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

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I have an annoying habit of not using comments :)

Explanations are inline.

On Mar 28, 2008, at 7:10 PM, Lamonte <php4food@xxxxxxxxx> wrote:

Casey wrote:
On Mar 28, 2008, at 4:27 PM, Lamonte <php4food@xxxxxxxxx> 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";
}
?>

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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.

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