#include "internal.h"
#include "drawutils.h"
-static const char *var_names[] = {
+static const char * const var_names[] = {
"main_w", "W", ///< width of the main video
"main_h", "H", ///< height of the main video
"overlay_w", "w", ///< width of the overlay video
return 0;
}
-static enum PixelFormat alpha_pix_fmts[] = {
+static const enum PixelFormat alpha_pix_fmts[] = {
PIX_FMT_YUVA420P, PIX_FMT_ARGB, PIX_FMT_ABGR, PIX_FMT_RGBA,
PIX_FMT_BGRA, PIX_FMT_NONE
};
const int dr = over->main_rgba_map[R];
const int dg = over->main_rgba_map[G];
const int db = over->main_rgba_map[B];
+ const int da = over->main_rgba_map[A];
const int dstep = over->main_pix_step[0];
const int sr = over->overlay_rgba_map[R];
const int sg = over->overlay_rgba_map[G];
const int sb = over->overlay_rgba_map[B];
const int sa = over->overlay_rgba_map[A];
const int sstep = over->overlay_pix_step[0];
+ const int main_has_alpha = over->main_has_alpha;
if (slice_y > y)
sp += (slice_y - y) * src->linesize[0];
for (i = 0; i < height; i++) {
uint8_t *d = dp, *s = sp;
for (j = 0; j < width; j++) {
alpha = s[sa];
+
+ // if the main channel has an alpha channel, alpha has to be calculated
+ // to create an un-premultiplied (straight) alpha value
+ if (main_has_alpha && alpha != 0 && alpha != 255) {
+ // apply the general equation:
+ // alpha = alpha_overlay / ( (alpha_main + alpha_overlay) - (alpha_main * alpha_overlay) )
+ alpha =
+ // the next line is a faster version of: 255 * 255 * alpha
+ ( (alpha << 16) - (alpha << 9) + alpha )
+ /
+ // the next line is a faster version of: 255 * (alpha + d[da])
+ ( ((alpha + d[da]) << 8 ) - (alpha + d[da])
+ - d[da] * alpha );
+ }
+
switch (alpha) {
case 0:
break;
d[dg] = FAST_DIV255(d[dg] * (255 - alpha) + s[sg] * alpha);
d[db] = FAST_DIV255(d[db] * (255 - alpha) + s[sb] * alpha);
}
+ if (main_has_alpha) {
+ switch (alpha) {
+ case 0:
+ break;
+ case 255:
+ d[da] = s[sa];
+ break;
+ default:
+ // apply alpha compositing: main_alpha += (1-main_alpha) * overlay_alpha
+ d[da] += FAST_DIV255((255 - d[da]) * s[sa]);
+ }
+ }
d += dstep;
s += sstep;
}
alpha = (alpha_v + alpha_h) >> 1;
} else
alpha = a[0];
- *d = (*d * (0xff - alpha) + *s++ * alpha + 128) >> 8;
+ *d = FAST_DIV255(*d * (255 - alpha) + *s * alpha);
+ s++;
d++;
a += 1 << hsub;
}
.query_formats = query_formats,
- .inputs = (AVFilterPad[]) {{ .name = "main",
+ .inputs = (const AVFilterPad[]) {{ .name = "main",
.type = AVMEDIA_TYPE_VIDEO,
.start_frame = start_frame,
.get_video_buffer= get_video_buffer,
.min_perms = AV_PERM_READ,
.rej_perms = AV_PERM_REUSE2, },
{ .name = NULL}},
- .outputs = (AVFilterPad[]) {{ .name = "default",
+ .outputs = (const AVFilterPad[]) {{ .name = "default",
.type = AVMEDIA_TYPE_VIDEO,
.config_props = config_output, },
{ .name = NULL}},