[cairo] [PATCH] CAIRO_FILTER_BEST uses NEAREST filter when possible

[Bill Spitzak]

This avoids slow filtering for identity transforms when BEST is used.
Pixman is already handling the GOOD case.
---
 src/cairo-image-source.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/cairo-image-source.c b/src/cairo-image-source.c
index b6b6b9f..3d10953 100644
--- a/src/cairo-image-source.c
+++ b/src/cairo-image-source.c
@@ -955,6 +955,25 @@ _pixman_image_set_properties (pixman_image_t *pixman_image,
 	    }
 	    break;
 	case CAIRO_FILTER_BEST:
+	    /* Check for 1:1 pixel transfer and use NEAREST for that */
+	    if (_cairo_fixed_is_integer (_cairo_fixed_from_double
+					 (pattern->matrix.x0)) &&
+		_cairo_fixed_is_integer (_cairo_fixed_from_double
+					 (pattern->matrix.y0))) {
+		cairo_fixed_t xx = _cairo_fixed_from_double(pattern->matrix.xx);
+		cairo_fixed_t xy = _cairo_fixed_from_double(pattern->matrix.xy);
+		cairo_fixed_t yx = _cairo_fixed_from_double(pattern->matrix.yx);
+		cairo_fixed_t yy = _cairo_fixed_from_double(pattern->matrix.yy);
+		if ((xy == 0 && yx == 0 &&
+		     abs(xx) == CAIRO_FIXED_ONE &&
+		     abs(yy) == CAIRO_FIXED_ONE) ||
+		    (xx == 0 && yy == 0 &&
+		     abs(xy) == CAIRO_FIXED_ONE &&
+		     abs(yx) == CAIRO_FIXED_ONE)) {
+		    pixman_filter = PIXMAN_FILTER_NEAREST;
+		    break;
+		}
+	    }
 	    pixman_filter = PIXMAN_FILTER_BEST;
 	    pixman_filter = PIXMAN_FILTER_SEPARABLE_CONVOLUTION;
 	    kernel = KERNEL_CATMULL_ROM; /* LANCZOS3 is better but not much */
-- 
1.7.9.5