Pixel density revisited

Started Oct 22, 2008 | Discussions thread
DSPographer Senior Member • Posts: 2,464
Re: FastStone Resampling

I tried FastStone and its Lanczos3 resampling is the correct implementation to avoid aliasing except for what it does at the image borders. When you shrink the image to half size horizontally; instead of the first output pixel being located between the first two input pixels, and the last output pixel being located between the last two output pixels; the first and last output pixels are centered on the input pixels. FastStone then spaces the remaining pixel locations to get the desired image size. So to get a spacing of exactly every two input pixels you could for instance scale a 1001 pixel wide image to 501 pixels wide. The problem with this method is that the boundary pixels do not get as much filtering in the downsampling process as the other pixels. This results in a glitch occurring along the right edge of the downsampled in half version of my test image.

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