included in the scRGB space can be encoded with a high compression rate.

Next, the overall operation of the decoding device 8 will be described.
FIG. 7 is a flowchart showing the operation (S20) of the decoding device 8 (decoding program 50).
As shown in FIG. 7, in step 200 (S200), the data receiving unit 52 sends encoded data (RGB 8 bits + tag 8 bits) to be decoded via the communication device 20 or the recording device 22. ) And outputs the encoded data to the decoding control unit 54.

In step 202 (S202), the decoding control unit 54 determines whether or not the pixel value to be decoded belongs to a virtual expression range less than 0.0 based on the tag. If it belongs to the virtual expression range less than 0, the decryption program 50 proceeds to the process of S204, and otherwise proceeds to the process of S206.
In step 204 (S204), the decoding control unit 54 outputs the pixel value (8 bits) to the first decoding unit 56a. The first decoding unit 56a converts the pixel value that can represent the range from −0.5 to 0.0 into 16 bits that can represent the range from −0.5 to 7.5 based on the DLUT. Decrypt into The first decoding unit 56a outputs the decoded pixel value (16 bits) to the data output unit 58.

In step 206 (S206), the decoding control unit 54 determines whether or not the pixel value to be decoded belongs to the actual expression range from 0.0 to 1.0 based on the tag, and this pixel When the value belongs to the real expression range from 0.0 to 1.0, the decryption program 50 proceeds to the process of S208, and otherwise proceeds to the process of S210.
In step S208 (S208), the decoding control unit 54 outputs the pixel value (8 bits) to the second decoding unit 56b. The second decoding unit 56b decodes the pixel value that can represent the range from 0.0 to 1.0 into the same 16 bits, and outputs the decoded pixel value to the data output unit 58. Output.

In step S210 (S210), the decoding control unit 54 outputs the pixel value (8 bits) to the third decoding unit 56c. The third decoding unit 56c decodes the pixel value that can represent the range from 1.0 to 7.5 into the same 16 bits, and outputs the decoded pixel value to the data output unit 58. Output.
In step S212 (S212), the decoding control unit 54 determines whether or not the decoding of all the pixel values has been completed. If the decoding has been completed, the decoding program 50 proceeds to the process of S214. Otherwise, the process returns to S202.
In step S214 (S214), the data output unit 58 decodes the decoded pixel value (16 bits) input from each of the decoding units 56 into image data having a data format as shown in FIG. The image data is output to the recording device 22.

  As described above, according to the decoding device 8 in the present embodiment, the encoded data encoded to 32 bits by the encoding device 6 is converted into 16 bits for each of RGB based on the tag included in the encoded data. It is possible to decode the image data expressed by the above. Note that the decryption program 50 operates not only on the decryption apparatus 8 but also on the image forming apparatus 10. The image forming apparatus 10 can receive the encoded data encoded by the encoding apparatus 6, decode the encoded data in the same manner as the decoding apparatus 8, and print it.

Next, an encoding device 6 according to the second embodiment of the present invention will be described.
FIG. 8 is a diagram showing a data format encoded by the encoding device 6 according to the present embodiment. As shown in FIG. 8, the encoding device 6 according to the present embodiment uses the 5 bits of the 8-bit tag to represent a range including pixels, and thus the encoding device according to the first embodiment. Different from 6.

  Each pixel value has three ranges: a virtual representation range from −0.5 to 0.0, a real representation range from 0.0 to 1.0, or a virtual representation range from 1.0 to 7.5. Belonging to either. Further, the pixel is represented by RGB three components. For this reason, the range to which a pixel can belong is expressed in 27 ways. Accordingly, in which range the pixel values of RGB are included is expressed in 5 bits.

As shown in FIG. 8, in this embodiment, bit7, bit6, and bit5 are empty bits.
For example, among the 27 types shown in FIG. 8, the tags shown at the top are all “0” from bit 0 to bit 4. This tag indicates that the pixel values of all RGB components belong to the actual expression range from 0.0 to 1.0. Here, in FIG. 8, “−” indicates that this component is smaller than 0.0, “·” indicates that this component is included in the range of 0.0 to 1.0, and “ “+” Indicates that this component is greater than 1.0.
Further, for example, in the second tag from the top, only bit 0 is “1”, and bits 1 to 4 are “0”. This tag indicates that the pixel values of the R component and the G component belong to the actual expression range from 0.0 to 1.0, and the pixel value of the B component belongs to the virtual expression range of less than 0.0.
Further, for example, in the tag shown at the bottom, bit0 and bit2 are “0”, and bit1, bit3, and bit4 are “1”. This tag indicates that the pixel values of all RGB components belong to a virtual expression range exceeding 1.0.

The analysis unit 34 (FIG. 4) analyzes whether each pixel value of the pixel belongs to the actual expression range, and stores the analysis result in the tag (FIG. 8). At this time, if the tag already stores the analysis result of other pixel values included in this pixel, the analysis unit 34 updates bits 0 to 4 so that the tag indicates an appropriate analysis result. To do.
Thus, according to the encoding device 6 in the present embodiment, the number of empty bits in the tag is increased, so that the image data included in the scRGB space can be encoded with a higher compression rate.

Next, an encoding apparatus 6 according to the third embodiment of the present invention will be described.
FIG. 9 is a diagram showing a data format encoded by the encoding device 6 according to the present embodiment. As illustrated in FIG. 9, the encoding device 6 according to the present embodiment uses 3 bits of the 8-bit tag to indicate whether or not the pixel value is included in the actual expression range, and the pixel value is the actual expression range. Is different from the encoding device 6 according to the first embodiment in that the pixel value is encoded as a predetermined value.

When the pixel value belongs to the actual expression range from 0.0 to 1.0, the pixel value is stored in the tag to belong to the actual expression range, and the pixel value is any of 0 to 255 Is encoded. The encoding range is set to an actual expression range from 0.0 to 1.0, and this range is encoded in 256 stages.
When the pixel value belongs to a virtual expression range that is less than 0.0 or exceeds 1.0, it is stored in the tag that the pixel value belongs to a virtual expression range that is less than 0.0 or exceeds 1.0. In addition, pixel values that are less than 0.0 are all encoded as 0, and pixel values that exceed 1.0 are all encoded as 255.

  As shown in FIG. 9, in this embodiment, bit7, bit6, bit5, bit4, and bit3 are empty bits. Bit 2 represents whether the R component is smaller than 0.0 or whether the R component is larger than 1.0. bit1 represents whether the G component is smaller than 0.0 or whether the G component is larger than 1.0. Bit 0 represents whether the B component is smaller than 0.0 or whether the B component is larger than 1.0.

  As described above, according to the encoding device 6 of the present embodiment, image data represented by 16 bits of RGB (total 48 bits) is stored as pixel values belonging to the virtual representation range, Since the encoding is performed with a total of 32 bits including the tag 8 bits, the image data included in the scRGB space can be encoded with a high compression rate.

Next, an encoding apparatus 6 according to the fourth embodiment of the present invention will be described.
FIG. 10 is a diagram illustrating a data format encoded by the encoding device 6 according to the present embodiment. As shown in FIG. 10, the encoding device 6 according to the present embodiment uses bit 7 and bit 6 among the 8-bit tags as data representing pixel values, and each of the component pixel values or at least one of the tags is the other. Is different from the encoding device 6 according to the first embodiment in that it is encoded with a different number of bits.

FIG. 10A is a diagram illustrating a data format in which one of the components is encoded with a different number of bits from the other components. In particular, FIG. 10A is a diagram illustrating a case where the R component is encoded with 10 bits. is there. As shown in FIG. 10A, in the present embodiment, the encoding device 6 encodes the R component with 10 bits using R8 bits and bits 7 and 6 included in the tag.
When the pixel value of the R component belongs to the actual expression range from 0.0 to 1.0, it is stored in the tag that the pixel value belongs to the actual expression range, and the encoding range falls within this range. This pixel value is encoded in 1,024 stages from 0 to 1,023. Similarly, if the pixel value of the R component belongs to the virtual representation range from −0.5 to 0.0, or belongs to the virtual representation range from 1.0 to 7.5, the pixel value is Being belonging to each range is stored in the tag, the encoding range is set to each range, and the pixel value is encoded in 1,024 stages from 0 to 1,023.

  In this way, according to the encoding device 6 of the present embodiment, the pixel value is encoded using bit 7 and bit 6 of the tag 8 bits, so that the pixel value is encoded with higher quantization accuracy. be able to. The component encoded with 10 bits may be set in advance in consideration of importance, or may be set when image data is analyzed. For example, when only the pixel value of one component belongs to the virtual expression range, it may be set so that only this component is encoded with 10 bits. Further, when only the pixel value of one component belongs to the actual expression range, it may be set so that only this component is encoded with 10 bits.

FIG. 10B is a diagram illustrating a data format in which two components are encoded with a different number of bits from the other components. In particular, FIG. 10B is a diagram illustrating a case where the R component and the G component are encoded with 9 bits. is there. As shown in FIG. 10 (b), in this embodiment, the encoding device 6 encodes the R component with 9 bits using R8bit and bit7 included in the tag, and uses G8bit and bit6 included in the tag. , G component is encoded with 9 bits.
When the pixel value of the R component or the G component belongs to the actual expression range from 0.0 to 1.0, it is stored in the tag that the pixel value belongs to the actual expression range, and the encoding range is This range is set, and this pixel value is encoded in 512 steps from 0 to 511. Similarly, when the pixel value of the R component or G component belongs to the virtual representation range from −0.5 to 0.0, or belongs to the virtual representation range from 1.0 to 7.5, It is stored in the tag that the pixel value belongs to each range, the encoding range is set to each range, and the pixel value is encoded in 512 steps from 0 to 511.

  Thus, according to the encoding device 6 of the present embodiment, the bit 7 and the bit 6 of the tag 8 bits are used for encoding each of the two pixel values, so that the quantization accuracy of each of the pixel values is increased. Pixel values can be encoded. Note that the component encoded with 9 bits may be set in advance in consideration of the importance, or may be set when image data is analyzed. In this embodiment, bit 7 and bit 6 are used as data representing the pixel value. However, when the empty bit is further included in the tag, the pixel value is expressed using the empty bit. May be.

It is a figure explaining the outline of the image processing system 2 which concerns on this invention. It is a figure which illustrates the hardware constitutions of the encoding apparatus 6 which concerns on this invention. It is a figure which illustrates the data format which represents a pixel, (a) is a data format of sRGB, (b) is a data format of scRGB, (c) is a 1st embodiment of the present invention. This is a data format encoded by the encoding device 6 according to FIG. It is a figure which illustrates the structure of the encoding program 30 performed by the control apparatus 12 of the encoding apparatus 6. FIG. 3 is a diagram illustrating a configuration of a decoding program 50 executed by the decoding device 8 or the control device 12 of the image forming apparatus 10. It is a flowchart which shows operation | movement (S10) of the encoding apparatus 6 (encoding program 30). It is a flowchart which shows operation | movement (S20) of the decoding apparatus 8 (decoding program 50). It is a figure which illustrates the data format encoded by the encoding apparatus 6 which concerns on the 2nd Embodiment of this invention. It is a figure which illustrates the data format encoded by the encoding apparatus 6 which concerns on the 3rd Embodiment of this invention. It is a figure which illustrates the data format encoded by the encoding apparatus 6 which concerns on the 4th Embodiment of this invention.

Explanation of symbols

2 Image processing system 4 Network 6 Encoding device 8 Decoding device 10 Image forming device 12 Control device 14 CPU
16 memory 18 display / input device 20 communication device 22 recording device 24 recording medium 30 encoding program 32 data receiving unit 34 analysis unit 36 encoding control unit 38a first encoding unit 38b second encoding unit 38c third Encoding unit 40 Data output unit 50 Decoding program 52 Data receiving unit 54 Decoding control unit 56a First decoding unit 56b Second decoding unit 56c Third decoding unit 58 Data output unit

Claims (11)

An accepting means for accepting image data exceeding the actual expression range;
Analyzing means for analyzing whether or not the pixel value of the image data received by the receiving means belongs to the actual expression range;
According to the analysis result of this analysis means, an encoding means for encoding image data;
An encoding device. The encoding device according to claim 1, wherein the encoding unit encodes a pixel value of image data and adds an analysis result of the analysis unit as a tag. The encoding device according to claim 1, wherein the encoding unit sets an encoding range according to an analysis result of the analysis unit, and encodes a pixel value based on the encoding range. The encoding device according to any one of claims 1 to 3, wherein the encoding unit encodes each pixel value or at least one of the analysis results with a different number of bits. The encoding device according to any one of claims 1 to 4, wherein the encoding means encodes the pixel value as a predetermined value when the pixel value exceeds an actual expression range. Whether the analysis unit belongs to any of a real expression range in which a pixel value of an image received by the reception unit is 0 or more and 1.0 or less, or a virtual expression range less than 0 or more than 1.0 The encoding device according to any one of claims 1 to 5. When the analysis unit analyzes that the pixel value belongs to the actual expression range, the encoding unit sets the encoding range to the actual expression range, encodes the pixel value, and the analysis unit calculates the pixel value. The encoding apparatus according to claim 6, wherein when it is analyzed that it belongs to a virtual representation range, the encoding range is set to a virtual representation range including the pixel value and the pixel value is encoded. The encoding device according to claim 1, wherein the reception unit receives image data expressed in an scRGB color space. An image processing system including an encoding device and a decoding device,
The encoding device includes:
An accepting means for accepting image data exceeding the actual expression range;
Analyzing means for analyzing whether or not the pixel value of the image data received by the receiving means belongs to the actual expression range;
According to the analysis result of this analysis means, an encoding means for encoding image data;
Have
The decoding device
An image processing system comprising decoding means for decoding encoded data encoded by the encoding device. Accept image data that exceeds the real expression range,
Analyzes whether or not the pixel value of this accepted image belongs to the actual expression range,
An encoding method that encodes image data according to the analysis result. In an encoding device including a computer,
An accepting step for accepting image data exceeding the actual expression range;
An analysis step for analyzing whether the pixel value of the received image belongs to the actual expression range;
According to the analysis result, an encoding step for encoding image data;
A program for causing the encoding apparatus to execute.

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