The old default for alpha -> non-alpha conversion was discarding the
alpha channel without. This meant that parts of the image which were not
meant to be visible became visible. This was a problem for video which
actually contained and used alpha. It can affect PNGs with an alpha
channel as well - PNGs often have garbage data in completely transparent
regions of the image.
Change the default to blend with black, which gives generally expected
results.
Fixes track issue #4746.
---
libswscale/options.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libswscale/options.c b/libswscale/options.c
index 18a6594..717b6a4 100644
--- a/libswscale/options.c
+++ b/libswscale/options.c
@@ -78,7 +78,7 @@ static const AVOption swscale_options[] = {
{ "gamma", "gamma correct scaling", OFFSET(gamma_flag),
AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX,
VE, "gamma" },
{ "true", "enable", 0,
AV_OPT_TYPE_CONST, { .i64 = 1 }, INT_MIN, INT_MAX,
VE, "gamma" },
{ "false", "disable", 0,
AV_OPT_TYPE_CONST, { .i64 = 0 }, INT_MIN, INT_MAX,
VE, "gamma" },
- { "alphablend", "mode for alpha -> non alpha",
OFFSET(alphablend),AV_OPT_TYPE_INT, { .i64 = SWS_ALPHA_BLEND_NONE}, 0,
SWS_ALPHA_BLEND_NB-1, VE, "alphablend" },
+ { "alphablend", "mode for alpha -> non alpha",
OFFSET(alphablend),AV_OPT_TYPE_INT, { .i64 = SWS_ALPHA_BLEND_UNIFORM}, 0,
SWS_ALPHA_BLEND_NB-1, VE, "alphablend" },
{ "none", "ignore alpha", 0,
AV_OPT_TYPE_CONST, { .i64 = SWS_ALPHA_BLEND_NONE}, INT_MIN, INT_MAX,
VE, "alphablend" },
{ "uniform_color", "blend onto a uniform color", 0,
AV_OPT_TYPE_CONST, { .i64 = SWS_ALPHA_BLEND_UNIFORM},INT_MIN, INT_MAX,
VE, "alphablend" },
{ "checkerboard", "blend onto a checkerboard", 0,
AV_OPT_TYPE_CONST, { .i64 = SWS_ALPHA_BLEND_CHECKERBOARD},INT_MIN, INT_MAX,
VE, "alphablend" },
--
2.5.0
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