put media stamps on animated gifs

1 files changed, 34 insertions, 1 deletions

diff --git a/init.php b/init.php
index cb97ecb..056ec85 100644
--- a/init.php
+++ b/init.php
@@ -60,7 +60,9 @@ class Api_Resize_Media extends Plugin {
 			$t_im = imageCreateTrueColor($t_width, $t_height);
 			$need_stamp = false;
 
-			if ($force_stamp /*|| ($enable_stamp && $imageinfo && $imageinfo["mime"] == "image/gif")*/) {
+			if ($force_stamp || ($imageinfo && $imageinfo["mime"] == "image/gif" &&
+									$this->is_animated_gif($input_filename))) {
+
 				$need_stamp = true;
 				imageFill($t_im, 0, 0, 0xffffff);
 			/*} else { -- this might make resized image significantly larger
@@ -297,6 +299,37 @@ class Api_Resize_Media extends Plugin {
 		return $article;
 	}
 
+	// https://stackoverflow.com/questions/280658/can-i-detect-animated-gifs-using-php-and-gd
+	function is_animated_gif ($filename) {
+		$raw = file_get_contents($filename);
+
+		if ($raw) {
+			$offset = 0;
+			$frames = 0;
+			while ($frames < 2 && $offset <= 500000) {
+				$where1 = strpos($raw, "\x00\x21\xF9\x04", $offset);
+
+				if ($where1 === false) {
+					break;
+				} else {
+					$offset = $where1 + 1;
+					$where2 = strpos($raw, "\x00\x2C", $offset);
+					if ($where2 === false) {
+						break;
+					} else {
+						if ($where1 + 8 == $where2) {
+							$frames++;
+						}
+						$offset = $where2 + 1;
+					}
+				}
+			}
+			return $frames > 1;
+		}
+
+		return false;
+	}
+
 	function api_version() {
 		return 2;
 	}