+# make a thumbnail image.
+#
+# Thumbnail will have the same filename, except "_thumb" will be added right
+# before the dot preceding the extension. so foo.png yields foo_thumb.png
+#
+# Thumbnail will retain aspect ratio, and be either $max_width wide or
+# $max_height tall (or, if the aspect is just right, both)
+function make_thumbnail($filename, $max_width = '70', $max_height = '70') {
+ $thumb = ereg_replace('[.]([a-z]+)$', "_thumb.\\1", $filename);
+ if($thumb == $filename) {
+ die("couldn't make thumbnail because filename has no extension.");
+ }
+
+ $convert = path_to_convert();
+
+ # can't be too careful
+ $max_width = ereg_replace('[^0-9]', '', $max_width);
+ if($max_width == '') {
+ $max_width = '70';
+ }
+ $max_height = ereg_replace('[^0-9]', '', $max_height);
+ if($max_height == '') {
+ $max_height = '70';
+ }
+
+ $command = "$convert -geometry ${max_width}x$max_height " . escapeshellarg($filename) . ' ' . escapeshellarg($thumb);
+
+ exec($command, $dummy, $ret);
+ if($ret != 0) {
+ die("Thumbnail creatin failed. convert did exit($ret)");
+ }
+
+ return $thumb;
+}
+