sergiotarxz/libvips
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

start revising composite again

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
libvips/conversion/composite.cpp
View File

@ -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: