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better bounds check for nohalo

This commit is contained in:
John Cupitt 2009-01-28 10:01:18 +00:00
parent dfe09d565b
commit 603c7f9cee
1 changed files with 30 additions and 16 deletions
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46
libsrc/mosaicing/nohalo.cpp
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@ -52,16 +52,16 @@
*
* The key parameter, which may be described as a "quality" parameter,
* is an integer which specifies the number of "levels" of binary
* subdivision which are performed. If level = 0 can be thought of as
* being plain vanilla bilinear resampling; level = 1 is the first
* "non-classical" method.
* subdivision which are performed. level = 0 can be thought of as
* being plain vanilla bilinear resampling; level = 1 is then the
* first "non-classical" method of the familiy.
*
* Besides increasing computational cost, increasing the number of
* levels increases the quality of the resampled pixel value unless
* the resampled location happens to be exactly where a subdivided
* grid point (for this level) is located, in which case further
* levels do not change the answer, and consequently do not increase
* its quality.
* Although it increases computational cost, additional levels
* increase the quality of the resampled pixel value unless the
* resampled location happens to be exactly where a subdivided grid
* point (for this level) is located, in which case further levels do
* not change the answer, and consequently do not increase its
* quality.
*
* ============================================================
* WARNING: THIS CODE ONLY IMPLEMENTS THE LOWEST QUALITY NOHALO
@ -145,7 +145,13 @@
* input pixel values (in the stencil) are obtained from a function of
* the form f(x,y) = a + b*x + c*y (a, b, c constants), then the
* computed pixel value is exactly the value of f(x,y) at the
* asked-for sampling location.
* asked-for sampling location. The boundary condition which is
* emulated by VIPS throught the "extend" extension of the input
* image---this corresponds to the nearest neighbour abyss
* policy---does NOT make this resampler exact on linears at the
* boundary. It does, however, guarantee that no clamping is required
* even when resampled values are computed at positions outside of the
* extent of the input image (when extrapolation is required).
*
* ===================
* Nohalo is nonlinear
@ -183,8 +189,8 @@
*/
/*
#define DEBUG
*/
#define DEBUG
#ifdef HAVE_CONFIG_H
#include <config.h>
@ -526,7 +532,7 @@ nohalo_sharp_level_1(
*/
#define NOHALO_SHARP_LEVEL_1_INTER( inter ) \
template <typename T> static void inline \
nohalo_sharp_level_1_ ## inter( PEL *pout, const PEL *pin, const int bands, \
nohalo_sharp_level_1_ ## inter( PEL *pout, const PEL *pin, const int bands, \
const int pskip, const int lskip, \
const double w_times_z, \
const double x_times_z_over_2, \
@ -701,18 +707,27 @@ vips_interpolate_nohalo_interpolate( VipsInterpolate *interpolate,
const PEL * restrict p =
(PEL *) IM_REGION_ADDR( in, target_x, target_y );
/* Optional bounds checking.
*/
#ifdef DEBUG
{
/* Corner of pixel we are interpolating. No round up here!
*/
const int vix = FAST_PSEUDO_FLOOR (absolute_x);
const int viy = FAST_PSEUDO_FLOOR (absolute_y);
/* Top-left corner of our window.
*/
const PEL * restrict tl =
(PEL *) IM_REGION_ADDR( in, ix - 2, iy - 2 );
(PEL *) IM_REGION_ADDR( in, vix - 2, viy - 2 );
/* Bottom-right corner of our window.
*/
const PEL * restrict br =
(PEL *) IM_REGION_ADDR( in, ix + 2, iy + 2 );
(PEL *) IM_REGION_ADDR( in, vix + 2, viy + 2 );
g_assert( p >= tl );
g_assert( p <= br );
/* Last pixel we address.
*/
@ -724,7 +739,6 @@ vips_interpolate_nohalo_interpolate( VipsInterpolate *interpolate,
g_assert( last >= tl );
g_assert( last <= br );
}
#endif /*DEBUG*/