When using nearest neighbor interpolation and not actually scaling, just copy the data. (Note we don't do this for other kinds of interpolation, because the filtering on those interpolations could have an effect even when not actually scaling.)

mdboom · mdboom · commit 1c9f9b5f6cb3 · 2012-05-14T14:06:05.000-04:00
diff --git a/src/_image.cpp b/src/_image.cpp
@@ -439,11 +439,15 @@ Image::resize(const Py::Tuple& args, const Py::Dict& kwargs)
 
     case NEAREST:
     {
-        typedef agg::span_image_filter_rgba_nn<img_accessor_type, interpolator_type> span_gen_type;
-        typedef agg::renderer_scanline_aa<renderer_base, span_alloc_type, span_gen_type> renderer_type;
-        span_gen_type sg(ia, interpolator);
-        renderer_type ri(rb, sa, sg);
-        agg::render_scanlines(ras, sl, ri);
+        if (colsIn == numcols && rowsIn == numrows) {
+            memcpy(bufferOut, bufferIn, colsIn * rowsIn * 4);
+        } else {
+            typedef agg::span_image_filter_rgba_nn<img_accessor_type, interpolator_type> span_gen_type;
+            typedef agg::renderer_scanline_aa<renderer_base, span_alloc_type, span_gen_type> renderer_type;
+            span_gen_type sg(ia, interpolator);
+            renderer_type ri(rb, sa, sg);
+            agg::render_scanlines(ras, sl, ri);
+        }
     }
     break;
 
