Soeren Sandmann <sandm...@cs.au.dk> writes:
> The new code only computes the transformation once, and then it add the
> absolute value of the 00 and 10 components to get a conservative
> estimate of the transformed destination boundary. I'm especially
> interested in review of this part, both of the code and of whether it's
> actually correct mathematically.
It is in fact not at all correct. It's completely bogus in fact. For
affine matrices the idea may not be entirely wrong, but the correct
thing to add to the X coordinates would be |m00| + |m01| + |m11| and not
just |m00|. Similar for Y coordinates.
But that fails to take projective matrices into account, so I just went
back to computing the transformed bounding box twice. New patch below.
Soren
>From e02d17612531fb8556d30fc2dde3ad2680f2b739 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B8ren=20Sandmann=20Pedersen?= <s...@redhat.com>
Date: Mon, 5 Sep 2011 00:19:51 -0400
Subject: [PATCH] Eliminate compute_sample_extents() function
In analyze_extents(), instead of calling compute_sample_extents() call
compute_transformed_extents() and inline the remaining part of
compute_sample_extents(). The upcoming bilinear->nearest optimization
will do something different with these two pieces of code.
---
pixman/pixman.c | 100 +++++++++++++++++++++++--------------------------------
1 files changed, 42 insertions(+), 58 deletions(-)
diff --git a/pixman/pixman.c b/pixman/pixman.c
index 264a56b..19eda08 100644
--- a/pixman/pixman.c
+++ b/pixman/pixman.c
@@ -514,45 +514,9 @@ compute_transformed_extents (pixman_transform_t *transform,
return TRUE;
}
-static pixman_bool_t
-compute_sample_extents (pixman_transform_t *transform,
- pixman_box32_t *extents,
- pixman_fixed_t x_off, pixman_fixed_t y_off,
- pixman_fixed_t width, pixman_fixed_t height)
-{
- box_48_16_t transformed;
-
- if (!compute_transformed_extents (transform, extents, &transformed))
- return FALSE;
-
- /* Expand the source area by a tiny bit so account of different rounding
that
- * may happen during sampling. Note that (8 * pixman_fixed_e) is very far
from
- * 0.5 so this won't cause the area computed to be overly pessimistic.
- */
- transformed.x1 += x_off - 8 * pixman_fixed_e;
- transformed.y1 += y_off - 8 * pixman_fixed_e;
- transformed.x2 += x_off + width + 8 * pixman_fixed_e;
- transformed.y2 += y_off + height + 8 * pixman_fixed_e;
-
- if (transformed.x1 < pixman_min_fixed_48_16 || transformed.x1 >
pixman_max_fixed_48_16 ||
- transformed.y1 < pixman_min_fixed_48_16 || transformed.y1 >
pixman_max_fixed_48_16 ||
- transformed.x2 < pixman_min_fixed_48_16 || transformed.x2 >
pixman_max_fixed_48_16 ||
- transformed.y2 < pixman_min_fixed_48_16 || transformed.y2 >
pixman_max_fixed_48_16)
- {
- return FALSE;
- }
- else
- {
- extents->x1 = pixman_fixed_to_int (transformed.x1);
- extents->y1 = pixman_fixed_to_int (transformed.y1);
- extents->x2 = pixman_fixed_to_int (transformed.x2) + 1;
- extents->y2 = pixman_fixed_to_int (transformed.y2) + 1;
-
- return TRUE;
- }
-}
-
#define IS_16BIT(x) (((x) >= INT16_MIN) && ((x) <= INT16_MAX))
+#define ABS(f) (((f) < 0)? (-(f)) : (f))
+#define IS_16_16(f) (((f) >= pixman_min_fixed_48_16 && ((f) <=
pixman_max_fixed_48_16)))
static pixman_bool_t
analyze_extent (pixman_image_t *image,
@@ -563,7 +527,8 @@ analyze_extent (pixman_image_t *image,
pixman_fixed_t *params;
pixman_fixed_t x_off, y_off;
pixman_fixed_t width, height;
- pixman_box32_t ex;
+ box_48_16_t transformed;
+ pixman_box32_t exp_extents;
if (!image)
return TRUE;
@@ -633,17 +598,6 @@ analyze_extent (pixman_image_t *image,
default:
return FALSE;
}
-
- /* Check whether the non-expanded, transformed extent is entirely within
- * the source image, and set the FAST_PATH_SAMPLES_COVER_CLIP if it is.
- */
- ex = *extents;
- if (compute_sample_extents (transform, &ex, x_off, y_off, width,
height) &&
- ex.x1 >= 0 && ex.y1 >= 0 &&
- ex.x2 <= image->bits.width && ex.y2 <= image->bits.height)
- {
- *flags |= FAST_PATH_SAMPLES_COVER_CLIP;
- }
}
else
{
@@ -653,17 +607,47 @@ analyze_extent (pixman_image_t *image,
height = 0;
}
- /* Check that the extents expanded by one don't overflow. This ensures that
- * compositing functions can simply walk the source space using 16.16
- * variables without worrying about overflow.
+ if (!compute_transformed_extents (transform, extents, &transformed))
+ return FALSE;
+
+ /* Expand the source area by a tiny bit so account of different rounding
that
+ * may happen during sampling. Note that (8 * pixman_fixed_e) is very far
from
+ * 0.5 so this won't cause the area computed to be overly pessimistic.
*/
- ex.x1 = extents->x1 - 1;
- ex.y1 = extents->y1 - 1;
- ex.x2 = extents->x2 + 1;
- ex.y2 = extents->y2 + 1;
+ transformed.x1 += x_off - 8 * pixman_fixed_e;
+ transformed.y1 += y_off - 8 * pixman_fixed_e;
+ transformed.x2 += x_off + width + 8 * pixman_fixed_e;
+ transformed.y2 += y_off + height + 8 * pixman_fixed_e;
+
+ if (image->common.type == BITS &&
+ pixman_fixed_to_int (transformed.x1) >= 0 &&
+ pixman_fixed_to_int (transformed.y1) >= 0 &&
+ pixman_fixed_to_int (transformed.x2) < image->bits.width &&
+ pixman_fixed_to_int (transformed.y2) < image->bits.height)
+ {
+ *flags |= FAST_PATH_SAMPLES_COVER_CLIP;
+ }
- if (!compute_sample_extents (transform, &ex, x_off, y_off, width, height))
+ /* Check we don't overflow when the destination extents are expanded by
one.
+ * This ensures that compositing functions can simply walk the source space
+ * using 16.16 variables without worrying about overflow.
+ */
+ exp_extents = *extents;
+ exp_extents.x1 -= 1;
+ exp_extents.y1 -= 1;
+ exp_extents.x2 += 1;
+ exp_extents.y2 += 1;
+
+ if (!compute_transformed_extents (transform, &exp_extents, &transformed))
+ return FALSE;
+
+ if (!IS_16_16 (transformed.x1 + x_off - 8 * pixman_fixed_e) ||
+ !IS_16_16 (transformed.y1 + y_off - 8 * pixman_fixed_e) ||
+ !IS_16_16 (transformed.x2 + x_off + 8 * pixman_fixed_e + width) ||
+ !IS_16_16 (transformed.y2 + y_off + 8 * pixman_fixed_e + height))
+ {
return FALSE;
+ }
return TRUE;
}
--
1.7.4
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