JPH10178528A - System and device for image storage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To store image in an efficient data form by selectively using a data form which uniformly represents an image as the same color, a data form which represents the image in a reversible type or a data form which represent the image as irreversible type and storing it. SOLUTION: Multivalued image data is inputted to an image inputting part 1. This storage system has a 1st storage step which generates 1st image data that uniformly represents an image in a prescribed area which is shown by multivalued image data as the same color and stores it in an image file 21, a 2nd storage step which generates 2nd image data that similarly represents the image in the prescribed area as a reversible type and stores it in the file 21 and a 3rd step which generates 3rd image data that similarly represents the image in the prescribed area as irreversible type and stores it in the file 21. Multivalued image data is stored in the file 21 by selectively using any of the 1st to 3rd storage steps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image storage method and apparatus capable of storing an input image in a plurality of data formats.

[0002]

2. Description of the Related Art Heretofore, as a method of encoding a color image, there has been known a method of dividing an image into blocks, performing orthogonal transformation, and then quantizing and encoding the coefficients.

However, in the above-mentioned conventional example, since the coefficients after the orthogonal transformation are quantized, high-frequency components are lost, ringing occurs at an edge portion, and the quality of a character portion of a document is degraded.

In addition, when coding at a low bit rate, block distortion occurs at the boundary between blocks,
The outline of the text was unsightly.

On the other hand, in order to improve the quality of the most frequently used black characters and multi-color characters, the present applicant has proposed a technique of separating and encoding a multi-color character portion and other portions. I have.

In this method, after separating a character and other parts, DCT coding is performed on the other parts.

[0007]

SUMMARY OF THE INVENTION However, DCT
In encoding, it is converted into a YCbCr signal, and Y, C
Since each of b and Cr is DCT-coded and the transform coefficient is quantized, converted to a one-dimensional sequence and Huffman-coded, the “white” signal, that is, when the input signal values are all 255 in the block , A data amount of at least 3 bits / block is required for each signal (Y, Cb, Cr). Further, the DC component obtained as a result of the orthogonal transform is encoded separately (DPCM).
, And at least 1 bit / bloc
k is required, and loss of coding efficiency is large.

Further, when a line drawing portion of a predetermined color of input image data is extracted, and the portion is separated from other portions and encoded, simply removing only the line drawing portion requires accuracy of the extracting means. In some cases, for example, high-frequency portions around color characters may remain. Such a problem,
This has also occurred in image processing other than encoding, such as color conversion processing.

The present invention has been made in view of the above conventional example, and has as its object to provide an image storage method capable of storing images in an efficient data format.

[0010]

According to an image storing method of the present invention, an inputting step of inputting multi-valued image data and an image in a predetermined area indicated by the multi-valued image data are provided. Generating first image data uniformly expressed as the same color, and storing the first image data in a predetermined storage unit; and a second image processing in which an image in a predetermined area indicated by the multi-valued image data is expressed as a reversible format. Generate two image data,
A second storing step of storing the image in the predetermined area indicated by the multi-valued image data as third image data in an irreversible format, and storing the third image data in the predetermined storing means. And storing the multi-valued image data in the predetermined storage means by selectively using any of the first to third storage steps.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

1. FIG. 1 is a diagram illustrating an overall configuration of an image encoding device according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an image input unit for inputting an image signal representing an original, which scans the original with a CCD line sensor and outputs R (red), G (green), and B (blue) for each pixel. It is configured by an image sensor that outputs an 8-bit color component signal. Reference numeral 2 denotes an edge detection unit that detects a high-frequency component portion of a document image by a method described later. Reference numeral 3 denotes a color detection unit that detects pixels of a predetermined color component. Reference numeral 4 denotes a specific color determination circuit that determines whether all pixel values in a block are a specific color (for example, all white). Reference numeral 5 denotes a color character determination unit which determines an edge portion and a pixel of a predetermined color component. Reference numeral 6 denotes a first arithmetic encoding circuit, which encodes an output from the specific color determination circuit 4 by a dynamic arithmetic encoding algorithm. Reference numeral 7 denotes a binary sequence conversion unit that converts pixel data representing a plurality of colors into a binary sequence signal suitable for arithmetic coding. Reference numeral 8 denotes a second arithmetic coding unit, which performs no processing based on the signal output from the specific color determination circuit 4 if the target pixel to be coded is a block composed of a specific color. If the color is not a specific color, the binary sequence signal is encoded by dynamic arithmetic encoding. Reference numeral 9 denotes a color character removal unit that replaces data of a pixel determined as a color character with average value data of a block to which the pixel belongs. Reference numeral 10 denotes an orthogonal transform unit, which performs DC for each block.
T (Discrete Cosine Transfo
rm) and further performs Huffman coding, so-called A
DCT coding is performed. However, as in the case of the second arithmetic coding unit 8, if the target block to be subjected to ADCT coding is a specific color, the processing is not performed, and the ADCT coding is performed only when the block is not the specific color. Do. 1
Reference numeral 1 denotes a code data transmitting unit, and a first arithmetic coding unit 6
And the outputs of the second arithmetic coding unit 8 and the orthogonal transformation unit 10 are integrated to generate code data to be transmitted. A code data receiving unit 12 separates the received code data into two arithmetic code sequences and a Huffman code sequence. 13 is the first
, Decodes the arithmetic code, and outputs a signal indicating whether or not the block is a specific color block. Reference numeral 14 denotes a second inverse arithmetic encoding unit, which decodes an arithmetic code and outputs color character data. Reference numeral 15 denotes an inverse orthogonal transform unit, which performs Huffman decoding,
Performs inverse orthogonal transformation and outputs multi-valued image data.

When the target pixel and the target block are of a specific color, the second inverse arithmetic coding unit 14 and the inverse orthogonal transform unit 15 stop the decoding operation, output the value of the specific color, and output the value of the specific color. When the color is not the color, the decoding operation is performed and the decoded data is output. Reference numeral 16 denotes a smoothing unit which performs smoothing to remove block distortion of the decoded image. A synthesizing unit 17 synthesizes the color characters and the multi-valued image data and outputs image data to be reproduced. Reference numeral 18 denotes an image output unit for forming image data into a visible image.

Hereinafter, each part will be described.

<Edge Detection Unit 2> The edge detection unit 2 performs the following calculation on the target pixel X between the peripheral pixels A, B, C, and D as shown in FIG. , The distance between two points in the RGB space is calculated, and edges in the image are detected. That is, the image data of the pixel of interest and the peripheral pixels are respectively represented by (Xr, Xg, Xb) (Ar,
Ag, Ab), S = ((Xr-Ar) ² + (Xg-Ag) ² + (Xb-Ab) ² ) ^1/2 (1) S> TH1 (= 100) (2) If so, it is determined that there is an edge between X and A.

Similarly, the presence or absence of an edge between B, C, and D is determined. If any one of A, B, C, and D is determined to be an edge, the target pixel X is determined to be an edge. It is determined that there is.

As described above, the presence or absence of an edge is determined by calculating the distance in the three-dimensional color space between the target pixel and the peripheral pixels. For example, color edges having the same lightness but different hues and saturations are also determined. Can be determined. Therefore, the present invention is extremely effective in detecting a color character.

In addition to the above-described edge determination for each pixel, it also determines whether or not an edge pixel is included in an 8 × 8 pixel block for performing color character removal and orthogonal transformation described later, and outputs a determination signal.

The method of obtaining peripheral pixels is not limited to the above example, and for example, eight peripheral pixels may be used.

Further, for example, an average value of the image data of A, B, C, and D may be calculated, and the above calculation may be performed between the average value and the pixel X.

<Color Detecting Unit 3> The color detecting unit 3 detects a plurality of predetermined limited colors by the following equation. Now
Assuming that the image data of the target pixel X is (r, g, b), when r, g, b <th1 and | r−g |, | g−b |, | br− <th3 (3) , The target pixel X is determined to be K (black).

Similarly, when r> th2 and g, b <th1 and | g−b | <th3 (4), X = R (red), g> th2 and r, b <th1 and | r −b | <th3 (5), X = G (green), b> th2 and r, g <th1 and | r−g | <th3 (6), X = B (blue), When r, g> th2, b <th1, and | r−g | <th3 (7), X = Y (yellow), r, b> th2, g <th1, and | rb− <th3 ( 8), X = M (magenta), g, b> th2, r <th1, and | g−b | <th3 (9), and color detection is performed as X = C (cyan).

Here, th1, th2, and th3 are predetermined thresholds, for example, th1 = 50, th2 = 20.
5, when th3 = 30, the detection result is good.

The color detection signal is represented by three bits (R, G, B). The correspondence between each detected color and the values of R, G, B is shown in FIG.
As shown in FIG.

<Specific Color Determination Unit 4> The specific color determination unit 4 determines that a block is a specific color block when all the pixel values in the block match the specific color value.

<Color character determination unit 5> The color character determination unit 5 is a pixel in a block in which it is determined by the edge detection unit 2 that a pixel corresponding to an edge exists. Pixels satisfying any of (1) to (9) are determined as color characters.

<First Arithmetic Encoding Unit 6> In the arithmetic encoding unit 6, the binary signal is encoded by an arithmetic code which is lossless encoding. The arithmetic coding method and circuit configuration are as disclosed in JP-A-2-65372.

<Binary sequence converter 7> Binary sequence converter 7
Converts eight color signals represented by a three-bit color character determination signal into a binary sequence signal shown in FIG.

FIG. 4 shows a block diagram of the binary sequence converter 7. The input data 200 to 202 are converted into a signal 212 having a maximum of 7 bits for each pixel as shown in FIG. Here, a plurality of ROMs are assigned to the conversion table 91 so that a short bit length can be assigned to a color having a high appearance frequency.
Are prepared, and a plurality of ROs are
M may be selectable.

The signal output unit 92 has a shift register configuration, in which a 7-bit input signal 212 is input in parallel, and is output serially from the MSB one bit at a time. This is a binary sequence signal D203. When the binary sequence signal becomes 1 or when 7 signals are output, the signal output device 92 terminates the output of the color signal of one pixel, and receives the next input data. Also, a signal B representing the bit of the binary sequence signal that the currently output bit is
t204 is output.

As described above, by converting the 3-bit color character determination signal into a binary sequence and encoding it as a 1-bit serial signal, 3-bit signals having mutual correlation are separately encoded. Encoding can be performed without preserving the color correlation. In addition, for example, when performing encoding while predicting a target pixel as in arithmetic encoding, R,
Prediction and encoding can be performed as color information without performing prediction and encoding for each of the G and B color components, and encoding efficiency can be improved.

Further, since each color component of R, G, and B representing the color of each pixel is represented as one data, one data is decoded at the time of decoding, so that R, G, B corresponding to each pixel is decoded.
A signal can be obtained at a time, and a color image can be reproduced quickly.

<Arithmetic Encoding Unit 8> The arithmetic encoding unit 8 encodes a binary sequence signal representing several colors by arithmetic encoding which is lossless encoding. The arithmetic coding method and circuit configuration are as disclosed in Japanese Patent Application Laid-Open No. 2-65372. However, here, only the data of the non-specific color block is encoded, and the data of the specific color block is not encoded.

<Colored character removing unit 9> The colored character removing unit 9 converts the data of the pixel determined as a colored character by the colored character determining unit 5 into a value corresponding to the data of another pixel in the block to which the pixel belongs. Replace with

That is, the color character data is removed from the image having the color character as shown in FIG. 5A, as shown in FIG. 5B. At this time, the color characters are subtracted to
FIG. 5C also shows the removal of the edge as shown in FIG.
As described above, data of pixels surrounding the color character and having the same hue as the color character pixel are also subtracted and replaced with the average value of other pixel data in the block.

At this time, the size of the block for the color character removal processing and the size of the block for the orthogonal transform described later are the same.

FIG. 6 shows the structure of the color character removing section 9.

Each of the 8-bit pixel image data r, g, and b is input to a color detector 71, and a pixel of a color to be removed is detected based on the above equations (3) to (9). At this time, in order to detect the peripheral portion of the color character, the threshold value is determined as follows, for example.

Th1 = 120, th2 = 130, th3 = 30 As described above, the above-described color detection threshold is changed to change the color detection unit 3
By performing color detection in a wider range, it is possible to extract a portion having a color similar to a color character, and to remove the input image data of this portion.

Detection signals R ', G', B 'of the color detector 71
When at least one of them is 1, it is determined that the pixel has a color to be removed, and the values of r, g, and b of the pixel are set to 0 in the subtraction circuit 72. Next, the average value calculation circuit 73 calculates the average value of the r, g, and b data in the 8 × 8 pixel block, and replaces the average value as the image data of the pixel from which the color has been removed. ′,
Output as g 'and b'.

Not only the replacement with the average value, but also the replacement with the most frequent value or the replacement with the median value of the pixels in the block using a median filter can be performed.

Further, in order to more accurately extract only a portion of the actual color approximating the color character, which is a pixel surrounding the color character, a signal obtained by ORing the color character determination signals R, G, and B is The processing in the subtraction circuit 72 and the replacement unit 74 may be performed by taking the AND of the output signals of the two OR circuits in FIG.

<Orthogonal Transformation Unit 10> The orthogonal transformation unit 10
A two-dimensional discrete cosine transform is performed in units of × 8 pixel blocks, and the obtained transform coefficients are quantized and then subjected to Huffman coding.

FIG. 7 shows the configuration of the orthogonal transform unit 10. In the pre-processing unit 81, an 8-bit signal of r ', g', b 'is converted into a luminance signal Y and chromaticity signals Cr, Cb for each pixel. Next, in the sub-sampling unit 82, Cr,
The Cb signal is averaged for each 2 × 2 pixel block.
This makes use of the property that deterioration of the chromaticity signal is less noticeable to human vision than deterioration of the luminance signal. Finally, in the orthogonal transform unit 83, Y, Cr, C
ADCC encoding is performed independently for each surface of b. This encoding can be performed by configuring a dedicated arithmetic circuit or by software of a computer.

However, the orthogonal transform unit 10 performs the encoding process only when the block to be processed is a non-specific color, and does not perform encoding when the block is a specific color. Normal Cb, Cr
The data is divided into two blocks by subsampling.
When one of the two blocks is a specific color, the sub-sampling is not performed, and the Cb and Cr data of the block of the non-specific color is used as it is for the orthogonal transformation.

<Code Data Transmitting Unit 11> The code data transmitting unit 11 first transmits a color character pattern code, and then transmits Y, Cr, and Cb code data in a frame-sequential manner. Prior to transmission of each surface, a flag indicating which component the data is is transmitted. At this time, a memory for compensating for a time lag according to the transmission order of each data is provided.

As described above, by encoding a color character pattern by reversible encoding, highly efficient data compression can be performed while maintaining the quality of the color character pattern.

On the other hand, when color characters are separated from the original data, by performing a predetermined replacement including the surrounding parts, the efficiency of orthogonal transform coding can be improved.

<Code Data Reception Unit 12> The code data reception unit 12 receives the code data from the transmission unit 11, and determines whether the code data is an arithmetic code or any one of Y, Cr, and Cb based on a flag. And outputs the respective data to the inverse arithmetic encoding unit 11 and the inverse orthogonal transform encoding unit 12.

<First Inverse Arithmetic Encoder 13, Second Inverse Arithmetic Encoder 14, Inverse Orthogonal Transform Encoder 15> First Inverse Arithmetic Encoder 13, Second Inverse Arithmetic Encoder 14, Inverse Orthogonal The transform coding unit 15 performs the reverse procedure of the arithmetic coding and the orthogonal transform coding,
The data representing the specific color block, the color character data, and the multi-valued data r ', g', b 'are decoded. However, since the data decoded by the second inverse arithmetic coding unit 14 and the inverse orthogonal transform unit 15 is data excluding the specific color block, it is necessary to reconstruct the specific color block portion in each case. There is. For example, the specific color here is white. For the sake of simplicity, the entire image size is 8 × 8 pixels and the block size is 2 × 2 pixels.

It is assumed that a specific color block exists as shown in FIG. However, 1 represents a specific color block, and 0
Represents a non-specific color block. The number of data decoded by the second inverse arithmetic coding unit 14 is only the portion of the non-specific block, and here is 20 pixels (4 × 5 blocks). Therefore, as shown in FIG. 8B, a portion corresponding to the specific color block is supplemented with the specific color 0, and the decoded data is inserted into a portion corresponding to the non-specific color block (hatched portion in the drawing). . The inverse orthogonal transform unit 15 operates similarly.

The decoded multivalued data of r ', g', and b 'is smoothed by the smoothing unit 16 on each surface. The reason why the smoothing is not performed on the color character data but only on the multi-valued data is to prevent the resolution of the color character from deteriorating and to reproduce a clear color character.

<Synthesizing Unit 17> The synthesizing unit 17 synthesizes the decoded color character data and r ', g', b 'multi-value data.

That is, the result (R × a, G × a, B × a) of multiplying the color character data (R, G, B) by a predetermined coefficient a and the multi-value data (r ′, g ′, b ′) ) And. In this combination, the color character data is prioritized as the image data of the pixel where the color character exists. As a result, color characters can be clearly reproduced.

<Image Output Unit 18> The image output unit 18 is an image output device such as a laser beam printer, an LED printer, a liquid crystal printer, a thermal transfer printer, a dot printer, an ink jet printer, or an image display device such as a CRT. A visible image is formed on a recording medium according to the signal.

In particular, the ink jet printer includes a so-called bubble jet printer using a head of a type that ejects liquid droplets by film boiling using thermal energy.

2. FIG. 9 shows an embodiment in which the two arithmetic coding units of the present invention are partially changed. 1 to 18 are the same as those in FIG. Reference numeral 41 denotes a mixer for mixing the color character data and the specific color block determination data.
For example, this mixer inserts specific color block determination data at the beginning of the data of each block. FIG. 10 shows the output from the mixer 41 in a diagram. The hatched portion is the specific color block determination data. With this configuration, it is not necessary to use a plurality of arithmetic coding units. In the arithmetic encoding unit 8, the specific color block determination data is always encoded. However, the encoding of the other color character data is not encoded if the data of the specific color block is as described above. Encoded only for data. 42 in FIG.
Is a memory for storing the decoded specific color block determination data.

3. The present invention can be applied not only to an image communication device such as a color facsimile but also to a storage device such as an image file.

FIG. 11 shows an example in which the present invention is applied to a storage device. In FIG. 11, 1 to 18 are the same as those in FIG. 21 is a hard disk, R
This is an image file including an OM, a RAM, and the like, and can store a plurality of images. When remembering,
The arithmetic code and the Huffman code may be stored separately, or may be stored collectively for each image. Further, for example, when only the character portion is to be used for display or hard copy, only the arithmetic code needs to be decoded, and in that case, the processing time can be reduced.

4. In the present embodiment, in addition to the configuration of the first embodiment, a smoothing unit 31 is further provided after the image synthesizing unit 14 at the time of decoding.

For smoothing, for example, a smoothing filter of a 3 × 3 pixel block can be used. Further, as the filter coefficient, a coefficient for obtaining a weighted average of the target pixel and the peripheral pixels may be used.

According to the present embodiment, since the smoothing is performed even after the combination of the color character and the multi-valued image, it is possible to prevent the boundary between the color character portion and the multi-valued image from becoming unnatural. This is particularly effective when a document in which characters and natural images are mixed is read by the CCD sensor. Therefore, for example, in the case of an image in which characters can be clearly separated like computer graphics, this smoothing may not be performed.

As described above, according to the above embodiment of the present invention, a specific color (for example, white) having a high appearance frequency in an input image
Is extracted, and the specific color block portion is not encoded, so that the encoding efficiency can be improved.

Since the color character portions existing in the input image are detected at the same time and are simultaneously coded, a plurality of color characters can be coded quickly. By separately encoding, highly efficient encoding can be performed while maintaining high quality. That is, irreversible high-efficiency encoding is performed on the gradation image, and in order to compensate for the disadvantage that the high-frequency component is lost due to the encoding of the gradation image, the edge part, especially the color character part is used. By performing entropy coding, ringing can be prevented, and a color character portion can be reproduced with high quality.

Further, in addition to the color character portion, the color portion around the hue substantially equal to the color character portion is also removed from the gradation image, and a predetermined replacement is performed, thereby significantly improving the efficiency of the gradation image.

The image input unit 1 is not limited to a CCD line sensor, but may be an interface for outputting a processing result of a computer, a still video camera for recording a still image, a video camera for recording a moving image, or the like.

In particular, examples of the computer interface include an interprinter in a page description language such as PostScript or PCL.

The input signal is not limited to the R, G, and B color components, but may be, for example, (Y, I, Q), (L ^* , a ^* , b ^* ),
It may be a signal such as (L ^* , u ^* , v ^* ), (Y, M, C).

Similarly, the color component signals for color detection are not limited to the above-described R, G, and B signals.

The color character encoding method is not limited to binary sequence conversion and arithmetic encoding, but may be run-length encoding, M
Other lossless coding such as H, MR, and MMR may be used.

The encoding method of the multi-valued image is not limited to ADCT, but may be vector quantization or other orthogonal transform encoding.

The type and number of color characters to be detected are not limited to those described above.

The present invention is not limited to the hybrid system of lossless coding and irreversible coding as described above,
You may apply to the encoding apparatus only by T. In this case, the configuration is as shown in FIG. 1 to 18 are the same as those in FIG.

In addition to the case where all the pixels in the block are completely white (level 255), for example, a block in which the average value in the block is equal to or higher than a certain level (extremely close to white) may be set as the specific color block.

Conversely, in the case of an image having a lot of black, a block in which all the pixels in the block are black (level 0) may be set as the specific color block. Further, blue, red, green, and the like may be used as the specific colors.

The present invention can be applied not only to an encoding device but also to a pixel processing device, in particular, a copying machine, a color image editing device, and the like for performing a color conversion process and a line drawing extraction process.

[0078]

As described above, according to the present invention, a data format in which an image is uniformly expressed in the same color, a data format in which an image is expressed in a reversible format, or a data format in which an image is expressed in an irreversible format is used. Since the data is selectively used and stored in the storage unit, the image can be stored in an efficient data format.

[Brief description of the drawings]

FIG. 1 is a block diagram of an encoding device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating edge detection.

FIG. 3 is a diagram illustrating binary sequence conversion.

FIG. 4 is a block diagram showing a configuration of a binary sequence conversion unit.

FIG. 5 is a view for explaining color character removal.

FIG. 6 is a block diagram illustrating a configuration of a color character removing unit.

FIG. 7 is a block diagram showing a configuration of an orthogonal transform unit.

FIG. 8 is a diagram illustrating specific color blocks and interpolation in decoding processing.

FIG. 9 is a block diagram showing the configuration of a second embodiment of the present invention.

FIG. 10 is a view showing where in the binary signal sequence determination data of a specific color block is inserted;

FIG. 11 is a block diagram showing a configuration of a third embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram showing an example in which the present invention is applied to an encoding device using only DCT.

[Explanation of symbols]

 4 Specific color determination unit 6 First arithmetic coding unit

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 11/04 H04N 7/13 Z

Claims (7)

[Claims] An input step of inputting multi-valued image data; generating first image data in which an image in a predetermined area indicated by the multi-valued image data is uniformly expressed as the same color; A first storage step of storing; a second storage step of generating second image data expressing an image in the predetermined area indicated by the multi-valued image data in a reversible format, and storing the second image data in the predetermined storage unit; Generating a third image data representing an image in the predetermined area indicated by the multi-valued image data in an irreversible format, and storing the generated third image data in the predetermined storage means; An image storage method, wherein data is stored in said predetermined storage means by selectively using any of first to third storage steps. 2. The apparatus according to claim 1, wherein the predetermined storage unit is a hard disk, a ROM, or a RAM.
Image storage method described in 1. 3. The apparatus according to claim 1, wherein said first image data is encoded by a reversible encoding method.
Image storage method described in 1. 4. The apparatus according to claim 1, wherein said second image data is encoded by a lossless encoding method.
Image storage method described in 1. 5. The image storage method according to claim 1, wherein the second image data is encoded by a lossy method. 6. The image storage method according to claim 1, wherein the selection of the first to third storage steps is performed for each of the predetermined areas. 7. An input means for inputting multi-value image data, and first image data which uniformly expresses an image in a predetermined area indicated by the multi-value image data input by the input means as the same color. First generating means, second generating means for generating second image data representing an image in the predetermined area indicated by the multi-valued image data input by the input means in a reversible format, and inputting by the input means A third image representing the image in the predetermined area indicated by the obtained multi-valued image data as an irreversible format.
An image storage, comprising: third generation means for generating image data; and storage means for selectively storing the first to third image data generated from any of the first to third generation means. apparatus.