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load non-transparent GIFs as RGB 

And GIFs with transparent elements as RGBA. This can make downstream
processing (eg. in vipsdisp) much quicker since it can save a
composite.
This commit is contained in:
John Cupitt 2021-06-07 09:54:53 +01:00
parent f39e2e271d
commit 6804ff61df
2 changed files with 31 additions and 4 deletions
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33
libvips/foreign/nsgifload.c
View File

@ -125,6 +125,10 @@ typedef struct _VipsForeignLoadNsgif {
*/
int gif_delay;
/* If the GIF contains any frames with transparent elements.
*/
gboolean has_transparency;
} VipsForeignLoadNsgif;
typedef VipsForeignLoadClass VipsForeignLoadNsgifClass;
@ -275,7 +279,8 @@ vips_foreign_load_nsgif_set_header( VipsForeignLoadNsgif *gif,
VIPS_DEBUG_MSG( "vips_foreign_load_nsgif_set_header:\n" );
vips_image_init_fields( image,
gif->anim->width, gif->anim->height * gif->n, 4,
gif->anim->width, gif->anim->height * gif->n,
gif->has_transparency ? 4 : 3,
VIPS_FORMAT_UCHAR, VIPS_CODING_NONE,
VIPS_INTERPRETATION_sRGB, 1.0, 1.0 );
vips_image_pipelinev( image, VIPS_DEMAND_STYLE_FATSTRIP, NULL );
@ -388,6 +393,14 @@ vips_foreign_load_nsgif_header( VipsForeignLoad *load )
return( -1 );
}
/* Check for any transparency.
*/
for( i = 0; i < gif->frame_count_displayable; i++ )
if( gif->anim->frames[i].transparency ) {
gif->has_transparency = TRUE;
break;
}
if( gif->n == -1 )
gif->n = gif->frame_count_displayable - gif->page;
@ -456,7 +469,20 @@ vips_foreign_load_nsgif_generate( VipsRegion *or,
p = gif->anim->frame_image +
line * gif->anim->width * sizeof( int );
q = VIPS_REGION_ADDR( or, 0, r->top + y );
memcpy( q, p, VIPS_REGION_SIZEOF_LINE( or ) );
if( gif->has_transparency )
memcpy( q, p, VIPS_REGION_SIZEOF_LINE( or ) );
else {
int i;
for( i = 0; i < r->width; i++ ) {
q[0] = p[0];
q[1] = p[1];
q[2] = p[2];
q += 3;
p += 4;
}
}
}
return( 0 );
@ -856,7 +882,8 @@ vips_foreign_load_nsgif_source_init( VipsForeignLoadNsgifSource *source )
* rendered in a vertical column. Set to -1 to mean "until the end of the
* document". Use vips_grid() to change page layout.
*
* The output image is always RGBA.
* The output image is RGBA for GIFs containing transparent elements, RGB
* otherwise.
*
* See also: vips_image_new_from_file().
*

2
test/test-suite/test_foreign.py
View File

@ -823,7 +823,7 @@ class TestForeign:
assert_almost_equal_objects(a, [33, 33, 33, 255])
assert im.width == 159
assert im.height == 203
assert im.bands == 4
assert im.bands == 3
self.file_loader("gifload", GIF_FILE, gif_valid)
self.buffer_loader("gifload_buffer", GIF_FILE, gif_valid)