Fix opacity calculation problem with the agg renderer (#5697) (#7085)

Fixes #56974
MapServer · Jun 21, 2024 · a8f6aca · a8f6aca
1 parent 5f6f317
commit a8f6aca
Show file tree

Hide file tree

Showing 5 changed files with 4 additions and 3 deletions.
diff --git a/msautotest/renderers/expected/compop_hsl_color.agg.png b/msautotest/renderers/expected/compop_hsl_color.agg.png
diff --git a/msautotest/renderers/expected/compop_hsl_hue.agg.png b/msautotest/renderers/expected/compop_hsl_hue.agg.png
diff --git a/msautotest/renderers/expected/compop_hsl_luminosity.agg.png b/msautotest/renderers/expected/compop_hsl_luminosity.agg.png
diff --git a/msautotest/renderers/expected/compositing.png b/msautotest/renderers/expected/compositing.png
diff --git a/src/mapagg.cpp b/src/mapagg.cpp
@@ -1345,7 +1345,7 @@ static int aggCompositeRasterBufferPixman(imageObj *dest,
     if (opacity == 100) {
       alpha_mask_i_ptr = NULL;
     } else {
-      unsigned char alpha = (unsigned char)(opacity * 2.55);
+      unsigned char alpha = (unsigned char)(MS_NINT(opacity * 2.55));
       if (!alpha_mask_i) {
         alpha_mask = (unsigned char *)msSmallMalloc(dest->width * dest->height);
         alpha_mask_i =
@@ -1379,12 +1379,13 @@ static int aggCompositeRasterBufferNoPixman(imageObj *dest,
   pixel_format pf(b);
   mapserver::comp_op_e comp_op = ms2agg_compop(comp);
   if (comp_op == mapserver::comp_op_src_over) {
-    r->m_renderer_base.blend_from(pf, 0, 0, 0, unsigned(opacity * 2.55));
+    r->m_renderer_base.blend_from(pf, 0, 0, 0,
+                                  unsigned(MS_NINT(opacity * 2.55)));
   } else {
     compop_pixel_format pixf(r->m_rendering_buffer);
     compop_renderer_base ren(pixf);
     pixf.comp_op(comp_op);
-    ren.blend_from(pf, 0, 0, 0, unsigned(opacity * 2.55));
+    ren.blend_from(pf, 0, 0, 0, unsigned(MS_NINT(opacity * 2.55)));
   }
   return MS_SUCCESS;
 }