JP3820815B2 - Image processing apparatus and image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus that receives image data via a public line or a network line and outputs the image data as a visible image, and an image processing method used in the image processing apparatus.
[0002]
[Prior art]
In recent years, with the progress of colorization of documents, in addition to the widespread use of color copies, color printers, and the like, the opportunity to transmit color documents is also increasing. In general households, the use of color facsimiles in addition to monochrome facsimiles is increasing due to the spread of ISDN (Integrated Services Digital Network) networks.
[0003]
Conventionally, transmission of a color document using a color facsimile or the like is performed as follows.
For example, on the transmitting side, in order to improve transmission efficiency, color image data read by a color optical system is generally subjected to multiple compression at a predetermined resolution by a JPEG (Joint Photographic Experts Group) method. . However, the current G3 color facsimile transmission / reception resolution is 100dpi (dot per inch), 200dpi, 300dpi, 400dpi, but it is an indispensable standard considering transmission time, communication cost, receiving side capability, etc. In most cases, color image data is transmitted at a resolution of 200 dpi.
[0004]
On the other hand, on the receiving side, when color image data that has been multiple-compressed by the JPEG method is received, it is decoded and then printed out as a visible image on recording paper. However, as described above, 200 dpi is the main resolution for transmitting color image data. However, with respect to output devices (printer engines, etc.) on the receiving side, the resolution has been increasing year by year, and currently it is about 600 dpi and 1200 dpi. High resolution output is becoming common. Therefore, on the receiving side, for example, when color image data is received at a resolution of 200 dpi, the color image data is converted to a resolution of 600 dpi or 1200 dpi to match the characteristics of the output device.
[0005]
[Problems to be solved by the invention]
By the way, since the JPEG method, which is one of the standards used when transmitting color image data, is an irreversible compression method, it is possible to increase the compression rate in order to reduce the data amount. There is a risk that mosquito noise that deteriorates the image quality in the peripheral area of characters or block noise that makes block boundaries become conspicuous according to changes in density such as the background of the photograph may occur. . Furthermore, it is conceivable that the entire character is blurred due to image quality degradation at the edge portion of the character, making the character unreadable. That is, in the irreversible compression method, as the compression rate is increased, a defect (image quality degradation or the like) appears in the output image.
[0006]
Therefore, as described above, when resolution conversion is performed on the color image data after decoding on the receiving side in accordance with the characteristics of the output device, defects occurring in the output image become more conspicuous. . For example, when the reception resolution is 200 dpi and the output resolution is 600 dpi, mosquito noise, block noise, and the like are enlarged to about three times and become more conspicuous. In addition, the blur of the deteriorated portion is enlarged about three times in the edge portion of the character, and it becomes more difficult to read.
[0007]
The present invention has been made in view of such problems, and an object of the present invention is to decode image data after irreversible compression received via a public line or a network line, and to decode and resolve the image data. An object of the present invention is to provide an image processing apparatus and an image processing method capable of outputting a high-quality image even when output after conversion.
[0008]
[Means for Solving the Problems]
The present invention has been devised to achieve the above object. Image data of the first resolution is irreversibly compressed by the image processing device Decoding means for decoding the compressed image data, resolution conversion means for converting the image data decoded by the decoding means to a second resolution higher than the first resolution, and edge of the image data converted by the resolution conversion means One or both of edge enhancement processing and noise removal processing as correction processing for image data after conversion by the resolution conversion unit based on the determination result of the edge determination unit Correction processing means The correction processing means performs correction processing on the image data after conversion by the resolution conversion means for each of a plurality of areas constituting the image data, and the size of the area is set in the lossy compression. Is determined based on the size of the processing unit block and the resolution conversion magnification in the resolution conversion means. It is characterized by that.
[0010]
Also, The present invention is an image processing method devised to achieve the above object, and irreversibly compresses image data of the first resolution. Decoding the compressed image data, converting the decoded image data to a second resolution higher than the first resolution, determining the presence or absence of an edge portion of the image data after the conversion to the second resolution, Based on the determination result, either or both of edge enhancement processing and noise removal processing are performed as correction processing for the image data after conversion to the second resolution. It is performed for each of a plurality of areas constituting the image data, and the size of the area is set to the size of the processing unit block in the lossy compression and the resolution conversion from the first resolution to the second resolution. Determine based on magnification It is like that.
[0012]
Image processing apparatus having the above-described configuration and image processing method having the above-described procedure According to Correction processing for image data after resolution conversion is performed for each of a plurality of areas constituting the image data, and density difference for each processing unit block at the time of irreversible compression is prevented from appearing as block noise. Because the size of the area is determined based on the size of the processing unit block and the magnification of resolution conversion, Even if noise or the like is superimposed on the image data by decoding the compressed image data and converting the resolution, the noise or the like is removed by the correction process. Therefore, even if the corrected image data is output as a visible image, image quality deterioration due to decoding of the compressed image data and subsequent resolution conversion is not conspicuous.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image processing apparatus and an image processing method according to the present invention will be described with reference to the drawings.
[0015]
[First Embodiment]
here, First embodiment Will be described.
[0016]
First, the configuration of the image processing apparatus in the present embodiment will be described.
FIG. 1 is a block diagram illustrating a schematic configuration of an image processing apparatus according to the present embodiment.
[0017]
As shown in the figure, the image processing apparatus 10 according to this embodiment includes a receiving unit 11, a decoding unit 12, a resolution conversion unit 13, a correction processing unit 14, and an output unit 15.
[0018]
The receiving unit 11 includes an interface connected to a public line such as a public telephone line network or a network line for constituting a wide area network called the Internet, and is transmitted from a facsimile apparatus on the public line or a computer apparatus on the network line. The received image data is received. However, it is assumed that the compressed image data after being compressed by, for example, the JPEG method is transmitted from the facsimile apparatus or the computer apparatus at a resolution of 200 dpi, for example.
[0019]
The decoding unit 12 is for decoding the compressed image data received by the receiving unit 11. The decoding of the compressed image data by the decoding unit 12 uses a well-known technique, and thus detailed description thereof is omitted here.
[0020]
The resolution converter 13 converts the image data decoded by the decoder 12 to an output resolution higher than the resolution at the time of reception so as to match the characteristics of the output unit 15. Specifically, for example, image data received at a resolution of 200 dpi is converted to an output resolution of 600 dpi.
[0021]
The resolution conversion at this time may be performed using an arbitrary method according to the reception resolution and output resolution, the apparatus configuration of the image processing apparatus 10, and the like. That is, a suitable method may be selected according to the characteristics of image data to be received, processing time, resolution conversion magnification, or the like, or a preset conversion method may be used. For example, as a resolution conversion method, the simple scaling method is used as a simple method, the nearest neighbor method is used as a method to prevent the character edge from being rounded, and the linear approximation is used if the gradation of a photograph or a picture is maintained. There are conversion methods by interpolation such as the bilinear method used and the cubic convolution method using a zinc function. It is also conceivable to distinguish between a character portion and a photograph portion included in the received image data and switch between different conversion methods for each portion.
[0022]
The correction processing unit 14 performs correction processing, which will be described in detail later, on the image data after the resolution conversion by the resolution conversion unit 13. For this purpose, the correction processing unit 14 includes a block size determination unit 14a, an edge determination unit 14b, an edge enhancement unit 14c, a noise removal unit 14d, and a selector 14e.
[0023]
Among these, the block size determination unit 14 a determines the size of the pixel block that is the target of the correction processing in the correction processing unit 14. Here, the determination of the block size by the block size determination unit 14a will be described in detail.
[0024]
FIG. 2 is an explanatory diagram showing a specific example of the correction processing block.
The block size determination unit 14 a determines the block size based on the resolution conversion magnification by the resolution conversion unit 13. Specifically, for example, in the case of the JPEG method, since the compression is performed in units of blocks of 8 pixels × 8 pixels, the block size determination unit 14a, as shown in FIG. More specifically, the size of the block of interest and the size of its peripheral blocks are (8 × n) pixels × (8 × n) pixels. If the resolution conversion unit 13 converts the 200 dpi reception resolution into the 600 dpi output resolution, for example, the value of n at this time is “3” according to the resolution conversion magnification.
[0025]
The reason why the block unit is 8 pixels × 8 pixels is to prevent the density difference for each block from appearing as block noise. The reason why the block size to be corrected is multiplied by n in accordance with the resolution conversion magnification is that when the resolution conversion is performed, the corresponding block size is also converted.
Therefore, if irreversible compression other than JPEG is used and the processing is performed with a different block size, the target block size may be changed as appropriate. Further, when the value of 8 × n becomes other than an integer, the block size may be changed each time by rounding off the value.
[0026]
In FIG. 1, the edge determination unit 14 b determines the presence or absence of an edge portion for each block size determined by the block size determination unit 14 a with respect to the image data after the resolution conversion by the resolution conversion unit 13. . The determination of the presence or absence of an edge portion may be performed using a known technique. Specifically, for example, it is conceivable to carry out using the optimum binarization as disclosed in JP-A-3-126180.
[0027]
As a result of the determination by the edge determination unit 14b, the edge enhancement unit 14c performs edge enhancement processing on the edge pixels of the edge portion if the edge portion is present in the block to be corrected. . The edge enhancement process may be performed using any known method, but the most common example is to apply an edge enhancement filter as shown in FIG. Needless to say, even when an edge enhancement filter is used, the filter size can be arbitrarily determined.
[0028]
In FIG. 1, the noise removing unit 14d determines that noise is described in detail later for a block that is not subject to correction processing as a result of the determination by the edge determining unit 14b. A removal process is performed.
[0029]
The selector 14e, based on the determination result in the edge determination unit 14b, either one of the image data after the edge enhancement processing in the edge enhancement unit 14c and the image data after the noise removal processing in the noise removal unit 14d or Both are used as image data to be sent to the output unit 15.
[0030]
The output unit 15 includes a printer engine or the like that supports full color, and outputs the image data sent from the selector 14e of the correction processing unit 14 on a recording sheet as a visible image. However, the output unit 15 may display and output the image data from the correction processing unit 14 on a CRT (Cathode Ray Tube), an LED (Light Emitting Diode), or the like.
[0031]
Next, an operation example when performing correction processing on received image data in the image processing apparatus 10 configured as described above, that is, an image processing method in the present embodiment will be described.
FIG. 4 is a flowchart showing the flow of the correction processing operation in the present embodiment.
[0032]
In this image processing apparatus 10, when the receiving unit 11 receives the compressed image data, after the decoding of the compressed image data by the decoding unit 12 and the resolution conversion by the resolution conversion unit 13, the correction processing unit 14 performs the resolution conversion after the resolution conversion. Correction processing is performed on the image data.
[0033]
In the correction processing unit 14, when performing the correction processing, as shown in FIG. 4, first, the block size determination unit 14a determines the sizes of the block of interest and the peripheral blocks. For example, if the compressed image data received by the receiving unit 11 is compressed by the JPEG method, the block size determining unit 14a converts the size of the target block and the size of the peripheral block into resolution conversion as already described. According to the magnification, it is determined as (8 × n) pixels × (8 × n) pixels (step 101, hereinafter, step is abbreviated as S).
[0034]
When the block size determination unit 14a determines the sizes of the target block and the peripheral blocks, the correction processing unit 14 then determines whether the edge determination unit 14b has an edge portion for the target block whose size is determined by the block size determination unit 14a. Is determined (S102).
[0035]
If the result of this determination is that there are edge pixels in the block of interest, the edge enhancement unit 14c performs edge enhancement processing on the edge pixels in the block of interest (S103), and the selector 14e performs the noise removal processing. Is sent to the output unit 15 to finish the processing in the block of interest. Thereafter, the output unit 15 outputs the image data after the edge enhancement process sent from the selector 14e as a visible image.
[0036]
As described above, in the image processing apparatus 10, if there is an edge pixel in the target block of the image data, it is determined that the edge portion of the character exists in the target block, and the edge enhancement unit is applied to the edge pixel. 14c performs edge emphasis processing, so that even after decoding of the compressed image data by the decoding unit 12 and resolution conversion by the resolution conversion unit 13, the edge portion of the character on the output image deteriorates and becomes blurred. You can prevent it.
[0037]
On the other hand, when there is no edge pixel in the target block, the noise removing unit 14d subsequently determines whether or not there is a density difference between the target block and the surrounding blocks (S104). Whether or not there is a density difference may be determined as described below.
[0038]
As shown in FIG. 2, the noise removing unit 14d obtains an average value of pixel data in each block for the target block and the four peripheral blocks 1 to 4 located in the vicinity thereof, and an average pixel value av5 for the target block. Is compared with the pixel average values av1 to av4 for the peripheral blocks 1 to 4. That is, when the predetermined threshold value set in advance is “C”, the noise removing unit 14d determines whether or not the respective pixel average values av1 to av5 satisfy the relationship represented by the following expression (1). .
[0039]
| Avj−av5 | <C (where j = 1, 2, 3, 4) (1)
[0040]
When this relationship is satisfied, the density difference between the target block and each of the peripheral blocks 1 to 4 is small, and block noise is likely to occur at the boundary between the target block and the peripheral blocks 1 to 4. Noise removal processing is performed on the target block (S105).
[0041]
The noise removal processing at this time may be performed, for example, by replacing the density value of each pixel data in the target block with the average value of the pixel average values av1 to av5, or by changing the density value of each pixel data in the target block. You may make it change in steps with reference to each pixel average value av1-av4. Further, it is not always necessary to refer to the pixel average values av1 to av5, and the density values of the pixel data constituting the peripheral blocks 1 to 4 may be referred to. Furthermore, instead of replacing all the pixel data in the target block, only the pixel data in the vicinity of the boundary with the peripheral blocks 1 to 4 may be replaced while referring to the average pixel values av1 to av5. That is, the noise removal unit 14d may perform noise removal processing on the block of interest using one of known noise removal processing methods or by arbitrarily combining a plurality of methods.
[0042]
When the noise removal processing is completed, the selector 14e sends the data after the noise removal processing to the output unit 15 to complete the processing in the block of interest. Thereafter, the output unit 15 outputs the image data after the noise removal processing sent from the selector 14e as a visible image.
[0043]
As described above, in this image processing apparatus 10, if there is no edge pixel in the target block of the image data, the noise removing unit 14 d performs noise removal processing on the target block. Even after data decoding and resolution conversion by the resolution converter 13, block noise can be prevented from being noticeable on the output image.
[0044]
However, when the pixel average values av1 to av5 do not satisfy the relationship shown in the above-described equation (1), the noise removal unit 14d has the above-described possibility because the possibility of block noise generation according to the density change is extremely small. The process for the pixel data in the block of interest is terminated without performing the noise removal process.
[0045]
Note that the criterion for determining whether or not the noise removing unit 14d performs the noise removing process is not limited to the relationship represented by the above-described equation (1). That is, the pixel average value av5 of the block of interest does not necessarily satisfy the relationship shown in Expression (1) for all of the pixel average values av1 to av4 of the peripheral blocks 1 to 4. For example, the expression ( Different noise removal processing may be performed when the relationship shown in 1) is satisfied and when the relationship shown in Expression (1) is satisfied for the peripheral blocks 3 and 4.
[0046]
Further, the sizes of the peripheral blocks 1 to 4 are not necessarily the same as the size of the block of interest. Furthermore, the number of peripheral blocks is not limited to four located around the block of interest, and may be limited to, for example, peripheral blocks 1 and 2 or peripheral blocks 3 and 4, or More peripheral blocks may be referenced.
[0047]
That is, the determination as to whether or not to perform noise removal processing is not limited to the case where the determination is made based on the density difference between the block of interest and the four surrounding blocks, and an arbitrary criterion may be used.
[0048]
By the way, here, when the correction processing unit 14 performs the correction processing, the edge enhancement processing by the edge enhancement unit 14c and the noise removal processing by the noise removal unit 14d are performed based on the determination result of the edge presence / absence in the edge determination unit 14b. The case where either one of the above is selectively performed has been described as an example. However, as the correction processing by the correction processing unit 14, it is possible to perform both edge enhancement processing and noise removal processing. Specifically, the edge emphasizing unit 14c performs edge emphasis processing on the target block for which it is determined that the edge pixel exists, and the noise removing unit 14d refers to the peripheral pixels of the edge part to determine the mosquito noise generation part. It may be determined and the noise removal process may be performed.
[0049]
As described above, when there is an edge pixel in the target block of the image data, not only the edge enhancement processing by the edge enhancement unit 14c but also both the edge enhancement processing by the edge enhancement unit 14c and the noise removal processing by the noise removal unit 14d. As a result, even after the decoding of the compressed image data by the decoding unit 12 and the resolution conversion by the resolution conversion unit 13, mosquito noise appears that deteriorates the image quality of the peripheral portion of the character on the output image. You can prevent it.
[0050]
As described above, in the image processing apparatus 10 of this embodiment and the image processing method performed by the image processing apparatus 10, the correction processing unit 14 performs edge enhancement on the image data after the resolution conversion by the resolution conversion unit 13. One or both of processing and noise removal processing are performed. Therefore, even if noise that causes defects such as character blur, block noise, or mosquito noise is superimposed due to the high compression rate of the compressed image data received by the receiving unit 11, the noise is corrected. Since it can be removed by correction processing in the processing unit 14, it is possible to prevent defects from appearing on the output image.
[0051]
In addition, since the correction processing by the correction processing unit 14 is performed on the image data after the resolution conversion by the resolution conversion unit 13, the defects appearing at the resolution conversion are not limited to the defects occurring at the time of decoding. Can be prevented. That is, since the correction processing unit 14 performs the correction process after converting the image data from the reception resolution to the output resolution, it is possible to surely prevent the appearance of defects in the output image, and as a result, the output of a high-quality image is achieved. Can be realized.
[0052]
Furthermore, in the image processing apparatus 10 and the image processing method performed by the image processing apparatus 10 according to the present embodiment, when the correction processing unit 14 performs the correction process, the block size to be corrected is determined as a block size determination unit. Since 14a is determined according to the magnification of resolution conversion performed by the resolution conversion unit 13, the determination can be facilitated. In addition, despite the fact that the determination is easy, it is possible to surely remove this without missing the occurrence position of block noise or the like. In other words, by determining the block size based on the resolution conversion magnification, appropriate correction can be made with a simple configuration even for images with arbitrary resolution and irreversibly compressed by an arbitrary method. Processing can be performed.
[0053]
[Second Embodiment]
next, Second embodiment Will be described. However, here, only differences from the first embodiment described above will be described.
[0054]
First, the configuration of the image processing apparatus in the present embodiment will be described.
FIG. 5 is a block diagram illustrating a schematic configuration of the image processing apparatus according to the present embodiment. In the figure, the same reference numerals are given to the same components as those in the first embodiment.
[0055]
As shown in the figure, the image processing apparatus 20 in the present embodiment is different from the first embodiment described above in the correction processing unit 21 and the resolution conversion unit 22.
[0056]
The correction processing unit 21 performs correction processing on the image data decoded by the decoding unit 12. That is, the correction processing unit 21 performs correction processing on the image data before the resolution conversion by the resolution conversion unit 22 is performed. Therefore, the correction processing unit 21 does not have the block size determination unit 14a unlike the case of the first embodiment, and the block size to be corrected is always a fixed value, for example, the JPEG method. In the case of compressed image data according to the above, 8 pixels × 8 pixels are set. This corresponds to the case of n = 1 in FIG.
[0057]
The resolution conversion unit 22 converts the image data after the correction processing by the correction processing unit 21 into an output resolution higher than the resolution at the time of reception so as to match the characteristics of the output unit 15. It is. Note that the resolution conversion at this time may be performed in the same manner as described in the first embodiment.
[0058]
Next, an operation example when performing correction processing on received image data in the image processing apparatus 20 configured as described above, that is, an image processing method in the present embodiment will be described.
FIG. 6 is a flowchart showing the flow of the correction processing operation in the present embodiment.
[0059]
In the image processing apparatus 20, when the receiving unit 11 receives the compressed image data, the decoding unit 12 performs a correction process on the decoded image data after the decoding unit 12 decodes the compressed image data.
[0060]
In the correction processing unit 21, when performing the correction processing, as shown in FIG. 6, first, the edge determination unit 14b determines the presence or absence of an edge portion for the block of interest (S201). At this time, since the size of the target block is, for example, a fixed size of 8 pixels × 8 pixels, the determination of the target block size and the peripheral block size as described in the first embodiment is not performed.
[0061]
If the result of this determination is that there is an edge pixel in the block of interest, the edge enhancement unit 14c performs edge enhancement processing on the edge pixel in the block of interest (S201), and the data after the edge enhancement processing Is transmitted to the resolution conversion unit 22 by the selector 14e, and the processing in the block of interest is completed.
[0062]
On the other hand, when there is no edge pixel in the target block, the noise removing unit 14d subsequently compares the pixel average value av5 for the target block with the pixel average values av1 to av4 for the peripheral blocks 1 to 4. However, since block noise is likely to occur when the density difference is small, noise removal processing is performed (S204). The noise removal processing at this time is performed in the same manner as described in the first embodiment.
[0063]
As in the case described in the first embodiment, the correction processing unit 21 uses the edge enhancement processing by the edge enhancement unit 14c and the noise removal unit 14d based on the determination result of the edge presence / absence in the edge determination unit 14b. You may make it perform both with the noise removal process by.
[0064]
When the correction processing unit 21 performs the correction process, the resolution conversion unit 22 converts the resolution of the image data after the correction processing, and then the output unit 15 displays the image data after the resolution conversion. Output as an image.
[0065]
As described above, also in the image processing apparatus 20 of this embodiment and the image processing method performed by the image processing apparatus 20, the correction processing unit 21 performs the edge enhancement process as in the case of the first embodiment. One or both of the noise removal processing is performed. Therefore, even if noise that causes defects such as character blur, block noise, or mosquito noise is superimposed by decoding the compressed image data, the noise can be removed by correction processing in the correction processing unit 21. It is possible to prevent defects from appearing on the output image. Further, since noise and the like are removed by the correction processing, even if the resolution conversion unit 22 performs resolution conversion thereafter, the defect does not become conspicuous due to the resolution conversion.
[0066]
Moreover, the correction processing by the correction processing unit 21 is performed before the resolution conversion by the resolution conversion unit 22. That is, correction processing is performed with the size of a block to be processed always fixed (for example, 8 pixels × 8 pixels) in a state where the resolution before resolution conversion is low. Therefore, a configuration (processing) for determining the block size is not required, and a large amount of memory is not required for the correction processing, so that the correction processing can be performed quickly with a simple device configuration. Become. In addition, for example, switching the resolution conversion method for each pixel based on the determination result in the edge determination unit 14b can be easily realized. However, it goes without saying that a fixed method may be used.
[0067]
In the first and second embodiments described above, the case where the compressed image data compressed by the JPEG method is received has been described as an example. However, the present invention is not limited to this. Needless to say, the present invention can also be applied to image data compressed by other lossy compression methods.
[0068]
【The invention's effect】
As described above, according to the image processing apparatus and the image processing method of the present invention, the first resolution subjected to the lossy compression is used. Decrypt image data Even when this is converted to a second resolution higher than the first resolution, the presence or absence of an edge portion is determined for the image data, and the edge enhancement processing and noise removal processing are performed based on the determination result. Do one or both. Therefore, even if noise that causes a defect such as character blur, block noise, or mosquito noise is superimposed due to the high compression rate of the image data, the noise is removed and the defect is displayed on the output image. Can be prevented from appearing. In other words, even if decoding and resolution conversion are performed on the received compressed image data, a high-quality image with no blurring at the edge portion and with reduced noise can be output.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an image processing apparatus according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating a specific example of a correction processing block according to the first embodiment.
FIG. 3 is an explanatory diagram illustrating a specific example of an edge enhancement filter according to the first embodiment.
FIG. 4 is a flowchart showing a flow of a correction processing operation in the first embodiment.
FIG. 5 is a block diagram showing a schematic configuration of a second embodiment of an image processing apparatus according to the present invention.
FIG. 6 is a flowchart showing a flow of a correction processing operation in the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10,20 ... Image processing apparatus, 11 ... Reception part, 12 ... Decoding part, 13, 22 ... Resolution conversion part, 14, 21 ... Correction processing part, 14a ... Block size determination part, 14b ... Edge determination part, 14c ... Edge Emphasis unit, 14d ... noise removal unit, 14e ... selector, 15 ... output unit

Claims (3)

Decoding means for decoding compressed image data obtained by irreversibly compressing image data of the first resolution ;
Resolution conversion means for converting the image data decoded by the decoding means to a second resolution higher than the first resolution;
Edge determination means for determining the presence or absence of an edge portion for the image data converted by the resolution conversion means;
Correction processing means for performing either or both of edge enhancement processing and noise removal processing as correction processing for the image data after conversion by the resolution conversion means based on the determination result by the edge determination means ,
The correction processing means performs correction processing on the image data after conversion by the resolution conversion means for each of a plurality of areas constituting the image data, and the size of the area is a processing unit block for the lossy compression. An image processing apparatus characterized in that it is determined on the basis of the size of the image and the resolution conversion magnification of the resolution conversion means . When the irreversibly compressed image data is compressed by the JPEG method, the size of the processing unit block in the correction processing means is set to 8 pixels × 8 pixels.
The image processing apparatus according to claim 1. Decoding compressed image data obtained by irreversibly compressing first resolution image data;
Converting the decoded image data to a second resolution higher than the first resolution;
Determining the presence or absence of an edge for the image data after conversion to the second resolution;
As a correction process for the image data after conversion to the second resolution based on the determination result, either or both of an edge enhancement process and a noise removal process are performed for each of a plurality of areas constituting the image data. The size of the area is determined based on the size of the processing unit block in the lossy compression and the magnification of resolution conversion from the first resolution to the second resolution.
An image processing method.

Images