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Merge pull request #92 from flangelo/encoding_artifacts

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GUAC-1366: Adjust WebP and JPEG image sizes before compressing to avo…
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Mike Jumper 2015-10-19 11:48:39 -07:00
commit 8a91965b07
1 changed files with 30 additions and 0 deletions
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30
src/common/guac_surface.c
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@ -104,6 +104,20 @@
*/
#define GUAC_SURFACE_WEBP_IMAGE_QUALITY 90
/**
* The JPEG compression min block size. This defines the optimal rectangle block
* size factor for JPEG compression. Usually 8x8 would suffice, but use 16 to
* reduce the occurrence of ringing artifacts further.
*/
#define GUAC_SURFACE_JPEG_BLOCK_SIZE 16
/**
* The WebP compression min block size. This defines the optimal rectangle block
* size factor for WebP compression. WebP does utilize variable block size, but
* ensuring a block size factor reduces any noise on the image edges.
*/
#define GUAC_SURFACE_WEBP_BLOCK_SIZE 8
/**
* Updates the coordinates of the given rectangle to be within the bounds of
* the given surface.
@ -1308,6 +1322,14 @@ static void __guac_common_surface_flush_to_jpeg(guac_common_surface* surface) {
guac_socket* socket = surface->socket;
const guac_layer* layer = surface->layer;
guac_common_rect max;
guac_common_rect_init(&max, 0, 0, surface->width, surface->height);
/* Expand the dirty rect size to fit in a grid with cells equal to the
* minimum JPEG block size */
guac_common_rect_expand_to_grid(GUAC_SURFACE_JPEG_BLOCK_SIZE,
&surface->dirty_rect, &max);
/* Get Cairo surface for specified rect */
unsigned char* buffer = surface->buffer + surface->dirty_rect.y * surface->stride + surface->dirty_rect.x * 4;
cairo_surface_t* rect = cairo_image_surface_create_for_data(buffer, CAIRO_FORMAT_RGB24,
@ -1345,6 +1367,14 @@ static void __guac_common_surface_flush_to_webp(guac_common_surface* surface) {
guac_socket* socket = surface->socket;
const guac_layer* layer = surface->layer;
guac_common_rect max;
guac_common_rect_init(&max, 0, 0, surface->width, surface->height);
/* Expand the dirty rect size to fit in a grid with cells equal to the
* minimum WebP block size */
guac_common_rect_expand_to_grid(GUAC_SURFACE_WEBP_BLOCK_SIZE,
&surface->dirty_rect, &max);
/* Get Cairo surface for specified rect */
unsigned char* buffer = surface->buffer
+ surface->dirty_rect.y * surface->stride