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prevent int overflow for int pixels in shrinkh 

by using double for an accumulator
This commit is contained in:
John Cupitt 2019-08-06 17:00:53 +01:00
parent 6ba34e479e
commit 5ddc154a81
1 changed files with 13 additions and 11 deletions
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24
libvips/resample/shrinkh.c
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@ -6,6 +6,8 @@
* - reorganise loops, 30% faster, vectorisable
* 15/8/16
* - rename xshrink -> hshrink for greater consistency
* 6/8/19
* - use a double sum buffer for int32 types
*/
/*
@ -71,13 +73,13 @@ G_DEFINE_TYPE( VipsShrinkh, vips_shrinkh, VIPS_TYPE_RESAMPLE );
/* Integer shrink.
*/
#define ISHRINK( TYPE, BANDS ) { \
#define ISHRINK( ACC_TYPE, TYPE, BANDS ) { \
TYPE * restrict p = (TYPE *) in; \
TYPE * restrict q = (TYPE *) out; \
\
for( x = 0; x < width; x++ ) { \
for( b = 0; b < BANDS; b++ ) { \
int sum; \
ACC_TYPE sum; \
\
sum = 0; \
x1 = b; \
@ -137,26 +139,26 @@ vips_shrinkh_gen2( VipsShrinkh *shrink, VipsRegion *or, VipsRegion *ir,
*/
switch( bands ) {
case 1:
ISHRINK( unsigned char, 1 ); break;
ISHRINK( int, unsigned char, 1 ); break;
case 3:
ISHRINK( unsigned char, 3 ); break;
ISHRINK( int, unsigned char, 3 ); break;
case 4:
ISHRINK( unsigned char, 4 ); break;
ISHRINK( int, unsigned char, 4 ); break;
default:
ISHRINK( unsigned char, bands ); break;
ISHRINK( int, unsigned char, bands ); break;
}
break;
case VIPS_FORMAT_CHAR:
ISHRINK( char, bands ); break;
ISHRINK( int, char, bands ); break;
case VIPS_FORMAT_USHORT:
ISHRINK( unsigned short, bands ); break;
ISHRINK( int, unsigned short, bands ); break;
case VIPS_FORMAT_SHORT:
ISHRINK( short, bands ); break;
ISHRINK( int, short, bands ); break;
case VIPS_FORMAT_UINT:
ISHRINK( unsigned int, bands ); break;
ISHRINK( double, unsigned int, bands ); break;
case VIPS_FORMAT_INT:
ISHRINK( int, bands ); break;
ISHRINK( double, int, bands ); break;
case VIPS_FORMAT_FLOAT:
FSHRINK( float ); break;
case VIPS_FORMAT_DOUBLE: