Try to improve match of image-rendering values to cairo filters

Specifically image-rendering="crisp-edges" should use a scaling
algorithm that does *not* blur edges.

Unfortunately this only leaves CAIRO_FILTER_NEAREST, but seems to
be the most suitable choice.

1 files changed, 13 insertions, 14 deletions

diff --git a/src/display/drawing-image.cpp b/src/display/drawing-image.cpp
index fb1342edf..0ac716dfb 100644
--- a/src/display/drawing-image.cpp
+++ b/src/display/drawing-image.cpp
@@ -116,26 +116,25 @@ unsigned DrawingImage::_renderItem(DrawingContext &dc, Geom::IntRect const &/*ar
 
         if (_style) {
             // See: http://www.w3.org/TR/SVG/painting.html#ImageRenderingProperty
-            //      http://www.w3.org/TR/css4-images/#the-image-rendering
-            //      It's back in CSS Images 3 now. 
-            //      style.h/style.cpp
+            //      https://drafts.csswg.org/css-images-3/#the-image-rendering
+            //      style.h/style.cpp, cairo-render-context.cpp
+            //
+            // CSS 3 defines:
+            //   'optimizeSpeed' as alias for "pixelated"
+            //   'optimizeQuality' as alias for "smooth"
             switch (_style->image_rendering.computed) {
+                case SP_CSS_IMAGE_RENDERING_OPTIMIZESPEED:
+                case SP_CSS_IMAGE_RENDERING_PIXELATED:
+                // we don't have an implementation for crisp-edges, but it should *not* smooth or blur
+                case SP_CSS_IMAGE_RENDERING_CRISPEDGES:
+                    dc.patternSetFilter( CAIRO_FILTER_NEAREST );
+                    break;
                 case SP_CSS_IMAGE_RENDERING_AUTO:
                 case SP_CSS_IMAGE_RENDERING_OPTIMIZEQUALITY:
-                case SP_CSS_IMAGE_RENDERING_CRISPEDGES:
-                    // CSS 3 defines:
-                    //   'auto' to use smoothing
-                    //   'optimize-quality' as alias for auto
-                    //   We don't have special rendering for 'crisp-edges' yet
-                    //   so follow what browsers do.
+                default:
                     // In recent Cairo, BEST used Lanczos3, which is prohibitively slow
                     dc.patternSetFilter( CAIRO_FILTER_GOOD );
                     break;
-                case SP_CSS_IMAGE_RENDERING_OPTIMIZESPEED:
-                case SP_CSS_IMAGE_RENDERING_PIXELATED:
-                default:
-                    dc.patternSetFilter( CAIRO_FILTER_NEAREST );
-                    break;
             }
         }