Fix rendering of masks with non-opaque alpha channel

(bzr r9508.1.55)

3 files changed, 30 insertions, 22 deletions

diff --git a/src/display/cairo-templates.h b/src/display/cairo-templates.h
index 3c8a6fea3..2b97dd6d6 100644
--- a/src/display/cairo-templates.h
+++ b/src/display/cairo-templates.h
@@ -686,22 +686,6 @@ pxclamp(gint32 v, gint32 low, gint32 high) {
 #define ASSEMBLE_ARGB32(px,a,r,g,b) \
     guint32 px = (a << 24) | (r << 16) | (g << 8) | b;
 
-// this is also used for masks, so it resides in this header
-struct ColorMatrixLuminanceToAlpha {
-    guint32 operator()(guint32 in) {
-        // original computation in double: r*0.2125 + g*0.7154 + b*0.0721
-        EXTRACT_ARGB32(in, a, r, g, b)
-        // unpremultiply color values
-        if (a != 0) {
-            r = unpremul_alpha(r, a);
-            g = unpremul_alpha(g, a);
-            b = unpremul_alpha(b, a);
-        }
-        guint32 ao = r*54 + g*182 + b*18;
-        return ((ao + 127) / 255) << 24;
-    }
-};
-
 #endif
 /*
   Local Variables:
diff --git a/src/display/nr-arena-item.cpp b/src/display/nr-arena-item.cpp
index d9c04ae95..fe50f7753 100644
--- a/src/display/nr-arena-item.cpp
+++ b/src/display/nr-arena-item.cpp
@@ -308,11 +308,20 @@ nr_arena_item_invoke_update (NRArenaItem *item, NRRectL *area, NRGC *gc,
     return item->state;
 }
 
-/**
- *    Render item to pixblock.
- *
- *    \return Has NR_ARENA_ITEM_STATE_RENDER set on success.
- */
+struct MaskLuminanceToAlpha {
+    guint32 operator()(guint32 in) {
+        // original computation in double: r*0.2125 + g*0.7154 + b*0.0721
+        EXTRACT_ARGB32(in, a, r, g, b)
+        // unpremultiply color values
+        if (a != 0) {
+            r = unpremul_alpha(r, a);
+            g = unpremul_alpha(g, a);
+            b = unpremul_alpha(b, a);
+        }
+        guint32 ao = r*54 + g*182 + b*18;
+        return premul_alpha((ao + 127) / 255, a) << 24;
+    }
+};
 
 unsigned int
 nr_arena_item_invoke_render (cairo_t *ct, NRArenaItem *item, NRRectL const *area,
@@ -462,7 +471,7 @@ nr_arena_item_invoke_render (cairo_t *ct, NRArenaItem *item, NRRectL const *area
         cairo_pattern_t *p = mask->cobj();
         cairo_surface_t *s;
         cairo_pattern_get_surface(p, &s);
-        ink_cairo_surface_filter(s, s, ColorMatrixLuminanceToAlpha());
+        ink_cairo_surface_filter(s, s, MaskLuminanceToAlpha());
     }
 
     // render the object (possibly to the intermediate surface)
diff --git a/src/display/nr-filter-colormatrix.cpp b/src/display/nr-filter-colormatrix.cpp
index d77898180..7ab606182 100644
--- a/src/display/nr-filter-colormatrix.cpp
+++ b/src/display/nr-filter-colormatrix.cpp
@@ -135,6 +135,21 @@ private:
     gint32 _v[9];
 };
 
+struct ColorMatrixLuminanceToAlpha {
+    guint32 operator()(guint32 in) {
+        // original computation in double: r*0.2125 + g*0.7154 + b*0.0721
+        EXTRACT_ARGB32(in, a, r, g, b)
+        // unpremultiply color values
+        if (a != 0) {
+            r = unpremul_alpha(r, a);
+            g = unpremul_alpha(g, a);
+            b = unpremul_alpha(b, a);
+        }
+        guint32 ao = r*54 + g*182 + b*18;
+        return ((ao + 127) / 255) << 24;
+    }
+};
+
 void FilterColorMatrix::render_cairo(FilterSlot &slot)
 {
     cairo_surface_t *input = slot.getcairo(_input);