Abstract
When the contrast of an image provided by photography is not good, a method to improve contrast by the software is effective for the image. The linear gray-level conversion and the histogram equalization are proposed as the conventional contrast improvement methods based on the distribution of gray-level included in the input image. However, because the conventional method does not use a spatial feature included in an image, contrast improvement is insufficient and unnatural. There is the method for contrast improvement of the image based on the differential gray-level histogram. This method can get a good result for the whole image, but it is sometimes arisen that the details of the image deteriorate. The objective of this research improves contrast of both the whole image and the image details. This paper proposes a spatial characteristic, the image segmentation, linear interpolation in order to improve contrast method. First, I divide an image into some blocks. I generate the Look-Up-Table from the differential gray-level histogram in each block. Finally, the output gray-level of each pixel is determined based on linear interpolation from the vicinity of the four LUT. The experimental results show that the image had good and natural contrast by the proposed method.
