Patent Application
20080317374
1. Field of the Invention
The present invention relates to a method of simplifying the implementation of image processing, and more particularly to a method of modifying the brightness of color pixels.
2. Description of the Related Art
When image processing is involved, it is common practice to multiply YUV or RGB of video signals by a certain gain value. The gain value is obtained by dividing the post-process value of one parameter of YUV or RGB by its pre-process value. It is apparent that a divider is unavoidable when the above method is implemented. However, the divider is usually implemented by a look-up table (LUT), which results in inaccuracy of calculation. In addition, the error caused by the dividing process will further be amplified by a later multiplying process. Therefore, the prior method which adopts LUT needs more bits to do quantization so as to reduce the error to within an acceptable range. However, the more bits the circuit needs, the more expensive it is. Therefore, providing a new method to avoid an LUT operation is a very important issue.
The method of modifying the brightness of a color pixel in accordance with one embodiment of the present invention comprises the steps of: providing a first, a second, and a third image value, wherein the first, the second and the third image values are associated with the brightness of the color pixel; calculating a first offset between the first image value and a first expected image value; calculating a first difference between the first and the second image values, and a second difference between the first and the third image values; defining a linear relation on the basis of the first offset and the first image value; obtaining a second offset on the basis of the first difference according to the linear relation, and a third offset on the basis of the second difference according to the linear relation; and generating a second expected image value by adding the second image value and the second offset, and a third expected image value by adding the third image value and the third offset.
The method of modifying the brightness of a color pixel in accordance with one embodiment of the present invention comprises the steps of: providing a first and a second image value, wherein the first and the second image values are associated with the brightness of the color pixel; calculating a first offset between the first image value and a first expected image value; obtaining a second offset corresponding to the second image values according to the relation between the first offset and the first image value; and generating a second expected image value by adding the second image value and the second offset.
The apparatus of modifying the brightness of a color pixel in accordance with one embodiment of the present invention comprises an extractor, a first subtractor, a second subtractor, a third subtractor, an offset generator and an adder. The extractor is configured to receive the color pixel and to provide a first, a second, and a third image value, wherein the first, the second, and the third image values are associated with the brightness of the color pixel. The first subtractor is configured to calculate a first offset between the first image value and a first expected image value. The second subtractor is configured to calculate a first difference between the first and the second image values. The third subtractor is configured to calculate a second difference between the first and the third image values. The offset generator is configured to define a linear relation on the basis of the first offset and the first image value, and to generate a second and a third offset. The adder is configured to receive the second offset, the third offset, the second image value and the third image value to generate a second and a third expected image value.
The invention will be described according to the appended drawings in which:
a) and 1(b) exemplify the concept in accordance with an embodiment of the present invention;
a) and 1(b) exemplify the concept in accordance with an embodiment of the present invention. Assuming that the pre-process and post-process values of the parameter Y are denoted as MAX and MAX_Out, respectively, where MAX_Out is equal to Gain x MAX. In prior art methods, the gain is pursued by dividing MAX_Out by MAX first, and then adjusting the post-process values MID_Out and MIN_Out of the parameters U and V by multiplying the pre-process values MID and MIN of the parameter U and V by such a gain. In contrast to the prior art methods, the present invention converts the multiplication operations in prior art into addition operations. Therefore, the problems of hardware complexity of the prior art divider and calculation error can be solved. Assuming that Δ1, Δ2 and Δ3 are denoted as the differences between the post-process and pre-process values of the parameters Y, U and V, respectively, and MD1 and MD2 are denoted as the differences between the pre-process values of the parameters Y and U, and between the pre-process values of the parameters Y and V, respectively. Because the enlargement ratio of the parameter Y has to be the same as that of the parameters U and V, a linear correspondence is obtained as shown in
The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be devised by persons skilled in the art without departing from the scope of the following claims.
