| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 96 === Nowadays digital camera is a necessary tool for people to record their daily life, but images taken by current cameras are usually different from the realistic view. We can use some image post-process techniques to get more pleasant, clearer image or make it nearer to the realistic view, but these techniques need manual adjustment. If there are a large amount of images need to be enhanced, then manual adjustment is not practical; another truth is that not everyone can do image post-process. Thus an automatic image enhancement technique can be very helpful, especially an embedded automatic processor for camera. Our goal is to develop an automatic image enhanced system.
Basic image enhancement is accomplished by adjusting the intensity, the contrast, and the color balance. The conventional automatic image enhancements use global adjustment. Here, we introduce Retinex method to perform the local image enhancement. It can adjust images locally depending on the content of the image. We implement and compare several published algorithms. By combining the advantages of these algorithms and determining the parameters by testing them on known images, we implement an automatic system successfully. It can enhance images without any manual control or adjustment. It is robust enough to deal with almost any kind of images. Those fine details in dark and bright region are both revealed clearly after process. The unclear part in the shadow of sunlight and the low contrast of foggy image can be resolved by our system. It can deal with much more varieties of images as compared to the conventional techniques. It also gives a pleasant, nature image. The local contrast and tonal rendition are both quiet good. This study shows that automatic image enhanced system can be a reality and no longer be an unreachable dream.
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