function _imageapi_gd_pixel_contrast in ImageAPI 5
Same name and namespace in other branches
- 6 imagefilter.inc \_imageapi_gd_pixel_contrast()
1 string reference to '_imageapi_gd_pixel_contrast'
File
- ./
imagefilter.inc, line 72
Code
function _imageapi_gd_pixel_contrast(&$r, &$g, &$b, &$a, $contrast) {
// normalize color value between -0.5 - 0.5
// multiply by contrast value to accentuate positive/negative value.
// denormalize to 0-255 range.
$r = (($r / 255 - 0.5) * $contrast + 0.5) * 255;
$g = (($g / 255 - 0.5) * $contrast + 0.5) * 255;
$b = (($b / 255 - 0.5) * $contrast + 0.5) * 255;
}