SIFT keypoint detector

It seems that nothing changes on开发者_JAVA百科 a jpg file after running the SIFT demo program here http://www.cs.ubc.ca/~lowe/keypoints/. Does anyone know how it works?

Thanks a lot.

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SIFT is an algorithm that generate keypoints based on its renowned automatic feature detection capabilities. Those keypoints would most likely be taken to compare with or match against other images. The image itself is not being modified. Rather, we are looking for 'distinguishable clusters of pixels' so that it would 1) distinguish itself from other pictures 2) liken itself to similar images. I have used this beautifully crafted algorithm in several occasions in my research. If you need more clarifications, let me know.

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@Gary Tsui: can we use SIFT to search for similar parts in one image? If we copy some part of the image and paste it to another part of the same image, is there possibility to detect copy - pasted area by using SIFT ?