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Make x11grab cursor drawing suck less 

This new version:
1.  Works on 24-bit and 32-bit input, not just 32-bit.
2.  Doesn't try to run on 16-bit or 8-bit, instead of outright crashing.
3.  Does proper alpha-blending, so cursor shadows look correct.
4.  Doesn't swap R and B.

Mostly fixes issue 1997.
Fixes issue 2056.

Originally committed as revision 25690 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Jason Garrett-Glaser 2010-11-07 18:04:46 +00:00
parent 46db10ed0e
commit 8ce803db51
1 changed files with 25 additions and 8 deletions
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33
libavdevice/x11grab.c
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@ -256,7 +256,16 @@ paint_mouse_pointer(XImage *image, struct x11_grab *s)
int x, y;
int line, column;
int to_line, to_column;
int image_addr, xcim_addr;
int pixstride = image->bits_per_pixel >> 3;
/* Warning: in its insanity, xlib provides unsigned image data through a
* char* pointer, so we have to make it uint8_t to make things not break.
* Anyone who performs further investigation of the xlib API likely risks
* permanent brain damage. */
uint8_t *pix = image->data;
/* Code doesn't currently support 16-bit or PAL8 */
if (image->bits_per_pixel != 24 && image->bits_per_pixel != 32)
return;
xcim = XFixesGetCursorImage(dpy);
@ -268,14 +277,22 @@ paint_mouse_pointer(XImage *image, struct x11_grab *s)
for (line = FFMAX(y, y_off); line < to_line; line++) {
for (column = FFMAX(x, x_off); column < to_column; column++) {
xcim_addr = (line - y) * xcim->width + column - x;
int xcim_addr = (line - y) * xcim->width + column - x;
int image_addr = ((line - y_off) * width + column - x_off) * pixstride;
int r = (uint8_t)(xcim->pixels[xcim_addr] >> 0);
int g = (uint8_t)(xcim->pixels[xcim_addr] >> 8);
int b = (uint8_t)(xcim->pixels[xcim_addr] >> 16);
int a = (uint8_t)(xcim->pixels[xcim_addr] >> 24);
if ((unsigned char)(xcim->pixels[xcim_addr] >> 24) != 0) { // skip fully transparent pixel
image_addr = ((line - y_off) * width + column - x_off) * 4;
image->data[image_addr] = (unsigned char)(xcim->pixels[xcim_addr] >> 0);
image->data[image_addr+1] = (unsigned char)(xcim->pixels[xcim_addr] >> 8);
image->data[image_addr+2] = (unsigned char)(xcim->pixels[xcim_addr] >> 16);
if (a == 255) {
pix[image_addr+0] = r;
pix[image_addr+1] = g;
pix[image_addr+2] = b;
} else if (a) {
/* pixel values from XFixesGetCursorImage come premultiplied by alpha */
pix[image_addr+0] = r + (pix[image_addr+0]*(255-a) + 255/2) / 255;
pix[image_addr+1] = g + (pix[image_addr+1]*(255-a) + 255/2) / 255;
pix[image_addr+2] = b + (pix[image_addr+2]*(255-a) + 255/2) / 255;
}
}
}