Image enhancement methods and systems using the same
An embodiment of an image enhancement method is introduced for use in an electronic device. An image composed of a plurality of pixel values is first received, and each pixel therein is separated into two channels. The image is further divided into a plurality of blocks. A distribution of a selected channel is determined for each block, which is selected from the two channels. For each pixel, the pixel value of the selected channel is adjusted according to at least one distribution corresponding to at least one neighboring block. For each pixel, the pixel value of the other channel is adjusted according to the adjusted pixel value of the selected channel. As a result, the adjusted image is provided.
1. An image processing system implemented for processing an image in an electronic device, comprising:
a general-purpose processor that is programmed using microcode or software to partition the image into a plurality of blocks, determine a representative luminance value for each block of the image and assign one of plurality luminance profiles for each block according to the representative luminance value, wherein at least two blocks of the plurality of blocks correspond to different luminance profiles respectively; and
receive the luminance profile assignment to each block, and, for each pixel of the image, determine at least one neighboring block for the pixel, determine a distance from the pixel to the neighboring block, and adjust a luminance value of each pixel of the image according to at least one luminance profile of the neighboring block and the distance.
2. The image processing system of claim 1 , wherein the luminance profile is used to map one of the luminance values to a new one.
3. The image processing system of claim 1 , wherein the general-purpose processor that is programmed using microcode or software further adjusts a chrominance value of each pixel of the image according to the adjustment results on the corresponding luminance value.
4. The image processing system of claim 3 , wherein the general-purpose processor that is programmed using microcode or software adjusts the chrominance value using equations as follows:
PiC′=C×S×PiC;
and
C= 1+( Pi′−Pi )/ Pi,
where PiC denotes original chrominance value, S is a constant, which is a predefined saturation factor, Pi denotes an original luminance value corresponding to the chrominance value, and Pi′ denotes adjusted luminance value corresponding to the chrominance value.
5. The image processing system of claim 1 , wherein the general-purpose processor that is programmed using microcode or software adjusts the luminance value of each pixel using an equation as follows:
Pl′=Σ i=1 n di×F ( Bi, Pl ),
where n denotes a total number of the neighboring blocks for the luminance value, di denotes a distance from the pixel to the center of the (i)-th neighboring block Bi, and F(Bi, Pi) denotes a mapping function to map an original luminance Pl according to the luminance profile assigned to the (i)-th neighboring block Bi.
6. The image processing system of claim 5 , wherein the general-purpose processor that is programmed using microcode or software further adjusts the luminance value of each pixel by calculating weighted sum of the adjusted luminance value and the original luminance value according to a saturation value corresponding to the pixel.
7. The image processing system of claim 1 , wherein the general-purpose processor that is programmed using microcode or software determines whether the image needs to be enhanced according to a luminance distribution of the image, and if so, activate the block determination unit.
8. The image processing system of claim 7 , wherein the luminance distribution is generated from a plurality of low frequency components of the luminance values.