JP2002010086A - Image processing apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem where when a gradation image formed on a computer is converted to an sRGB space or a JFIF format supported by JPEG, a signal value to be smoothly changed is disturbed slightly by operation errors in the case of conversion, a pseudo outline is generated by a monitor, printer, etc., and image quality is deteriorated. SOLUTION: An image signal wherein a color space is converted by a second color space conversion part 206 is synthesized with an image signal having a prescribed spatial frequency and amplitude by a first image synthesizing part 207. The synthesized image signal is compressed by a JPEG compression part 208.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method, and more particularly to an image processing apparatus and method for compressing and outputting a color image.

[0002]

2. Description of the Related Art Electronic data exchanged between computers is mainly text data such as e-mails having a relatively small amount of data due to the data transfer speed of computers and networks.

[0003] In recent years, as the availability of high-performance computers has become easier and the data transfer speed of networks has increased, the World Wide Web (W
With the spread of WW), electronic data exchanged between computers also includes color image data.

[0004] The data transfer rate of the network is increasing year by year.
Although the speed is increased, the transfer of a color image with a large amount of data still requires a lot of time. Therefore, it is common to transfer a color image after compressing it, and the technology is also standardized. In particular, JPEG (J
oint Photographic Experts Group of ITU-T-ISO / IEC)
Is an industry standard supported by many drawing applications.

Further, in order to match the color of the color image on the monitor of the source and destination of the color image,
The color space of color image data has been defined.
As one of such color spaces, the sRGB color space recommended by IEC 61966 has been adopted as a standard color space for monitors, and is used in many drawing applications.

[0006]

However, when a gradation image having a gradation created on a computer is converted into an sRGB space or a JFIF format supported by JPEG, the image is smoothly converted due to a calculation error at the time of conversion. The signal value to be changed is slightly disturbed, and a pseudo contour is generated depending on a device (a monitor or a printer) for reproducing an image.
There is a problem of deteriorating image quality.

[0007] When an image converted to the sRGB space or the JFIF format is JPEG-compressed, gradation and sub-sampling cause further deterioration in gradation, thereby deteriorating image quality.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to prevent deterioration in gradation when an image is compressed or expanded.

[0009]

The present invention has the following configuration as one means for achieving the above object.

An image processing apparatus according to the present invention is an image processing apparatus for compressing and outputting a color image, wherein the first input means for inputting an image signal and a color space of the input image signal are converted. First converting means, first synthesizing means for generating an image signal having a predetermined spatial frequency and amplitude, and synthesizing the image signal with the color space converted image signal, and compression means for compressing the synthesized image signal And characterized in that:

Preferably, further, second input means for inputting the compressed image signal, expansion means for expanding the input image signal, and second input means for converting the color space of the expanded image signal The image processing apparatus further includes a conversion unit and a second combination unit that generates an image signal having a predetermined spatial frequency and amplitude and combines the generated image signal with the color space converted image signal.

An image processing method according to the present invention is an image processing method for compressing and outputting a color image, wherein an image signal is input, the color space of the input image signal is converted, and a predetermined spatial frequency and An image signal having an amplitude is generated, the color space-converted image signal and the generated image signal are combined, and the combined image signal is compressed.

[0013] Preferably, further, the compressed image signal is input, the input image signal is expanded, the color space of the expanded image signal is converted, and the image signal having a predetermined spatial frequency and amplitude is converted. It is characterized in that the generated and color space converted image signal and the generated image signal are combined.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Configuration] FIG. 1 is a block diagram showing a configuration example of an image processing apparatus according to the present embodiment and peripheral devices connected to the image processing apparatus.

In FIG. 1, a scanner unit 100 scans a document and generates a color image signal from the document image. Further, the controller unit 101 includes an image processing unit 201, an image control unit 202, and the like that realize image processing described later (see FIG. 2). The controller unit 101 transfers the processed image to a network 103 to which a printer unit 102, a WWW server, and the like are connected, and conversely, receives the image via the network 103. The printer unit 102 is an image output device that prints out an image processed by the controller unit 101 and a color image captured from the network 103.

The scanner unit 100 is, for example, a CCD linear sensor having a resolution of 600 dpi, and after performing processing such as A / D conversion and shading correction, generates an 8-bit RGB digital image signal.

The printer unit 102 includes an image processing unit 201 described later.
An electrophotographic color printer that forms a color image on recording paper through a latent image exposure, latent image toner development, toner image transfer and toner image fixing processes based on the CMYK signal generated in This is an ink jet color printer that forms a color image on recording paper by discharging ink of a corresponding color based on a signal. Of course, a color printer of a thermal transfer type such as a fusion type or a sublimation type may be used.

FIG. 2 is a block diagram showing a configuration example of the controller unit 101. As described above, the controller unit 101
Is composed of an image processing unit 201, an image control unit 202, and the like, and the image processing unit 201 implements image processing of the present embodiment. Further, the image control unit 202 transmits the image signal processed by the image processing unit 201 to the printer unit 102 or the network 103.
Function, and the image signal sent via the network 103, the image processing unit 201 to process,
It has a function of sending it to the printer unit 102.

[Image Processing Unit and Image Control Unit] Next, the operations of the image processing unit 201 and the image control unit 202 will be described in detail. First, a case where the image processing apparatus operates as a copying machine will be described.

When the image processing apparatus operates as a copying machine, the scanner unit
The image signal sent from the first color space conversion unit 203
Converts the color space. The first color space conversion unit 203
For example, according to the following equation, the image signals R0, G0, and B0 in the color space depending on the scanner unit 100 are converted into image signals R1, G1, and B1 in a standard color space such as sRGB. R1 = a11 x R0 + a12 x G0 + a13 x B0 G1 = a21 x R0 + a22 x G0 + a23 x B0 ... (1) B1 = a31 x R0 + a32 x G0 + a33 x B0 where a11 to a33 are coefficients Is a linearly independent matrix

The coefficients a11 to a33 represent a color space reproduced by a color filter attached to the scanner unit 100, for example,
It is a coefficient to be converted to sRGB space which is the standard color space of the monitor. The converted color space is not particularly limited, or the converted color space (conversion coefficient) may be changed according to the operation of the apparatus, such as when copying an image or transmitting an image. .

The R1, G1 and B1 signals obtained by the color space conversion are given specific spatial frequency characteristics by the filtering unit 204. For example, a filtering process is realized by performing a convolution operation on a specific coefficient in a 5 × 5 pixel area of the R1, G1, and B1 signals and dividing the result of the convolution operation by 128. As a coefficient for this purpose, for example, there is a coefficient shown in FIG. When the original to be copied is a character-centered image, the coefficient shown in FIG. 3A is used, and when the original is a photographic image, the coefficient shown in FIG. 3B is used.

These coefficients are stored in a non-volatile memory (for example, a ROM) in the CPU control unit 214, and are stored in FIG. 3A or FIG.
One of the coefficients shown in 3 (b) is set in the filtering unit 204 via the interface (I / F) 216.

The R2, G2, and B2 signals obtained by the filtering are converted by the multi-value data conversion unit 205 into the scanner unit 100.
Gamma correction is performed in accordance with the gradation characteristics of. The output signals R3, G3 and B3 of the multi-level data conversion unit 205 are
Entered in 06. The second color space conversion unit 206 converts the R3, G3, and B3 signals into CMY signals by logarithmic conversion, generates a K signal, and performs a masking process that matches the CMYK signals to the characteristics of the color material of the printer unit 103. The output signals C0, M0, Y0, and K0 of the second color space conversion unit 206 are gamma-corrected by the gamma conversion unit 212. If the gradation characteristic of the scanner unit 100 is linear, the CPU control unit 214 controls the multi-value data conversion unit 205 so that the image signal passes through.

The gamma conversion unit 212 corrects the gradation characteristics of the printer unit 102, for example, a look-up table (L
UT). Gamma corrected image signals C1, M
1, Y1 and K1 are binary, ternary or quaternary signals C2 by quantization processing such as error diffusion by a quantization unit 213,
Quantized to M2, Y2 and K2. The image signal needs to be quantized when an ink-jet color printer or the like is used for the printer unit 102.
When the printer unit 102 is an electrophotographic color printer capable of forming an image from a multi-valued image signal,
The U control unit 214 controls the quantization unit 213 so that the image signal passes through.

The CMYK signal thus created is sent to the printer unit 102 via the image control unit 202, and a color image is printed.

Next, a case where the image signal obtained by the scanner unit 100 is transmitted to another image reproducing device via the network 103 will be described. In this case, there are cases where a JPEG-compressed image is transmitted to the network 103 and cases where RGB multi-valued data is transmitted to the network 103. These will be described in order. When sending JPEG compressed images to a network

The image signal output from the scanner unit 100 is converted into an image signal in the sRGB color space by the first color space converter 203 as in the case of the copier operation. Given. The image signal output from the filtering unit 204 is gamma-converted by the multi-level data conversion unit 205. In this case, the multi-level data conversion unit 205 corrects the gradation characteristics of the scanner unit 100 (if necessary) and corrects the gradation characteristics of the image reproducing apparatus (for example, a monitor) of the transmission destination via the network 103. .
FIG. 4 shows an example of the gamma characteristic to be corrected. When γ = 1.0, out = 255 × (in / 255) ^{1.0 When} γ = 1.4, out = 255 × (in / 255) ^{1 / 1.4 When} γ = 1.8, out = 255 × (in / 255) ^{1 /1.8 When} γ = 2.2, out = 255 × (in / 255) ^{1 / 2.2} … (2) where in is the input signal value (0 ≦ in ≦ 255) and out is the converted signal value

In this embodiment, four gamma values are prepared as monitor characteristics. However, when an image is printed out at a destination, the gamma value of a printer driver or the like is not necessarily set to a standard value. This is because it is not always true. Therefore, when transmitting an image to another image reproducing apparatus via the network 103, the above-described four gamma values can be selected and set by the operation unit 215.
Of course, not only can you choose one of the four gamma values,
By setting the gamma value input from the operation unit 215 to the multi-level data conversion unit 205 by the CPU control unit 214, the operator of the image processing apparatus can also arbitrarily set the gamma value.

When transmitting a JPEG-compressed image to the network 103, the second color space conversion unit 206 performs an operation of converting an image signal in the sRGB space into a YCbCr signal in the JFIF format. The signal K0 having a value of zero is also output from the second color space conversion unit 206. However, since the copying function is not executed here, the signal K0 does not affect the subsequent processing. In this case, the calculation performed by the second color space conversion unit 206 is shown in the following equation. Luminance signal Y: C0 = 0.299 × R3 + 0.587 × G3 + 0.144 × B3 Color difference signal Cr: M0 = -0.1687 × R3-0.3313 × G3 + 0.5 × B3 + 128 Color difference signal Cb: Y0 = 0.5 × R3-0.4187 × G3 -0.0813 × C0 + 128… (3)

The signals C0, M0 and Y0 corresponding to the YCrCb signal thus obtained are input to the first image synthesizing unit 207, and an image signal having certain characteristics set from the operation unit 215 is added.

FIG. 5 is a flowchart showing the above addition processing. Note that the first image combining unit 207 gives an arbitrary spatial frequency to the image to be combined, sets the amplitude component to a predetermined level, and adds the amplitude component to the input signal.

In the image synthesizing procedure, since the JPEG compressing section 208 is provided at the subsequent stage of the first image synthesizing section 207, if an image including a component having a very high frequency characteristic is added, the compression ratio will be reduced. Therefore, first, the spatial frequency of the synthesized image is determined from the relationship with the quantization parameter of JPEG compression (S5001), and the amplitude level of the synthesized image is determined (S5002). The spatial frequency and the amplitude level may be determined in advance and stored in a ROM or the like in the CPU control unit 214. Note that if the amplitude level of the image to be synthesized is too large, the periodic components of the synthesized image are conspicuous, which degrades the image quality. Therefore, in this embodiment, the amplitude level is set to 1 level. Actually, the first color space conversion unit 2
03 and the gradation characteristics disturbed by the calculation of the second color space conversion unit 206 are inconspicuous if the amplitude level is about two levels.
Of course, the deterioration of the image quality also depends on the reproducing apparatus.

Next, an image is synthesized with the input image (S500
3). Although an example in which an image having a specific image cycle (spatial frequency) is synthesized has been described here, the image cycle itself may be changed irregularly, or a JPEG compression unit in a subsequent stage may be used.
If it is desired to further increase the compression ratio in 208, the configuration may be such that the amplitude level of the synthesized signal is set to 0 and no image is synthesized.
Finally, the combined image signal is clipped so that the combined image signal falls within the dynamic range (0 to 255 levels) of the image signal (S5004).

FIG. 6 is a block diagram showing a configuration example for synthesizing an image in the first image synthesizing unit 207. In FIG. 6, an input signal and an image signal to be combined are added by an adder 601, and the added image signal is clipped by a limiter 602. In FIG. 6, the image synthesis is described using a one-dimensional signal as an example.
Its essence remains the same.

The image signals X0, Y0 and Z0 synthesized by the first image synthesizing unit 207 are JPEG-compressed by the JPEG compression unit 208. Note that, for example, an appropriate quantization (Q) parameter differs depending on whether a document is mainly composed of characters or thin lines or a photo document.
The parameter can be selected from the operation unit 215. Further, the processing of the first image synthesizing unit 207, which is a preceding stage of the JPEG compressing unit 208, is set in consideration of the quantization parameter and the sub-sampling so as not to affect the compression ratio. In addition, JP
Regarding the configuration of the EG compression unit 208, since there is a standard specification, the description thereof is omitted.

As described above, the JPEG-compressed image (J in FIG. 2)
PG0) is transmitted to the external network 103 under the control of the image control unit 202 by the CPU control unit 214. When sending RGB multi-value data to a network

When transmitting multi-valued data to the network 103, the present embodiment assumes that an sRGB signal is transmitted. In this case, the JPEG-compressed image
The difference from the configuration for sending to 3 is that the image processed by the JPEG compression unit 208 is expanded to become an sRGB signal. Therefore, also in this case, the processing until the JPEG compression is performed is exactly the same as the case where the above-described JPEG compressed image is transmitted to the network.

The JPEG decompression unit 209 receives the JPEG image JPG
The JPEG image JPG0 is decompressed according to the information in the header section of 0.
At this time, the JPEG decompression unit 209 sends the number of lines, the number of samples, the color space information, and the quantization table information of the image before compression described in the header part to the CPU control unit 214.

The image signals X1, Y1, and Z1 obtained by the JPEG decompression process are sent to the third color space conversion unit 210. FIG. 7 is a flowchart for explaining processing in the third color space conversion unit 210.

First, the CPU control section 214 executes the JPEG decompression section 209
The color space of the image before JPEG compression is checked from the information sent from the PC (specifically, whether the color space is JFIF or not) (S700
1) In the case of JFIF, since the color space before compression has been converted to the YCbCr color space, the third color space conversion unit 210 executes the operation shown in Expression (4) to convert the color space of the image signal into sRGB. The color space is converted (S7002). On the other hand, it is not JFIF color space, that is, RGB
In the case of the color space, the image signal is passed through the third color space conversion unit 210 (S7003). The image signals R4, G4, and B4 output from the third color space conversion unit 210 are input to the second image synthesis unit 211. R4 = X1 + 1.402 × (Z1-128) G4 = X1-0.34414 × (Y1-128)-0.71414 × (Z1-128) B4 = X1 + 1.772 × (Y1-128)… (4)

The basic image processing in the second image synthesizing unit 211 is the same as that of the first image synthesizing unit 207, except that the characteristics of the image to be synthesized are changed according to the quantization parameter and the compression ratio at the time of compression. Is different. Therefore, a method of changing the characteristics of an image to be synthesized according to the quantization parameter will be described.

FIG. 8 shows a table in which quantization parameters are stored.
It is a table of × 8 pixels, and shows a spatial frequency band used by the second image synthesizing unit 211 for obtaining the average value AVE. This table actually stores coefficients (quantization coefficients) for dividing DCT coefficients.
Note that this quantization table is stored in the JPEG compression unit 208 or the like in advance as a parameter for JPEG compression.

In this embodiment, the coefficients of the 4 × 4 pixel area 80 corresponding to the high frequency components in the quantization table shown in FIG.
The characteristics of the image to be synthesized are determined from the relationship with the compression ratio.
Note that the area of the quantization table that refers to the coefficient is not necessarily the area 80 shown in FIG.

The processing for determining the characteristics of the image to be synthesized will be described below. FIG. 9 is a flowchart showing processing for determining characteristics of an image to be synthesized by the second image synthesis unit 211, and FIG.
6 is a diagram illustrating an example of characteristics of an image synthesized by a second image synthesis unit 211. FIG.

The CPU control unit 214 calculates a 4 × 4 pixel area 80 corresponding to a high frequency component from the quantization table described in the header section.
Is calculated (S9001), and a compression ratio P is calculated from the image size (number of bits) described in the header portion and the image size (number of bits) after compression (S9002). The compression ratio P is given by the formula
Calculated by (5). P = (number of bits after compression) / (number of bits before compression)… (5)

The average value AVE and the compression ratio P obtained in this way are
Then, the characteristics of the image to be synthesized are determined (S9003).

Since the operator can switch the image processing mode depending on the characteristics of the input document, the coefficients of the quantization table differ depending on the set image processing mode. Here, “Compression rate P ≦ 1/8, average value AVE ≧ 80” (Condition 1)
In the case of, the amplitude characteristic is a characteristic of ± 2 level with a random period shown in FIG. In FIG. 10, the horizontal axis represents the pixel position, and the vertical axis represents the amplitude of the added signal. In addition, in the case of “compression ratio P ≦ 1/8, average value AVE <80” (condition 2),
As shown in FIG. 10B, the amplitude characteristic has a characteristic of ± 1 level in a random cycle. When the conditions 1 and 2 are not satisfied (condition 3), the amplitude characteristic is a ± 1 level characteristic in the Nyquist cycle of the image resolution. For example, 600dp
In the case of having a resolution of i, the period corresponds to 300 dpi.

In this embodiment, the conditions are set as p: 1/8 and AVE: 80. However, other setting values may be used depending on the system configuration.

An image signal having the above characteristics is combined with an input signal by the configuration shown in FIG. 6, and the image signal R shown in FIG.
5, G5 and B5 are obtained. At the time of the synthesis, an image profile (image size, RGB data, bit number, etc.) is added as header information. Then, the image signals R5, G5, and B5 are sent to the image control unit 202.

The multivalued data of R5, G5 and B5 is
The image data is transmitted to the external network 103 under the control of the image control unit 202 by the CPU control unit 214.

Next, a case where image data received from the network 103 is output to the printer unit 102 will be described. Below, when the received image data is a JPEG image, and
The case of RGB multi-value data will be described. When a JPEG image is received

FIG. 11 is a flowchart showing an example of a procedure for processing an image received from the network 103.

The image input from the network 103 via the image control unit 202 is judged by the JPEG decompression unit 209 as a JPEG image, RGB data, or other data (S1101).
If it is determined that the data is a JPEG image, the color space of the data is analyzed (S1102). In the case of JFIF, the color space of the JPEG-decompressed image is calculated by the third color space conversion unit 210 using the formula
The image data is converted into the sRGB color space according to (4) (S1103). However, when outputting to the printer unit 102, the color space is not necessarily sRGB
The color space does not need to be changed, and may be converted to another color space. On the other hand, in the case of RGB instead of JFIF, color space conversion is not performed (S1104).

If the image format cannot be analyzed or the color space is other than JFIF and RGB, the operation unit 215
An error message is displayed on the LCD or the like (S1105), and the process ends.

The image signals R4, G4 and B4 converted into the sRGB color space are subjected to the same image synthesizing process as in the case where the above-mentioned image is transmitted to the network 103 by the second image synthesizing unit 211 (S1106). . The image signal obtained by synthesizing the image is controlled by the CPU control unit 214 via the image control unit 202.
R6, G6, and B6 are input to the multi-level data conversion unit 205.

The multi-value data conversion unit 205 converts the image signals R6, G6
And B6 are subjected to gamma correction (S1107). As a specific gamma value, γ = 1.8 shown in the conversion characteristic of FIG. 12 is used. In addition,
Other gamma values γ (1.0, 1.
4, 2.2) can also be used.

The image signals R3, G3, and B3 output from the multi-value data conversion unit 205 are subjected to logarithmic conversion and masking processing by the second color space conversion unit 206 in the same manner as in the above-described copier operation. Then (S1108), image signals C0, M0, Y0 and K0 are generated. Thereafter, the gamma conversion unit 212 performs gamma correction according to the engine characteristics (gamma characteristics) of the printer unit 102 (S1109). And the signals C1, M
1, Y1, and K1 are binarized by the quantization unit 213 according to the engine of the printer unit 102, for example, by an error diffusion method or the like (S1110).

The quantized signals C2, M2, Y2 and K2 are sent to the printer unit 102 via the image control unit 202, and a color image is formed on a recording sheet by a predetermined print sequence. When RGB multi-value data is received

When the RGB multi-value data is input from the image control unit 202 to the JPEG decompression unit 209, the process jumps to step 1107 according to the determination in step 1101. That is, the JPEG control unit 209 and the third color space conversion unit 21 are controlled by the CPU control unit 214.
0 and the second image synthesizing unit 211 are passed through, and the RGB multi-valued data is passed through the image control unit 202 to the multi-value data converting unit 2.
Input to 05. Subsequent processing (S1107 to S1110) is JP
This is the same as when an EG image is received.

As described above, according to the present embodiment, the color space of the input color image signal is converted, and the converted color image signal is subjected to the spatial frequency conversion to generate the converted image signal. An image signal having a predetermined spatial frequency and a predetermined level of amplitude is generated, and a compression process (for example, JPEG compression) is performed on an image signal obtained by combining the spatial frequency converted image signal and the generated image signal. Therefore, it is possible to improve the gradation jump that occurs at the time of reproducing such an image due to an arithmetic error generated at the time of color space conversion and a loss of information due to irreversible compression processing.

In particular, by controlling the amplitude component and the frequency component of the synthesized image, the synthesized image can be reproduced without being emphasized, and can be reproduced with good image quality.

In the above description, an example has been described in which the characteristics of an image to be synthesized are changed by the compression ratio P and the average value AVE of the quantization coefficient. However, regardless of the compression ratio P and the average value AV of the quantization coefficient, An image having the characteristic given by the above condition 2 may always be synthesized.

In the above description, an example in which the image processing apparatus includes a scanner, a controller, and a printer and is connected to a network has been described. However, the present invention is not limited to this. For example, by connecting a computer to the controller,
By operating a GUI on a monitor connected to the computer, a configuration in which predetermined control is performed can be adopted. Also, this computer is directly connected to the controller
The connection may be established, but the same control as described above can be performed via a network.

[0066]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Further, an object of the present invention is to supply a storage medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or an apparatus, and a computer (a computer) of the system or the apparatus. It is needless to say that the present invention can also be achieved by a CPU or an MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. Also,
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the operating system (OS) running on the computer based on the instructions of the program code.
It goes without saying that a case where the functions of the above-described embodiments are implemented by performing some or all of the actual processing, and the processing performs the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. Needless to say, the CPU included in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.

[0070]

As described above, according to the present invention,
When the image is compressed or decompressed, deterioration of gradation can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an image processing apparatus according to an embodiment and peripheral devices connected to the image processing apparatus.

FIG. 2 is a block diagram illustrating a configuration example of a controller unit.

FIG. 3 is a diagram showing an example of a spatial filter coefficient.

FIG. 4 is a diagram illustrating an example of a gamma characteristic of a monitor.

FIG. 5 is a flowchart illustrating an addition process performed by an image synthesis unit;

FIG. 6 is a block diagram showing a configuration example for synthesizing images;

FIG. 7 is a flowchart for explaining processing in a third color space conversion unit;

FIG. 8 is a view showing an example of a table in which quantization parameters are stored;

FIG. 9 is a flowchart illustrating processing for determining characteristics of an image to be combined by a second image combining unit;

FIG. 10 is a diagram illustrating a characteristic example of an image synthesized by a second image synthesis unit;

FIG. 11 is a flowchart illustrating an example of a procedure for processing an image received from a network,

FIG. 12 is a diagram illustrating an example of a gamma correction characteristic applied to an image received from a network.

Continued on front page F-term (reference)

Claims (11)

[Claims] An image processing apparatus for compressing and outputting a color image, comprising: first input means for inputting an image signal; first conversion means for converting a color space of the input image signal; Generating an image signal having a predetermined spatial frequency and amplitude,
An image processing apparatus, comprising: first combining means for combining with a color space converted image signal; and compression means for compressing the combined image signal. 2. The image processing apparatus according to claim 1, wherein a spatial frequency of the image signal generated by the first synthesizing unit is determined based on a quantization parameter used in the compression processing. Image processing device. 3. A second input means for inputting the compressed image signal, an expansion means for expanding the input image signal, and a second conversion for converting the color space of the expanded image signal. Means for generating an image signal having a predetermined spatial frequency and amplitude;
2. The image processing apparatus according to claim 1, further comprising a second combining unit that combines the image signal with the color space converted image signal. 4. A spatial frequency and an amplitude of an image signal generated by said second synthesizing means are determined by a quantization parameter and a compression ratio used for a compression process of the image signal input by said second input means. 4. The image processing apparatus according to claim 3, wherein the image processing apparatus is determined based on: 5. The image processing apparatus according to claim 1, further comprising a limiting unit that limits a dynamic range of the synthesized image signal to a predetermined range. 6. An image processing method for compressing and outputting a color image, comprising inputting an image signal, converting a color space of the input image signal, and generating an image signal having a predetermined spatial frequency and amplitude. An image processing method comprising: synthesizing the color space converted image signal and the generated image signal; and compressing the synthesized image signal. 7. A compressed image signal is input, the input image signal is expanded, the color space of the expanded image signal is converted, and an image signal having a predetermined spatial frequency and amplitude is generated. 7. The image processing method according to claim 6, wherein the color space-converted image signal and the generated image signal are combined. 8. The method according to claim 1, wherein a dynamic range of the image signal after the synthesis is limited to a predetermined range.
8. The image processing method according to claim 6 or 7. 9. A recording medium on which a program code for image processing for compressing and outputting a color image is recorded, wherein the program code includes at least a code for inputting an image signal and a code for the input image signal. A code of a step of converting a color space, a code of a step of generating an image signal having a predetermined spatial frequency and an amplitude, a code of a step of synthesizing the image signal subjected to the color space conversion and the generated image signal, And a code for compressing the compressed image signal. 10. A code of a step of inputting a compressed image signal, a code of a step of expanding the input image signal, a code of a step of converting a color space of the expanded image signal, 10. The code according to claim 9, further comprising a code of a step of generating an image signal having a predetermined spatial frequency and an amplitude, and a code of a step of synthesizing the color space-converted image signal and the generated image signal. Recording media. 11. The recording medium according to claim 9, further comprising a code for limiting a dynamic range of the synthesized image signal to a predetermined range.