Re: GD, changing an images pixel color, color matching, fuzzy picture

I have an annoying habit of not using comments :) Explanations are inline. On Mar 28, 2008, at 7:10 PM, Lamonte <php4food@gmail.com> wrote:

Casey wrote:

On Mar 28, 2008, at 4:27 PM, Lamonte <php4food@gmail.com> wrote:

Okay I created a script that changes a basic smiley face into a red smiley face..but it doesn't replace all the yellow, it looks like a yellow shadow in the background: <?php $image = "smiley.png"; $data = getimagesize($image); $width = intval($data[0]); $height = intval($data[1]); $cloneH = 0; $hex = "FF0000"; $oldhex = "FCFF00"; $im = imagecreatefrompng($image); $color = imagecolorallocate($im,hexdec(substr($hex,0,2)),hexdec(substr($hex,2,2)),hexdec(substr($hex,4,6))); for($cloneH=0;$cloneH<$height;$cloneH++) { for($x=0;$x<$width;$x++) {

     if( colormatch($im,$x,$cloneH, $oldhex) )
         imagesetpixel($im, $x, $cloneH, $color);

} } header("Content-Type: {$data['mime']}"); imagepng($im); function colormatch($image,$x,$y,$hex) { $rgb = imagecolorat($image,$x,$y); $r = ($rgb >> 16) & 0xFF; $g = ($rgb >> 8) & 0xFF; $b = $rgb & 0xFF; $r2 = hexdec(substr($hex,0,2)); $g2 = hexdec(substr($hex,2,2)); $b2 = hexdec(substr($hex,4,6)); if( $r == $r2 && $b == $b2 && $g == $g2 )

     return true;

return false; //echo "$r $r2, $g $g2, $b $b2"; } ?> --PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php

Hi! I have absolutely no clue if this will work. This has been typed directly into my mail client, so no guarantees. <?php function toRGB($color) { return array('r' => ($color >> 16) & 0xFF, 'g' => ($color >> 8) & 0xFF, 'b' => $color & 0xFF); } This function returns an array of red, green, and blue from an integer like 0xFFFFFF.

function toColor($r, $g, $b) { return $r * $g * $b; } This function is basically the opposite of the above. (the integer value from red, green, and blue)

$image = 'smiley.png'; list($w, $h) = getimagesize($image); $im = imagecreatefrompng($image); for ($y = 0; $y < $h; $y++) { for ($x = 0; $x < $w; $x++) { Loop through the pixels.

extract(toRGB(imagecolorat($im, $x, $y))); Take the values from the array return of toRGB so we can use $r, $g, and $b instead of $array['r'], etc.

if ($r >= 0xCC && $g >= 0xCC && $b <= 0x33) After some trial and error (looking at color charts), any red > CC, green > CC, and blue < 33 is some shade of yellow.

imagesetpixel($im, $x, $y, toColor(($r + $g) / 2, 0, $b)); The expression inside toColor() is my attempt to calculate the correct shade of red from the shade of yellow.

} } header('Content-type: image/png'); imagepng($im); ?> :)

I don't understand half of that, can you explain what you did? (it works) I was more trying to "fix" my problem then recoding the whole thing though. I hope that helps.