JP2016158014A - Image processing apparatus, display unit, and image compression method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus that can quickly transfer image data while suppressing a deterioration in image quality, a display unit, and an image compression method.SOLUTION: An image processing part 30 comprises: a conversion part 39 that converts image data of a first color space into image data of a second color space that is a color space in a polar coordinate system including elements of brightness, chroma, and hue; and a compression part 38 that compresses the image data converted by the conversion part 39 at least in terms of chroma by applying a compressibility ratio different from that of other elements. The image processing part transfers the image data compressed by the compression part 38.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image processing device, a display device, and an image compression method.

  2. Description of the Related Art Conventionally, a display device that displays an image converts an input image signal into a signal in an HLS color space that represents a color using a hue component, a lightness component, and a saturation component (for example, Patent Documents). 1). The image signal thus converted can be adjusted for each of the hue component, lightness component, and saturation component.

JP 2010-232773 A

In general, an apparatus that processes image data writes image data in a memory and performs various processes on the image data written in the memory. For example, a liquid crystal projector described in Patent Document 1 performs processing by a CPU, and it is a normal method that data processed by the CPU is stored in a memory.
In the case of writing image data into the memory and the process of reading out image data from the memory, the transfer speed decreases as the data amount of the image data increases. Therefore, in order to prevent a decrease in transfer speed, it is conceivable to transfer image data after compressing it. In this case, if the compression rate is increased, the amount of data can be reduced and image data can be transferred efficiently and at a high speed, but there is a problem that the image quality deteriorates.
The present invention has been made in view of the circumstances described above, and provides an image processing device, a display device, and an image compression method capable of suppressing image quality deterioration and transferring image data at high speed when transferring image data. The purpose is to provide.

In order to achieve the above object, an image processing apparatus according to the present invention converts image data of a first color space into a second color space that is a color space of a polar coordinate system having elements of brightness, saturation, and hue. A conversion unit that converts the image data into image data; and a compression unit that compresses the image data converted by the conversion unit by applying a compression rate that is different from that of the other elements at least in terms of saturation. Transfers the compressed image data.
According to the present invention, image data can be compressed at a high compression rate while suppressing deterioration in image quality.

In the image processing apparatus according to the present invention, the compression rate of at least one of the elements of lightness, saturation, and hue is set based on the other elements.
According to the present invention, it is possible to further suppress deterioration in image quality.

Further, the present invention is characterized in that, in the image processing apparatus, the saturation compression rate is set to a compression rate different from at least one of the lightness compression rate and the hue compression rate.
According to the present invention, it is possible to set a compression rate that can suppress deterioration in image quality and speed up transfer of image data.

Further, the present invention is characterized in that, in the image processing apparatus, a saturation compression rate is set to a compression rate lower than at least one of a lightness compression rate and a hue compression rate.
According to the present invention, it is possible to appropriately set a compression rate, suppress deterioration in image quality, and speed up transfer of image data.

In the image processing apparatus, the hue compression rate is set based on the saturation data of the image data converted by the conversion unit.
According to the present invention, an appropriate compression rate can be set using human visual characteristics.

According to the present invention, the image processing apparatus includes a compression rate changing unit that changes the compression rate.
According to the present invention, the compression rate applied to the image data can be set to an appropriate compression rate.

In the image processing apparatus, the present invention further includes an operation unit that receives an operation, and the compression rate changing unit sets a compression rate of at least one of the elements of brightness, saturation, and hue as the operation unit. It changes based on operation with respect to.
According to the present invention, the compression rate applied to the image data can be changed according to the operation.

The image processing apparatus may further include a processing unit that processes image data in a color space of an orthogonal coordinate system, and the conversion unit converts image data in a color space of a polar coordinate system into a color space of an orthogonal coordinate system. The image data is converted into image data and output to the processing unit, and the image data output from the processing unit is converted into image data in a color space of a polar coordinate system.
According to the present invention, when processing image data in an orthogonal coordinate system, image data can be compressed and transferred at a high compression rate while suppressing deterioration in image quality.

According to the present invention, in the image processing apparatus, the image data compressed by the compression unit is transferred to a memory.
According to the present invention, when image data is transferred to a memory, the transfer speed can be increased by compressing the image data at a high compression rate while suppressing deterioration in image quality.

In order to achieve the above object, the display device of the present invention uses the image data of the first color space as the second color space, which is a polar coordinate color space having elements of brightness, saturation, and hue. A conversion unit that converts the image data into image data; and a compression unit that compresses the image data converted by the conversion unit by applying a compression rate that is different from that of the other elements at least in terms of saturation. An image processing device that transfers the compressed image data, and a display unit that displays an image based on image data including R, G, and B elements. , G, and B are output.
According to the present invention, it is possible to increase the efficiency of data processing in a display device and display a high-quality image by compressing and transferring image data at a high compression rate while suppressing deterioration in image quality.

Further, the present invention is characterized in that, in the above display device, the display unit is a projector including a projection unit that projects an image on a projection surface.
ADVANTAGE OF THE INVENTION According to this invention, in the projector which projects an image based on the image data containing the element of R, G, B, the efficiency of the data processing in a display apparatus can be improved, and a high quality image can be displayed.

In order to achieve the above object, the image compression method of the present invention uses the image data of the first color space as the second color that is a polar coordinate color space having elements of brightness, saturation, and hue. The image of the second color space is converted into the image data of the space, the image data of the second color space is compressed by applying a compression rate different from that of the other elements at least for the saturation, and the compressed image of the second color space Transferring data.
According to the present invention, image data can be compressed at a high compression rate while suppressing deterioration in image quality.

FIG. 2 is a functional block diagram of the projector according to the embodiment. The flowchart which shows operation | movement of a projector. The flowchart which shows operation | movement of a projector.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
FIG. 1 is a functional block diagram of a projector 1 according to an embodiment to which the invention is applied.
The projector 1 (display device) is connected to an image supply device (not shown), and projects an image on a screen SC (projection surface) based on input image data D1 output from the image supply device.
The projector 1 projects (displays) an image on a screen SC, a control unit 10 that controls each unit of the projector 1, an image processing unit 30 (image processing device) that processes input image data D1 under the control of the control unit 10. A projection unit 20 (display unit).

The projection unit 20 includes a light source unit 21, a spectroscopic unit 22, a light modulation unit 23, and a projection optical system 24.
The light source unit 21 includes a light source including a xenon lamp, an ultrahigh pressure mercury lamp, an LED, and the like. The light source unit 21 includes a drive circuit (not shown) that supplies a drive current to the light source under the control of the control unit 10 to turn on / off the light source. The light source unit 21 reduces the amount of light on a reflector that guides light emitted from the light source to the spectroscopic unit 22, a lens group for enhancing the optical characteristics of light emitted from the light source, a polarizing plate, and a path from the light source to the spectroscopic unit 22. You may provide a light control element etc. (all are omitted illustration).

The spectroscopic unit 22 includes, for example, a mirror or a prism that separates color light, and splits the light emitted from the light source unit 21. In the present embodiment, the light emitted from the light source unit 21 is split into R (red), G (green), and B (blue) color light 20 a and is incident on the light modulation unit 23.
The light modulation unit 23 includes three liquid crystal panels 23R, 23G, and 23B that modulate each of the color light 20a dispersed by the spectroscopic unit 22. R light out of the color light 20a is incident on the liquid crystal panel 23R. Further, G light enters the liquid crystal panel 23G, and B light enters the liquid crystal panel 23B. The liquid crystal panels 23R, 23G, and 23B are, for example, transmissive liquid crystal panels, and each modulates incident light, and the modulated color light 20b enters the projection optical system 24.
The projection optical system 24 includes a prism that synthesizes the RGB color light 20b modulated by the light modulator 23, a lens group that forms a projection image synthesized by the prism on the screen SC, and the like.

  An operation panel 11 disposed on the upper surface or the rear surface of the main body of the projector 1 is connected to the control unit 10. The operation panel 11 includes a plurality of operation elements, generates operation signals corresponding to the operations of these operation elements, and outputs them to the control unit 10. Further, a remote control light receiving unit 12 is connected to the control unit 10. The remote control light receiving unit 12 receives an infrared signal transmitted from the remote control 15, generates an operation signal corresponding to an operation on the remote control 15, and outputs the operation signal to the control unit 10. The remote controller 15 includes various keys for operating the projector 1 and transmits an infrared signal corresponding to the key operation. The remote controller 15 includes, for example, a power key for instructing power on / off of the projector 1, a number key corresponding to a number, an arrow key for instructing a direction, or a cross key. The operation panel 11 and the remote controller 15 correspond to an operation unit that receives a user operation.

Digital image data is input to the projector 1 from a storage device (not shown) built in the projector 1 or an external image supply device (not shown) such as a personal computer or various image players. The image signal input to the projector 1 may be still image data or moving image (video) image data. In the present embodiment, as an example, moving image image data is input. Will be described. This input image data may be stereoscopic video data in addition to normal video data.
The format of the stereoscopic video data includes a frame sequential method in which a left-eye image frame (left image frame) and a right-eye image frame (right image frame) are input alternately, as well as a top-and-bottom method and a side-by-side method. It can be.

The projector 1 includes an image input interface (I / F) 31 through which input image data D1 is input. The image input I / F 31 outputs the input image data D1 to the image processing unit 30.
As described above, the input image data D1 input to the image input I / F 31 is image data stored in a storage device (not shown) built in the projector 1 or an image supply device (not shown) outside the projector 1. ) Is output image data. The image input I / F 31 may include a connector and an interface circuit connected to the image supply device, or the projector 1 may be provided with a connector and an interface circuit different from the image input I / F 31. The image input I / F 31 may be configured to be able to input an analog image signal. In this case, the image input I / F 31 may include an A / D converter that converts an analog image signal into digital image data, and may output the converted digital image data to the image processing unit 30.

The input image data D1 output from the image input I / F 31 to the image processing unit 30 is an image signal in a three-dimensional color space, and in particular, R (red), G (green), and B (blue) image signals. It is the image data of the color space of the orthogonal coordinate system containing. In the present embodiment, the case where the input image data D1 is image data in the RGB color space will be described as an example, but this is only an example. The input image data D1 is an object to which the present invention is applied as long as it is image data in an orthogonal coordinate system. For example, YUV color composed of Y (luminance signal), U (first color difference signal), and V (second color difference signal). It may be image data in a space, image data in a YCbCr color space, or image data in a YPbPr color space.
The image processing unit 30 includes a plurality of processing units that process input image data D1 input from the image input I / F 31. As examples of processing units included in the image processing unit 30, FIG. 1 illustrates a resizing unit 33, an OSD (On-Screen Display) processing unit 34, a frame rate conversion unit 35, and an OD (Over-Drive) processing unit 36. . These are collectively referred to as a processing unit.

A DRAM (Dynamic Random Access Memory) 40 that temporarily stores image data is connected to the image processing unit 30.
The image processing unit 30 includes a DRAM I / F (interface) 37 connected to the DRAM 40 (memory). The image processing unit 30 writes the input image data D1 input from the image input I / F 31 to the DRAM 40 by the DRAM I / F 37. Here, the frame data of the input image data D1 is written in the DRAM 40. The DRAM I / F 37 is connected to each processing unit of the resizing unit 33, the OSD processing unit 34, the frame rate conversion unit 35, and the OD processing unit 36. These processing units access the DRAM I / F 37 to acquire image data (frame data) stored in the DRAM 40 as processing target frame data, perform processing described later, and process the processed image data. The data is transmitted to the DRAM I / F 37 and stored in the DRAM 40.

The resizing unit 33 executes a resolution conversion (resizing) process for converting the resolution of the image data to be processed into a resolution set by the control of the control unit 10. For example, the resizing unit 33 performs conversion to a resolution suitable for the display resolution of the liquid crystal panel 23R, the liquid crystal panel 23B, and the liquid crystal panel 23G.
The OSD processing unit 34 performs processing of generating a composite image by superimposing a menu screen, a notification image to a user, a guidance image, and the like as an OSD image on image data to be processed.
The frame rate conversion unit 35 converts the frame rate of the image data to be processed into a frame rate set under the control of the control unit 10.
The OD processing unit 36 generates image data for overdrive driving based on the image data to be processed when the liquid crystal panel 23R, the liquid crystal panel 23G, and the liquid crystal panel 23B are overdriven.
The processing unit included in the image processing unit 30 is not limited to these. For example, when the input image data D1 is 3D (stereoscopic) image data, 3D conversion processing for generating image data for the left eye frame and image data for the right eye frame from the image data to be processed You may provide the 3D conversion process part which performs. For example, when the input image data D1 is 2D (planar) image data, the processing unit that generates 3D image data having parallax set by the control unit 10, or the input image data D1 is 3D image data. In some cases, a processing unit that generates 2D image data may be provided. In addition, a processing unit that performs distortion correction processing for correcting trapezoidal distortion and pincushion distortion in the screen SC may be provided, and other image processing performed by a known projector can be applied to the image processing unit 30 without limitation.

The image processing unit 30 reads out image data processed by processing units such as the resizing unit 33, the OSD processing unit 34, the frame rate conversion unit 35, and the OD processing unit 36 from the DRAM 40 and outputs the image data to the light modulation unit driving circuit 32. To do.
Here, it is not necessary for the resizing unit 33, the OSD processing unit 34, the frame rate conversion unit 35, and the OD processing unit 36 to process the image data. The image processing unit 30 only needs to perform processing specified by the control of the control unit 10. For example, some of the processing units process image data, and other processing units do not perform processing. The image data may be output to the light modulation unit driving circuit 32.

  The light modulation unit driving circuit 32 drives the liquid crystal panel 23R, the liquid crystal panel 23G, and the liquid crystal panel 23B based on the image data input from the image processing unit 30, and draws an image. Thereby, the projection unit 20 projects (displays) an image based on the image data processed by the image processing unit 30 on the screen SC.

  As described above, the input image data D1 is image data in a three-dimensional color space of an orthogonal coordinate system. Each processing unit included in the image processing unit 30 processes image data in a three-dimensional color space in an orthogonal coordinate system, and image data output from the image processing unit 30 to the light modulation unit driving circuit 32 is also a color in the orthogonal coordinate system. It is image data of space. For example, when the input image data D1 is image data in the RGB color space, the processing unit of the image processing unit 30 processes RGB image data, and the image processing unit 30 sends the RGB image data to the light modulation unit driving circuit 32. Output. Here, the same applies when processing image data in the YUV color space instead of image data in the RGB color space.

  When image data is stored in the DRAM 40, the capacity of the DRAM 40 increases in order to store uncompressed image data as it is. In addition, there is a demand for increasing the transfer speed (transfer band) between the DRAM 40 and the image processing unit 30. Further, in order to improve the display image quality of the projector 1, it is conceivable to increase the resolution of the input image data D1 or the display resolution of the light modulator 23, or to increase the frame rate of the projector 1. In such a case, the demands on the capacity and transfer speed of the DRAM 40 are further increased. Therefore, the projector 1 includes a compression unit 38 that compresses data stored in the DRAM 40 in the DRAM I / F 37. The compression unit 38 compresses the input image data D1 input from the image input I / F 31 or the image data processed by the processing unit of the image processing unit 30 and transfers the compressed image data to the DRAM 40. The compression unit 38 restores the image data read from the DRAM 40 to uncompressed or low-compressed image data, and transfers the image data to the processing unit of the image processing unit 30 or the light modulation unit driving circuit 32. Thereby, the demand for the storage capacity of the DRAM 40 can be reduced. Further, the demand for the transfer speed between the DRAM 40 and the DRAM I / F 37 can be reduced.

  By the way, image data in RGB color space or YUV color space is likely to be deteriorated by compression processing. For this reason, when the compression rate compressed by the compression unit 38 is increased, the deterioration of the image quality becomes remarkable, and there is a concern about the influence on the display quality of the projector 1. This problem is conspicuous for image data in the RGB color space and the YUV color space, but is a common problem for image data in an orthogonal coordinate system.

  Therefore, the projector 1 has a configuration in which the image data is converted into image data in a polar coordinate system color space and then compressed by the compression unit 38. Specifically, the image forming apparatus includes a conversion unit 39 that converts rectangular coordinate system image data into polar coordinate system color space image data, and the compression unit 38 converts the polar coordinate system color space image data converted by the conversion unit 39. Compress and decompress.

The conversion unit 39 converts the image data into HLS color space image data including, for example, H (hue: hue), L (luminance: luminance, brightness), and S (saturation: saturation).
The compression unit 38 sets a compression rate according to the control of the control unit 10 and compresses image data at the set compression rate. Here, the compression unit 38 performs a process of individually compressing the image data in the HLS color space for each element of H, L, and S. That is, the compression unit 38 performs a process of compressing the H signal, a process of compressing the L signal, and a process of compressing the S signal.
In this compression processing, the compression rate of all the elements may be set to the same compression rate, but in the projector 1 of the present embodiment, at least the compression rate related to S (saturation) is set to be different from that of other elements (H, L). Can be set to different compression rates. More preferably, the compression rate can be set individually for each element of hue, lightness, and saturation. For this reason, the compression rate according to the characteristic of the physical quantity of each element of H, L, and S can be set.

The process for setting the compression rate of the compression unit 38 may be executed by the control unit 10 or may be executed by the compression unit 38. Of the control unit 10 and the compression unit 38, the functional unit that sets the compression rate corresponds to a compression rate changing unit. In the present embodiment, an example in which the compression unit 38 determines the compression rate will be described. When the control unit 10 performs setting, the control unit 10 functions as an image processing apparatus together with the image processing unit 30. In addition to the control unit 10 and the compression unit 38, a function unit (corresponding to a compression rate changing unit) that sets a compression rate may be provided.
Further, the user may input the compression rate by operating the operation panel 11 or the remote controller 15, and in this case, the control unit 10 sets the compression rate based on the input.
In image data in the HLS color space, it is known that the S (saturation) signal has a lower human eye sensitivity than the H (hue) signal and L (lightness). Therefore, even if the resolution of the S signal is lower than that of the H signal and the L signal, the image quality of the projected image on the screen SC is unlikely to deteriorate.
An example will be described in which each of the H, L, and S signals is discretized and compressed. When the H, L, and S signals are 8-bit (0 to 255) gradation values, the H and L signals are discretized into 64 levels (levels), and the representative values are 2, 6, and 10 , 14... In this case, the S signal can be discretized in 32 steps (levels) with representative values of 4, 12, 20,. In this example, the S signal can be compressed at a higher compression rate than when the H, L, and S signals are all discretized at 64 levels.

  Moreover, the compression part 38 is good also as a structure which sets the compression rate of each element of H, L, and S based on another element. For example, in a region with low saturation in the HLS color space, the color is close to an achromatic color, so that human eyes are less likely to detect a change in hue. Therefore, when the value of the S signal is low, the image quality of the projected image on the screen SC is unlikely to deteriorate even if the compression rate of the H signal is increased. Therefore, when the H, L, and S signals have 8-bit (0 to 255) gradation values and the S signal value is equal to or greater than the threshold value, the compression unit 38 outputs the H signal. The discretization is performed in 64 steps (levels), and representative values are set to 2, 6, 10, 14,. Here, the value of the S signal is a maximum value of saturation data in the processing target frame, or an average value or a representative value obtained by a predetermined calculation. When the value of the S signal is low saturation smaller than the threshold value, the level of discretization of the H signal is set to 32 levels, and the discretization is performed with representative values of 4, 12, 20,. In this example, the H signal can be compressed at a higher compression rate than when the H, L, and S signals are all discretized at 64 levels.

To summarize the above two examples, the compression rate is set as follows.
L (brightness) signal: Discretized at 64 levels (representative values are 2, 6, 10, 14,...).
S (saturation) signal: Discretized at 32 levels (typical values are 4, 12, 20,...).
H (hue) signal (1) Discretized at 64 levels (typical values are 2, 6, 10, 14,...) In a normal state where the saturation is equal to or greater than the threshold value, and (2) saturation is greater than the threshold value. Discretized at 32 levels in a small low saturation state (typical values are 4, 12, 20,...).
In this way, the compression unit 38 can compress the image data in the HLS color space for each element of H, L, and S, and can set the compression rate of at least some elements to a compression rate different from other elements. The compression rate can be increased so that the image quality of the projected image on the screen SC is not deteriorated. For this reason, it is possible to set a high compression ratio while preventing degradation of image quality by utilizing human visual characteristics, and to reduce the demand for the storage capacity of the DRAM 40 and the transfer speed between the DRAM 40 and the DRAM I / F 37. it can.

  In the image processing unit 30, each processing unit and the DRAM I / F 37 may be configured by independent hardware, or may be configured by a single SoC (System On Chip) LSI. Alternatively, each processing unit and the DRAM I / F 37 may be realized by software by the CPU executing a program. The same applies to the compression unit 38 and the conversion unit 39 included in the DRAM I / F 37. Furthermore, the process in which the compression unit 38 sets the compression rate may be executed by the control unit 10 as described above. In this case, the control unit 10 acquires the image data in the HLS color space converted by the conversion unit 39 and outputs the compression rate for each element to the image processing unit 30.

2 and 3 are flowcharts showing the operation of the projector 1, (A) shows the operation of the processing unit of the image processing unit 30, and (B) shows the operation of the DRAM I / F 37.
FIG. 2 shows an operation when data is transferred from the processing unit to the DRAM 40.
The processing unit of the image processing unit 30 transmits a data transfer request to the DRAM I / F 37 (step S11). When the DRAM I / F 37 receives a data transfer request from the processing unit (step S21), the DRAM I / F 37 transmits a response to the data transfer request to the processing unit that has made the data transfer request (step S22). This response is control data indicating that a data transfer request has been accepted, and the DRAM I / F 37 may transmit the response after the DRAM 40 and the DRAM I / F 37 are in a state capable of transferring data. .
The processing unit receives a response transmitted from the DRAM I / F 37 (step S12), and transmits image data to the DRAM I / F 37 (step S13). The image data transmitted by the processing unit is image data in a color space of an orthogonal coordinate system.

The DRAM I / F 37 receives the image data transmitted by the processing unit (step S23), and the conversion unit 39 converts the received image data into image data in the HLS color space (step S24). Subsequently, the compression unit 38 analyzes the image data in the converted HLS color space and sets the compression rate for each of the H, L, and S elements (step S25). Here, the compression unit 38 may select a compression rate of each element from a plurality of preset compression rates.
The compression unit 38 compresses the image data according to the compression rate set in step S25 (step S26), and accesses the DRAM 40 (step S27). In step S27, the DRAM I / F 37 transmits, for example, control data that requests the DRAM 40 to store data, data that specifies an address of a storage area in which the data is stored, and the like.
The DRAM I / F 37 transfers the image data compressed by the compression unit 38 to the DRAM 40 and executes writing to the DRAM 40 (step S28).
After transferring the image data to the DRAM 40, the DRAM I / F 37 transmits a notification indicating that the writing has been completed to the processing unit that has transmitted the data transfer request in step S11 (step S29). The processing unit receives a write completion notification from the DRAM I / F 37 (step S14), and ends this process.

  Further, when the input image data D1 is input from the image input I / F 31, the image processing unit 30 operates in the same manner as the processing unit of FIG. 2A and transmits the input image data D1 to the DRAM I / F 37. To do. In this case, the DRAM I / F 37 converts the input image data D1, compresses it, and stores it in the DRAM 40.

FIG. 3 shows an operation when the processing unit acquires data from the DRAM 40.
The processing unit of the image processing unit 30 transmits a data read request to the DRAM I / F 37 (step S31). The data read request includes, for example, control data requesting reading and data specifying image data to be read.
The DRAM I / F 37 receives a data read request from the processing unit (step S41), and accesses the DRAM 40 (step S42). In step S42, the DRAM I / F 37 transmits, for example, control data requesting data transmission to the DRAM 40, data specifying the address of the storage area in which the target data is stored, and the like. The DRAM I / F 37 receives the image data transmitted from the DRAM 40 and reads the image data from the DRAM 40 (step S43). The compression unit 38 restores the image data read from the DRAM 40 to the state before compression (step S44). When the image data is compressed by irreversible processing in step S26 of FIG. 2, the image data cannot be restored to the same state as before compression in step S44, but the influence on the image quality is small as described above. So there is no problem.

After the compression unit 38 restores the image data, the conversion unit 39 converts the restored image data into image data in the color space of the orthogonal coordinate system (step S45). Here, the conversion unit 39 may convert the image data into image data in a preset color space (for example, RGB image data), or the image data corresponding to the processing unit that transmitted the data read request in step S31. The format of the image data to be converted may be determined by determining the format.
The DRAM I / F 37 transmits the image data in the color space of the orthogonal coordinate system converted by the conversion unit 39 to the processing unit that transmitted the data read request in Step S41 (Step S46), and the processing unit transmits the DRAM I / F 37. Image data is received (step S32), and this process is terminated.

  In addition, when the image processing unit 30 transmits the image data processed by the processing unit to the light modulation unit driving circuit 32, the image processing unit 30 operates in the same manner as the processing unit of FIG. .

As described above, the image processing unit 30 of the projector 1 according to the embodiment of the present invention is a polar coordinate system color space having image data of the first color space having elements of brightness, saturation, and hue. A conversion unit 39 that converts the image data into the second color space, and a compression unit 38 that compresses the image data converted by the conversion unit 39 by applying a compression rate that is different from that of other elements at least for saturation. The image data compressed by the compression unit 38 is transferred. Thereby, image data can be compressed at a high compression rate while suppressing deterioration in image quality.
Since the projector 1 sets the compression rate of at least one of lightness, saturation, and hue based on other elements in the process of compression by the compression unit 38, the deterioration in image quality is further suppressed. be able to. In addition, by setting the compression rate corresponding to the element characteristics, a high compression rate can be set so as not to cause deterioration of the image quality of the projected image. Thereby, the quality of a projection image is maintained and image data can be processed efficiently.

  The image processing unit 30 sets the saturation compression rate to a compression rate different from at least one of the lightness compression rate and the hue compression rate. For this reason, it is possible to set a compression rate that can suppress deterioration in image quality and speed up transfer of image data. The saturation compression rate may be set to a compression rate lower than at least one of the lightness compression rate and the hue compression rate. Further, the hue compression rate may be set based on the saturation data of the image data converted into the color space of the polar coordinate system.

  Furthermore, the compression unit 38 may set or change the lightness, saturation, and hue compression rate applied by the compression unit 38, or the control unit 10 may set or change the compression rate. Further, the compression ratio of at least one of the brightness, saturation, and hue may be changed based on an operation received by the remote controller 15 or the operation panel 11 by the control unit 10 or the compression unit 38.

The image processing unit 30 includes a processing unit that processes image data in the color space of the orthogonal coordinate system, and the conversion unit 39 converts the image data in the color space of the polar coordinate system into image data in the color space of the orthogonal coordinate system. Then, the image data is output to the processing unit, and the image data output from the processing unit is converted into image data in the color space of the polar coordinate system. For this reason, when processing image data in an orthogonal coordinate system, image data can be compressed and transferred at a high compression rate while suppressing deterioration in image quality.
Further, since the image processing unit 30 transfers the image data compressed by the compression unit 38 to the DRAM 40, the image processing unit 30 compresses the image data at a high compression rate while suppressing the deterioration of the image quality, increases the transfer speed, and increases the transfer efficiency. Can do. In addition, the bus connecting the DRAM 40 and the DRAM I / F 37 can be used efficiently.
Further, in the projector 1 including the projection unit 20 that projects an image on the screen SC, when an image is projected based on image data including R, G, and B elements, the efficiency of data processing is improved and a high-quality image is displayed. Can be displayed. In particular, the color space of the polar coordinate system in the projector 1 including the processing unit that processes the image data including the R, G, and B elements and the liquid crystal panels 23R, 23G, and 23B corresponding to the R, G, and B elements. By converting to the image data, it is possible to suppress the deterioration of the image quality and improve the efficiency of data processing and transfer.

  The above-described embodiment is merely an example of a specific mode to which the present invention is applied, and the present invention is not limited. The present invention can be applied as a mode different from the above-described embodiment. For example, the memory in which the projector 1 stores the image data is not limited to the DRAM 40 as long as it can provide a storage area for temporarily storing the image data, and may be an SRAM. Is optional. 1 may be realized by, for example, an IC (Integrated Circuit) or SoC, or may be realized by software by a CPU or MPU executing a program. Good. Accordingly, FIG. 1 does not limit the physical implementation of the image processing unit 30.

  In addition, the light modulation unit 23 has been described as a configuration including three transmissive liquid crystal panels 23R, 23G, and 23B corresponding to RGB colors, for example, but a reflective liquid crystal panel may be used. Further, for example, a configuration including three DMDs (digital mirror devices), or a configuration in which one transmissive liquid crystal panel or DMD and a color wheel are combined may be used.

  Furthermore, the display device of the present invention is not limited to the projector 1 that projects an image on the screen SC as described above, but is applied to a liquid crystal monitor or a liquid crystal television that displays an image on a liquid crystal display panel, or a plasma display panel (PDP). Self-luminous type such as a monitor device or a television receiver that displays an image on an organic EL display panel called an OLED (Organic Electro-Luminescence), etc. Various display devices such as these display devices are also included in the display system of the present invention. In this case, a liquid crystal display panel, a plasma display panel, and an organic EL display panel correspond to the display unit. In addition, it is not necessary to individually implement hardware corresponding to each function unit of the projector 1 illustrated in FIG. 1, and a plurality of functions can be performed by executing a program for each unit except the image processing unit 30. It is of course possible to adopt a configuration that realizes the functions of the units.

DESCRIPTION OF SYMBOLS 1 ... Projector (display apparatus), 10 ... Control part (compression rate change part), 11 ... Operation panel (operation part), 15 ... Remote control (operation part), 20 ... Projection part (display part), 23 ... Light modulation part , 23R, 23G, 23B ... liquid crystal panel, 30 ... image processing unit (image processing device), 31 ... image input I / F, 32 ... light modulation unit drive circuit, 33 ... resizing unit (processing unit), 34 ... OSD processing Unit (processing unit), 35 ... frame rate conversion unit (processing unit), 36 ... OD processing unit (processing unit), 37 ... DRAM I / F, 38 ... compression unit, 39 ... conversion unit, 40 ... DRAM (memory) , D1 ... input image data, SC ... screen (projection surface).

Claims (12)

A conversion unit that converts image data of the first color space into image data of a second color space that is a color space of a polar coordinate system having elements of brightness, saturation, and hue;
A compression unit that compresses the image data converted by the conversion unit by applying a compression rate different from that of the other elements at least for saturation;
Transferring the image data compressed by the compression unit;
An image processing apparatus.   The image processing apparatus according to claim 1, wherein a compression ratio of at least one of the lightness, saturation, and hue is set based on the other elements.   3. The image processing apparatus according to claim 1, wherein the saturation compression rate is set to a compression rate different from at least one of the lightness compression rate and the hue compression rate.   4. The image processing apparatus according to claim 3, wherein the saturation compression ratio is set to a lower compression ratio than at least one of the lightness compression ratio and the hue compression ratio.   The image processing apparatus according to claim 2, wherein a hue compression rate is set based on saturation data of the image data converted by the conversion unit.   The image processing apparatus according to claim 1, further comprising a compression rate changing unit that changes the compression rate. It has an operation unit that accepts operations,
The image processing according to claim 6, wherein the compression rate changing unit changes the compression rate of at least one of the elements of lightness, saturation, and hue based on an operation on the operation unit. apparatus. A processing unit that processes image data in a color space of an orthogonal coordinate system;
The conversion unit converts image data in a polar coordinate system color space into image data in a Cartesian coordinate system color space and outputs the image data to the processing unit, and the image data output by the processing unit is converted into the polar coordinate system color space. Converting to image data,
An image processing apparatus according to claim 1, wherein:   The image processing apparatus according to claim 1, wherein the image data compressed by the compression unit is transferred to a memory. A conversion unit that converts image data of the first color space into image data of a second color space that is a color space of a polar coordinate system having elements of brightness, saturation, and hue;
A compression unit that compresses the image data converted by the conversion unit by applying a compression rate different from that of the other elements at least for saturation;
An image processing device for transferring the image data compressed by the compression unit;
A display unit that displays an image based on image data including R, G, and B elements,
The image processing apparatus outputs image data including R, G, and B elements to the display unit;
A display device.   The display device according to claim 10, wherein the display device is a projector including a projection unit that projects an image on a projection surface. Converting the image data of the first color space into image data of the second color space, which is a color space of a polar coordinate system having elements of brightness, saturation, and hue;
Compressing the image data of the second color space by applying a compression rate different from that of the other elements at least for saturation;
Transferring the compressed image data of the second color space;
An image compression method characterized by the above.

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