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use a contiguious buffer for the frame 

fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=48021
This commit is contained in:
John Cupitt 2022-06-19 12:57:47 +01:00
parent 89615465b7
commit 01d5fbd6a4
1 changed files with 24 additions and 11 deletions
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35
libvips/foreign/cgifsave.c
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@ -105,6 +105,11 @@ typedef struct _VipsForeignSaveCgif {
VipsRegion *frame;
int write_y;
/* VipsRegion is not always contiguious, but we need contiguious RGBA
* forthe quantizer. We need to copy each frame to a local buffer.
*/
VipsPel *frame_bytes;
/* The current frame as seen by libimagequant.
*/
VipsQuantiseAttr *attr;
@ -165,6 +170,7 @@ vips_foreign_save_cgif_dispose( GObject *gobject )
VIPS_UNREF( cgif->target );
VIPS_FREE( cgif->index );
VIPS_FREE( cgif->frame_bytes );
VIPS_FREE( cgif->previous_frame );
G_OBJECT_CLASS( vips_foreign_save_cgif_parent_class )->
@ -422,17 +428,13 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( cgif );
VipsRect *frame_rect = &cgif->frame->valid;
int page_index = frame_rect->top / frame_rect->height;
/* We know this fits in an int since we limit frame size.
*/
VipsPel *frame_bytes =
VIPS_REGION_ADDR( cgif->frame, 0, frame_rect->top );
int n_pels = frame_rect->height * frame_rect->width;
gboolean has_transparency;
gboolean has_alpha_constraint;
VipsPel * restrict p;
int i;
int y;
VipsQuantiseImage *image;
gboolean use_local;
VipsQuantiseResult *quantisation_result;
@ -445,8 +447,14 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
printf( "vips_foreign_save_cgif_write_frame: %d\n", page_index );
#endif/*DEBUG_VERBOSE*/
/* Threshold the alpha channel. It's safe to modify the region since
* it's a buffer we made.
/* We need the frame as a contiguious RGBA buffer for the quantiser.
*/
for( y = 0; y < frame_rect->height; y++ )
memcpy( cgif->frame_bytes + y * 4 * frame_rect->width,
VIPS_REGION_ADDR( cgif->frame, 0, frame_rect->top + y ),
4 * frame_rect->width );
/* Threshold the alpha channel.
*
* Also, check if the alpha channel of the current frame matches the
* frame before.
@ -456,7 +464,7 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
* for the alpha channel instead of for the transparency size
* optimization (maxerror).
*/
p = frame_bytes;
p = cgif->frame_bytes;
has_alpha_constraint = FALSE;
for( i = 0; i < n_pels; i++ ) {
if( p[3] >= 128 )
@ -480,7 +488,7 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
/* Set up new frame for libimagequant.
*/
image = vips__quantise_image_create_rgba( cgif->attr,
frame_bytes, frame_rect->width, frame_rect->height, 0 );
cgif->frame_bytes, frame_rect->width, frame_rect->height, 0 );
/* Quantise.
*/
@ -566,7 +574,7 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
int trans = has_transparency ? 0 : n_colours;
vips_foreign_save_cgif_set_transparent( cgif,
cgif->previous_frame, frame_bytes, cgif->index,
cgif->previous_frame, cgif->frame_bytes, cgif->index,
n_pels, trans );
if( has_transparency )
@ -577,7 +585,7 @@ vips_foreign_save_cgif_write_frame( VipsForeignSaveCgif *cgif )
else {
/* Take a copy of the RGBA frame.
*/
memcpy( cgif->previous_frame, frame_bytes, 4 * n_pels );
memcpy( cgif->previous_frame, cgif->frame_bytes, 4 * n_pels );
}
if( cgif->delay &&
@ -728,6 +736,11 @@ vips_foreign_save_cgif_build( VipsObject *object )
*/
vips__region_no_ownership( cgif->frame );
/* This RGBA frame as a contiguious buffer.
*/
cgif->frame_bytes = g_malloc0( (size_t) 4 *
frame_rect.width * frame_rect.height );
/* The previous RGBA frame (for spotting pixels which haven't changed).
*/
cgif->previous_frame = g_malloc0( (size_t) 4 *