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imagegammacorrect — Changes gamma values in an image.


int imagegammacorrect(image, original, new);
int image: Image identifier
int original: Original gamma value
int new: New gamma value


TRUE on succes


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 423. Lighten an image

header("Content-type: image/png");
$im = imagecreatefrompng("test_image.png");
imagegammacorrect($im, 1.0, 5.0);

PHP Functions Essential Reference. Copyright © 2002 by New Riders Publishing (Authors: Zak Greant, Graeme Merrall, Torben Wilson, Brett Michlitsch). This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at The authors of this book have elected not to choose any options under the OPL. This online book was obtained from and is designed to provide information about the PHP programming language, focusing on PHP version 4.0.4 for the most part. The information is provided on an as-is basis, and no warranty or fitness is implied. All persons and entities shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from the information contained in this book.

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