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better rounding in vector reducev

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add before downshift to round to nearest on 16->8 fixed-point conversion
This commit is contained in:
John Cupitt 2016-03-25 06:07:58 +00:00
parent 8a74609172
commit 2ab14a3590
1 changed files with 7 additions and 1 deletions
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8
libvips/resample/reducev.cpp
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@ -235,10 +235,13 @@ vips_reducev_compile_section( VipsReducev *reducev, Pass *pass, gboolean first )
* image, otherwise write the 16-bit intermediate to our temp buffer.
*/
if( i >= reducev->n_point - 1 ) {
char sixteen[256];
char five[256];
char zero[256];
char twofivefive[256];
CONST( sixteen, 16, 2 );
ASM3( "addw", "sum", "sum", sixteen );
CONST( five, 5, 2 );
ASM3( "shrsw", "sum", "sum", five );
@ -250,6 +253,7 @@ vips_reducev_compile_section( VipsReducev *reducev, Pass *pass, gboolean first )
ASM3( "maxsw", "sum", zero, "sum" );
CONST( twofivefive, 255, 2 );
ASM3( "minsw", "sum", twofivefive, "sum" );
ASM2( "convwb", "d1", "sum" );
}
else
@ -736,8 +740,10 @@ vips_reducev_raw( VipsReducev *reducev, VipsImage *in )
generate = vips_reducev_gen;
if( in->BandFmt == VIPS_FORMAT_UCHAR &&
vips_vector_isenabled() &&
!vips_reducev_compile( reducev ) )
!vips_reducev_compile( reducev ) ) {
vips_info( object_class->nickname, "using vector path" );
generate = vips_reducev_vector_gen;
}
if( vips_image_pipelinev( resample->out,
VIPS_DEMAND_STYLE_FATSTRIP, in, NULL ) )