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

allow to apply maxerror optimization to frames with alpha channel (#2778)

Browse Source
This commit is contained in:
Daniel Löbl 2022-05-07 13:16:13 +02:00 committed by GitHub
parent 20fd8ac0fc
commit cb55fdcfd8
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 40 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
libvips/foreign/cgifsave.c
View File

@ -166,10 +166,14 @@ static gboolean
vips_foreign_save_cgif_pixels_are_equal( const VipsPel *cur, const VipsPel *bef,
double maxerror )
{
if( bef[3] != 0xFF )
/* Solid pixels only.
if( bef[3] != cur[3] )
/* Alpha channel must be identical.
*/
return FALSE;
if( bef[3] == 0 && cur[3] == 0)
/* RGB component can be ignored.
*/
return TRUE;
/* Test Euclidean distance between the two points.
*/
@ -180,6 +184,25 @@ vips_foreign_save_cgif_pixels_are_equal( const VipsPel *cur, const VipsPel *bef,
return( sqrt( dR * dR + dG * dG + dB * dB ) <= maxerror );
}
/* Check if the alpha channel of the current frame matches the frame before.
* If the current frame has an alpha component which is not identical to the
* frame from before we are forced to use the transparency index for the
* alpha channel instead of for the transparency size optimization (maxerror).
*/
static gboolean
vips_foreign_save_cgif_check_alpha_constraint( const VipsPel *cur,
const VipsPel *bef, int n_pels )
{
while( n_pels-- ) {
if( cur[3] == 0 && bef[3] != 0) {
return TRUE;
}
cur += 4;
bef += 4;
}
return FALSE;
}
/* We have a complete frame --- write!
*/
static int
@ -355,13 +378,24 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
*/
if( cgif->frame_bytes_head ) {
VipsPel *cur, *bef;
gboolean has_alpha_constraint;
cur = frame_bytes;
bef = cgif->frame_bytes_head;
if( !cgif->has_transparency ) {
const uint8_t trans_index = cgif->lp->count;
has_alpha_constraint =
vips_foreign_save_cgif_check_alpha_constraint(cur, bef, n_pels);
/* Transparency trick is only possible
* when no alpha channel constraint is present.
*/
if( !has_alpha_constraint ) {
int i;
uint8_t trans_index;
trans_index = cgif->lp->count;
if( cgif->has_transparency ) {
trans_index = 0;
frame_config.attrFlags &= (~CGIF_FRAME_ATTR_HAS_ALPHA);
}
for( i = 0; i < n_pels; i++ ) {
if( vips_foreign_save_cgif_pixels_are_equal(
@ -383,7 +417,7 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
frame_config.transIndex = trans_index;
}
else {
/* Transparency trick not possible (alpha channel
/* Transparency trick not possible (constraining alpha channel
* present). Update head.
*/
memcpy( bef, cur, 4 * n_pels);