Re: [GD-DEVEL] Replacing one color with another

Hi Andrie,

On 5/4/07, Andrei Stebakov <[email protected]> wrote:
> I was wondering if there is a way to replace one color for another in an
> image? Let's say I have an image with a white background and a number of
> solid color figures (circles) in say red color. I need to replace those red
> circles into black ones. If not gdlib, could you suggest a way I can go
> here?

Something like this should work for both truecolor and palette image:
black = gdImageColorAllocate(im, 0,0,0);
red = gdImageColorAllocate(im, 255,0,0); //red

for (y=0; y < gdImageSY(im); y++) {
 for (x=0; x < gdImageSx(im); x++) {
  int c =  gdImageGetPixel(im, x,y);
  if (c == red) {
    gdImageSetPixel(im, x, y, black);
  }
 }
}

For palette images only, you can replace the red color index values
directly, it should do it as well (a bit hackish though with the
current API).


--Pierre