JP6262571B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus that employs an overdrive system that is a general system for compensating for a slow response speed of a liquid crystal panel or the like.

  In an image processing apparatus for a liquid crystal panel, an overdrive method is generally used to improve the response speed of the liquid crystal panel. In the overdrive method, the pixel value of the image data for output after the overdrive process is determined by comparing the pixel value of the current image data with the pixel value of the past image data. Generally, a pixel value of image data for output after overdrive processing is determined by referring to a lookup table from the pixel value of current image data and the pixel value of past image data.

  In order to compare pixel values of image data, it is necessary to save past image data. However, if the image data is stored as it is, the data becomes enormous, and a large-capacity memory is required, resulting in an increase in cost. Therefore, the image data is generally compressed and stored from the viewpoint of cost reduction. Various methods of compressing image data have been proposed, but most of them are irreversible compression, and image quality may be deteriorated due to an error (compression error) generated in the compression / decompression process. This is noticeable in the dark part (the part where the pixel value is small).

  FIG. 4 is a block diagram illustrating an example of a configuration of a conventional image processing apparatus. The image processing apparatus 30 shown in the figure includes a first overdrive processing circuit 36, a second overdrive processing circuit 38, a compression circuit 40, a memory circuit 42, and a decompression circuit 44.

  In the image processing apparatus 30, a first look-up table 37 that receives the pixel value of the current image data and the pixel value of the past image data by the first overdrive processing circuit 36 and the second overdrive processing circuit 38, respectively. And the second look-up table 39, the pixel value of the image data for output and the pixel value of the image data for storage after the overdrive processing corresponding to the pixel value of the current image data and the pixel value of the past image data The value is output.

  The first look-up table 37 and the second look-up table 39 include image data for storage after overdrive processing corresponding to the representative value of the pixel value of the current image data and the representative value of the pixel value of the past image data. Are stored.

  When the pixel value of the current image data and the pixel value of the past image data are both representative values, the pixel of the current image data output from the first look-up table 37 is output from the first overdrive processing circuit 36. The pixel value of the output image data after the overdrive processing stored in the lattice point corresponding to the representative value of the value and the representative value of the pixel value of the past image data is output as it is.

  On the other hand, when the pixel value of the current image data or the pixel value of the past image data is not a representative value, the current image output from the first lookup table 37 is output from the first overdrive processing circuit 36, for example. Interpolation is performed using the pixel values of the output image data after the overdrive processing stored in the plurality of grid points in the vicinity of the pixel value of the data and the pixel value of the past image data, and the current image The pixel value of the output image data after the overdrive processing corresponding to the pixel value of the data and the pixel value of the past image data is output.

  The same applies to the second overdrive processing circuit 38.

As the first look-up table 37 and the second look-up table 39, as shown in FIG. 5, the pixel values are assigned evenly or as shown in FIG. 6, the pixel values are assigned unevenly. Things are used.
5 and 6 are examples of lookup tables when the current image data is 8 bits and the pixel value is a value from 0 to 255. FIG. In the lookup table shown in FIG. 5, the pixel values of the current image data and the pixel values of the past image data are allocated evenly every 16 pixels. On the other hand, in the lookup table shown in FIG. 6, the pixel values of the current image data and the pixel values of the past image data are allocated unevenly.

  Subsequently, the image data for storage is irreversibly compressed by the compression circuit 40 and the compressed image data is output and stored in the memory circuit 42. The compressed image data read from the memory circuit 42 is expanded by the expansion circuit 44 and output as past image data.

  Thereafter, the above operation is repeated.

  As described above, when past image data is irreversibly compressed, a compression error occurs. Therefore, the pixel values of the past image data input to the first overdrive processing circuit 36 and the second overdrive processing circuit 38 are values including a compression error.

  In this case, since the ratio of the compression error to the pixel value is larger in the dark part (part where the pixel value is relatively small) than in the bright part (part where the pixel value is comparatively large), the sensitivity to the change in the pixel value is high. Becomes higher. Therefore, even when the amount of change in the pixel value due to the compression error is small, for example, when the pixel value changes by 1, the brightness in the dark part is felt as if the brightness has changed more greatly than the bright part. .

  Therefore, even in the prior art, there is known a technique for improving the image quality using a look-up table in which dark portions are finely divided and unevenly allocated, but there is a problem that sufficient image quality is not obtained due to a compression error. . In addition, when compression is performed without considering that the dark portion is finely carved, the compression error becomes a substantially constant value regardless of the pixel value of the original data, so the dark portion is more influenced by the compression error. .

  Here, there are patent documents 1 to 5 as prior art documents relevant to the present invention.

  In Patent Document 1, an encoding unit replaces an amount corresponding to each pixel and an amount corresponding to pixels existing around the pixel on the screen when displayed on the screen with an average of both. There is described a data conversion device that stores compressed data in a memory, reads compressed data from a frame memory by a decoding unit, and assigns the aforementioned average value as display data for each corresponding pixel.

  In Patent Document 2, the current frame data is converted from the RGB format to the YUV format by the RGB-YUV conversion unit, the YUV format frame data is compressed by the compression unit and stored in the memory, and the YUV-RGB re-conversion unit The overdrive circuit that reconverts the frame data stored in the YUV format into the RGB format and determines the overdrive amount based on the current frame data and the previous frame data input in the RGB format by the overdrive amount calculation unit. Is described.

  In Patent Document 3, the previous frame image data is compressed by the compression circuit and the compressed previous frame image data is stored in the frame memory, and the compressed previous frame image data read from the frame memory is decompressed by the decompression circuit, The LUT generates a correction value based on a plurality of representative overdrive values corresponding to a combination of representative values close to the luminance value of the previous frame and the current frame, and the correction circuit generates image data of the current frame based on the correction value. An overdrive circuit that corrects the image and generates output image data is described.

  In Patent Document 4, compression processing and decompression processing are performed on current frame compression decompression data obtained by performing compression processing and decompression processing on compression data corresponding to image data on the current frame and image data on the previous frame. Generates data after overdrive processing from the previous frame compression and expansion data obtained in this way and detects the appropriate direction of overdrive drive, and corrects the data after overdrive processing according to the detected proper direction. A display device control circuit for a display device that generates data after overdrive processing is described.

  Patent Document 5 discloses a first process for performing a first overdrive process based on an input image stored in a frame memory, a second overdrive process and a second overdrive based on an input image. An image processing apparatus including an image processing unit that performs a second process that performs a process other than the process is described.

JP 2006-47993 A JP 2006-113359 A JP 2008-281734 A JP 2013-11769 A JP 2014-2304 A

  An object of the present invention is to solve the above-mentioned problems of the prior art and reduce the influence of a compression error on the dark part and improve the image quality in the dark part even when the past image data is irreversibly compressed. Is to provide.

In order to achieve the above object, the present invention provides a pixel in the first range of the current image data including a pixel value equal to or less than the first set value within a range not exceeding the maximum value of the pixel value of the current image data. A first pixel value conversion circuit that converts a value to a pixel value in a second range of the current converted image data that is wider than the first range;
A first overdrive that outputs a pixel value of output image data after overdrive processing corresponding to a pixel value of the current converted image data and a pixel value of past converted image data using a first lookup table A processing circuit;
A second over-output is used to output a pixel value of the image data for storage after overdrive processing corresponding to the pixel value of the current converted image data and the pixel value of the past converted image data using the second look-up table. A drive processing circuit;
The pixel value of the first range of the image data for storage is changed to the pixel value of the second range of the converted image data for storage within a range that does not exceed the maximum pixel value of the image data for storage. A second pixel value conversion circuit for conversion;
A compression circuit that outputs compressed image data obtained by irreversibly compressing the converted image data for storage;
A memory circuit for storing the compressed image data;
A decompression circuit that decompresses the compressed image data read from the memory circuit and outputs the decompressed converted image data as the past converted image data;
The first overdrive processing circuit and the second overdrive processing circuit are respectively output image data after overdrive processing corresponding to a pixel value of the current converted image data and a pixel value of the past converted image data. The first pixel value conversion circuit and the second pixel value conversion for the pixel value of the current converted image data and the pixel value of the previous converted image data The pixel value of the current image data and the pixel value of the output image data after the overdrive processing corresponding to the pixel value of the past image data and the image data for storage obtained by performing the inverse conversion of the conversion by the circuit The present invention provides an image processing apparatus that outputs a pixel value.

  Here, the first look-up table and the second look-up table include over-values corresponding to the representative value of the pixel value of the current converted image data and the representative value of the pixel value of the previous converted image data, respectively. For output after overdrive processing corresponding to the pixel value of the current image data and the pixel value of the past image data as the pixel value of the image data for output after the drive processing and the pixel value of the image data for storage It is preferable that pixel values of the image data are stored.

The first pixel value conversion circuit further includes a pixel value that is greater than a second set value that is greater than the first set value and less than or equal to a third set value that is greater than the second set value. A pixel value in the third range of the image data is converted to a pixel value in the fourth range of the current converted image data that is larger than the pixel value in the second range and narrower than the third range. And
The second pixel value conversion circuit further converts the pixel value of the third range of the image data for storage into the pixel value of the fourth range of the conversion image data for storage. preferable.

  The first pixel value conversion circuit and the second pixel value conversion circuit divide the first range into a sixth range including pixel values larger than the pixel values of the fifth range and the fifth range, In the case where the second range is divided into a seventh range and an eighth range including pixel values larger than the seventh range, and the pixel values in the fifth range are converted into the pixel values in the seventh range. It is preferable that the magnification is larger than the magnification when the pixel value in the sixth range is converted into the pixel value in the eighth range.

  According to the present invention, the first pixel value conversion circuit and the second pixel value conversion circuit greatly convert the pixel value of the dark portion before compression, and the first look-up table and the second look-up table increase the dark portion. Restore the pixel value. Since the compression error is almost constant regardless of the pixel value of the original data, the compression error becomes relatively small as the pixel value of the original data increases. Thereby, according to this invention, the influence of the compression error with respect to a dark part can be reduced, and an image quality can be improved.

It is a block diagram of one embodiment showing composition of an image processing device of the present invention. It is a conceptual diagram showing an example of conversion from the pixel value of the current image data to the pixel value of the current converted image data by the first pixel value conversion circuit. FIG. 3 is a conceptual diagram illustrating an example of a configuration of a first lookup table corresponding to pixel value conversion illustrated in FIG. 2. It is a block diagram of an example showing the structure of the conventional image processing apparatus. It is a conceptual diagram of an example showing the structure of the look-up table to which the pixel value was allocated equally. It is a conceptual diagram of an example showing the structure of the look-up table to which the pixel value was allocated unevenly.

  Hereinafter, an image processing apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  FIG. 1 is a block diagram of an embodiment showing a configuration of an image processing apparatus of the present invention. The image processing apparatus 10 shown in the figure outputs image data for output after overdrive processing corresponding to the pixel value of the current image data and the pixel value of the past image data, and the first pixel value conversion The circuit 12, the second pixel value conversion circuit 14, the first overdrive processing circuit 16, the second overdrive processing circuit 18, the compression circuit 20, the memory circuit 22, and the expansion circuit 24 are provided.

The first pixel value conversion circuit 12 receives current image data from the outside.
The first pixel value conversion circuit 12 converts the pixel value of the current image data into the pixel value of the current converted image data so as to increase the pixel value in the dark portion and decrease the pixel value in the bright portion. It is.
Specifically, the first pixel value conversion circuit 12 includes current image data including a pixel value equal to or less than the first set value corresponding to the dark portion within a range not exceeding the maximum value of the pixel values of the current image data. The pixel value in the first range is converted to a pixel value in the second range of the current converted image data that is wider than the first range, and is larger than the first set value corresponding to the bright portion A pixel value in the third range of the current image data that includes a pixel value greater than the second set value and less than or equal to the third set value greater than the second set value is greater than the pixel value in the second range, The pixel value is converted into a pixel value in the fourth range of the current converted image data, which is a range narrower than the range.

  As a result, the dark part assignment in the lookup table is increased and the bright part assignment is reduced. This is based on the grounds that the dark part has high sensitivity to changes in pixel values, while the bright part has low sensitivity, and some compression errors cannot be discerned by human eyes.

  FIG. 2 is a conceptual diagram illustrating an example of conversion from the pixel value of the current image data to the pixel value of the current converted image data by the first pixel value conversion circuit. This figure shows an example in which the current image data is 8 bits and the pixel value is a value from 0 to 255.

  In the case of this example, as shown on the left side of the figure, the maximum value of the pixel value of the current image data is 255, the first set value is 32, and the first range is 0 to 32 pixels of the current image data. A range that includes a value. The second range is a range including pixel values 0 to 96 of the current converted image data, as shown on the right side of the figure. That is, the first pixel value conversion circuit 12 sets 0 to 32 pixel values in the first range of the current image data to 0 to 0 in the second range of the current converted image data that is wider than the first range. Convert to 96 pixel values.

  In the case of this example, as shown on the left side of the drawing, the first range is further divided into a fifth range and a sixth range including pixel values larger than the pixel values of the fifth range. The fifth range is a range including pixel values 0 to 8 of the current image data, and the sixth range is a range including pixel values 8 to 32 of the current image data. Accordingly, as shown on the right side of the figure, the second range is further divided into a seventh range and an eighth range including pixel values larger than the pixel values of the seventh range. The seventh range is a range including pixel values 0 to 48 of the current converted image data, and the eighth range is a range including pixel values 48 to 96 of the current converted image data. The first pixel value conversion circuit 12 uses a magnification when converting a pixel value of the fifth range to a pixel value of the seventh range, and a magnification when converting a pixel value of the sixth range to a pixel value of the eighth range. Also make it bigger. That is, the magnification for converting the darker pixel value (the smaller pixel value) is increased.

  The second set value is 80, the third set value is 224, and the third range is a range including pixel values 80 to 224 of the current image data, as shown on the left side of the figure. The fourth range is a range including the pixel values 144 to 224 of the current converted image data, as shown on the right side of the figure. That is, the first pixel value conversion circuit 12 sets the pixel values of 80 to 224 in the third range of the current image data to 144 to 144 in the fourth range of the current converted image data that is a range narrower than the third range. Convert to 224 pixel values.

When the first range and the third range of the current image data are converted into the second range and the fourth range of the current converted image data, respectively, the ranges other than the first range and the third range of the current image data The pixel value needs to be converted.
In the case of the example in FIG. 2, the first pixel value conversion circuit 12 calculates 32 to 80 pixel values in the ninth range of the current image data including pixel values that are larger than the first set value and less than or equal to the second set value. , The pixel value of 96 to 144 in the tenth range of the current converted image data, which is the same range. In addition, the first pixel value conversion circuit 12 converts the current converted image data in which the pixel values of 224 to 255 in the eleventh range of the current image data including the pixel value equal to or greater than the third set value are in the same range. Are converted into pixel values of 224 to 255 in the twelfth range.

Subsequently, image data for storage is input from the second overdrive processing circuit 18 to the second pixel value conversion circuit 14.
The second pixel value conversion circuit 14 saves image data corresponding to a dark portion within a range that does not exceed the maximum value of pixel values of image data for storage, that is, the maximum value of pixel values of current image data. Are converted into pixel values of the second range of the converted image data for storage, and the pixel values of the third range of the image data for storage corresponding to the bright portion are stored. The converted image data is converted into pixel values in the fourth range.

  Instead of converting the pixel value of the current image data into the current converted image data, the second pixel value conversion circuit 14 converts the pixel value of the image data for storage into the pixel value of the converted image data for storage. Except for, the same conversion as the first pixel value conversion circuit 12 is performed.

Subsequently, current converted image data from the first pixel value conversion circuit 12 and past converted image data from the decompression circuit 24 are input to the first overdrive processing circuit 16.
The first overdrive processing circuit 16 uses the first lookup table 17 to store the image data for output after overdrive processing corresponding to the pixel value of the current converted image data and the pixel value of the previous converted image data. A pixel value is output.

  In the first look-up table 17, pixel values of image data for output after overdrive processing corresponding to the representative values of the pixel values of the current converted image data and the representative values of the pixel values of the past converted image data are as follows: It is obtained by performing inverse conversion of conversion by the first pixel value conversion circuit 12 and the second pixel value conversion circuit 14, that is, the pixel value of the current image data and the pixel value of the past image data when not converted. The pixel value of the image data for output after the corresponding overdrive processing is stored.

  When both the pixel value of the current converted image data and the pixel value of the past converted image data are representative values, the first overdrive processing circuit 16 outputs the current converted image data output from the first lookup table 17. The pixel value of the output image data after the overdrive processing stored in the grid point corresponding to the representative value of the pixel value and the representative value of the pixel value of the past converted image data is output as it is.

  On the other hand, when the pixel value of the current converted image data or the pixel value of the past converted image data is not the representative value, the first overdrive processing circuit 16 outputs the current value output from the first lookup table 17, for example. Perform an interpolation operation using the pixel values of the output image data after overdrive processing stored in a plurality of grid points in the vicinity of the pixel values of the converted image data and the past converted image data, The pixel value of the output image data after the overdrive processing corresponding to the pixel value of the current converted image data and the pixel value of the past converted image data is output.

FIG. 3 is a conceptual diagram illustrating an example of the configuration of the first lookup table corresponding to the pixel value conversion illustrated in FIG. 2.
In the figure, the representative value of the pixel value of the current converted image data and the representative value of the pixel value of the past converted image data, the representative value of the pixel value of the current converted image data, and the pixel value of the past converted image data The representative value of the pixel value of the current image data and the representative value of the pixel value of the past image data corresponding to each of the representative values are shown.
As shown in the figure, the first look-up table 17 is such that the pixel values of the current converted image data and the pixel values of the past converted image data are evenly allocated for every 16 pixels.

Here, the pixel value of the current converted image data and the pixel value of the past converted image data are the first pixel value of the current image data and the past image data (the pixel value of the image data for storage), respectively. The pixel value conversion circuit 12 and the second pixel value conversion circuit 14 are non-uniformly converted by the pixel value conversion shown in FIG.
Therefore, as shown in FIG. 3, the first look-up table 17 substantially constitutes the current image data and the past image data that are allocated unevenly.

  In other words, the first overdrive processing circuit 16 uses the current converted image data as the pixel value of the output image data after the overdrive processing corresponding to the pixel value of the current converted image data and the pixel value of the past converted image data. The pixel value of the current image data and the past obtained by performing the inverse transformation of the conversion by the first pixel value conversion circuit 12 and the second pixel value conversion circuit 14 on the pixel value of the data and the pixel value of the past converted image data The pixel value of the image data for output after the overdrive processing corresponding to the pixel value of the image data is output.

Similarly, current converted image data from the first pixel value conversion circuit 12 and past converted image data from the decompression circuit 24 are input to the second overdrive processing circuit 18.
The second overdrive processing circuit 18 uses the second lookup table 19 to store the image data for storage after the overdrive processing corresponding to the pixel value of the current converted image data and the pixel value of the past converted image data. A pixel value is output.

The second overdrive processing circuit 18 performs the same overdrive processing as the first overdrive processing circuit 16 except that the image data for storage is output instead of outputting the image data for output.
The pixel value of the image data for storage after overdrive processing stored in the second lookup table 19 is the pixel value of the image data for output after overdrive processing stored in the first lookup table 17. It may be the same or different.

The compressed image data for storage is input to the compression circuit 20 from the second pixel value conversion circuit 14.
The compression circuit 20 outputs compressed image data obtained by irreversibly compressing stored converted image data.

Compressed image data is input from the compression circuit 20 to the memory circuit 22.
The memory circuit 22 stores compressed image data.

The decompression circuit 24 receives the compressed image data read from the memory circuit 22.
The decompression circuit 24 decompresses the compressed image data read from the memory circuit 22 and outputs it as past converted image data.

  Next, the operation of the image processing apparatus 10 will be described.

  In the image processing apparatus 10, the first pixel value conversion circuit 12 converts the pixel value of the current image data into the pixel value of the current converted image data, and the pixel value corresponding to the dark portion of the current image data is increased. Thus, the pixel value corresponding to the bright part is converted so as to be small.

  Subsequently, the first overdrive processing circuit 16 and the second overdrive processing circuit 18 use the first look-up table 17 and the second look-up table 19, respectively, The pixel value of the image data for output after the overdrive process and the pixel value of the image data for storage corresponding to the pixel value of the converted image data are output.

  Subsequently, the pixel value of the image data for storage is converted into the pixel value of the converted image data for storage by the second pixel value conversion circuit 14, and the pixel value corresponding to the dark portion of the image data for storage is increased. Thus, the pixel value corresponding to the bright part is converted so as to be small.

  Subsequently, the compressed image data for storage is irreversibly compressed by the compression circuit 20, and the compressed image data is stored in the memory circuit 22. The compressed image data read from the memory circuit 22 is decompressed by the decompression circuit 24 and output as past converted image data.

  Thereafter, the above operation is repeated.

Also in the image processing apparatus 10, the past converted image data is not the same as the stored converted image data, and includes a compression error.
However, in the image processing apparatus 10, the first pixel value conversion circuit 12 and the second pixel value conversion circuit 14 greatly convert the pixel value of the dark part before compression, and the first lookup table 17 and the second lookup table 19. Thus, the enlarged dark pixel value is restored. As described above, since the compression error is a substantially constant value regardless of the pixel value of the original data, the compression error becomes relatively small as the pixel value of the original data increases. Thereby, the influence of the compression error with respect to a dark part can be reduced, and an image quality can be improved.

The first pixel value conversion circuit 12 only needs to convert at least the pixel values in the first range of the current image data into the pixel values in the second range of the current converted image data. The pixel value conversion method is not limited at all. For example, it is not essential to convert the pixel values in the third range of the current image data into the pixel values in the fourth range of the current converted image data. The same applies to the second pixel value conversion circuit 14.
Each set value such as the first set value to the third set value and each range such as the first range to the twelfth range can be determined as appropriate.
Also, the representative values of the pixel values of the current converted image data and the representative values of the pixel values of the past converted image data in the first lookup table 17 and the second lookup table 19 are as shown in FIG. The number is not limited to 17 × 17.
The compression / decompression method by the compression circuit 20 and the decompression circuit 24 is not limited at all.

The present invention is basically as described above.
Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and modifications may be made without departing from the gist of the present invention.

10, 30 Image processing device 12 First pixel value conversion circuit 14 Second pixel value conversion circuit 16, 36 First overdrive processing circuit 17, 37 First lookup table 18, 38 Second overdrive processing circuit 19, 39 First 2 Look-up table 20, 40 Compression circuit 22, 42 Memory circuit 24, 44 Expansion circuit

Claims (4)

Within a range that does not exceed the maximum pixel value of the current image data, the pixel value of the first range of the current image data that includes a pixel value that is less than or equal to the first set value is a range that is wider than the first range. A first pixel value conversion circuit for converting to a second range of pixel values of the present converted image data;
A first overdrive that outputs a pixel value of output image data after overdrive processing corresponding to a pixel value of the current converted image data and a pixel value of past converted image data using a first lookup table A processing circuit;
A second over-output is used to output a pixel value of the image data for storage after overdrive processing corresponding to the pixel value of the current converted image data and the pixel value of the past converted image data using the second look-up table. A drive processing circuit;
The pixel value of the first range of the image data for storage is changed to the pixel value of the second range of the converted image data for storage within a range that does not exceed the maximum pixel value of the image data for storage. A second pixel value conversion circuit for conversion;
A compression circuit that outputs compressed image data obtained by irreversibly compressing the converted image data for storage;
A memory circuit for storing the compressed image data;
A decompression circuit that decompresses the compressed image data read from the memory circuit and outputs the decompressed converted image data as the past converted image data;
The first overdrive processing circuit and the second overdrive processing circuit are respectively output image data after overdrive processing corresponding to a pixel value of the current converted image data and a pixel value of the past converted image data. The first pixel value conversion circuit and the second pixel value conversion for the pixel value of the current converted image data and the pixel value of the previous converted image data The pixel value of the current image data and the pixel value of the output image data after the overdrive processing corresponding to the pixel value of the past image data and the image data for storage obtained by performing the inverse conversion of the conversion by the circuit An image processing apparatus that outputs a pixel value.   In the first look-up table and the second look-up table, after the overdrive processing corresponding to the representative value of the pixel value of the current converted image data and the representative value of the pixel value of the past converted image data, respectively. Output image data after overdrive processing corresponding to the pixel value of the current image data and the pixel value of the past image data as the pixel value of the output image data and the pixel value of the image data for storage The image processing apparatus according to claim 1, wherein the pixel value is stored. The first pixel value conversion circuit further includes the current image data including a pixel value that is greater than a second set value that is greater than the first set value and less than or equal to a third set value that is greater than the second set value. The pixel value of the third range is converted to the pixel value of the fourth range of the current converted image data that is larger than the pixel value of the second range and narrower than the third range. ,
The second pixel value conversion circuit further converts a pixel value in the third range of the image data for storage into a pixel value in the fourth range of the converted image data for storage. The image processing apparatus according to 1 or 2.   The first pixel value conversion circuit and the second pixel value conversion circuit divide the first range into a fifth range and a sixth range including pixel values larger than the pixel values of the fifth range, and The second range is divided into a seventh range and an eighth range including pixel values larger than the seventh range, and a magnification when converting the pixel values in the fifth range into the pixel values in the seventh range is calculated. The image processing apparatus according to claim 1, wherein the pixel value in the sixth range is set to be larger than a magnification in the case of converting the pixel value in the eighth range into the pixel value in the eighth range.

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