private function diffusion($image)
{
$pixel = array();
// Localize vars
$width = $image->getWidth();
$height = $image->getHeight();
$old = $image->getCore();
$new = imagecreatetruecolor($width, $height);
for ($y = 0; $y < $height; $y += 1) {
for ($x = 0; $x < $width; $x += 1) {
$color = imagecolorat($old, $x, $y);
$r = $color >> 16 & 0xff;
$g = $color >> 8 & 0xff;
$b = $color & 0xff;
$gray = round($r * 0.3 + $g * 0.59 + $b * 0.11);
if (isset($pixel[$x][$y])) {
// Add errors to color if there are
$gray += $pixel[$x][$y];
}
if ($gray <= 127) {
// Determine if black or white. Also has the benefit of clipping excess val due to adding the error
$blackOrWhite = 0;
} else {
$blackOrWhite = 255;
}
$oldPixel = $gray;
$newPixel = $blackOrWhite;
// Current pixel
imagesetpixel($new, $x, $y, imagecolorallocate($new, $newPixel, $newPixel, $newPixel));
$qError = $oldPixel - $newPixel;
// Quantization error
// Propagate error on neighbor pixels
if ($x + 1 < $width) {
$pixel[$x + 1][$y] = (isset($pixel[$x + 1][$y]) ? $pixel[$x + 1][$y] : 0) + $qError * (7 / 16);
}
if ($x - 1 > 0 and $y + 1 < $height) {
$pixel[$x - 1][$y + 1] = (isset($pixel[$x - 1][$y + 1]) ? $pixel[$x - 1][$y + 1] : 0) + $qError * (3 / 16);
}
if ($y + 1 < $height) {
$pixel[$x][$y + 1] = (isset($pixel[$x][$y + 1]) ? $pixel[$x][$y + 1] : 0) + $qError * (5 / 16);
}
if ($x + 1 < $width and $y + 1 < $height) {
$pixel[$x + 1][$y + 1] = (isset($pixel[$x + 1][$y + 1]) ? $pixel[$x + 1][$y + 1] : 0) + $qError * (1 / 16);
}
}
}
imagedestroy($old);
// Free resource
// Create new image with updated core
return new Image($new, $image->getImageFile(), $width, $height, $image->getType());
}
