[Pixman] [PATCH pixman 11/11] pixman-image: Implement PIXMAN_FILTER_GOOD/BEST as separable convolutions
Bill Spitzak
spitzak at gmail.com
Fri Sep 26 19:06:10 PDT 2014
GOOD uses the BOX.BOX filter, with a filter size of 1 for all scales larger
than .75, which is identical to BILINEAR. At very small scales it clamps the
filter size to 16. Uses the BILINEAR code if both directions are bilinear
or are exactly .5 scale with integer translations.
BEST uses the IMPULSE.LANCZOS2 filter up to a scale of 2 with the filter size
clamped to 1. At higher scales it switches to BOX.LANCZOS2 with a size of scale-1
to produce square pixels with only slight blurry borders. At very small scales
it switches to BOX.BOX and then at smaller ones it clamps the filter size to 24.
Detects and uses NEAREST for reflections as well as 90 degree rotations.
---
pixman/pixman-image.c | 292 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 213 insertions(+), 79 deletions(-)
diff --git a/pixman/pixman-image.c b/pixman/pixman-image.c
index 1ff1a49..6d2cde5 100644
--- a/pixman/pixman-image.c
+++ b/pixman/pixman-image.c
@@ -28,6 +28,7 @@
#include <stdio.h>
#include <string.h>
#include <assert.h>
+#include <math.h>
#include "pixman-private.h"
@@ -274,112 +275,245 @@ compute_image_info (pixman_image_t *image)
FAST_PATH_X_UNIT_POSITIVE |
FAST_PATH_Y_UNIT_ZERO |
FAST_PATH_AFFINE_TRANSFORM);
+ switch (image->common.filter)
+ {
+ case PIXMAN_FILTER_CONVOLUTION:
+ break;
+ case PIXMAN_FILTER_SEPARABLE_CONVOLUTION:
+ flags |= FAST_PATH_SEPARABLE_CONVOLUTION_FILTER;
+ break;
+ default:
+ flags |= (FAST_PATH_NEAREST_FILTER | FAST_PATH_NO_CONVOLUTION_FILTER);
+ break;
+ }
}
else
{
+ pixman_fixed_t (*m)[3] = image->common.transform->matrix;
+ double dx, dy;
+ int xsubsample, ysubsample;
+ int nearest_ok, bilinear_ok;
+
flags |= FAST_PATH_HAS_TRANSFORM;
- if (image->common.transform->matrix[2][0] == 0 &&
- image->common.transform->matrix[2][1] == 0 &&
- image->common.transform->matrix[2][2] == pixman_fixed_1)
+ nearest_ok = FALSE;
+ bilinear_ok = FALSE;
+
+ if (m[2][0] == 0 &&
+ m[2][1] == 0 &&
+ m[2][2] == pixman_fixed_1)
{
flags |= FAST_PATH_AFFINE_TRANSFORM;
- if (image->common.transform->matrix[0][1] == 0 &&
- image->common.transform->matrix[1][0] == 0)
+ if (m[0][1] == 0 && m[1][0] == 0)
{
- if (image->common.transform->matrix[0][0] == -pixman_fixed_1 &&
- image->common.transform->matrix[1][1] == -pixman_fixed_1)
+ flags |= FAST_PATH_SCALE_TRANSFORM;
+ if (abs(m[0][0]) == pixman_fixed_1 &&
+ abs(m[1][1]) == pixman_fixed_1)
{
- flags |= FAST_PATH_ROTATE_180_TRANSFORM;
+ nearest_ok = TRUE;
+ if (m[0][0] < 0 && m[1][1] < 0)
+ flags |= FAST_PATH_ROTATE_180_TRANSFORM;
}
- flags |= FAST_PATH_SCALE_TRANSFORM;
}
- else if (image->common.transform->matrix[0][0] == 0 &&
- image->common.transform->matrix[1][1] == 0)
+ else if (m[0][0] == 0 && m[1][1] == 0)
{
- pixman_fixed_t m01 = image->common.transform->matrix[0][1];
- pixman_fixed_t m10 = image->common.transform->matrix[1][0];
-
- if (m01 == -pixman_fixed_1 && m10 == pixman_fixed_1)
- flags |= FAST_PATH_ROTATE_90_TRANSFORM;
- else if (m01 == pixman_fixed_1 && m10 == -pixman_fixed_1)
- flags |= FAST_PATH_ROTATE_270_TRANSFORM;
+ if (abs(m[0][1]) == pixman_fixed_1 &&
+ abs(m[1][0]) == pixman_fixed_1)
+ {
+ nearest_ok = TRUE;
+ if (m[0][1] < 0 && m[1][0] > 0)
+ flags |= FAST_PATH_ROTATE_90_TRANSFORM;
+ else if (m[0][1] > 0 && m[1][0] < 0)
+ flags |= FAST_PATH_ROTATE_270_TRANSFORM;
+ }
}
}
- if (image->common.transform->matrix[0][0] > 0)
+ if (nearest_ok)
+ {
+ /* reject non-integer translation: */
+ if (pixman_fixed_frac (m[0][2] | m[1][2]))
+ nearest_ok = FALSE;
+ /* FIXME: there are some affine-test failures, showing
+ * that handling of BILINEAR and NEAREST filter is not
+ * quite equivalent when getting close to 32K for the
+ * translation components of the matrix. That's likely
+ * some bug, but for now just skip BILINEAR->NEAREST
+ * optimization in this case.
+ */
+ else if (abs(m[0][2] | m[1][2]) > pixman_int_to_fixed (30000))
+ nearest_ok = FALSE;
+ }
+
+ if (m[0][0] > 0)
flags |= FAST_PATH_X_UNIT_POSITIVE;
- if (image->common.transform->matrix[1][0] == 0)
+ if (m[1][0] == 0)
flags |= FAST_PATH_Y_UNIT_ZERO;
- }
- /* Filter */
- switch (image->common.filter)
- {
- case PIXMAN_FILTER_NEAREST:
- case PIXMAN_FILTER_FAST:
- flags |= (FAST_PATH_NEAREST_FILTER | FAST_PATH_NO_CONVOLUTION_FILTER);
- break;
+ switch (image->common.filter)
+ {
+ case PIXMAN_FILTER_NEAREST:
+ case PIXMAN_FILTER_FAST:
+ flags |= (FAST_PATH_NEAREST_FILTER | FAST_PATH_NO_CONVOLUTION_FILTER);
+ break;
- case PIXMAN_FILTER_BILINEAR:
- case PIXMAN_FILTER_GOOD:
- case PIXMAN_FILTER_BEST:
- flags |= (FAST_PATH_BILINEAR_FILTER | FAST_PATH_NO_CONVOLUTION_FILTER);
+ case PIXMAN_FILTER_BILINEAR:
+ if (nearest_ok)
+ flags |= (FAST_PATH_NEAREST_FILTER | FAST_PATH_NO_CONVOLUTION_FILTER);
+ else
+ flags |= (FAST_PATH_BILINEAR_FILTER | FAST_PATH_NO_CONVOLUTION_FILTER);
+ break;
- /* Here we have a chance to optimize BILINEAR filter to NEAREST if
- * they are equivalent for the currently used transformation matrix.
- */
- if (flags & FAST_PATH_ID_TRANSFORM)
- {
- flags |= FAST_PATH_NEAREST_FILTER;
- }
- else if (
- /* affine and integer translation components in matrix ... */
- ((flags & FAST_PATH_AFFINE_TRANSFORM) &&
- !pixman_fixed_frac (image->common.transform->matrix[0][2] |
- image->common.transform->matrix[1][2])) &&
- (
- /* ... combined with a simple rotation */
- (flags & (FAST_PATH_ROTATE_90_TRANSFORM |
- FAST_PATH_ROTATE_180_TRANSFORM |
- FAST_PATH_ROTATE_270_TRANSFORM)) ||
- /* ... or combined with a simple non-rotated translation */
- (image->common.transform->matrix[0][0] == pixman_fixed_1 &&
- image->common.transform->matrix[1][1] == pixman_fixed_1 &&
- image->common.transform->matrix[0][1] == 0 &&
- image->common.transform->matrix[1][0] == 0)
- )
- )
- {
- /* FIXME: there are some affine-test failures, showing that
- * handling of BILINEAR and NEAREST filter is not quite
- * equivalent when getting close to 32K for the translation
- * components of the matrix. That's likely some bug, but for
- * now just skip BILINEAR->NEAREST optimization in this case.
+ case PIXMAN_FILTER_GOOD:
+ if (nearest_ok) {
+ flags |= (FAST_PATH_NEAREST_FILTER | FAST_PATH_NO_CONVOLUTION_FILTER);
+ break;
+ }
+
+ /* Compute filter sizes. This is the bounding box of a
+ * diameter=1 circle transformed by the matrix. Scaling
+ * down produces values greater than 1.
+ *
+ * For non-affine the circle is centered on one of the 4
+ * points 1,1 away from the origin. Which one depends on
+ * the signs of the values in the last row of the matrix,
+ * chosen to avoid dividing by zero.
+ *
+ * This division factor both accounts for the w component
+ * and converts from fixed to float.
*/
- pixman_fixed_t magic_limit = pixman_int_to_fixed (30000);
- if (image->common.transform->matrix[0][2] <= magic_limit &&
- image->common.transform->matrix[1][2] <= magic_limit &&
- image->common.transform->matrix[0][2] >= -magic_limit &&
- image->common.transform->matrix[1][2] >= -magic_limit)
- {
- flags |= FAST_PATH_NEAREST_FILTER;
+ dy = 1.0 / (abs(m[2][0]) + abs(m[2][1]) + abs(m[2][2]));
+ /* There are some signs that hypot is faster with numbers near 1
+ * so the division is done first. Mathematically it should work
+ * to divide afterwards.
+ */
+ dx = hypot (m[0][0] * dy, m[0][1] * dy);
+ dy = hypot (m[1][0] * dy, m[1][1] * dy);
+
+ /* At scales above 1/1.35 this uses the bilinear filter.
+ * This is identical to box at size 1, and I judged the
+ * artifacts for the smaller scales to not be worse than
+ * the box filter. Bilinear can also be used for a scale
+ * of exactly 1/2 with integer translate.
+ *
+ * Filters size is clamped to 16 to prevent extreme slowness.
+ */
+ if (dx <= 1.35) {
+ dx = 1.0;
+ bilinear_ok = TRUE;
+ } else if (dx > 16.0) {
+ dx = 16.0;
+ } else if (dx > 1.999 && dx < 2.001 &&
+ abs(m[0][0] * m[0][1]) < 4 &&
+ abs(pixman_fixed_frac(m[0][2]) < 2))
+ bilinear_ok = TRUE;
+ if (dy <= 1.35)
+ dy = 1.0;
+ else if (dy > 16.0) {
+ dy = 16.0;
+ bilinear_ok = FALSE;
+ } else if (bilinear_ok) {
+ if (dy > 1.999 && dy < 2.001 &&
+ abs(m[1][0] * m[1][1]) < 4 &&
+ abs(pixman_fixed_frac(m[1][2]) < 2))
+ ;
+ else bilinear_ok = FALSE;
}
- }
- break;
+ if (bilinear_ok) {
+ printf("Using bilinear\n");
+ flags |= (FAST_PATH_BILINEAR_FILTER |
+ FAST_PATH_NO_CONVOLUTION_FILTER);
+ break;
+ }
+ printf("Not using bilinear\n");
+
+ xsubsample = 0;
+ while (dx * (1 << xsubsample) <= 128.0) xsubsample++;
+ ysubsample = 0;
+ while (dy * (1 << ysubsample) <= 128.0) ysubsample++;
+
+ if (image->common.filter_params)
+ free (image->common.filter_params);
+
+ image->common.filter_params =
+ pixman_filter_create_separable_convolution
+ ( & image->common.n_filter_params,
+ pixman_double_to_fixed(dx),
+ pixman_double_to_fixed(dy),
+ PIXMAN_KERNEL_BOX,
+ PIXMAN_KERNEL_BOX,
+ PIXMAN_KERNEL_BOX,
+ PIXMAN_KERNEL_BOX,
+ xsubsample, ysubsample);
+
+ flags |= FAST_PATH_SEPARABLE_CONVOLUTION_FILTER;
+ break;
- case PIXMAN_FILTER_CONVOLUTION:
- break;
+ case PIXMAN_FILTER_BEST:
+ if (nearest_ok) {
+ flags |= (FAST_PATH_NEAREST_FILTER |
+ FAST_PATH_NO_CONVOLUTION_FILTER);
+ break;
+ }
+ /* See notes above about filter sizes */
+ dy = 1.0 / (abs(m[2][0]) + abs(m[2][1]) + abs(m[2][2]));
+ dx = hypot (m[0][0] * dy, m[0][1] * dy);
+ dy = hypot (m[1][0] * dy, m[1][1] * dy);
+
+ /* To prevent extreme slowness this switches to BOX at
+ * 1/16 scale and stops making the filter larger at 1/24
+ * scale.
+ *
+ * When enlarging this produces normal blur up to 2x, then
+ * square pixels with a 1-pixel blurry border between them
+ * for larger sizes. At scales larger than 128x the blur
+ * is increased to avoid making lots of subsamples.
+ */
+ if (dx > 24.0) dx = 24.0;
+ else if (dx < 1.0) {
+ if (dx >= 0.5) dx = 1.0;
+ else if (dx > 1.0/128) dx = 1.0 / (1.0 / dx - 1.0);
+ else dx = 1.0/127;
+ }
+ if (dy > 24.0) dy = 24.0;
+ else if (dy < 1.0) {
+ if (dy >= 0.5) dy = 1.0;
+ else if (dy > 1.0/128) dy = 1.0 / (1.0 / dy - 1.0);
+ else dy = 1.0/127;
+ }
- case PIXMAN_FILTER_SEPARABLE_CONVOLUTION:
- flags |= FAST_PATH_SEPARABLE_CONVOLUTION_FILTER;
- break;
+ xsubsample = 0;
+ while (dx * (1 << xsubsample) <= 128.0) xsubsample++;
+ ysubsample = 0;
+ while (dy * (1 << ysubsample) <= 128.0) ysubsample++;
+
+ image->common.filter_params =
+ pixman_filter_create_separable_convolution
+ ( & image->common.n_filter_params,
+ pixman_double_to_fixed(dx),
+ pixman_double_to_fixed(dy),
+ dx < 1.0 ? PIXMAN_KERNEL_BOX : PIXMAN_KERNEL_IMPULSE,
+ dy < 1.0 ? PIXMAN_KERNEL_BOX : PIXMAN_KERNEL_IMPULSE,
+ dx < 16.0 ? PIXMAN_KERNEL_LANCZOS2 : PIXMAN_KERNEL_BOX,
+ dy < 16.0 ? PIXMAN_KERNEL_LANCZOS2 : PIXMAN_KERNEL_BOX,
+ xsubsample, ysubsample);
+
+ flags |= FAST_PATH_SEPARABLE_CONVOLUTION_FILTER;
+ break;
- default:
- flags |= FAST_PATH_NO_CONVOLUTION_FILTER;
- break;
+ case PIXMAN_FILTER_CONVOLUTION:
+ break;
+
+ case PIXMAN_FILTER_SEPARABLE_CONVOLUTION:
+ flags |= FAST_PATH_SEPARABLE_CONVOLUTION_FILTER;
+ break;
+
+ default:
+ flags |= FAST_PATH_NO_CONVOLUTION_FILTER;
+ break;
+ }
}
/* Repeat mode */
--
1.7.9.5
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