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revise DISPOSE_PREVIOUS, again 

Perhaps it now works :(

See https://github.com/libvips/libvips/issues/1649
This commit is contained in:
John Cupitt 2020-07-02 17:41:40 +01:00
parent e4d38d1d3e
commit 5789ac905d
1 changed files with 46 additions and 37 deletions
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83
libvips/foreign/gifload.c
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@ -41,6 +41,7 @@
* - fix DISPOSE_BACKGROUND and DISPOSE_PREVIOUS
* 2/7/20
* - clip out of bounds images against canvas
* - fix PREVIOUS handling, again
*/
/*
@ -216,11 +217,6 @@ typedef struct _VipsForeignLoadGif {
*/
int transparent_index;
/* Params for DGifOpen(). Set by subclasses, called by base class in
* _open().
*/
InputFunc read_func;
} VipsForeignLoadGif;
typedef VipsForeignLoadClass VipsForeignLoadGifClass;
@ -927,14 +923,14 @@ vips_foreign_load_gif_render( VipsForeignLoadGif *gif )
*/
vips_foreign_load_gif_build_cmap( gif );
/* PREVIOUS means we init the frame with the last un-disposed frame.
* So the last un-disposed frame is used as a backdrop for the new
* frame.
/* If this is PREVIOUS, then after we're done, we'll need to restore
* the frame to what it was previously. Make a note of the current
* state.
*/
if( gif->dispose == DISPOSE_PREVIOUS )
memcpy( VIPS_IMAGE_ADDR( gif->scratch, 0, 0 ),
VIPS_IMAGE_ADDR( gif->previous, 0, 0 ),
VIPS_IMAGE_SIZEOF_IMAGE( gif->scratch ) );
memcpy( VIPS_IMAGE_ADDR( gif->previous, 0, 0 ),
VIPS_IMAGE_ADDR( gif->frame, 0, 0 ),
VIPS_IMAGE_SIZEOF_IMAGE( gif->previous ) );
if( file->Image.Interlace ) {
int i;
@ -996,39 +992,52 @@ vips_foreign_load_gif_render( VipsForeignLoadGif *gif )
VIPS_IMAGE_SIZEOF_IMAGE( gif->frame ) );
if( gif->dispose == DISPOSE_BACKGROUND ) {
/* BACKGROUND means we reset the frame to transparent before we
* render the next set of pixels.
/* BACKGROUND means we reset the area we just painted to
* transparent. We have to clip against the canvas.
*/
guint32 *q = (guint32 *) VIPS_IMAGE_ADDR( gif->scratch,
file->Image.Left, file->Image.Top );
VipsRect canvas;
VipsRect image;
VipsRect overlap;
/* What we write for transparent pixels. We want RGB to be
* 255, and A to be 0.
*/
guint32 ink = GUINT32_TO_BE( 0xffffff00 );
canvas.left = 0;
canvas.top = 0;
canvas.width = gif->file->SWidth;
canvas.height = gif->file->SHeight;
image.left = file->Image.Left,
image.top = file->Image.Top,
image.width = file->Image.Width,
image.height = file->Image.Height,
vips_rect_intersectrect( &canvas, &image, &overlap );
int x, y;
if( !vips_rect_isempty( &overlap ) ) {
guint32 *q = (guint32 *) VIPS_IMAGE_ADDR( gif->scratch,
overlap.left, overlap.top );
/* Generate the first line a pixel at a time, memcpy() for
* subsequent lines.
*/
if( file->Image.Height > 0 )
for( x = 0; x < file->Image.Width; x++ )
q[x] = ink;
/* What we write for transparent pixels. We want RGB
* to be 255, and A to be 0.
*/
guint32 transparent = GUINT32_TO_BE( 0xffffff00 );
for( y = 1; y < file->Image.Height; y++ )
memcpy( q + gif->scratch->Xsize * y,
q,
file->Image.Width * sizeof( guint32 ) );
int x, y;
/* Generate the first line a pixel at a time,
* memcpy() for subsequent lines.
*/
for( x = 0; x < overlap.width; x++ )
q[x] = transparent;
for( y = 1; y < overlap.height; y++ )
memcpy( q + gif->scratch->Xsize * y,
q,
overlap.width * sizeof( guint32 ) );
}
}
else if( gif->dispose == DISPOSAL_UNSPECIFIED ||
gif->dispose == DISPOSE_DO_NOT )
/* Copy the frame to previous, so it can be restored if
* DISPOSE_PREVIOUS is specified in a later frame.
else if( gif->dispose == DISPOSE_PREVIOUS )
/* If this is PREVIOUS, put everything back.
*/
memcpy( VIPS_IMAGE_ADDR( gif->previous, 0, 0 ),
VIPS_IMAGE_ADDR( gif->frame, 0, 0 ),
VIPS_IMAGE_SIZEOF_IMAGE( gif->previous ) );
memcpy( VIPS_IMAGE_ADDR( gif->scratch, 0, 0 ),
VIPS_IMAGE_ADDR( gif->previous, 0, 0 ),
VIPS_IMAGE_SIZEOF_IMAGE( gif->scratch ) );
/* Reset values, as Graphic Control Extension is optional
*/