Taorluath Posted February 24, 2008 Share Posted February 24, 2008 I'm trying to make a PHP script that increases the blue value of each pixel in an image by 1. It's important that the script goes pixel by pixel. For some reason, however, it outputs an image that is one solid color; a brownish red block. Why isn't this script only slightly increasing the values?? ??? ??? <?php $img = imagecreatefromgif('logo.gif'); // get height and width $h=imagesy($img); $w=imagesx($img); //display image echo "<img src='out.gif' />"; //cycle through every pixel and add 1 to the blue value of the pixel's rgb value $y=1; while($y < $h) { $x=1; while($x < $w) { $rgb = imagecolorat($img, $x, $y); $red = ($rgb >> 16) & 0xFF; $green = ($rgb >> & 0xFF; $blue = $rgb & 0xFF; $blue++; //define the new color and assign it to the pixel //this is where things go wrong $color = imagecolorallocate($img, $red, $green, $blue); imagesetpixel($img, $x, $y, $color); $x++; } $y++; } echo imagegif($img, 'out.gif'); ?> I know the problem is in these two lines by the way. $color = imagecolorallocate($img, $red, $green, $blue); imagesetpixel($img, $x, $y, $color); Quote Link to comment Share on other sites More sharing options...
ratcateme Posted February 24, 2008 Share Posted February 24, 2008 i added this after $blue++; echo "{$x},{$y} RGB: {$rgb}|RED: {$red}|Greeen: {$green}|Blue: {$blue}\n\n"; it shows that the problem is not in setting the color but getting the old color however i don't no what causes this problem Scott. Quote Link to comment Share on other sites More sharing options...
Barand Posted February 24, 2008 Share Posted February 24, 2008 Allocating a new color in the pallette for every pixel doesn't look like a good idea. You could try attacking the pallette rather than every single pixel. Much quicker. <?php $img = imagecreatefromgif('baa.gif'); //cycle through pallette add 1 to the blue value of color's rgb value $t = imagecolorstotal($img); for ($i=0; $i<$t; $i++) { $cols = imagecolorsforindex($img, $i); $blue = $cols['blue'] < 255 ? $cols['blue']+1 : $cols['blue'] ; imagecolorset($img, $i, $cols['red'], $cols['green'], $blue); } imagegif($img); ?> Quote Link to comment Share on other sites More sharing options...
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