function imageapi_gd_unsharp_mask in ImageAPI 6

Same name and namespace in other branches

1. 5 imageapi_gd.module \imageapi_gd_unsharp_mask()

$sigma is currently unused for _gd_sharp_mask due to 3x3 convolution matrix limit. we should explore properly implementing sigma.

1 call to imageapi_gd_unsharp_mask()

imageapi_gd_image_sharpen in ./imageapi_gd.module

File

./imageapi_gd.module, line 277

GD2 toolkit functions

Code

function imageapi_gd_unsharp_mask($img, $radius, $sigma, $amount, $threshold) {

  //////////////////////////////////////////////////////////////

  ////

  ////                  Unsharp Mask for PHP - version 2.1.1

  ////

  ////    Unsharp mask algorithm by Torstein H�nsi 2003-07.

  ////             thoensi_at_netcom_dot_no.

  ////               Please leave this notice.

  ////

  //////////////////////////////////////////////////////////////

  // http://vikjavev.no/computing/ump.php
  // $img is an image that is already created within php using
  // imgcreatetruecolor. No url! $img must be a truecolor image.
  // Attempt to calibrate the parameters to Photoshop:
  if ($amount > 500) {
    $amount = 500;
  }
  $amount = $amount * 0.016;
  if ($radius > 50) {
    $radius = 50;
  }
  $radius = $radius * 2;
  if ($threshold > 255) {
    $threshold = 255;
  }
  $radius = abs(round($radius));

  // Only integers make sense.
  if ($radius == 0) {
    return $img;
    imagedestroy($img);
    break;
  }
  $w = imagesx($img);
  $h = imagesy($img);
  $img_canvas = imagecreatetruecolor($w, $h);
  $img_blur = imagecreatetruecolor($w, $h);

  // Gaussian blur matrix:
  //
  //    1    2    1
  //    2    4    2
  //    1    2    1
  //

  //////////////////////////////////////////////////
  $matrix = array(
    array(
      1,
      2,
      1,
    ),
    array(
      2,
      4,
      2,
    ),
    array(
      1,
      2,
      1,
    ),
  );
  imagecopy($img_blur, $img, 0, 0, 0, 0, $w, $h);
  imageconvolution($img_blur, $matrix, 16, 0);
  if ($threshold > 0) {

    // Calculate the difference between the blurred pixels and the original
    // and set the pixels
    for ($x = 0; $x < $w - 1; $x++) {

      // each row
      for ($y = 0; $y < $h; $y++) {

        // each pixel
        $rgb_orig = imagecolorat($img, $x, $y);
        $r_orig = $rgb_orig >> 16 & 0xff;
        $g_orig = $rgb_orig >> 8 & 0xff;
        $b_orig = $rgb_orig & 0xff;
        $rgb_blur = imagecolorat($img_blur, $x, $y);
        $r_blur = $rgb_blur >> 16 & 0xff;
        $g_blur = $rgb_blur >> 8 & 0xff;
        $b_blur = $rgb_blur & 0xff;

        // When the masked pixels differ less from the original
        // than the threshold specifies, they are set to their original value.
        $r_new = abs($r_orig - $r_blur) >= $threshold ? max(0, min(255, $amount * ($r_orig - $r_blur) + $r_orig)) : $r_orig;
        $g_new = abs($g_orig - $g_blur) >= $threshold ? max(0, min(255, $amount * ($g_orig - $g_blur) + $g_orig)) : $g_orig;
        $b_new = abs($b_orig - $b_blur) >= $threshold ? max(0, min(255, $amount * ($b_orig - $b_blur) + $b_orig)) : $b_orig;
        if ($r_orig != $r_new || $g_orig != $g_new || $b_orig != $b_new) {
          $pix_col = imagecolorallocate($img, $r_new, $g_new, $b_new);
          imagesetpixel($img, $x, $y, $pix_col);
        }
      }
    }
  }
  else {
    for ($x = 0; $x < $w; $x++) {

      // each row
      for ($y = 0; $y < $h; $y++) {

        // each pixel
        $rgb_orig = imagecolorat($img, $x, $y);
        $r_orig = $rgb_orig >> 16 & 0xff;
        $g_orig = $rgb_orig >> 8 & 0xff;
        $b_orig = $rgb_orig & 0xff;
        $rgb_blur = imagecolorat($img_blur, $x, $y);
        $r_blur = $rgb_blur >> 16 & 0xff;
        $g_blur = $rgb_blur >> 8 & 0xff;
        $b_blur = $rgb_blur & 0xff;
        $r_new = $amount * ($r_orig - $r_blur) + $r_orig;
        if ($r_new > 255) {
          $r_new = 255;
        }
        elseif ($r_new < 0) {
          $r_new = 0;
        }
        $g_new = $amount * ($g_orig - $g_blur) + $g_orig;
        if ($g_new > 255) {
          $g_new = 255;
        }
        elseif ($g_new < 0) {
          $g_new = 0;
        }
        $b_new = $amount * ($b_orig - $b_blur) + $b_orig;
        if ($b_new > 255) {
          $b_new = 255;
        }
        elseif ($b_new < 0) {
          $b_new = 0;
        }
        $rgb_new = ($r_new << 16) + ($g_new << 8) + $b_new;
        imagesetpixel($img, $x, $y, $rgb_new);
      }
    }
  }
  imagedestroy($img_canvas);
  imagedestroy($img_blur);
  return $img;
}