Fix bug #66887 imagescale - poor quality of scaled image

Issue with signed char overflow.

Upstream fix:
https://bitbucket.org/libgd/gd-libgd/commits/4b86e06937bc5ff116be969137f8da9d1a7869d5

diff --git a/ext/gd/libgd/gd_interpolation.c b/ext/gd/libgd/gd_interpolation.c
index 76327be7df4559e5ab6d1a276a3d400dcab34ca1..65e2360776bc22eb4eaf734941519db608f4499f 100644 (file)
--- a/ext/gd/libgd/gd_interpolation.c
+++ b/ext/gd/libgd/gd_interpolation.c
@@ -1324,8 +1324,8 @@ static gdImagePtr gdImageScaleBilinearTC(gdImagePtr im, const unsigned int new_w
                        gdFixed f_j = gd_itofx(j);
                        gdFixed f_a = gd_mulfx(f_i, f_dy);
                        gdFixed f_b = gd_mulfx(f_j, f_dx);
-                       const long m = gd_fxtoi(f_a);
-                       const long n = gd_fxtoi(f_b);
+                       const gdFixed m = gd_fxtoi(f_a);
+                       const gdFixed n = gd_fxtoi(f_b);
                        gdFixed f_f = f_a - gd_itofx(m);
                        gdFixed f_g = f_b - gd_itofx(n);
 
@@ -1365,10 +1365,10 @@ static gdImagePtr gdImageScaleBilinearTC(gdImagePtr im, const unsigned int new_w
                        f_a3 = gd_itofx(gdTrueColorGetAlpha(pixel3));
                        f_a4 = gd_itofx(gdTrueColorGetAlpha(pixel4));
                        {
-                               const char red = (char) gd_fxtoi(gd_mulfx(f_w1, f_r1) + gd_mulfx(f_w2, f_r2) + gd_mulfx(f_w3, f_r3) + gd_mulfx(f_w4, f_r4));
-                               const char green = (char) gd_fxtoi(gd_mulfx(f_w1, f_g1) + gd_mulfx(f_w2, f_g2) + gd_mulfx(f_w3, f_g3) + gd_mulfx(f_w4, f_g4));
-                               const char blue = (char) gd_fxtoi(gd_mulfx(f_w1, f_b1) + gd_mulfx(f_w2, f_b2) + gd_mulfx(f_w3, f_b3) + gd_mulfx(f_w4, f_b4));
-                               const char alpha = (char) gd_fxtoi(gd_mulfx(f_w1, f_a1) + gd_mulfx(f_w2, f_a2) + gd_mulfx(f_w3, f_a3) + gd_mulfx(f_w4, f_a4));
+                               const unsigned char red   = (unsigned char) gd_fxtoi(gd_mulfx(f_w1, f_r1) + gd_mulfx(f_w2, f_r2) + gd_mulfx(f_w3, f_r3) + gd_mulfx(f_w4, f_r4));
+                               const unsigned char green = (unsigned char) gd_fxtoi(gd_mulfx(f_w1, f_g1) + gd_mulfx(f_w2, f_g2) + gd_mulfx(f_w3, f_g3) + gd_mulfx(f_w4, f_g4));
+                               const unsigned char blue  = (unsigned char) gd_fxtoi(gd_mulfx(f_w1, f_b1) + gd_mulfx(f_w2, f_b2) + gd_mulfx(f_w3, f_b3) + gd_mulfx(f_w4, f_b4));
+                               const unsigned char alpha = (unsigned char) gd_fxtoi(gd_mulfx(f_w1, f_a1) + gd_mulfx(f_w2, f_a2) + gd_mulfx(f_w3, f_a3) + gd_mulfx(f_w4, f_a4));
 
                                new_img->tpixels[dst_offset_v][dst_offset_h] = gdTrueColorAlpha(red, green, blue, alpha);
                        }