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revise kernel mask calculations #1647

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Merged
merged 1 commit into from
May 11, 2020
Merged

revise kernel mask calculations #1647

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8 changes: 4 additions & 4 deletions libvips/resample/reduceh.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -101,19 +101,19 @@ vips_reduce_get_points( VipsKernel kernel, double shrink )
return( 1 );

case VIPS_KERNEL_LINEAR:
return( rint( 2 * shrink ) + 1 );
return( 2 * rint( shrink ) + 1 );

case VIPS_KERNEL_CUBIC:
case VIPS_KERNEL_MITCHELL:
return( rint( 4 * shrink ) + 1 );
return( 2 * rint( 2 * shrink ) + 1 );

case VIPS_KERNEL_LANCZOS2:
/* Needs to be in sync with calculate_coefficients_lanczos().
*/
return( rint( 2 * 2 * shrink ) + 1 );
return( 2 * rint( 2 * shrink ) + 1 );

case VIPS_KERNEL_LANCZOS3:
return( rint( 2 * 3 * shrink ) + 1 );
return( 2 * rint( 3 * shrink ) + 1 );

default:
g_assert_not_reached();
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15 changes: 9 additions & 6 deletions libvips/resample/templates.h
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Expand Up @@ -321,14 +321,15 @@ calculate_coefficients_triangle( double *c,
{
/* Needs to be in sync with vips_reduce_get_points().
*/
const int n_points = rint( 2 * shrink ) + 1;
const int n_points = 2 * rint( shrink ) + 1;
const double half = x + n_points / 2.0 - 1;

int i;
double sum;

sum = 0;
for( i = 0; i < n_points; i++ ) {
double xp = (i - (shrink - 0.5) - x) / shrink;
const double xp = (i - half) / shrink;

double l;

Expand Down Expand Up @@ -358,14 +359,15 @@ calculate_coefficients_cubic( double *c,
{
/* Needs to be in sync with vips_reduce_get_points().
*/
const int n_points = rint( 4 * shrink ) + 1;
const int n_points = 2 * rint( 2 * shrink ) + 1;
const double half = x + n_points / 2.0 - 1;

int i;
double sum;

sum = 0;
for( i = 0; i < n_points; i++ ) {
const double xp = (i - (2 * shrink - 1) - x) / shrink;
const double xp = (i - half) / shrink;
const double axp = VIPS_FABS( xp );
const double axp2 = axp * axp;
const double axp3 = axp2 * axp;
Expand Down Expand Up @@ -406,14 +408,15 @@ calculate_coefficients_lanczos( double *c,
{
/* Needs to be in sync with vips_reduce_get_points().
*/
const int n_points = rint( 2 * a * shrink ) + 1;
const int n_points = 2 * rint( a * shrink ) + 1;
const double half = x + n_points / 2.0 - 1;

int i;
double sum;

sum = 0;
for( i = 0; i < n_points; i++ ) {
double xp = (i - (n_points - 2) / 2 - x) / shrink;
double xp = (i - half) / shrink;

double l;

Expand Down