JP2005266576A - Image processor and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor in which the large color disorder or the like of a display image is not caused even dualing the rewriting of the lookup table without increasing the memory size of a lookup table. <P>SOLUTION: The image processor has a gradation value as data in a lookup table (LUT) address and a LUT storage means stores it. In addition, the image processor has a means for rewriting the data in the address of a LUT by dividing it into plurality of times. For example, when gamma setting, contrast emphasis, chroma emphasis, etc. of an image are desired to be adjusted, the LUT is rewritten. As for reading, while the rewriting means performs writing, only data in an address to which no writing is performed is read. Thus, since address contents of both new and old LUTs are not read even in the middle of rewriting the LUT, the large color disorder, etc. is not generated in the displayed image. Since the writing means performs writing by dividing it into a plurality of times, the memory size in the image processor is not increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus that performs color correction using a lookup table.

  In the image processing apparatus, for example, image processing such as gamma correction and color correction of a liquid crystal panel is performed. At this time, a look-up table (not shown) showing a non-linear correspondence between the tone values of the red (R), green (G), and blue (B) color signals and the tone values for correcting the gamma characteristics. Hereinafter, the image signal is corrected by “LUT”.

  In an image processing apparatus that performs color correction using the LUT as described above, the LUT is rewritten when it is desired to adjust characteristics such as gamma setting, contrast enhancement, and saturation enhancement of the displayed image. However, since rewriting of the LUT requires a relatively long time, the LUT may be rewritten during image display. When rewriting occurs during the display, the color of the displayed image may be disturbed (flickering, color balance collapse, etc.).

  As a technique for solving such a problem, Patent Document 1 discloses that when an image processing apparatus has a total of four LUTs in which an empty LUT is added to an RGB3 channel LUT and the LUT needs to be rewritten, the empty LUT The new R-LUT, the old G-LUT, the new G-LUT, the old G-LUT, the new B-LUT, etc. are rewritten in order, and the other three LUTs are rewritten while one LUT is being rewritten. Techniques for displaying images using them are described.

  However, in the method described in Patent Document 1, double buffering is performed in principle, and there is a problem that the capacity of the LUT increases. In addition, since an image is displayed in a state where only one channel LUT of RGB is updated, the image must be displayed in a state where color balance is lost.

  Patent Document 2 describes a technique in which a LUT memory is configured by a dual port (2 port) SRAM, and LUT rewriting and reading (ie, LUT reference of input image data) are performed simultaneously. However, in this method, since the LUT is used as it is during the LUT rewriting, the image is displayed using the LUT in a state where the data before rewriting and the data after rewriting are mixed. The problem of the color of the mess was not solved.

JP 2001-356754 A JP-A-8-194457

  The present invention has been made in view of the above points, and it is an object of the present invention to provide an image processing apparatus that does not increase the memory size of the lookup table and does not cause large color distortion of the display image even during rewriting of the lookup table. Let it be an issue.

  In one aspect of the present invention, the image processing apparatus has means for acquiring image data to be processed, lookup table storage means for storing a lookup table having gradation values as data in an address, and the acquisition Means for reading data in the address of the lookup table based on a gradation value of the image data; and writing means for writing the data in the address of the lookup table in a plurality of times, the reading means When the writing means is writing, the data in the address where the writing is not performed is read.

  The image processing apparatus includes means for reading data in an address of a look-up table (hereinafter also simply referred to as “LUT”) based on the gradation value of the acquired image data. The LUT has a gradation value as data in the address, and is stored in the lookup table storage means. In addition, the image processing apparatus has writing means for writing the data in the address of the LUT in a plurality of times (hereinafter also referred to as “rewriting”). For example, when image data is displayed on the display device based on the address contents read from the LUT, the LUT is rewritten when it is desired to adjust the gamma setting, contrast enhancement, saturation enhancement, etc. of the displayed image. When the writing unit is writing, the reading unit reads only the data in the address where writing is not performed. That is, the writing means rewrites the address contents of the LUT at a plurality of stages, and the reading means reads the address contents that are not being rewritten. As a result, when displaying image data using the LUT, even when the LUT is being rewritten, the address contents of both the original LUT and the new LUT are not read out, so that there is no large color distortion in the displayed image. . Further, since the writing means writes the data in a plurality of times, it is not necessary to provide a separate memory for rewriting the LUT. Therefore, the memory size in the image processing apparatus does not increase.

  In one aspect of the present invention, when the gradation value of the acquired image data matches the address at which the writing is performed, the image processing apparatus sets the gradation value of the image data in the vicinity of the address. Interpolation means for interpolating based on data in two or more addresses that are not written is provided. When the gradation value of the acquired image data matches the address number being written, the interpolation means performs interpolation based on data in two or more addresses that are not written in the vicinity of this address. Thereby, even when the writing unit is rewriting the LUT, the displayed image does not feel strange.

  In another aspect of the present invention, in the image processing apparatus, the writing means writes the data in the address separately for the even address and the odd address of the lookup table. That is, the writing unit rewrites the LUT in two steps. For example, the reading means first reads the contents of the even addresses of the LUT and then reads the contents of the odd addresses. Thereby, during rewriting of the LUT, the number of addresses of the LUT read by the reading unit is the same, and further, the difference in gradation value is small because it is an odd address or an even address. This also does not cause a sense of incongruity in the displayed image.

  According to another aspect of the present invention, in the image processing device, the lookup table includes a first lookup table corresponding to the number of gradations of the acquired image data, a second lookup table, And the second look-up table has null data inserted therein, and the writing means includes the gray scale at a time in a part of the first look-up table and the second look-up table. Write the data in the address for several minutes.

  In this aspect, the lookup table has a first lookup table corresponding to the number of gradation levels of the acquired image data, and a second lookup table in which null data is inserted. The writing means writes the data in the address corresponding to the number of gradations at a time to a part of the first lookup table and the second lookup table. That is, the LUT is rewritten by one rewriting. Thereby, the period during which the reading unit reads only a part of the address contents of the LUT can be shortened. Therefore, the displayed image does not feel strange. In addition, since the LUT can be rewritten in a normal order, the writing means and the like can be easily controlled.

  According to another aspect of the present invention, the lookup table includes a first lookup table corresponding to the number of gradations of the acquired image data, and a second lookup table, The writing means writes the data in the address in the second lookup table for the first time.

  In this aspect, the lookup table includes a first lookup table corresponding to the number of gradation levels of the acquired image data, and a second lookup table. The writing means writes the data in the address only in the second lookup table for the first time. At the time of the first rewrite, the reading means reads all the contents of the first lookup table that is not being written. From the second time onward, the writing means rewrites the first lookup table. Thereby, the period during which the reading unit reads only a part of the address contents of the LUT can be shortened.

  Preferably, the second look-up table has half the number of addresses of the first look-up table, has an intermediate value of data in the address of the first look-up table, and the writing means Writes the data in the address to the second lookup table for the first time, writes the data in the address to the even or odd address of the first lookup table for the second time, and The data in the address is written to the even address or the odd address that has not been rewritten in the second look-up table. In this case, since the interval between addresses to be rewritten is constant and the second look-up table has intermediate gradation values of the first look-up table, all images displayed during rewriting are uncomfortable. It will not be. In addition, a circuit that performs the above-described processing can be simply configured.

  Preferably, the lookup table storage means includes two 2-port RAMs. In this case, the one that can execute the writing of the write 1 channel and the read of the read 1 channel at the same time is used.

  Further preferably, the lookup table storage means includes four 1-port RAMs. In this case, four 1-port RAMs with selectable write 1 channel and read 1 channel are used.

  In another aspect of the present invention, a step of acquiring image data to be processed, a lookup table storage step of storing a lookup table having a gradation value as address contents, and a gradation value of the acquired image data A process of reading the address contents of the lookup table and a writing process of writing the address contents of the lookup table in a plurality of times, wherein the reading process is performed when the writing means is writing Read the address contents that have not been written. By executing this image processing method, as in the case of the above-described image processing apparatus, it is possible to prevent a large color distortion of the display image even during rewriting of the LUT without increasing the memory size of the LUT.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
First, an image display apparatus including an image processing unit according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a schematic configuration of an image display device 21 according to the first embodiment.

  The image display device 21 mainly includes an image forming unit 1, an LUT forming unit 2, an image processing unit 10, and an image display unit 7. In the image display device 21, the image processing unit 10 performs image processing on the image formed by the image forming unit 1 using the LUT formed by the LUT forming unit 2, and the processed image is displayed on the image display unit 7. .

  The image forming unit 1 includes a CPU, RAM, ROM, drawing device, disk drive device, control software, and the like (not shown). The image forming unit 1 supplies a signal S1 corresponding to the formed image to the image processing unit 10. The image display device 21 may be configured to include a receiving device that obtains an image to be processed or displayed from the outside without including the image forming unit 1 that forms an image to be displayed.

  The LUT forming unit 2 includes a CPU, a RAM, a ROM, and the like (not shown). The LUT forming unit 2 forms an LUT to be rewritten. For example, an LUT for adjusting gamma setting, contrast enhancement, saturation enhancement, and the like according to an instruction from the user is formed. Further, the LUT forming unit 2 can automatically form an LUT according to an external state (for example, whether the periphery of the image display unit 7 is bright or dark). The LUT forming unit 2 supplies a signal S2 corresponding to the formed LUT to the image processing unit 10.

  The image processing unit 10 includes an LUT write control unit 3, an LUT read control unit 4, and an LUT memory 5. The image processing unit 10 functions as the above-described image processing device.

  The LUT memory 5 stores the LUT. In this LUT, an address is associated with a tone value (R, G, and B tone values). That is, the gradation value associated with the address (corresponding to the gradation value of the input image data) is read based on the gradation value of the image data input to the image processing unit 10, and the input image The gradation value is converted into the read gradation value (hereinafter, this conversion is also referred to as “LUT conversion”). As described above, the LUT memory 5 functions as a lookup table storage unit that stores the LUT.

  The LUT read control unit 4 acquires the signal S1 corresponding to the image data from the image forming unit 1, and uses the image data (that is, the gradation value of the image data) as the address signal S11 of the LUT memory 5 to use the LUT memory. The read data S12 is acquired from 5. That is, the read data S12 of the corresponding LUT is acquired from the address signal S11 of the image data. As a result, the gradation value of the image data input to the image processing unit 10 is converted to an appropriate gradation value by LUT conversion. The signal S3 corresponding to the LUT-converted image data is supplied to the image display unit 7. In this way, the LUT read control unit 4 functions as the read means described above.

  The LUT writing control unit 3 writes the LUT stored in the LUT memory 5 in a plurality of times based on the signal S2 corresponding to the LUT supplied from the LUT forming unit 2 (hereinafter also referred to as “rewriting”). In this case, the LUT write control unit 3 supplies the LUT memory 5 with the gradation value (corresponding to the signal S22) of the new LUT and the address number (corresponding to the signal S21) corresponding to the gradation value. To do. Thus, the LUT write control unit 3 functions as the above-described writing means. Details of the rewriting of the LUT by the LUT writing control unit 3 and the reading of the LUT reading control unit 4 at the time of rewriting the LUT will be described later.

  Here, a specific example of LUT conversion will be described with reference to FIG. In FIG. 2, the horizontal axis indicates the gradation value (input gradation value) of the image data to be LUT converted, and the vertical axis indicates the gradation value (output gradation value) after the LUT conversion. Curves A1 and A2 are examples of curves indicating input / output characteristics by LUT conversion (hereinafter also referred to as “LUT patterns”). The LUT memory 5 stores one LUT pattern as described above. In the case described above, the LUT pattern is rewritten by the LUT write control unit 3.

  Returning to FIG. 1, the image display unit 7 will be described. The image display unit 7 includes a display device such as an LCD or a CRT, and displays the image data S3 after being processed by the image processing unit 10. Further, the image display unit 7 can further perform image processing on the acquired image data S5.

  Next, the LUT rewriting method according to the first embodiment of the present invention and the LUT reading method during rewriting will be described with reference to FIG. In the first embodiment, the LUT write control unit 3 rewrites the contents of the even address and the odd address of the LUT separately. That is, the LUT write control unit 3 rewrites the LUT in two steps. Then, the LUT read control unit 4 reads data in an address that is not being rewritten. The LUT writing and reading described below are performed by the LUT writing control unit 3 and the LUT reading control unit 4 described above.

  FIG. 3A shows reading of a normal LUT in which LUT rewriting is not performed. Reference numeral 31 indicates an LUT stored in the LUT memory 5, and a number written therein indicates an address number of the LUT. A gradation value (hereinafter also referred to as “address content” or “data in the address”) is associated with this address. As shown in FIG. 3A, in a normal time when the LUT 31 is not rewritten, the LUT read control unit 4 reads all the address contents of the LUT 31 and outputs a signal S3 corresponding to the image data after the LUT conversion. Output.

  FIG. 3B is a diagram illustrating LUT rewriting and reading when the first rewriting of the LUT is performed. At the first time, the LUT write control unit 3 rewrites only the data in the even address of the LUT with the new address contents. The LUT writing control unit 3 performs rewriting based on the signal S2 acquired from the LUT forming unit 2. This signal S2 includes the gradation value (previously described signal S22) of the new LUT and the corresponding address number (previously described signal S21).

  As described above, in the LUT after the first rewrite (indicated by reference numeral 32), only the data in the even address is rewritten (indicated by the address number with “′”), and the data in the odd address remains unchanged. . On the other hand, when the data in the even address of the LUT 32 is rewritten, the LUT read control unit 4 reads the data in the odd address that has not been rewritten, and the signal S3 corresponding to the image data subjected to the LUT conversion. Is output. In this case, if the address corresponding to the gradation value of the image data to be processed is being rewritten, the LUT read control unit 4 reads the data in the address adjacent to the address from the LUT 32. For example, if the gradation value of the image data to be processed is “2”, the LUT read control unit 4 reads the data in the address “1” or the address “3” of the LUT 32.

  FIG. 3C is a diagram showing LUT rewriting and reading when the LUT is rewritten for the second time. The second time, the LUT write control unit 3 rewrites the data in the odd address of the LUT with the new address contents (indicated by the arrow S2). Therefore, in the LUT after the second rewriting (indicated by reference numeral 33), all the data in the even address and the data in the odd address are rewritten. On the other hand, when the data in the odd address of the LUT 33 has been rewritten, the LUT read control unit 4 reads the data in the even address that has already been written. In this way, the LUT write control unit 3 completely rewrites the LUT 31 into the LUT 34 shown in FIG.

  As described above, in the first embodiment, the LUT write control unit 3 rewrites the address contents of the LUT in two steps, and the LUT read control unit 4 reads the address contents that are not being rewritten. As a result, the image displayed on the image display unit 7 does not cause color disturbance, flickering, or color balance collapse. Further, since the image processing unit 10 rewrites the LUT twice and does not perform double buffering or the like, the memory size of the LUT memory 5 does not increase.

  Although FIG. 3 shows an example in which even-numbered addresses are rewritten in the first time and odd-numbered addresses are rewritten in the second time, the present invention is not limited to this. The odd address may be rewritten at the first time, and the even address may be rewritten at the second time. Further, the number of times of rewriting the LUT is not limited to two.

  Further, the LUT memory 5 can be constituted by a 2-port RAM or a 1-port RAM. In the case of a 2-port RAM, a RAM that can execute writing of one write channel and reading of one read channel simultaneously is used. Further, in the case of a 1-port RAM, a physically configured RAM is used that can select one write channel and one read channel.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. First, FIG. 4 showing a schematic configuration of an image display apparatus according to the second embodiment will be described.

  As shown in FIG. 4, the image display device 22 mainly includes an image forming unit 1, an LUT forming unit 2, an image processing unit 11, and an image display unit 7. Since the image display device 22 according to the second embodiment is different from the image display device 21 shown in the first embodiment only in the configuration of the image processing unit 11, the configuration of the image processing unit 11 will be mainly described below.

  The image processing unit 11 includes an LUT writing control unit 3, an LUT reading control unit 4, an LUT memory 5, and an interpolation processing unit 8. The image processing unit 11 also functions as the above-described image processing device. Note that the LUT write control unit 3 and the LUT memory 5 are the same as those described in the first embodiment, and thus description thereof is omitted.

  The LUT read control unit 4 acquires the signal S1 corresponding to the image data from the image forming unit 1 and uses the image data as the address signal S11 of the LUT memory 5 to acquire the read data S12 and S13 from the LUT memory 5. To do. The two pieces of read data S12 and S13 are acquired if the address content corresponding to the gradation value to be LUT converted is currently being rewritten, by interpolation using the two pieces of read data S12 and S13. This is to generate corresponding data. The LUT read control unit 4 reads data at an address in the vicinity of the address currently being rewritten as read data S12 and S13. The LUT read control unit 4 supplies signals S41 and S42 corresponding to the read data S12 and S13 read in this way to the interpolation processing unit 8. If the address content corresponding to the gradation value to be LUT converted is not currently being rewritten, it is not necessary to perform interpolation, so the LUT read control unit 4 acquires only the read data S12 or S13 from the LUT memory 5. Shall.

  The interpolation processing unit 8 performs interpolation (hereinafter also referred to as “interpolation processing”) based on the signals S41 and S42 acquired from the LUT read control unit 4. The interpolation processing unit 8 performs interpolation processing on the acquired signals S41 and S42 by linear interpolation or the like. The interpolation processing unit 8 supplies the image display unit 7 with a signal S5 corresponding to the image data thus interpolated. If the address content corresponding to the gradation value to be LUT converted is not currently being rewritten, the interpolation processing unit 8 does not perform the interpolation processing. As described above, the interpolation processing unit 8 functions as the interpolation means described above.

  Next, a method for rewriting an LUT according to the second embodiment of the present invention and a method for reading the LUT at the time of rewriting will be described with reference to FIG. Note that the LUT writing and reading described below are performed by the LUT writing control unit 3 and the LUT reading control unit 4 described above. FIG. 5 shows a case where the LUT memory 5 for storing the LUT is composed of one RAM capable of simultaneously processing the write 1 channel and the read 2 channel.

  FIG. 5A shows reading of the LUT at normal time when the LUT is not rewritten. Reference numeral 31 indicates an LUT stored in the LUT memory 5, and a number written therein indicates an address number of the LUT. A gradation value (address content) is associated with this address. As shown in FIG. 5A, in a normal time when the LUT 31 is not rewritten, the LUT read control unit 4 reads all the address contents of the LUT 31 and outputs a signal S5 corresponding to the image data after the LUT conversion. Output.

  FIG. 5B is a diagram illustrating LUT rewriting and reading when the first rewriting of the LUT is performed. Also in the second embodiment, the LUT write control unit 3 rewrites the LUT by dividing the even address and the odd address twice. At the first time, the LUT write control unit 3 rewrites only the data in the even address of the LUT with the new address contents (indicated by the arrow S2). Therefore, in the LUT after the first rewriting (indicated by reference numeral 32), only the data in the even address is rewritten, and the data in the odd address remains as it is.

  On the other hand, when the data in the even address of the LUT 32 is rewritten, the LUT read control unit 4 reads the data in the odd address of the LUT 32 that has not been rewritten. At this time, when the gradation value of the image data to be LUT converted is an even number (that is, when the address content corresponding to the gradation value of the image data is being rewritten), the LUT read control unit 4 Two pieces of data of odd addresses adjacent to are read out. The interpolation processing unit 8 performs interpolation processing based on the contents of the two addresses. Further, when the gradation value of the image data to be LUT converted is an odd number (that is, when the address content corresponding to the gradation value of the image data is not in the middle of rewriting), the LUT read control unit 4 performs only the address content. Is read. In this case, the interpolation processing unit 8 does not perform interpolation processing. In this way, the signal S5 corresponding to the data processed by the interpolation processing unit 8 is generated.

  FIG. 5C is a diagram illustrating LUT rewriting and reading when the LUT is rewritten for the second time. At the second time, the LUT write control unit 3 rewrites the data in the odd address of the LUT with the new address contents (indicated by the arrow S2). Therefore, in the LUT (indicated by reference numeral 33) after completion of the second rewrite, all the data in the even address and the data in the odd address are rewritten. On the other hand, when the data in the odd address of the LUT 33 has been rewritten, the LUT read control unit 4 reads the data in the even address that has already been written. Then, when the gradation value of the image data to be LUT converted is an odd number, the interpolation processing unit 8 performs an interpolation process using data of two even addresses adjacent to the address. When the gradation value of the image data to be LUT converted is an even number, the interpolation processing unit 8 does not perform the interpolation process and uses the address contents corresponding to the gradation value as it is. In this way, the signal S5 corresponding to the data processed by the interpolation processing unit 8 is generated. As described above, the LUT write control unit 3 completely rewrites the LUT 31 to the LUT 34 shown in FIG.

  As described above, also in the second embodiment, the LUT write control unit 3 rewrites the address content of the LUT in two steps, and the LUT read control unit 4 reads the address content that is not being rewritten. Furthermore, in the second embodiment, the interpolation processing unit 8 performs interpolation processing based on the data in the address read by the LUT read control unit 4. Thereby, the quality of the displayed image does not deteriorate even during rewriting of the LUT.

  Next, a configuration example of the LUT memory 5 according to the second embodiment will be described with reference to FIG.

  FIG. 6A shows an example in which the LUT memory 5 is configured by using two 2-port RAMs that can simultaneously process one write channel and one read channel. As shown in FIG. 6A, the LUT memory 5 physically includes two RAMs (LUT memory 51 and LUT memory 52). In this case, the LUT write control unit 3 rewrites the LUT memory 51 and the LUT memory 52 at the same time. Further, the LUT read control unit 4 reads the LUT memory 51 and the LUT memory 52 at the same time.

  FIG. 6B shows an example in which the LUT memory 5 is configured by using four 1-port RAMs that can select one write channel and one read channel. The LUT memory 5 physically includes four RAMs (LUT memory 51, LUT memory 52, LUT memory 53, and LUT memory 54). In this case, the LUT write controller 3 selects the LUT memory 51 and the LUT memory 53 and rewrites them at the same time when rewriting even addresses, and rewrites the LUT memory 52 and LUT memory 54 at the same time when rewriting odd addresses. Further, the LUT read control unit 4 selects the LUT memory 52 and the LUT memory 54 when the even address is rewritten and simultaneously reads, and selects the LUT memory 51 and the LUT memory 53 when the odd address is rewritten. Read simultaneously.

  FIG. 7 shows the address contents read out in the LUT when the LUT memory 5 is configured by using the two 2-port RAMs of FIG. In FIG. 7, “LUT (x)” indicates data (that is, gradation value) in the address (x) in the LUT. Further, the LUT stored in the LUT memory 51 is referred to as “LUT 51”, and the LUT stored in the LUT memory 52 is referred to as “LUT 52”. “&” Indicates that interpolation processing is performed on the read data.

  First, the case where the even address of the LUT is being rewritten and the gradation value of the image data is an even number (= 2k) will be described. That is, the LUT address content corresponding to the gradation value of the image data is being rewritten. At this time, if k is an even number, the LUT read control unit 4 causes the data LUT 51 (k + 1) in the address (k + 1) of the LUT 51 stored in the LUT memory 51 and the address (k of the LUT 52 stored in the LUT memory 52). -1) to obtain the data LUT 52 (k-1). For example, when the gradation value of the image data is “4”, the LUT read control unit 4 acquires data corresponding to the address (3) of the LUT 51 and data corresponding to the address (1) of the LUT 52. The interpolation processing unit 8 performs interpolation processing using the LUT 51 (k + 1) and the LUT 52 (k−1) acquired from the LUT read control unit 4.

  On the other hand, when k is an odd number, the LUT read control unit 4 acquires the LUT 51 (k) and the LUT 52 (k). For example, when the gradation value of the image data is “6”, the LUT read control unit 4 acquires data corresponding to the address (3) of the LUT 51 and data corresponding to the address (3) of the LUT 52. The interpolation processing unit 8 performs interpolation processing using the LUT 51 (k) and the LUT 52 (k).

  Next, a case where the even address of the LUT is being rewritten and the gradation value of the image data is an odd number (= 2k + 1) will be described. The LUT read control unit 4 acquires the LUT 51 (k + 1) when k is an even number, and acquires the LUT 52 (k) when k is an even number. In such a case, the interpolation process is not performed because the address in the LUT corresponding to the gradation value of the image data is not being rewritten.

  Further, even when the odd address of the LUT is being rewritten, the LUT read control unit 4 reads the address contents in the LUT by the method shown in FIG.

  That is, the case where the odd address of the LUT is being rewritten and the gradation value of the image data is an odd number (= 2k + 1) will be described. The LUT read control unit 4 acquires the LUT 51 (k) when k is an even number, and acquires the LUT 52 (k−1) when k is an odd number. In such a case, the interpolation process is not performed because the address in the LUT corresponding to the gradation value of the image data is not being rewritten.

  Next, a case where the odd address of the LUT is being rewritten and the gradation value of the image data is an odd number (= 2k + 1) will be described. That is, the LUT address content corresponding to the gradation value of the image data is being rewritten. At this time, if k is an even number, the LUT read control unit 4 determines the data LUT 51 (k) in the address (k) of the LUT 51 stored in the LUT memory 51 and the address (k of the LUT 52 stored in the LUT memory 52. The data LUT 52 (k) in the parenthesis is acquired. Then, the interpolation processing unit 8 performs an interpolation process using the LUT 51 (k) and the LUT 52 (k) acquired from the LUT read control unit 4.

  On the other hand, when k is an odd number, the LUT read control unit 4 acquires the LUT 51 (k + 1) and the LUT 52 (k−1). The interpolation processing unit 8 performs interpolation processing using the LUT 51 (k + 1) and the LUT 52 (k−1).

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described.

  FIG. 8 shows an LUT rewriting method and an LUT reading method according to the third embodiment. The LUT rewriting method and reading method shown in FIG. 8 are performed by the image processing unit 10 shown in the first embodiment.

  FIG. 8A shows reading of the LUT at the normal time when the LUT is not rewritten. As shown in FIG. 8A, the LUT 62 includes an LUT 60 and an LUT 61. In the LUT 60, no data is contained in the address (that is, null data is inserted). The LUT 61 has an LUT corresponding to the number of gradations of image data to be processed. That is, the LUT 61 functions as a first lookup table, and the LUT 60 functions as a second lookup table. As shown in FIG. 8A, in a normal time when the LUT 62 is not rewritten, the LUT read control unit 4 reads only the address contents of the LUT 61 and outputs a signal S3 corresponding to the image data after the LUT conversion. doing.

  FIG. 8B is a diagram showing LUT rewriting and reading when the LUT 62 is rewritten. In the third embodiment, the LUT write control unit 3 rewrites the LUT 62 once. Specifically, the LUT write control unit 3 rewrites the even address (may be an odd address) of the LUT 61 and the LUT 60 into which null data has been inserted (indicated by reference sign S2). In this case, the LUT write control unit 3 rewrites the even address of the LUT 61 with data corresponding to the even address of the new LUT, and writes data corresponding to the odd address of the new LUT to the LUT 60. Thereby, in the LUT 63 after the rewriting is completed, all the address contents of the new LUT are written, and the contents of the odd addresses of the LUT before the rewriting remain as they are.

  At this time, the LUT read control unit 4 reads only the data in the odd address that has not been rewritten during the rewrite as described above. Then, the LUT read control unit 4 outputs a signal S3 corresponding to the LUT-converted image data.

  FIG. 8C shows the LUT 64 when the address contents of the new LUT are all rewritten. When all the writing of the address contents of the LUT is completed, the LUT writing control unit 3 inserts null data at odd addresses that were not written in the LUT 63. As a result, a new LUT 64 shown in FIG. 8C is generated. The LUT read control unit 4 then reads only the address contents that are not null data in the LUT 64. In addition, although shown about what inserts null data in the above, it is not limited to this. For example, an arbitrary value may be inserted without inserting null data. In this case, the inserted arbitrary data is not used for the LUT conversion.

  As described above, in the third embodiment, the LUT rewrite control unit 3 rewrites the LUT at a time using the second lookup table in which null data is inserted. As a result, the LUT conversion period using only the address contents of either the even address or the odd address of the LUT can be shortened. Therefore, a sense of incongruity is not caused in the displayed image as compared with the above-described embodiment. Further, since the LUT can be rewritten in the normal order of 0, 1, 2,..., The control of the LUT write control unit 3 and the like is simplified.

  Next, a modification according to the third embodiment will be described. In this modification, the above-described LUT writing method and reading method are performed by the image processing unit 11 shown in the second embodiment.

  FIG. 9 shows an LUT rewriting method according to a modification of the third embodiment and a reading method at the time of LUT rewriting.

  FIG. 9A shows reading of a normal LUT without rewriting the LUT, which is the same as FIG. 8A. FIG. 9B shows LUT rewriting and reading when the LUT 62 is rewritten. In this case, the LUT rewrite method by the LUT write control unit 3 is the same as described above.

  This modification differs from that described above in that the interpolation processing unit 8 performs interpolation processing on the data read by the LUT read control unit 4. When the address corresponding to the gradation value of the image data is being rewritten, the LUT read control unit 4 reads two address contents adjacent to the address that are not being written. The interpolation processing unit 8 performs interpolation processing based on the contents of the two addresses. In addition, when the address corresponding to the gradation value of the image data is not in the middle of rewriting, the LUT read control unit 4 reads only the data at the address. In this case, the interpolation processing unit 8 does not perform interpolation processing. In this way, the signal S5 corresponding to the data processed by the interpolation processing unit 8 is generated.

  As described above, the interpolation processing by the interpolation processing unit 8 can be added to the LUT rewriting method and reading method according to the third embodiment. Thereby, the displayed image can be made high quality.

[Fourth Embodiment]
Hereinafter, an LUT rewriting method according to the fourth embodiment and a reading method at the time of LUT rewriting will be described.

  FIG. 10 shows the LUT pattern A3 used for LUT conversion. In FIG. 10, the horizontal axis represents the input gradation value (corresponding to the address of the LUT), and the vertical axis represents the output gradation value. The area B1 indicates the range of the LUT (hereinafter, the LUT having the area B1 is referred to as “basic LUT”). If the number of gradations of the input image data is “256” gradations, the area B1 is equally divided into “256”. Has been. Therefore, the basic LUT has “256” addresses. In the fourth embodiment, an auxiliary LUT (indicated by a broken line B3) is inserted into a region B2 having a steep slope in the characteristic curve of the LUT pattern A3. That is, the area B2 is finely divided. The auxiliary LUT corresponds to the gradation value generated by finely dividing the area B2. As a result, when the gradation value of the input image data is within the area B2, this gradation value is subjected to LUT conversion in detail.

  In the present embodiment, the auxiliary LUT has a size that is ½ of the basic LUT. That is, if the basic LUT has “256” addresses, the auxiliary LUT has “128” addresses. The data in the auxiliary LUT address has an intermediate value of the data in the basic LUT address. As described above, the basic LUT functions as a first lookup table, and the auxiliary LUT functions as a second lookup table.

  Next, an LUT rewriting method and a reading method according to the fourth embodiment using the auxiliary LUT will be described with reference to FIG.

  FIG. 11A shows reading of the LUT at the normal time when the LUT is not rewritten. As shown in FIG. 11A, the LUT 72 includes a basic LUT 71a and an auxiliary LUT 70a. Here, for convenience of explanation, a case where the basic LUT 71a is 4 bits (16 gradations) and the auxiliary LUT 70a is 3 bits (8 gradations) is shown. The auxiliary LUT 70a has half the size of the basic LUT 71a, and the address number of the auxiliary LUT 70a is indicated as “0.5, 1.5, 2.5, 3.5. At normal times when the LUT 72 is not rewritten, the LUT read control unit 4 reads the address contents of both the basic LUT 71a and the auxiliary LUT 70a, and outputs a signal S3 corresponding to the image data after the LUT conversion. As a result, a gradation region having a large inclination in the LUT pattern A3 can be displayed with high image quality.

  FIG. 11B is a diagram showing LUT rewriting and reading when the first LUT 72 is rewritten. In the fourth embodiment, the LUT is rewritten in three steps. The new LUT to be rewritten has a basic LUT 71b and an auxiliary LUT 70b. First, in the first time, the LUT write control unit 3 rewrites only the auxiliary LUT 70a in the LUT 72 with the data of the even address of the new basic LUT 71b (indicated by reference numeral S2). As a result, in the LUT 73 after completion of rewriting, the contents of the even addresses of the basic LUT 71b of the new LUT are written, and the contents of the addresses of the original basic LUT 71a are all left as they are.

  During the above rewriting, the LUT read control unit 4 reads all the address contents of the basic LUT 71a that has not been rewritten. Then, the LUT read control unit 4 outputs a signal S3 corresponding to the LUT-converted image data.

  FIG. 11C is a diagram showing LUT rewriting and reading when the LUT 72 is rewritten for the second time. At the second time, the LUT write control unit 3 rewrites the contents of the even address of the original basic LUT 71a with the data of the odd address of the new basic LUT 71b. As a result, in the LUT 74 after completion of rewriting, all the address contents of the new basic LUT 71b are written, and the odd address contents of the original basic LUT 71a remain unchanged. During rewriting, the LUT read control unit 4 reads only the contents of the odd addresses of the original basic LUT 71a that has not been rewritten.

  FIG. 11D is a diagram illustrating LUT rewriting and reading when the LUT 72 is rewritten for the third time. At the third time, the LUT write control unit 3 rewrites the contents of the odd address of the original basic LUT 71a with the data of the new auxiliary LUT 70b. Thereby, in the LUT 75 after the rewriting is completed, all the contents of the basic LUT 71b and the auxiliary LUT 70b of the new LUT are rewritten. During the third rewrite, the LUT read control unit 4 reads all the contents of the new basic LUT 71b that has not been rewritten at that time. When the above processing is completed, the LUT having the new basic LUT 71b and the auxiliary LUT 70b is obtained, and the LUT read control unit 4 reads all the contents of the new LUT.

  As described above, in the fourth embodiment, the LUT write control unit 3 rewrites the LUT in three steps using the auxiliary LUT. If the even address is simply rewritten with the address content of the new even address (hereinafter referred to as “even number → even number”, etc.) or rewritten as auxiliary → auxiliary, the address interval becomes “0.5”, “1” or “2”. "Are mixed and ununiform timing occurs, and the displayed image is uncomfortable. However, since the method of the fourth embodiment is rewritten as even → odd → auxiliary, the period in which the basic LUT (not the entire LUT) is used is longer than in the above case. Therefore, in the method of the fourth embodiment, since the address of the basic LUT is always in increments of “1”, the image quality without interpolation does not cause a sense of incongruity, and the circuit for interpolation can be configured simply.

  Next, a modification according to the fourth embodiment will be described. In this modification, the LUT writing method and reading method described above are performed by the image processing unit 11 shown in the second embodiment.

  FIG. 12 shows an LUT rewriting method according to a modification of the third embodiment and a reading method at the time of LUT rewriting.

  12A and 12B are the same as FIGS. 11A and 11B described above. This modification differs from that described above in that interpolation processing is performed at the time of rewriting the LUT 72 for the second time, as shown in FIG. The reason why the interpolation process is performed at the time of the second rewrite is that the read LUT is only an odd address. In the fourth embodiment, the read-out LUT has only odd addresses only during the second rewrite. The interpolation processing is performed by the interpolation processing unit 8 of the image processing unit 11 shown in the second embodiment. Since this interpolation processing is the same as that described above, description thereof is omitted.

  As described above, the interpolation processing by the interpolation processing unit 8 can be added to the LUT rewriting method and reading method according to the fourth embodiment. Thereby, the displayed image can be made high quality. In addition, since the period for performing the interpolation process is short, the arithmetic circuit for the interpolation process can be simplified.

1 is a diagram illustrating a schematic configuration of an image display device according to a first embodiment of the present invention. It is a figure which shows an example of LUT conversion. It is a figure which shows the rewriting method and reading method of LUT which concern on 1st Embodiment of this invention. It is a figure which shows schematic structure of the image display apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the rewriting method and reading method of LUT which concern on 2nd Embodiment of this invention. It is a figure which shows the structural example of the LUT memory which concerns on 2nd Embodiment of this invention. It is a figure which shows the address content read from LUT. It is a figure which shows the rewriting method and reading method of LUT which concern on 3rd Embodiment of this invention. It is a figure which shows the rewriting method of another LUT and the reading method which concern on 3rd Embodiment. It is a figure which shows LUT conversion which concerns on 4th Embodiment of this invention. It is a figure which shows the rewriting method and reading method of LUT which concern on 4th Embodiment of this invention. It is a figure which shows the rewriting method and read-out method of other LUT which concern on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image formation part, 2 LUT formation part, 3 LUT write control part, 4 LUT read control part, 5 LUT memory, 7 Image display part, 8 Interpolation process part, 10, 11 Image process part, 21, 22 Image display apparatus

Claims (9)

Means for obtaining image data to be processed;
Lookup table storage means for storing a lookup table having gradation values as data in the address;
Means for reading data in the address of the lookup table based on the gradation value of the acquired image data;
Writing means for writing the data in the address of the lookup table in a plurality of times,
An image processing apparatus according to claim 1, wherein when the writing unit is writing, the reading unit reads data in an address where the writing is not performed. When the gradation value of the acquired image data matches the address at which the writing is performed, the gradation value of the image data is set in two or more addresses that are not written in the vicinity of the address. The image processing apparatus according to claim 1, further comprising interpolation means for performing interpolation based on data. 3. The image processing apparatus according to claim 1, wherein the writing unit writes the data in the address separately for the even address and the odd address of the lookup table. The lookup table has a first lookup table corresponding to the number of gradations of the acquired image data, and a second lookup table,
In the second lookup table, null data is inserted,
4. The writing unit according to claim 1, wherein the writing means writes data in addresses corresponding to the number of gradations at a time in a part of the first look-up table and the second look-up table. The image processing apparatus according to any one of claims. The lookup table has a first lookup table corresponding to the number of gradations of the acquired image data, and a second lookup table,
4. The image processing apparatus according to claim 1, wherein the writing unit writes data in an address in the second look-up table for the first time. The second look-up table is half the number of addresses of the first look-up table and has an intermediate value of the data in the address of the first look-up table;
The writing means writes the data in the address to the second lookup table for the first time, writes the data in the address to the even address or odd address of the first lookup table for the second time, and the third time. 6. The image processing apparatus according to claim 5, wherein data in the address is written to an even address or an odd address that has not been rewritten the second time in the first lookup table. 6. The image processing apparatus according to claim 2, wherein the lookup table storage unit includes two 2-port RAMs. 6. The image processing apparatus according to claim 2, wherein the lookup table storage unit includes four 1-port RAMs. Acquiring image data to be processed;
A look-up table storing step for storing a look-up table having gradation values as address contents;
Reading the address content of the lookup table from the gradation value of the acquired image data;
And writing the address contents of the lookup table in a plurality of times,
The image processing method according to claim 1, wherein, in the reading step, when the writing unit is writing, an address content that has not been written is read.

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