PHP将图像颜色更改为透明，然后用作遮罩

Question

I'm trying to change the background colour of an image from white, to transparent, then to use that as a mask to put over another image. (Cannot be transparent already, because another part is which is used as a mask over yet another image)... layers are fun :)

Full code:

<?
include '../includes/db.php';
include '../includes/checks.php';

$type = $_GET['t']; //shirt | shorts
$style = $_GET['s'];
$z = $_GET['z']; // home | away
$a = $_GET['a'];
$b = $_GET['b'];

$aR = hexdec($a['0'].$a['1']);
$aG = hexdec($a['2'].$a['3']);
$aB = hexdec($a['4'].$a['5']);
$bR = hexdec($b['0'].$b['1']);
$bG = hexdec($b['2'].$b['3']);
$bB = hexdec($b['4'].$b['5']);

// main top
$imgname = '../images/kits/test/'. $uTime .'.png';
$im = imagecreatetruecolor( 100, 100); 
$red = imagecolorallocate($im, $aR, $aG, $aB);
imagefill($im, 0, 0, $red);

$mask = imagecreatefrompng('../images/kits/test/6-space.png'); 
imagecopyresampled($im, $mask, 0, 0, 0, 0, imagesx($im), imagesy($im), imagesx($mask), imagesy($mask));
imagedestroy($mask);

$mask = imagecreatefrompng('../images/kits/test/4-shadows.png'); 
imagecopyresampled($im, $mask, 0, 0, 0, 0, imagesx($im), imagesy($im), imagesx($mask), imagesy($mask));
imagedestroy($mask);

$mask = imagecreatefrompng('../images/kits/test/1-tag.png'); 
imagecopyresampled($im, $mask, 0, 0, 0, 0, imagesx($im), imagesy($im), imagesx($mask), imagesy($mask));
imagedestroy($mask);

// design
$im2 = imagecreatetruecolor( 100, 100); 
$red = imagecolorallocate($im2, $bR, $bG, $bB);
imagefill($im2, 0, 0, $red);

$mask = imagecreatefrompng('../images/kits/test/5-logo.png'); 
imagecopyresampled($im2, $mask, 0, 0, 0, 0, imagesx($im2), imagesy($im2), imagesx($mask), imagesy($mask));
imagedestroy($mask);
imagecolortransparent($im2, imagecolorallocatealpha($im2, 0, 0, 0, 127));
imagealphablending($im2, false);
imagesavealpha($im2, true);
$white = imagecolorallocate($im2,255,255,255);
imagecolortransparent($im2, $white);

// merge and result
imagecopyresampled($im, $im2, 0, 0, 0, 0, imagesx($im), imagesy($im), imagesx($im2), imagesy($im2));
imagepng($im, $imgname);
imagedestroy($im2);
imagedestroy($im);
echo '<img src="', $imgname ,'">';
?>

Answer 1

A couple of methods with Imagemagick ( the second example came from http://www.imagemagick.org/Usage/masking/ )

Change all white in the image to transparent

convert input.jpg -matte -fuzz 1% -transparent rgb(255,255,255) mask.png

Change all the white in an image that is connected to the pixel in the top left corner.

convert input.jpg -alpha set -channel RGBA -fuzz 1% -fill none -floodfill +0+0 white mask.png

In php use like this:

exec("convert input.jpg -matte -fuzz 1% -transparent rgb\(255,255,255\) mask.png");

The command above is changing white rgb(255,255,255) actualy +- 1% of the rgb value to transparent