From b104a79502e2c01c508e40d83613ecfa001a2a4e Mon Sep 17 00:00:00 2001
From: Bertram Felgenhauer <int-e@gmx.de>
Date: Tue, 13 Jun 2006 20:07:28 -0400
Subject: [PATCH] Patch to fix pixman samping location bug (#2488).

---
 pixman/src/fbcompose.c                |  21 +++++++++++++++------
 test/pixman-rotate-rgb24-ref.png      | Bin 385 -> 244 bytes
 test/pixman-rotate-svg-argb32-ref.png | Bin 0 -> 258 bytes
 test/pixman-rotate-svg-rgb24-ref.png  | Bin 0 -> 358 bytes
 4 files changed, 15 insertions(+), 6 deletions(-)
 create mode 100644 test/pixman-rotate-svg-argb32-ref.png
 create mode 100644 test/pixman-rotate-svg-rgb24-ref.png

diff --git a/pixman/src/fbcompose.c b/pixman/src/fbcompose.c
index 9515edd46..46a34ecd4 100644
--- a/pixman/src/fbcompose.c
+++ b/pixman/src/fbcompose.c
@@ -2814,8 +2814,9 @@ static void fbFetchSourcePict(PicturePtr pict, int x, int y, int width, CARD32 *
         xFixed_32_32 l;
         xFixed_48_16 dx, dy, a, b, off;
 
-        v.vector[0] = IntToxFixed(x);
-        v.vector[1] = IntToxFixed(y);
+        /* reference point is the center of the pixel */
+        v.vector[0] = IntToxFixed(x) + xFixed1/2;
+        v.vector[1] = IntToxFixed(y) + xFixed1/2;
         v.vector[2] = xFixed1;
         if (pict->transform) {
             if (!PictureTransformPoint3d (pict->transform, &v))
@@ -2928,8 +2929,9 @@ static void fbFetchSourcePict(PicturePtr pict, int x, int y, int width, CARD32 *
 
         if (pict->transform) {
             PictVector v;
-            v.vector[0] = IntToxFixed(x);
-            v.vector[1] = IntToxFixed(y);
+            /* reference point is the center of the pixel */
+            v.vector[0] = IntToxFixed(x) + xFixed1/2;
+            v.vector[1] = IntToxFixed(y) + xFixed1/2;
             v.vector[2] = xFixed1;
             if (!PictureTransformPoint3d (pict->transform, &v))
                 return;
@@ -3068,8 +3070,9 @@ static void fbFetchTransformed(PicturePtr pict, int x, int y, int width, CARD32
     x += xoff;
     y += yoff;
 
-    v.vector[0] = IntToxFixed(x);
-    v.vector[1] = IntToxFixed(y);
+    /* reference point is the center of the pixel */
+    v.vector[0] = IntToxFixed(x) + xFixed1/2;
+    v.vector[1] = IntToxFixed(y) + xFixed1/2;
     v.vector[2] = xFixed1;
 
     /* when using convolution filters one might get here without a transform */
@@ -3184,6 +3187,12 @@ static void fbFetchTransformed(PicturePtr pict, int x, int y, int width, CARD32
             }
         }
     } else if (pict->filter == PIXMAN_FILTER_BILINEAR || pict->filter == PIXMAN_FILTER_GOOD || pict->filter == PIXMAN_FILTER_BEST) {
+        /* adjust vector for maximum contribution at 0.5, 0.5 of each texel. */
+        v.vector[0] -= v.vector[2]/2;
+        v.vector[1] -= v.vector[2]/2;
+        unit.vector[0] -= unit.vector[2]/2;
+        unit.vector[1] -= unit.vector[2]/2;
+
         if (pict->repeat == RepeatNormal) {
             if (PIXREGION_NUM_RECTS(pict->pCompositeClip) == 1) {
                 box = pict->pCompositeClip->extents;
diff --git a/test/pixman-rotate-rgb24-ref.png b/test/pixman-rotate-rgb24-ref.png
index c9d00fde7b9d96fdc039cd25c8bdca893d1185db..60d9b1c38b902e76979076dc38275804cc7a2df1 100644
GIT binary patch
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diff --git a/test/pixman-rotate-svg-argb32-ref.png b/test/pixman-rotate-svg-argb32-ref.png
new file mode 100644
index 0000000000000000000000000000000000000000..08d750bddd59ca686097215aa840fd0cad264110
GIT binary patch
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diff --git a/test/pixman-rotate-svg-rgb24-ref.png b/test/pixman-rotate-svg-rgb24-ref.png
new file mode 100644
index 0000000000000000000000000000000000000000..349fd5ce80ea248a99022891009e45d94bdf5fb9
GIT binary patch
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literal 0
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