imagegammacorrect
Name
imagegammacorrect — Changes gamma values in an image.
Synopsis
int imagegammacorrect
(image, original, new);
int image: Image
identifier
int original: Original gamma
value
int new: New gamma
value
Description
Changes the brightness/contrast, or "gamma," in an image.
Values can be either negative or positive, and the image
will become darker or lighter, respectively. By changing
the original value, you can alter which parts of the
image are affected. When using dynamically created
pictures or altering existing pictures, altering the
gamma to a setting of 2.2 can be useful, as images at
this gamma setting have a similar brightness and contrast
on Windows and Macintosh platforms.
Example
Example 423. Lighten an
image
header("Content-type: image/png");
$im = imagecreatefrompng("test_image.png");
imagegammacorrect($im, 1.0, 5.0);
imagepng($im);
imagedestroy($im);
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