Re: Is there anyone who has developed map projection library?

On Thu, 03 Nov 2005 18:31:29 +0100, willem van deursen
<wvandeursen_nospam@xxxxxxxxxxxxxxxxxx> wrote:

>To add a comment to Pauls thoughs on transformation of images:
>Instead of scanning through the input image, calculate a new location for each
>pixel in the output image and do a bilinear or other interpolation to fill in
>the gaps you might consider the following:
>calculate the corners of the transformed image and set up a large enough image
>to hold the entire transformed image. Now scan through the OUTPUT image and find
>the location of this pixel in the original image and fill it with that value.
>You actually are performing the REVERSE operation here: find the original
>location of output pixels. Now you don't need the interpolation afterwards,
>because your entire output image is filled with values (or outside the input image)
>
>Willem
>


Thanks, Willem. Of course that is a better way of doing it - though
you still need interpolation (or possibly averaging, if a single pixel
of the output crosses several pixels of the input) of the input image,
unless nearest neighbour is good enough. However, you avoid the
post-processing scan.

Paul
.

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