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Clear alpha in xRGB destination to avoid pixman setting it to 0xff

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Pixman sometimes sets the ignored high byte to 0xff during alpha
blending. This is correct according to pixman specs, as the high
byte is ignored. However its not what windows expects, and it causes
unnecessary regions with non-zero high byte, causing us to
send rgba data instead of rgb which compresses worse.

So, we detect this and clear the high byte.
This commit is contained in:
Alexander Larsson 2010-04-28 12:15:24 +02:00
parent 24bb8137ea
commit 2a4015bf8d
1 changed files with 66 additions and 0 deletions
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66
cairo_canvas.c
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@ -292,6 +292,57 @@ static void fill_tiled_rects_rop_from_surface(SpiceCanvas *spice_canvas,
offset_y, rop);
}
/* Some pixman implementations of OP_OVER on xRGB32 sets
the high bit to 0xff (which is the right value if the
destination was ARGB32, and it should be ignored for
xRGB32. However, this fills our alpha bits with
data that is not wanted or expected by windows, and its
causing us to send rgba images rather than rgb images to
the client. So, we manually clear these bytes. */
static void clear_dest_alpha(pixman_image_t *dest,
int x, int y,
int width, int height)
{
uint32_t *data;
int stride;
int w, h;
w = pixman_image_get_width(dest);
h = pixman_image_get_height(dest);
if (x + width <= 0 || x >= w ||
y + height <= 0 || y >= h ||
width == 0 || height == 0) {
return;
}
if (x < 0) {
width += x;
x = 0;
}
if (x + width > w) {
width = w - x;
}
if (y < 0) {
height += y;
y = 0;
}
if (y + height > h) {
height = h - y;
}
stride = pixman_image_get_stride(dest);
data = (uint32_t *) (
(uint8_t *)pixman_image_get_data(dest) + y * stride + 4 * x);
if ((*data & 0xff000000U) == 0xff000000U) {
spice_pixman_fill_rect_rop(dest,
x, y, width, height,
0x00ffffff, SPICE_ROP_AND);
}
}
static void __blit_image(SpiceCanvas *spice_canvas,
pixman_region32_t *region,
pixman_image_t *src_image,
@ -611,6 +662,11 @@ static void __blend_image(SpiceCanvas *spice_canvas,
width,
height);
if (canvas->base.format == SPICE_SURFACE_FMT_32_xRGB &&
!dest_has_alpha) {
clear_dest_alpha(dest, dest_x, dest_y, width, height);
}
if (mask) {
pixman_image_unref(mask);
}
@ -704,6 +760,11 @@ static void __blend_scale_image(SpiceCanvas *spice_canvas,
dest_x, dest_y, /* dst */
dest_width, dest_height);
if (canvas->base.format == SPICE_SURFACE_FMT_32_xRGB &&
!dest_has_alpha) {
clear_dest_alpha(dest, dest_x, dest_y, dest_width, dest_height);
}
pixman_transform_init_identity(&transform);
pixman_image_set_transform(src, &transform);
@ -1035,6 +1096,11 @@ static void canvas_draw_text(SpiceCanvas *spice_canvas, SpiceRect *bbox,
pos.x, pos.y,
pixman_image_get_width(str_mask),
pixman_image_get_height(str_mask));
if (canvas->base.format == SPICE_SURFACE_FMT_32_xRGB) {
clear_dest_alpha(canvas->image, pos.x, pos.y,
pixman_image_get_width(str_mask),
pixman_image_get_height(str_mask));
}
pixman_image_unref(brush);
pixman_image_set_clip_region32(canvas->image, NULL);