[gegl] Convert lohalo sampler to GIMP-style correspondence between pixel indices and position and clean up
- From: Nicolas Robidoux <nrobidoux src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [gegl] Convert lohalo sampler to GIMP-style correspondence between pixel indices and position and clean up
- Date: Sun, 18 Nov 2012 20:52:52 +0000 (UTC)
commit e760077020d1368d0b7edf0e0e77d932ae9524f4
Author: Nicolas Robidoux <nrobidoux git gnome org>
Date: Sun Nov 18 15:43:25 2012 -0500
Convert lohalo sampler to GIMP-style correspondence between pixel indices and position and clean up a bit
gegl/buffer/gegl-sampler-lohalo.c | 142 ++++++++++++++++++++----------------
1 files changed, 79 insertions(+), 63 deletions(-)
---
diff --git a/gegl/buffer/gegl-sampler-lohalo.c b/gegl/buffer/gegl-sampler-lohalo.c
index e3c2f75..3b8afd1 100644
--- a/gegl/buffer/gegl-sampler-lohalo.c
+++ b/gegl/buffer/gegl-sampler-lohalo.c
@@ -14,6 +14,7 @@
* License along with GEGL; if not, see
* <http://www.gnu.org/licenses/>.
*
+ * 2012 (c) Nicolas Robidoux
* 2009-2011 (c) Nicolas Robidoux, Adam Turcotte, Chantal Racette,
* Anthony Thyssen, John Cupitt and Ãyvind KolÃs.
*/
@@ -56,7 +57,8 @@
* Jacobian adaptive resampling was developed by N. Robidoux and
* A. Turcotte of the Department of Mathematics and Computer Science
* of Laurentian University in the course of A. Turcotte's Masters in
- * Computational Sciences.
+ * Computational Sciences. Later development was done while
+ * N. Robidoux was an independent consultant.
*
* Nohalo with LBB finishing scheme was developed by N. Robidoux and
* C. Racette of the Department of Mathematics and Computer Science of
@@ -97,10 +99,29 @@
* E. Daoust's image resampling programming was funded by GSoC 2010
* funding awarded to GIMP.
*
- * N. Robidoux thanks Ralf Meyer, Geert Jordaens, Craig DeForest and
- * Sven Neumann for useful comments.
+ * N. Robidoux thanks his co-authors, Ralf Meyer, Geert Jordaens,
+ * Craig DeForest, Massimo Valentini, Sven Neumann, Mitch Natterer for
+ * useful comments.
*/
+/*
+ * General convention:
+ *
+ * Looking at the image as a (linear algebra) matrix, the index j has
+ * to do with the x-coordinate, that is, horizontal position, and the
+ * index i has to do with the y-coordinate (which runs from top to
+ * bottom), that is, the vertical position.
+ *
+ * However, in order to match the GIMP convention that states that
+ * pixel indices match the position of the top left corner of the
+ * corresponding pixel, so that the center of pixel (i,j) is located
+ * at (i+1/2,j+1/2), pixel center positions do NOT match their index.
+ * Earlier versions of this code did not follow this convention: They
+ * assumed that the location of the center of a pixel matched its
+ * index.
+ */
+
+
#include "config.h"
#include <glib-object.h>
#include <math.h>
@@ -176,28 +197,6 @@
/*
- * FAST_PSEUDO_FLOOR is a floor replacement which has been found to be
- * faster. It returns the floor of its argument unless the argument is
- * a negative integer, in which case it returns one less than the
- * floor. For example:
- *
- * FAST_PSEUDO_FLOOR(0.5) = 0
- *
- * FAST_PSEUDO_FLOOR(0.) = 0
- *
- * FAST_PSEUDO_FLOOR(-.5) = -1
- *
- * as expected, but
- *
- * FAST_PSEUDO_FLOOR(-1.) = -2
- *
- * The discontinuities of FAST_PSEUDO_FLOOR are on the right of
- * negative numbers instead of on the left as is the case for floor.
- */
-#define LOHALO_FAST_PSEUDO_FLOOR(x) ( (gint)(x) - ( (x) < 0. ) )
-
-
-/*
* Special case of of Knuth's floored division, that is:
*
* FLOORED_DIVISION(a,b) (((a) - ((a)<0 ? (b)-1 : 0)) / (b))
@@ -214,15 +213,6 @@
/*
- * General convention:
- * Looking at the image as a (linear algebra) matrix, the index j has
- * to do with the x-coordinate, that is, horizontal position, and the
- * index i has to do with the y-coordinate (which runs from top to
- * bottom), that is, the vertical position.
- */
-
-
-/*
* Convenience macro:
*/
#define LOHALO_CALL_LEVEL_1_EWA_UPDATE(j,i) level_1_ewa_update ((j), \
@@ -277,20 +267,18 @@ gegl_sampler_lohalo_class_init (GeglSamplerLohaloClass *klass)
*
* 5x5 is the smallest "level 0" context_rect that works with the
* LBB-Nohalo component of the sampler. Because 5 = 1+2*2,
- * LOHALO_OFFSET should consequently be >= 2.
- */
-/*
- * Speed VS quality trade-off:
+ * LOHALO_OFFSET should be >= 2.
+ *
+ * Speed/quality trade-off:
*
* Downsampling quality will decrease around ratio 1/(LOHALO_OFFSET +
- * .5); in addition, the smaller LOHALO_OFFSET, the more noticeable
+ * .5). In addition, the smaller LOHALO_OFFSET, the more noticeable
* the artifacts. To maintain maximum quality for the widest
* downsampling range possible, a somewhat large LOHALO_OFFSET should
- * ideally be used. However, the larger the offset, the slower Lohalo
- * will run when no significant downsampling is done, because the
- * width and height of context_rect is (2*LOHALO_OFFSET+1), and
- * consequently there will be less data "tile" reuse when
- * LOHALO_OFFSET is large.
+ * be used. However, the larger the offset, the slower Lohalo will run
+ * when no significant downsampling is done, because the width and
+ * height of context_rect is (2*LOHALO_OFFSET+1), and consequently
+ * there will be less data "tile" reuse with large LOHALO_OFFSET.
*/
/*
* IMPORTANT: LOHALO_OFFSET SHOULD BE AN INTEGER >= 2.
@@ -1288,12 +1276,12 @@ level_1_ewa_update (const gint j,
static void
-gegl_sampler_lohalo_get ( GeglSampler* restrict self,
- const gdouble absolute_x,
- const gdouble absolute_y,
- GeglMatrix2 *scale,
- void* restrict output,
- GeglAbyssPolicy repeat_mode)
+gegl_sampler_lohalo_get ( GeglSampler* restrict self,
+ const gdouble absolute_x,
+ const gdouble absolute_y,
+ GeglMatrix2 *scale,
+ void* restrict output,
+ GeglAbyssPolicy repeat_mode)
{
/*
* Needed constants related to the input pixel value pointer
@@ -1307,10 +1295,12 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
/*
* The consequence of the following choice of anchor pixel location
* is that the sampling location is at most at a box distance of .5
- * from the anchor pixel location.
+ * from the anchor pixel location. That is: This computes the index
+ * of the closest pixel center (one of the closest when there are
+ * ties) within the GIMP convention.
*/
- const gint ix_0 = LOHALO_FAST_PSEUDO_FLOOR (absolute_x + (gdouble) 0.5);
- const gint iy_0 = LOHALO_FAST_PSEUDO_FLOOR (absolute_y + (gdouble) 0.5);
+ const gint ix_0 = GEGL_FAST_PSEUDO_FLOOR (absolute_x);
+ const gint iy_0 = GEGL_FAST_PSEUDO_FLOOR (absolute_y);
/*
* This is the pointer we use to pull pixel from "base" mipmap level
@@ -1321,10 +1311,12 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
/*
* (x_0,y_0) is the relative position of the sampling location
- * w.r.t. the anchor pixel:
+ * w.r.t. the anchor pixel. The "+1/2"s are because the center of
+ * the pixel with index (0,0) is located at (1/2,1/2) within the
+ * GIMP convention.
*/
- const gfloat x_0 = absolute_x - ix_0;
- const gfloat y_0 = absolute_y - iy_0;
+ const gfloat x_0 = absolute_x - ( ix_0 + (gdouble) 0.5 );
+ const gfloat y_0 = absolute_y - ( iy_0 + (gdouble) 0.5 );
const gint sign_of_x_0 = 2 * ( x_0 >= (gfloat) 0. ) - 1;
const gint sign_of_y_0 = 2 * ( y_0 >= (gfloat) 0. ) - 1;
@@ -2263,12 +2255,19 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
* Get pointer to mipmap level 1 data:
*/
const gfloat* restrict input_bptr_1 =
- (gfloat*) gegl_sampler_get_from_mipmap (self, ix_1, iy_1, 1, repeat_mode);
+ (gfloat*) gegl_sampler_get_from_mipmap (self,
+ ix_1,
+ iy_1,
+ 1,
+ repeat_mode);
/*
* Position of the sampling location in the coordinate
* system defined by the mipmap "pixel locations"
- * relative to the level 1 anchor pixel location:
+ * relative to the level 1 anchor pixel location. The
+ * "-1/2"s are because the center of a level 0 pixel
+ * is at a box distance of 1/2 from the center of the
+ * closest level 1 pixel.
*/
const gfloat x_1 =
x_0 + (gfloat) ( ix_0 - 2 * ix_1 ) - (gfloat) 0.5;
@@ -2297,7 +2296,11 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
(gint)
(
ceilf
- ( ( x_1 - bounding_box_half_width ) * (gfloat) 0.5 )
+ (
+ (float)
+ ( ( x_1 - bounding_box_half_width )
+ * (gfloat) 0.5 )
+ )
)
,
-LOHALO_OFFSET_1
@@ -2308,7 +2311,11 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
(gint)
(
floorf
- ( ( x_1 + bounding_box_half_width ) * (gfloat) 0.5 )
+ (
+ (float)
+ ( ( x_1 + bounding_box_half_width )
+ * (gfloat) 0.5 )
+ )
)
,
LOHALO_OFFSET_1
@@ -2319,7 +2326,11 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
(gint)
(
ceilf
- ( ( y_1 - bounding_box_half_height ) * (gfloat) 0.5 )
+ (
+ (float)
+ ( ( y_1 - bounding_box_half_height )
+ * (gfloat) 0.5 )
+ )
)
,
-LOHALO_OFFSET_1
@@ -2330,7 +2341,11 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
(gint)
(
floorf
- ( ( y_1 + bounding_box_half_height ) * (gfloat) 0.5 )
+ (
+ (float)
+ ( ( y_1 + bounding_box_half_height )
+ * (gfloat) 0.5 )
+ )
)
,
LOHALO_OFFSET_1
@@ -2338,7 +2353,8 @@ gegl_sampler_lohalo_get ( GeglSampler* restrict self,
/*
* Update using mipmap level 1 values.
- *
+ */
+ /*
* Possible future improvement: When the ellipse is
* slanted, one could avoid many pixel value loads and
* operations with Anthony Thyssen's formulas for the
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