Abstract:
An image processing circuit of a digital TV includes a graphic drawing module. The graphic drawing module is capable of selecting a first blending value or a second blending value to process a pixel to generate target image data and store the target image data in a memory. While performing a gradient operation that generates a plurality of pixel values, the graphic drawing module determines whether or not to limit the pixel values to a specific interval according to a saturation parameter.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a digital TV, and more particularly, to an image processing circuit for a digital TV.  
         [0003]     2. Description of the Prior Art  
         [0004]     Compared with conventional CRTs, LCD panels and PDP panels have the property of low thickness-to-display-size ratio, and thereby possess considerable predominance on high-level TVs of large displaying size. As the technology of LCD and PDP panels advances, high-level TVs equipped with LCD or PDP panels are becoming more and more popular. Because of the large screen size, the modern high-level TV generally supports a picture-in-picture (PIP) function. Therefore, a user can watch two TV programs on the one TV screen at the same time.  
         [0005]     However, some users are not satisfied with the PIP function of a digital TV which simply displays two pictures on the same large-sized screen. They expect more variations on the functionality of the digital TV. For example, the digital TV should be capable of performing specific image processing operations upon the displayed pictures for some special visual effects. However, the prior art digital TV is deficient in such kind of image processing abilities.  
       SUMMARY OF THE INVENTION  
       [0006]     It is therefore one of the objectives of the claimed invention to provide an image processing circuit for a digital TV, to solve the above-mentioned problem.  
         [0007]     The claimed invention provides an image processing circuit comprising: a memory for storing source image data having a first format, the source image data comprising a first blending value and first data; a storage unit for storing a blending selection value; and a graphic drawing module for producing a second blending value according to the first data, selecting the first blending value or the second blending value according to the blending selection value, and converting the source image data into target image data according to the selected blending value and the first data.  
         [0008]     The claimed invention further provides an apparatus for processing source image data. The apparatus comprises: a storage unit for storing at least one gradient parameter; a graphic drawing module for receiving the source image data to perform a gradient operation and outputting the target image data having a gradient effect, wherein the gradient parameter corresponds to the gradient effect; and a memory coupled to the graphic drawing module for storing the target image data.  
         [0009]     The claimed invention further provides an method for processing source image data, the method comprising: receiving the source image data from a memory, the source image data comprising a first blending value and first data; receiving a blending selection value from a storage unit; producing a second blending value according to the first data; selecting the first blending value or the second blending value according to the blending selection value; and converting the source image data into target image data according to the selected blending value.  
         [0010]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a diagram of a digital TV according to the present invention.  
         [0012]      FIG. 2  is a diagram of an image processing circuit according to the present invention.  
         [0013]      FIG. 3  is a diagram of a command format received by the graphic drawing module shown in  FIG. 1 .  
         [0014]      FIG. 4  is a diagram illustrating image format conversions performed by the graphic drawing module shown in  FIG. 1 .  
         [0015]      FIG. 5  is a reference table of different format conversions performed by the graphic drawing module shown in  FIG. 1 .  
         [0016]      FIG. 6  is a diagram of format conversion rules used by the graphic drawing module in response to the format conversions shown in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION  
       [0017]      FIG. 1  is a block diagram illustrating the system architecture of a digital TV  100  according to the present invention. As shown in  FIG. 1 , the digital TV  100  comprises an antenna  102 , a tuner  104 , a front-end processing circuit  106 , a bus  108 , a memory  110 , a central processing unit (CPU)  112 , a video scaler  114 , a graphic drawing module (GDM)  118 , a subtitle controller  120 , a plurality of video mixers  130  and  140 , an on-screen display (OSD) controller  150 , a hardware cursor controller  160 , and a mask windows module  170 . The front-end processing circuit  106 , after performing front-end processing on the digital TV signal received from the antenna  102  and the tuner  104 , stores the processed data into the memory  110  through the bus  108 . The CPU  112  can control other devices connected to the bus  108 .  
         [0018]     The video scaler  114  reads image data corresponding to a main-picture and a sub-picture from the memory  110 , and generates a main-video signal S 1  and a sub-video signal S 2  by scaling the image size of the read image data. After being processed by video mixers  130 ,  140 , the video signal S 1 , S 2  and other information are mixed to successively generate a corresponding mixed signal S_mix and an output signal S_out of a composed picture. The output signal S_out is further transmitted to a monitor, a video output port, or a video output end of the digital TV  100 . Users can watch the composed pictures through the monitor of digital TV  100  or a monitor of an external display unit coupled to the video output port or the video output end of the digital TV  100 .  
         [0019]     As shown in  FIG. 2 , the above-mentioned bus  108 , memory  1110 , and GDM  118  constitute an image processing circuit which provides the digital TV  100  with the image processing functionality. The GDM  118  comprises a command buffer  204 , a loader  210 , a first-in-fist-out (FIFO) controller  212 , a destination fill unit  214 , a palette table  220 , a color translation unit  222 , a block translation engine (BLT engine)  224 , a buffer  226 , and a scaling engine  228 . Additionally, the destination fill unit  214  comprises a color gradient unit  214 G and a destination buffer  214 B, and the BLT engine  224  comprises a source operand unit  224 S and a destination operand unit  224 D. Please note that the above-mentioned devices, the OSD/GDM arbitor  202 , and the coefficient table  230  could be positioned inside or outside the GDM  118 , which are design choices and are not meant to be limitations.  
         [0020]     In an embodiment, the GDM  118  can operate off-line and is not limited to performing the real-time image processing when the digital TV  100  is playing a TV program. Through the bus  108 , the GDM  118  can read the image data from the memory  110  for image processing, write the processed image data into the memory  110 , and even write image data generated by itself into the memory  110 . Therefore, the GDM  118  can cooperate with other devices at will. The GDM  118  can work according to commands issued from the CPU  112  shown in  FIG. 1 , and the bit information of each command is stored in the command buffer  204 . The command format is illustrated in  FIG. 3  and comprises some shared bit information, which may not be processed simultaneously. For example, in the last word, the function corresponding to bit information VIP and VFP will not be performed in conjunction with the function corresponding to the bit information BKC. Through the use of the shared bit information VIP, VFP and BKC, the present invention can realize a command format having a shorter length.  
         [0021]     When performing a gradient operation, the GDM  118  uses the color gradient unit  214 G to run the gradient operation according to the bit information RGRAX, GGRAX, BGRAX, PCX, RGRAY, GGRAY, BGRAY and PCY, as shown in the bottom left of  FIG. 3 . The bit information PCX, PCY defines the pixel number of each gradient step along X and Y axes in an image while remaining bit information RGRAX, GGRAX and BGRAX defines the gray level variations of red color (R), green color (G) and blue color (B) corresponding to each gradient step along the X axis. For example, if (RGRAX, GGRAX, BGRAX, PCX) is equal to (1,1,2,5), the GDM  118  will change the gray level every 5 pixels when performing the gradient operation along the X axis and the gray level variations corresponding to red color, green color and blue color are 1 gray level, 1 gray level and 2 gray levels for their respective gradient steps. The bit information RGRAY, GGRAY, BGRAY and PCY corresponds to the parameters for the gradient operation performed along the Y axis, and further description is omitted here for brevity. Due to the fact that there is no need for a division operation, the present invention can achieve the objective of having simple operation. As for the saturation bit (SAT bit)  312 , it is used for controlling the above-mentioned gradient operation. When the SAT bit  312  is enabled, if a pixel value ascends (or descends) to reach the maximum (or minimum) of a saturation color during the gradient operation, the following pixel values are set by this maximum (or minimum) of the saturation color. Conversely, when the SAT bit  312  is disabled, the GDM  118  will not stay at the maximum or minimum of the saturation color when performing the gradient operation.  
         [0022]     In this embodiment, when an image conversion is activated, the blending selection value AS shown in  FIG. 3  is a blending selection bit  314  used for alpha selection, i.e., used for controlling the image format conversion run in the GDM  118 . In this embodiment, the GDM  118  can receive a plurality of image formats and then convert them into other formats, respectively.  FIG. 4  is a diagram illustrating possible image format conversions performed by the GDM  118  according to the present invention.  
         [0023]     A 16-bit alpha color look-up table (ACLUT16) format of image data comprises 8-bit blending value (first alpha) and 8-bit color look-up table (CLUT) value. Another blending value (second alpha) and RGB data stored in the palette table  220  will be found according to the 8-bit CLUT value. That is, the 8-bit CLUT value is an index for looking up an alpha-RGB value from the palette table  220 . The alpha-RGB value comprises the second alpha and RGB data. For example, if the GDM  118  is activated to convert image data of an ACLUT16 format into image data of an RGB format, the GDM  118  converts the 8-bit CLUT value into an alpha-RGB value (that is, the alpha of the alpha-RGB value is a second blending value). The GDM  118  will select one of the first blending value or the second blending value to blending the RGB data and the background according to the selected blending value.  
         [0024]     The palette table  220  stores a second blending value corresponding to every color and the image data of the ACLUT format contains a first blending value corresponding to every pixel. The GDM  118  selects the first or the second blending value according to the blending selection bit  314  to process at least one pixel according to the selected blending value and generates target image data. The target image data is stored in the memory  110 . In some cases, the first blending value is more suitable for the image data; however, in other cases, the second blending value is more suitable for the image data. By selecting the above-mentioned blending values, the present invention ensures designers use the image data of the digital TV  100  effectively. This embodiment further comprises an input interface for designers to input the value of the blending selection bit  314 .  FIG. 5  is a reference table of different look-up table (LUT) format conversions performed by the graphic drawing module  118  according to the present invention, and  FIG. 6  is a diagram illustrating the conversion rules used by the graphic drawing module  118  according to the present invention.  
         [0025]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.