Fix #50194: imagettftext broken on transparent background w/o alphablending

We must not draw the background pixels of the character glyphs, what has
already been fixed in GD 2.0.26.

NEWS

@@ -18,6 +18,8 @@ PHP                                                                        NEWS
 - GD:
   . Fixed bug #67325 (imagetruecolortopalette: white is duplicated in palette).
     (cmb)
+  . Fixed bug #50194 (imagettftext broken on transparent background w/o
+    alphablending). (cmb)
 
 - Mbstring:
   . Fixed bug #72994 (mbc_to_code() out of bounds read). (Laruence, cmb)

ext/gd/libgd/gdft.c

@@ -659,6 +659,8 @@ static char * gdft_draw_bitmap (gdCache_head_t *tc_cache, gdImage * im, int fg,
 				} else {
 					return "Unsupported ft_pixel_mode";
 				}
+				if (level == 0)  /* if background */
+					continue;
 				if ((fg >= 0) && (im->trueColor)) {
 					/* Consider alpha in the foreground color itself to be an
 					 * upper bound on how opaque things get, when truecolor is

ext/gd/tests/bug50194.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Bug #50194 (imagettftext broken on transparent background w/o alphablending)
+--SKIPIF--
+<?php
+if (!extension_loaded('gd')) die('skip gd extension not available');
+if (!function_exists('imagettftext')) die('skip imagettftext() not available');
+?>
+--FILE--
+<?php
+require_once __DIR__ . DIRECTORY_SEPARATOR . 'func.inc';
+
+$im = imagecreatetruecolor(240, 55);
+$background = imagecolorallocatealpha($im, 60, 60, 60, 0); // no tranparency
+$black = imagecolorallocate($im, 0, 0, 0);
+imagealphablending($im, false); 
+imagefilledrectangle($im, 0, 0, 239, 54, $background);
+$text = 'Testing ... ';
+$font = __DIR__ . DIRECTORY_SEPARATOR . 'Tuffy.ttf';
+imagettftext($im, 40, 0, 10, 40, $black, $font, $text);
+imagesavealpha($im, true);
+
+test_image_equals_file(__DIR__ . DIRECTORY_SEPARATOR . 'bug50194.png', $im);
+
+imagedestroy($im);
+?>
+===DONE===
+--EXPECT--
+The images are equal.
+===DONE===