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PHP GD Grayscale
Posted on: November 9, 2009 at 12:00 AM
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This example shows how to Grayscale an image in php gd.

<?php

$file = 'images.jpg';

header('Content-type: image/jpeg');

list($width, $height) = getimagesize($file);

$source = imagecreatefromjpeg($file);

$bwimage= imagecreate($width, $height);

for ($c=0;$c<256;$c++)

{

$palette[$c] = imagecolorallocate($bwimage,$c,$c,$c);

}

function yiq($r,$g,$b)

{

return (($r*0.299)+($g*0.587)+($b*0.114));

}

for ($y=0;$y<$height;$y++)

{

for ($x=0;$x<$width;$x++)

{

$rgb = imagecolorat($source,$x,$y);

$r = ($rgb >> 16) & 0xFF;

$g = ($rgb >> 8) & 0xFF;

$b = $rgb & 0xFF;

 

$gs = yiq($r,$g,$b);

imagesetpixel($bwimage,$x,$y,$palette[$gs]);

}

}

imagejpeg($bwimage);

?>

After running the program you will get the following output

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Posted on: November 9, 2009

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