Changes one color already in an image to a new specified color. Useful for replacing a block of color in an image without having to do any possibly complex redrawing operations. In the following example, the closest blue is found in the image using imagecolorclosest() and then replaced with green. This demonstrates how a color doesn't even need to be known exactly to be replaced.
Example 400. Replace blue with green
header("Content-type: image/png"); $im = imagecreate(200, 200); $red = imagecolorallocate($im, 255, 0, 0); $offblue = imagecolorallocate($im, 90, 90, 200); imagefill($im, 0, 0, $red); imagefilledrectangle($im, 10, 10, 40, 40, $offblue); // above could come from an uploaded image // find a blue in the image $newblue = imagecolorclosest($im, 0, 0, 255); // change it to green imagecolorset($im, $newblue, 0, 255, 0); imagepng($im); imagedestroy($im);
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