JP5470875B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus that processes input image data for projection display.

  The projector includes an image processing device that performs predetermined processing on image data in order to project and display an image on a screen. An image processing apparatus uses an enlargement / reduction circuit (also referred to as a “resolution conversion unit” or “scaler”) that converts the resolution of image data to a desired resolution, or when trapezoidal distortion occurs in an image projected on a screen. In addition, a trapezoidal distortion correction circuit (also referred to as “keystone correction unit”) that performs trapezoidal distortion correction (also referred to as “keystone correction”) to correct the trapezoidal distortion is provided. Further, an image memory (also referred to as “frame memory”) for storing image data to be processed is provided (for example, Patent Document 1).

JP 2001-230991 A

  Various processes such as resolution conversion and keystone correction are often executed by reading image data stored in a frame memory. However, when the amount of image data increases, the access frequency of writing to and reading from the frame memory increases, leading to a decrease in image processing speed. Therefore, it has been desired to reduce the amount of image data.

  As a method for reducing the amount of image data, a method for compressing image data is known. However, when image data is compressed, there is a risk of image quality degradation such as block noise occurring in the decoded image. This deterioration in image quality becomes more pronounced as the compression rate increases.

  The above-mentioned problems are not limited to the case where the predetermined processing is performed on the image data by the image processing apparatus used in the projector, but the same problem occurs when the predetermined processing is performed on the image data by a computer or the like. It was.

  Accordingly, an object of the present invention is to provide a technique for suppressing a decrease in image quality while reducing the amount of image data in an image processing apparatus including a keystone correction unit based on the above-described problems.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 An image processing apparatus that processes image data to project and display an input image, and corrects the distortion when the image displayed on the projection surface is distorted. A keystone correction unit that performs keystone correction on the image data, a frame memory that is disposed at least one stage before or after the keystone correction unit, and at least one of the frame memories are provided. Before the image data is stored in the frame memory, at least one data compression / decoding unit that compresses the image data and decodes the compressed image data read from the frame memory; When the keystone correction unit performs keystone correction, at least one of the data compression / decryption units When the data is compressed, the compressed image data is stored in the corresponding frame memory, and the keystone correction unit does not perform the keystone correction, the data compression / decoding unit An image processing apparatus for storing the image data in the corresponding frame memory without performing compression.
According to the image processing apparatus of Application Example 1, when performing keystone correction, the image data is compressed, so that the amount of image data can be reduced. Further, image quality deterioration due to compression and decoding of image data can be suppressed by keystone correction. This is because the keystone correction has an effect of smoothing the image data, so that deterioration in image quality due to compression and decoding of the image data can be suppressed.

Application Example 2 In the image processing apparatus according to Application Example 1, the compression rate in the data compression / decoding unit is increased as the correction amount of the keystone correction performed by the keystone correction unit increases. Image processing device.
Keystone correction with a large correction amount can further reduce high-frequency components of the input image. Therefore, according to the image processing apparatus of the application example 2, it is possible to suppress the deterioration of the image quality by performing the keystone correction even when the compression rate of the image data is increased. Therefore, it is possible to suppress the deterioration of image quality while further reducing the amount of image data.

Application Example 3 In the image processing device according to Application Example 1 or Application Example 2, one of the frame memories is a keystone frame memory that stores image data before execution of the keystone correction. When the keystone correction unit is used and performs the keystone correction, a data compression / decryption unit (hereinafter referred to as “keystone data compression / decryption unit”) corresponding to the keystone frame memory is used. When compressing image data and storing the compressed image data in the keystone frame memory, if the keystone correction is only the vertical keystone correction, the keystone data compression / decoding is performed. The unit compresses the image data in units of line data composed of pixels constituting one horizontal line. When the keystone correction includes horizontal keystone correction, the keystone data compression / decoding unit compresses the image data in units of block data composed of block-like pixels. Processing equipment.
According to the image processing apparatus of Application Example 3, by changing the compression method of the image data, the keystone correction unit efficiently converts the pixel data of the pixel before the keystone correction corresponding to each pixel after the keystone correction. It can be read from the keystone frame memory. For this reason, keystone correction can be performed at high speed. The vertical keystone correction (hereinafter referred to as “vertical keystone correction”) refers to keystone correction for correcting trapezoidal distortion generated in the vertical direction projected on the screen. Further, horizontal keystone correction (hereinafter referred to as “horizontal keystone correction”) refers to keystone correction for correcting trapezoidal distortion generated in the horizontal direction projected on a screen.

  The present invention can be realized in various forms. In addition to the configuration as the above-described image processing device, the projector including the image processing device having any of the above-described configurations, the image processing method, and the like The present invention can be realized in the form of a computer program for realizing the functions of the apparatus or method, a storage medium storing the computer program, and the like.

1 is a diagram showing a configuration of a projector 10 as a first embodiment of an image processing apparatus of the present invention. It is a block diagram which shows the internal structure of the video processor 31 of 1st Example. 4 is an explanatory diagram illustrating a setting operation of the projector. FIG. It is a figure which shows the setting operation | movement performed by step S30. 3 is a block diagram showing an internal configuration of a first data compression / decoding unit 302. FIG. It is a figure for demonstrating the concept of a vertical keystone correction | amendment. It is a block diagram which shows the internal structure of the video processor 31a of 2nd Example. It is a figure for demonstrating the concept of a horizontal keystone correction | amendment. It is a figure which shows the setting operation performed by step S30 among the setting operations of the projector in 2nd Example. It is a block diagram which shows the internal structure of the video processor 31b of 3rd Example.

Next, embodiments of the present invention will be described in the following order.
A. First embodiment:
B. Second embodiment:
C. Third embodiment:
D. Variations:

A. First embodiment:
FIG. 1 is a diagram showing a configuration of a projector 10 as a first embodiment of the image processing apparatus of the present invention. The projector 10 includes an image input interface (I / F) unit 20, an image processing unit 30, a liquid crystal panel driving unit 40, a liquid crystal panel 50, an illumination optical system 60, a projection optical system 70, and a control unit 80. It has. The image processing unit 30 and the control unit 80 correspond to the image processing apparatus of the present invention.

  The image input I / F unit 20 converts the input image data VIn into a digital signal, and outputs the digitized image data DIn to the image processing unit 30.

  The image processing unit 30 includes a video processor 31 and two frame memories 32 and 34. The video processor 31 performs image processing on the input image data DIn and outputs image data DOut after the image processing. The frame memory 32 stores image data DIn, and the frame memory 34 stores image data after image processing described later. The internal configuration and operation of the video processor 31 will be described later.

  The liquid crystal panel driving unit 40 drives the liquid crystal panel 50 according to the pixel value (RGB gradation value) of the image data DOut. The liquid crystal panel 50 modulates the illumination light emitted from the illumination optical system 60 according to the pixel value. The projection optical system 70 enlarges and projects the light transmitted through the liquid crystal panel 50 onto the projection screen SC.

  The control unit 80 includes a CPU and a memory (not shown), reads and executes a control program stored in the memory, and controls operations of the image input I / F unit 20, the video processor 31, and the liquid crystal panel driving unit 40.

  FIG. 2 is a block diagram showing the internal configuration of the video processor 31 of the first embodiment. The video processor 31 includes two frame memory control units 306 and 316, two data compression / decoding units 302 and 312 provided corresponding to the two frame memories 32 and 34, a resolution conversion unit 308, a keystone And a correction unit 310. Note that the video processor 31 of the first embodiment has a function of performing only vertical keystone correction.

  The first frame memory control unit 306 writes the image data DIn and Den into the first frame memory 32 and reads out the written image data DIn and Den and outputs them to the resolution conversion unit 308.

  The first data compression / decryption unit 302 compresses the image data DIn when the keystone correction unit 310 performs vertical keystone correction, and outputs the compressed image data Den to the first frame memory 32. At the same time, the image data Den read from the first frame memory 32 is decoded, and the decoded image data Dde is output to the resolution converter 308. On the other hand, when the vertical keystone correction is not performed, the image data DIn is written into the first frame memory 32 without being compressed.

  The resolution conversion unit 308 converts the resolution of the image data DIn to a resolution equal to the resolution of the liquid crystal panel 50 set in advance, and outputs the converted image data Dp to the keystone correction unit 310. Further, data for conversion to the panel resolution preset in the resolution conversion unit 308 is supplied from the control unit 80 (see FIG. 1) at the time of operation setting described later.

  The keystone correction unit 310 performs vertical keystone correction on the image data Dp input from the resolution conversion unit 308, and outputs the image data Dk after the vertical keystone correction to the second frame memory 34. When the vertical keystone correction is not performed, the keystone correction unit 310 outputs the image data Dp to the second frame memory 34. Further, data for vertical keystone correction (hereinafter referred to as “vertical keystone correction data”) preset in the keystone correction unit 310 is supplied from the control unit 80 (see FIG. 1) at the time of operation setting described later. Is done.

  The second frame memory control unit 316 performs image data Dk that has undergone vertical keystone correction by the keystone correction unit 310 or image data Dp that has not undergone vertical keystone correction (that is, image data that has undergone only resolution conversion). Dp) is written into the second frame memory 34, and the written image data Den and Dp are read out and output as image data DOut to the liquid crystal panel drive unit 40 (see FIG. 1).

  When the keystone correction unit 310 performs the vertical keystone correction, the second data compression / decoding unit 312 compresses the image data Dk and outputs the compressed image data Den to the second frame memory 34. At the same time, the read image data Den is decoded, and the decoded image data Dde is output to the liquid crystal panel drive unit 40. When the vertical keystone correction is not performed, the image data Dp is written in the second frame memory 34 without being compressed, and the written image data Dp is read out and output to the liquid crystal panel driving unit 40.

  Here, the projector 10 of the first embodiment includes a first frame memory 32 and a second frame memory 34. Thus, resolution conversion and vertical keystone correction performed between the two frame memories 32 and 34 do not need to be synchronized with the horizontal synchronization signal of the liquid crystal panel driving unit 40. Therefore, since the resolution conversion and the vertical keystone correction can be performed in synchronization with only the vertical synchronization signal of the liquid crystal panel driving unit 40, the processing performance can be improved. In terms of reducing the memory capacity of the frame memory, the second frame memory 34, the second frame memory control unit 316, and the second data compression / decoding unit 312 need not be provided.

  FIG. 3 is an explanatory diagram showing the setting operation of the projector 10. The setting operation of the projector 10 is started by the control unit 80 at a predetermined timing at the time of initial setting that is started by turning on the power of the projector.

  When the setting operation is started, first, the resolution of the input image is detected (step S10). Next, resolution conversion data for conversion to the resolution of the liquid crystal panel 50 is obtained and set in the resolution conversion unit 308 (step 20). Next, vertical keystone correction and data compression / decryption are set (step 30). Details of step S30 will be described later. Then, based on the operating conditions set in steps S20 and S30, each block is operated and a projection operation is executed (step S40).

  Next, input / setting change determination (step S50) and operation stop determination (step S60) are performed. If there is no input from the outside by the user, no change in the setting by this input, or no change in the setting automatically executed by the control unit 80, and the operation is not stopped, the operating conditions already set in steps S20 and S30 Continue to perform projection operations with. When there is an input or a change in setting, the process returns to step S10, and after performing various setting operations again, the projection operation is executed under the reset operation conditions. When the operation is stopped, this setting operation is terminated.

  FIG. 4 is a diagram illustrating the setting operation performed in step S30. Once the setting in step S20 has been performed, the position of the projection screen SC for keystone correction is then detected (step S302), and whether or not vertical keystone correction is to be performed is determined based on the detected result (step S302). Step S304).

  When performing vertical keystone correction, the following setting operation is continued. First, setting is made to use the first and second data compression / decoding units 302 and 312 (step S306). Next, the vertical keystone correction data for vertical keystone correction is set in the keystone correction unit 310 (step S308), and the projection operation is executed in step S40. In other words, when performing vertical keystone correction, the frame memories 32 and 34 store the image data Den compressed by the first and second data compression / decoding units 302 and 312.

  On the other hand, when the vertical keystone correction is not performed, the first and second data compression / decoding units 302 and 312 are set not to be used (step S312), and the projection operation is executed in step S40. That is, when vertical keystone correction is not performed, uncompressed image data DIn and Dp are stored in the frame memories 32 and 34.

  FIG. 5 is a block diagram showing an internal configuration of the first data compression / decoding unit 302. Here, the internal configuration of the first data compression / decoding unit 302 will be described, but the second data compression / decoding unit 312 has the same internal configuration. The first data compression / decoding unit 302 includes a line unit compression / decoding unit 302a that performs compression / decoding of image data in units of line data, and a block unit compression / decoding that performs compression / decoding of image data in units of block data. Part 302b and switching parts 302c and 302d. The use of the line unit compression / decoding unit 302a and the block unit compression / decoding unit 302b can be switched by the switching units 302c and 302d. In the first embodiment, it is preferable to compress and decode image data using only the line unit compression / decoding unit 302a. The reason will be described later. In the first embodiment, the block unit compression / decoding unit 302b may not be provided.

  For example, prediction differential encoding can be used for compression / decoding of image data in units of line data. For example, JPEG (Joint Photographic Coding Experts Group) can be used for compression / decoding of image data in units of block data. The compression rate in the line unit compression / decoding unit image 302a and the block unit compression / decoding unit 302b is variable, and it is preferable to increase the compression rate of the image data as the correction amount of the keystone correction increases.

  FIG. 6 is a diagram for explaining the concept of vertical keystone correction. The vertical keystone correction of image data in units of line data is a process performed to correct the trapezoidal distortion caused by tilt projection, and the corrected image (image after vertical keystone correction) is applied to the liquid crystal panel 50. The trapezoidal distortion is corrected by displaying. In the vertical keystone correction, since vertical interpolation (interline interpolation) and horizontal interpolation are usually performed, the image is smoothed by these interpolations. In vertical keystone correction, image data for one line to several lines of the original image may be read and processed, so the image data is compressed in units of line data, and the compressed image data is If it is stored in the frame memory, only the line data necessary for processing can be easily read out. FIG. 6 shows an example in which image data for two lines of the original image is read in order to process image data for one line of the image after vertical keystone correction.

  As described above, when image processing is performed by the resolution conversion unit 308 and the keystone correction unit 310, image data necessary for image processing is read in units of compressed image data, and the processed image data is compressed. Since the data is written in the second frame memory 34, the amount of image data for reading and writing can be reduced even when the amount of image data is large. Therefore, it is possible to reduce the access frequency of writing and reading to the first and second frame memories 32 and 34 and to prevent the image processing speed from being lowered. In addition, there is a possibility that the image quality may be deteriorated by compression and decoding of the image data. However, since the high frequency component of the input image is reduced by smoothing the image data Dk by the vertical keystone correction, the image quality is reduced. Can be suppressed.

B. Second embodiment:
FIG. 7 is a block diagram showing the internal configuration of the video processor 31a of the second embodiment. The difference from the first embodiment is that the video processor 31a of the second embodiment has a function of performing both vertical keystone correction and horizontal keystone correction. Therefore, the difference in configuration from the first embodiment is that the third frame memory 36, the third frame memory control unit 376, the third data compression / decryption are between the resolution conversion unit 308 and the keystone correction unit 310. This is a point where a part 372 is newly provided. Since the configuration of the first frame memory control unit 306 and the like is the same as that of the first embodiment, the same configuration is denoted by the same reference numeral and description thereof is omitted. Further, the configuration of the projector other than the video processor (liquid crystal panel driving unit 40 and the like) is the same as that of the first embodiment.

  Here, before explaining the second embodiment with reference to FIG. 7, the reason why the third frame memory 36 is provided will be described with reference to FIG. FIG. 8 is a diagram for explaining the concept of horizontal keystone correction. In the horizontal keystone correction, in order to generate the image after the horizontal keystone correction shown in FIG. 8B, the image data corresponding to the horizontal line of the corrected image is obliquely extracted from the image data of the original image. It is necessary to read image data in the direction. For example, in order to generate an image of one horizontal line indicated by an arrow in FIG. 8B, it is necessary to read the image data in FIG. 8A in an oblique direction as indicated by an arrow. On the other hand, the resolution conversion unit 308 reads the image data stored in the first frame memory 32 by sequential scanning and performs resolution conversion. Therefore, since the reading direction of the image data differs between the resolution conversion unit 308 and the keystone correction unit 310, the third frame memory 36 for storing the image data for the keystone correction unit 310 to read the image data in an oblique direction is stored. Provided.

  The third frame memory control unit 376 of the second embodiment writes the image data Dp output from the resolution conversion unit 308 to the third frame memory 36 when keystone correction including horizontal keystone correction is performed. The written image data Den is read and output to the keystone correction unit 310. When keystone correction including horizontal keystone correction is not performed (that is, when only vertical keystone correction is performed or when neither keystone correction is performed), the image data output from the resolution conversion unit 308 is output. Dp is directly output to the keystone correction unit 310 without being written to the third frame memory 36.

  When performing keystone correction including horizontal keystone correction, the compression of the image data Dp performed by the third data compression / decoding unit 372 is performed in units of block data composed of M × N (block-shaped) pixels. Is preferred. By compressing in this way, when performing horizontal keystone correction, pixel data can be read obliquely in units of blocks, and keystone correction including horizontal keystone correction can be performed at high speed. Because. In this case, the compression of the image data performed by the first and second data compression / decoding units 302 and 312 may be performed in units of blocks including M × N pixels, or in the same way as in the first embodiment. It may be done in units. When only the vertical keystone correction is performed by the keystone correction unit 310, the compression of the image data DIn performed by the first data compression / decoding unit 302 forms one horizontal line as in the first embodiment. It is preferable to use line data composed of pixels to be used as a unit. The third frame memory 36 and the third data compression / decoding unit 372 when performing keystone correction including horizontal keystone correction, and the first frame memory 32 and first data compression / decoding unit 372 when performing only vertical keystone correction. The decryption unit 302 corresponds to the keystone frame memory and the keystone data compression / decryption unit of the present invention.

  FIG. 9 is a diagram illustrating the setting operation performed in step S30 among the setting operations of the projector in the second embodiment. The difference from the first embodiment is that Steps S324 to S334 are newly added. The other projector setting operations (step S10 and the like, see FIG. 3) are the same as those in the first embodiment, and thus description thereof is omitted. Of steps S30, steps S302 to S312 are the same as in the first embodiment, and therefore only the operation settings of steps S324 to S334 will be described here.

  When the determination of the presence / absence of the vertical keystone correction and the operation setting of the vertical keystone correction are performed (steps S302 to S312), it is determined whether to perform the horizontal keystone correction based on the result detected in step S302. (Step 324). When performing horizontal keystone correction, first, setting is made to use the third data compression / decryption unit 372 (step S326). Next, the horizontal keystone correction data for correcting the horizontal keystone is set in the keystone correction unit 310 (step S328), and the projection operation is executed in step S40.

  On the other hand, when the horizontal keystone correction is not performed, the third data compression / decoding unit 372 and the third frame memory 36 are set not to be used (step 332 and step 334), and the projection operation is executed in step S40. .

  As described above, in the second embodiment, by compressing image data, the amount of image data can be reduced, and a decrease in image processing speed can be prevented. Furthermore, it is possible to suppress deterioration in image quality by performing keystone correction.

C. Third embodiment:
FIG. 10 is a block diagram showing the internal configuration of the video processor 31b of the third embodiment. The difference in configuration from the first embodiment is that a resolution conversion unit 308b is arranged in the preceding stage of the first frame memory 32b, the first frame memory control unit 306b, and the first data compression / decoding unit 302b. Similar to the second embodiment, the video processor 31b according to the third embodiment has a function of performing both vertical keystone correction and horizontal keystone correction. The resolution conversion unit 308b includes a line buffer (not shown) that stores image data for several lines necessary for resolution conversion. Since the configuration of the second frame memory control unit 316 and the like is the same as that of the first embodiment, the same configuration is denoted by the same reference numeral and description thereof is omitted. Further, the configuration of the projector other than the video processor (the liquid crystal panel driving unit 40 and the like) is the same as that of the above embodiment.

  When keystone correction is performed, the first frame memory control unit 306b writes the image data Dp output from the resolution conversion unit 308b to the first frame memory 32b and reads the written image data Den to perform keystone correction. Output to the unit 310. On the other hand, when the keystone correction is not performed, the image data Dp output from the resolution conversion unit 308b is directly output to the keystone correction unit 310 without being written in the first frame memory 32b.

  The first data compression / decryption unit 302b performs compression in units of lines when the keystone correction unit 310 performs only vertical keystone correction, and M × N when performs keystone correction including horizontal keystone correction. It is preferable to perform compression in units of blocks made up of individual (block-shaped) pixels. The compression performed by the second data compression / decoding unit 312 does not need to correspond to the compression method performed by the first data compression / decoding unit 302b, and any compression method can be employed. Here, the first frame memory 32b and the first data compression / decryption unit 302b correspond to the keystone frame memory and the keystone data compression / decryption unit of the present invention.

D. Variations:
In addition, elements other than the elements described in the independent claims of the claims in the constituent elements in the above-described embodiments are additional elements and can be omitted as appropriate. Further, the present invention is not limited to the above-described examples and embodiments, and can be implemented in various forms without departing from the gist thereof. For example, the following modifications are possible.

D-1. First modification:
In the above embodiment, when performing the keystone correction, the operation is set so that all the data compression / decryption units 302, 302b, 312, and 372 compress the image data. Of these, only one data compression / decoding unit may be set to compress image data. This is because even when only one of the data compression / decoding units compresses image data, the amount of image data can be reduced as compared with the case where image data is not compressed. This is also because deterioration in image quality due to data compression and decoding can be suppressed by keystone correction.

D-2. Second modification:
In the above embodiment, the data compression / decoding unit is provided corresponding to each frame memory. Alternatively, the data compression / decoding unit may be provided corresponding to at least one frame memory. This is because if the image data is compressed by at least one data compression / decoding unit, the amount of image data can be reduced as compared with the case where the image data is not compressed. This is also because deterioration in image quality due to data compression and decoding can be suppressed by keystone correction.

D-3. Third modification:
In the above embodiment, when performing the keystone correction, the image data before the keystone correction is compressed and decoded. Instead, the image data before the keystone correction is compressed and decoded. Instead, compression and decoding may be performed only on the image data Dk after the keystone correction. This is because by performing compression and decoding on the image data Dk smoothed in advance by keystone correction, it is possible to suppress deterioration in image quality due to data compression and decoding.

DESCRIPTION OF SYMBOLS 10 ... Projector 20 ... Image input I / F part 30, 30a, 30b ... Image processing part 31, 31a, 31b ... Video processor 32 ... 1st frame memory 32b ... 1st frame memory 34 ... 2nd frame memory 36 ... 3rd Frame memory 40 ... Liquid crystal panel drive unit 50 ... Liquid crystal panel 60 ... Illumination optical system 70 ... Projection optical system 80 ... Control unit 302 ... First data compression / decoding unit 302a ... Line unit compression / decoding unit 302b ... Block unit compression / decoding Unit 302c, d ... switching unit 306, 306b ... first frame memory control unit 308, 308b ... resolution conversion unit 310 ... keystone correction unit 312 ... second data compression / decoding unit 316 ... second frame memory control unit 372 ... first 3 data compression / decoding unit 376 ... 3rd frame memory control unit SC Projection screen VIN: Input image data DIn: Digitized image data DOut: Image data after image processing Dk: Image data after keystone correction Dp: Image data after resolution conversion Den: Compressed image data Dde ... decoded image data

Claims (5)

An image processing apparatus that processes image data to project and display an input image,
A keystone correction unit that performs keystone correction on the image data so as to correct the distortion when distortion occurs in the image displayed on the projection surface;
At least one frame memory arranged before or after the keystone correction unit;
Before storing the image data in the frame memory, the compressed image provided corresponding to at least one of the frame memories is compressed and read out from the frame memory. And at least one data compression / decoding unit for decoding data,
When the keystone correction unit performs keystone correction, at least one of the data compression / decoding units compresses the image data, stores the compressed image data in the corresponding frame memory,
When the keystone correction unit does not perform keystone correction, the data compression / decoding unit stores the image data in the corresponding frame memory without performing compression on the image data.
Image processing device. The image processing apparatus according to claim 1,
An image processing apparatus that increases a compression rate in the data compression / decryption unit as a correction amount of keystone correction performed by the keystone correction unit increases. The image processing apparatus according to claim 1 or 2,
One of the frame memories is used as a keystone frame memory for storing image data before execution of the keystone correction,
When the keystone correction unit performs keystone correction, a data compression / decryption unit (hereinafter referred to as “keystone data compression / decryption unit”) provided corresponding to the keystone frame memory is used. When compressing the image data and storing the compressed image data in the keystone frame memory,
When the keystone correction is only vertical keystone correction, the keystone data compression / decoding unit compresses the image data in units of line data including pixels constituting one horizontal line. Done
When the keystone correction includes a horizontal keystone correction, the keystone data compression / decoding unit compresses the image data in units of block data including block-shaped pixels.
Image processing device.   A projector provided with the image processing apparatus according to claim 1. An image processing method for processing image data to project and display an input image,
When performing keystone correction on the image data so as to correct distortion of the image displayed on the projection surface, the image data is compressed, the compressed image data is stored in a frame memory,
If the keystone correction is not performed, the image data is stored in the frame memory without being compressed with respect to the image data ,
When the compressed image data is stored in the frame memory, the compressed image data read from the frame memory is decoded.
Image processing method.

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