Attachment 78522 Details for Bug 41745 – Downscaling patch

[patch] Downscaling patch

cairo-downscaling.patch (text/plain), 3.44 KB, created by Krzysztof Kosiński on 2013-04-26 14:12:11 UTC

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Creator: Krzysztof Kosiński

Created: 2013-04-26 14:12:11 UTC

Size: 3.44 KB

patch

obsolete

>diff --git a/src/cairo-image-source.c b/src/cairo-image-source.c
>index c5bd228..5795094 100644
>--- a/src/cairo-image-source.c
>+++ b/src/cairo-image-source.c
>@@ -554,24 +554,42 @@ _pixman_image_set_properties (pixman_image_t *pixman_image,
>     }
>     else
>     {
>+	double scale_x, scale_y;
>+	int shrink_x, shrink_y;
> 	pixman_filter_t pixman_filter;
>+	pixman_kernel_t pixman_kernel_sample, pixman_kernel_reconstruct;
>+
>+	/* Compute scale factors as the length of basis vectors transformed by
>+	 * the pattern matrix. These scale factors are from user to pattern space,
>+	 * and as such they are greater than 1.0 for downscaling and less than 1.0
>+	 * for upscaling.
>+	 * TODO: this approach may not be completely correct if the matrix
>+	 * contains a skew component. */
>+	scale_x = hypot (pattern->matrix.xx, pattern->matrix.yx);
>+	scale_y = hypot (pattern->matrix.yx, pattern->matrix.yy);
>+
>+	/* Use convolution filtering if the transformation shrinks the image
>+	 * by more than half a pixel */
>+	shrink_x = (extents->width / scale_x - extents->width) < -0.5;
>+	shrink_y = (extents->height / scale_y - extents->height) < -0.5;
> 
> 	switch (pattern->filter) {
> 	case CAIRO_FILTER_FAST:
>-	    pixman_filter = PIXMAN_FILTER_FAST;
>-	    break;
>-	case CAIRO_FILTER_GOOD:
>-	    pixman_filter = PIXMAN_FILTER_GOOD;
>-	    break;
>-	case CAIRO_FILTER_BEST:
>-	    pixman_filter = PIXMAN_FILTER_BEST;
>-	    break;
> 	case CAIRO_FILTER_NEAREST:
> 	    pixman_filter = PIXMAN_FILTER_NEAREST;
>+	    pixman_kernel_sample = PIXMAN_KERNEL_IMPULSE;
>+	    pixman_kernel_reconstruct = PIXMAN_KERNEL_BOX;
> 	    break;
>+	case CAIRO_FILTER_GOOD:
> 	case CAIRO_FILTER_BILINEAR:
> 	    pixman_filter = PIXMAN_FILTER_BILINEAR;
>+	    pixman_kernel_sample = PIXMAN_KERNEL_BOX;
>+	    pixman_kernel_reconstruct = PIXMAN_KERNEL_LINEAR;
> 	    break;
>+	case CAIRO_FILTER_BEST:
>+	    pixman_filter = PIXMAN_FILTER_BEST;
>+	    pixman_kernel_sample = PIXMAN_KERNEL_LANCZOS3;
>+	    pixman_kernel_reconstruct = PIXMAN_KERNEL_LANCZOS3;
> 	case CAIRO_FILTER_GAUSSIAN:
> 	    /* XXX: The GAUSSIAN value has no implementation in cairo
> 	     * whatsoever, so it was really a mistake to have it in the
>@@ -579,10 +597,40 @@ _pixman_image_set_properties (pixman_image_t *pixman_image,
> 	     * else inventing semantics and providing an actual
> 	     * implementation for it. */
> 	default:
>-	    pixman_filter = PIXMAN_FILTER_BEST;
>+	    pixman_filter = PIXMAN_FILTER_BILINEAR;
>+	    pixman_kernel_sample = PIXMAN_KERNEL_BOX;
>+	    pixman_kernel_reconstruct = PIXMAN_KERNEL_LINEAR;
> 	}
> 
>-	pixman_image_set_filter (pixman_image, pixman_filter, NULL, 0);
>+	if (pixman_filter != PIXMAN_FILTER_NEAREST && (shrink_x || shrink_y))
>+	{
>+	    pixman_kernel_t sampling_kernel_x, sampling_kernel_y;
>+	    int n_params;
>+	    pixman_fixed_t *params;
>+
>+	    sampling_kernel_x = shrink_x ? pixman_kernel_sample : PIXMAN_KERNEL_IMPULSE;
>+	    sampling_kernel_y = shrink_y ? pixman_kernel_sample : PIXMAN_KERNEL_IMPULSE;
>+
>+	    n_params = 0;
>+	    params = pixman_filter_create_separable_convolution (&n_params,
>+								 scale_x * 65536.0 + 0.5,
>+								 scale_y * 65536.0 + 0.5,
>+								 pixman_kernel_reconstruct,
>+								 pixman_kernel_reconstruct,
>+								 sampling_kernel_x,
>+								 sampling_kernel_y,
>+								 1, 1);
>+
>+	    pixman_image_set_filter (pixman_image,
>+				     PIXMAN_FILTER_SEPARABLE_CONVOLUTION,
>+				     params, n_params);
>+
>+	    free (params);
>+	}
>+	else
>+	{
>+	    pixman_image_set_filter (pixman_image, pixman_filter, NULL, 0);
>+	}
>     }
> 
>     {

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