Index: typo3/sysext/cms/tslib/class.tslib_gifbuilder.php
===================================================================
--- typo3/sysext/cms/tslib/class.tslib_gifbuilder.php	(revision 8265)
+++ typo3/sysext/cms/tslib/class.tslib_gifbuilder.php	(working copy)
@@ -357,10 +357,20 @@
 		$this->w = $XY[0];
 		$this->h = $XY[1];
 
-			// backColor is set
-		$BGcols = $this->convertColor($this->setup['backColor']);
-		$Bcolor = ImageColorAllocate($this->im, $BGcols[0],$BGcols[1],$BGcols[2]);
-		ImageFilledRectangle($this->im, 0, 0, $XY[0], $XY[1], $Bcolor);
+		if ($this->truecolor && $this->setup['alphaChannel']) {
+				// support alpha channel transparency
+			imagealphablending($this->im, FALSE);
+			imagesavealpha($this->im, TRUE);
+				// backColor is set to transparent
+			$BGcols = $this->convertColor($this->setup['backColor']);
+			$Bcolor = ImageColorAllocateAlpha($this->im, $BGcols[0], $BGcols[1], $BGcols[2], 127);
+			imagefill($this->im, 0, 0, $Bcolor);
+		} else {
+				// backColor is set
+			$BGcols = $this->convertColor($this->setup['backColor']);
+			$Bcolor = ImageColorAllocate($this->im, $BGcols[0], $BGcols[1], $BGcols[2]);
+			ImageFilledRectangle($this->im, 0, 0, $XY[0], $XY[1], $Bcolor);
+		}
 
 			// Traverse the GIFBUILDER objects an render each one:
 		if (is_array($this->setup))	{