Allow compilation with gdlib 1.8

diff --git a/ext/gd/gd.c b/ext/gd/gd.c
index ad2db04a3c6a7d1cfa1b7ffc025762d4d1555608..ae835a8db7e6daace25e1319ed4dffe33ce4c0ed 100644 (file)
--- a/ext/gd/gd.c
+++ b/ext/gd/gd.c
@@ -3755,9 +3755,11 @@ static void _php_image_bw_convert(gdImagePtr im_org, gdIOCtx *out, int threshold
                return;
        }
 
+#if HAVE_LIBGD20
        if (im_org->trueColor) {
                gdImageTrueColorToPalette(im_org, 1, 256);
        }
+#endif
 
        for (y = 0; y < dest_height; y++) {
                for (x = 0; x < dest_width; x++) {