Handle bitmap downsampling ourselves, see bug #804162 in launchpad.

(bzr r12227)

1 files changed, 112 insertions, 12 deletions

diff --git a/src/display/drawing-image.cpp b/src/display/drawing-image.cpp
index 0c8ac9681..185b62285 100644
--- a/src/display/drawing-image.cpp
+++ b/src/display/drawing-image.cpp
@@ -22,6 +22,7 @@ DrawingImage::DrawingImage(Drawing &drawing)
     : DrawingItem(drawing)
     , _pixbuf(NULL)
     , _surface(NULL)
+    , _new_surface(NULL)
     , _style(NULL)
 {}
 
@@ -30,6 +31,7 @@ DrawingImage::~DrawingImage()
     if (_style)
         sp_style_unref(_style);
     if (_pixbuf) {
+        if (_new_surface) cairo_surface_destroy(_new_surface);
         cairo_surface_destroy(_surface);
         g_object_unref(_pixbuf);
     }
@@ -118,26 +120,124 @@ unsigned DrawingImage::_renderItem(DrawingContext &ct, Geom::IntRect const &/*ar
 
     if (!outline) {
         if (!_pixbuf) return RENDER_OK;
-
+        
         Inkscape::DrawingContext::Save save(ct);
         ct.transform(_ctm);
         ct.newPath();
         ct.rectangle(_clipbox);
         ct.clip();
 
-        ct.translate(_origin);
-        ct.scale(_scale);
-        ct.setSource(_surface, 0, 0);
+        /////////////////////////////////////////////////////////////////////////////
+        // BEGIN: Hack to avoid Cairo bug
+        // The total transform (which is RIGHT-multiplied with the item points to get display points) equals:
+        //   scale*translate_origin*_ctm = scale*translate(origin)*expansion*expansionInv*_ctm
+        //                               = scale*expansion*translate(origin*expansion)*expansionInv*_ctm
+        // To avoid a Cairo bug, we handle the scale*expansion part ourselves.
+        // See https://bugs.launchpad.net/inkscape/+bug/804162
+        
+        Geom::Scale expansion(_ctm.expansion());
+        int orgwidth = cairo_image_surface_get_width(_surface);
+        int orgheight = cairo_image_surface_get_height(_surface);
+
+        if (_scale[Geom::X]*expansion[Geom::X]*orgwidth*255.0<1.0 || _scale[Geom::Y]*expansion[Geom::Y]*orgheight*255.0<1.0) {
+            // Resized image too small to actually see anything
+            return RENDER_OK;
+        }
+        
+        // Split scale*expansion in a part that is <= 1.0 and a part that is >= 1.0. We only take care of the part <= 1.0.
+        Geom::Scale scaleExpansionSmall(std::min<Geom::Coord>(fabs(_scale[Geom::X]*expansion[Geom::X]),1),std::min<Geom::Coord>(fabs(_scale[Geom::Y]*expansion[Geom::Y]),1));
+        Geom::Scale scaleExpansionLarge(_scale[Geom::X]*expansion[Geom::X]/scaleExpansionSmall[Geom::X],_scale[Geom::Y]*expansion[Geom::Y]/scaleExpansionSmall[Geom::Y]);
+
+        Geom::Point newSize(Geom::Point(orgwidth,orgheight)*scaleExpansionSmall);
+        if ((newSize-Geom::Point(orgwidth,orgheight)).length()<0.1) {
+            // Just use _surface directly.
+            ct.scale(expansion.inverse()); // This should not include scale (see derivation above)
+            ct.translate(_origin*expansion);
+            ct.scale(scaleExpansionLarge);
+            ct.setSource(_surface, 0, 0);
+        } else if (!_new_surface || (newSize-_rescaledSize).length()>0.1) {
+            // Rescaled image is sufficiently different from cached image to recompute
+            if (_new_surface) cairo_surface_destroy(_new_surface);
+            _rescaledSize = newSize;
+
+            // This essentially considers an image to be composed of rectangular pixels and computes the least-squares approximation of the original.
+            // When the scale factor is really large or small this essentially results in using a box filter, while for scale factors approaching 1 it is more like a "tent" kernel.
+            int newwidth = static_cast<int>(floor(orgwidth*scaleExpansionSmall[Geom::X])+1);
+            int newheight = static_cast<int>(floor(orgheight*scaleExpansionSmall[Geom::Y])+1);
+            std::vector<int> xBegin(newwidth, -1), yBegin(newheight, -1);
+            std::vector< std::vector<float> > xCoefs(xBegin.size()), yCoefs(yBegin.size());
+            for(int x=0; x<orgwidth; x++) {
+                double coordBegin = x*static_cast<double>(scaleExpansionSmall[Geom::X]); // x-coord in target coordinates where the current source pixel begins
+                double coordEnd = (x+1)*static_cast<double>(scaleExpansionSmall[Geom::X]); // x-coord in target coordinates where the current source pixel ends
+                int begin = static_cast<int>(floor(coordBegin)); // First pixel (x-coord) affected by the current source pixel
+                int end = static_cast<int>(ceil(coordEnd)); // First pixel (x-coord) NOT affected by the current source pixel (a zero contribution is counted as not affecting the pixel)
+                for(int nx=begin; nx<end; nx++) {
+                    // Set xBegin if this is the first source pixel contributing to the target pixel.
+                    if (xBegin[nx]==-1) xBegin[nx] = x;
+                    // This computes the fraction of the current target pixel (at nx) that is covered by the source pixel (at x).
+                    xCoefs[nx].push_back(static_cast<float>(std::min<double>(nx+1,coordEnd) - std::max<double>(nx,coordBegin)));
+                }
+            }
+            for(int y=0; y<orgheight; y++) {
+                double coordBegin = y*static_cast<double>(scaleExpansionSmall[Geom::Y]); // y-coord in target coordinates where the current source pixel begins
+                double coordEnd = (y+1)*static_cast<double>(scaleExpansionSmall[Geom::Y]); // y-coord in target coordinates where the current source pixel ends
+                int begin = static_cast<int>(floor(coordBegin)); // First pixel (y-coord) affected by the current source pixel
+                int end = static_cast<int>(ceil(coordEnd)); // First pixel (y-coord) NOT affected by the current source pixel (a zero contribution is counted as not affecting the pixel)
+                for(int ny=begin; ny<end; ny++) {
+                    // Set yBegin if this is the first source pixel contributing to the target pixel.
+                    if (yBegin[ny]==-1) yBegin[ny] = y;
+                    // This computes the fraction of the current target pixel (at ny) that is covered by the source pixel (at y).
+                    yCoefs[ny].push_back(static_cast<float>(std::min<double>(ny+1,coordEnd) - std::max<double>(ny,coordBegin)));
+                }
+            }
+
+            _new_surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, newwidth,newheight);
+            unsigned char * orgdata = cairo_image_surface_get_data(_surface);
+            unsigned char * newdata = cairo_image_surface_get_data(_new_surface);
+            int orgstride = cairo_image_surface_get_stride(_surface);
+            int newstride = cairo_image_surface_get_stride(_new_surface);
+            
+            cairo_surface_flush(_surface);
+            cairo_surface_flush(_new_surface);
+
+            for(int y=0; y<newheight; y++) {
+                for(int x=0; x<newwidth; x++) {
+                    float tempSum[4] = {0,0,0,0};
+                    for(int oy=0; oy<static_cast<int>(yCoefs[y].size()); oy++) {
+                        for(int ox=0; ox<static_cast<int>(xCoefs[x].size()); ox++) {
+                            for(int c=0; c<4; c++) {
+                                tempSum[c] += xCoefs[x][ox]*yCoefs[y][oy]*orgdata[c+4*(xBegin[x]+ox)+orgstride*(yBegin[y]+oy)];
+                            }
+                        }
+                    }
+                    for(int c=0; c<4; c++) {
+                        newdata[c+4*x+newstride*y] = static_cast<unsigned char>(tempSum[c]);
+                    }
+                }
+            }
+            
+            cairo_surface_mark_dirty(_new_surface);
+        
+            ct.scale(expansion.inverse()); // This should not include scale (see derivation above)
+            ct.translate(_origin*expansion); 
+            ct.scale(scaleExpansionLarge);
+            ct.setSource(_new_surface, 0, 0);
+        } else {
+            // No need to regenerate, but we do draw from _new_surface.
+            ct.scale(expansion.inverse()); // This should not include scale (see derivation above)
+            ct.translate(_origin*expansion); 
+            ct.scale(scaleExpansionLarge);
+            ct.setSource(_new_surface, 0, 0);
+        }
+        
+        // END: Hack to avoid Cairo bug
+        /////////////////////////////////////////////////////////////////////////////
 
-        cairo_matrix_t tt;
-        Geom::Affine total;
-        cairo_get_matrix(ct.raw(), &tt);
-        ink_matrix_to_2geom(total, tt);
+        // TODO: If Cairo's problems are gone, uncomment the following:
+        //ct.translate(_origin);
+        //ct.scale(_scale);
+        //ct.setSource(_surface, 0, 0);
 
-        if (total.expansionX() > 1.0 || total.expansionY() > 1.0) {
-            cairo_pattern_t *p = cairo_get_source(ct.raw());
-            cairo_pattern_set_filter(p, CAIRO_FILTER_NEAREST);
-        }
         //ct.paint(_opacity);
         ct.paint();