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start revising composite again 

we can get ugly sparkles in transparent areas in some cases ... start
reworking some modes

see https://github.com/libvips/libvips/issues/1301
This commit is contained in:
John Cupitt 2019-04-29 07:43:14 +01:00
parent efadb5dc42
commit b100f5a025
1 changed files with 25 additions and 5 deletions
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30
libvips/conversion/composite.cpp
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@ -635,8 +635,8 @@ vips_composite_base_blend( VipsCompositeBase *composite,
/* We have a vector path with gcc's vector attr.
*/
#ifdef HAVE_VECTOR_ARITH
/* Special path for RGBA with non-double output. This is overwhelmingly the most
* common case, and vectorises easily.
/* Special path for RGBA with non-double output. This is overwhelmingly the
* most common case, and vectorises easily.
*
* B is the float pixel we are accumulating, A is the new pixel coming
* in from memory.
@ -673,6 +673,13 @@ vips_composite_base_blend3( VipsCompositeBase *composite,
if( !composite->premultiplied )
A *= aA;
/* See https://www.cairographics.org/operators for a nice summary of
* the operators and their meaning.
*
* Some operators need the unpremultiplied values, so we have to do an
* extra unpremultiply/premultiply.
*/
switch( mode ) {
case VIPS_BLEND_MODE_CLEAR:
aR = 0;
@ -694,12 +701,20 @@ vips_composite_base_blend3( VipsCompositeBase *composite,
case VIPS_BLEND_MODE_IN:
aR = aA * aB;
B = A;
// we want to set B = A, but A has been premultiplied against
// aA ... we must undo that premul and redo against aR
// if aA == 0, then aR == 0 and so B will be set to 0
if( aA != 0 )
B = A * aR / aA;
break;
case VIPS_BLEND_MODE_OUT:
aR = aA * (1 - aB);
B = A;
// we want to set B = A, but A has been premultiplied against
// aA ... we must undo that premul and redo against aR
// if aA == 0, then aR == 0 and so B will be set to 0
if( aA != 0 )
B = A * aR / aA;
break;
case VIPS_BLEND_MODE_ATOP:
@ -721,7 +736,12 @@ vips_composite_base_blend3( VipsCompositeBase *composite,
case VIPS_BLEND_MODE_DEST_IN:
aR = aA * aB;
// B = B
// we need to simply copy B over, but B is premultiplied
// against aB ... we must unpremultiply and premultiply
// against aR instead
// if aB is 0, then B is 0 too
//if( aB != 0 )
//B *= aR / aB;
break;
case VIPS_BLEND_MODE_DEST_OUT: