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Fix handling of alpha when using luma file #1276

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Fix handling of alpha when using luma file #1276

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1a184ce
Fix handling of alpha when using luma file
j-b-m Jul 30, 2026
5cd14d2
Fix luma transition last alpha compositing issue with luma file
j-b-m Jul 31, 2026
08ece9f
Merge branch 'mltframework:master' into work/luma2
j-b-m Jul 31, 2026
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93 changes: 54 additions & 39 deletions src/modules/core/transition_luma.c
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Original file line number Diff line number Diff line change
Expand Up @@ -336,7 +336,8 @@ static void luma_composite_yuv422(mlt_frame a_frame,
int *width,
int *height,
int invert,
int fix_background_alpha)
int fix_background_alpha,
int alpha_over)
{
int width_src = *width, height_src = *height;
int width_dest = *width, height_dest = *height;
Expand Down Expand Up @@ -417,18 +418,21 @@ static void luma_composite_yuv422(mlt_frame a_frame,
while (j--) {
float weight = l[x_offset >> 16] / 65535.f;
float value = smoothstep_float(weight, softness + weight, field_pos[field]);
mix_a = calculate_mix(1.0f - value, alpha_dest ? *alpha_dest : 255);
mix_b = calculate_mix(value, alpha_src ? *alpha_src : 255);
if (invert && alpha_src) {
float mix2 = mix_b + mix_a;
*alpha_src = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
} else if (!invert && alpha_dest) {
float mix2 = mix_b + mix_a;
*alpha_dest = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
if (alpha_over) {
// Alpha over-blending, source alpha will be passed to dest
mix_a = calculate_mix(1.0f - value, alpha_dest ? *alpha_dest : 255);
if (invert && alpha_src) {
float mix2 = mix_b + mix_a;
*alpha_src = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
} else if (!invert && alpha_dest) {
float mix2 = mix_b + mix_a;
*alpha_dest = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
}
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}
*q = sample_mix(*q, *p++, mix_b);
q++;
Expand Down Expand Up @@ -474,7 +478,8 @@ static int luma_composite_rgba32(mlt_frame a_frame,
int field_order,
int width,
int height,
int invert)
int invert,
int alpha_over)
{
if (mlt_properties_get(&a_frame->parent, "distort"))
mlt_properties_set(&b_frame->parent,
Expand Down Expand Up @@ -535,18 +540,21 @@ static int luma_composite_rgba32(mlt_frame a_frame,
while (j--) {
float weight = l[x_offset >> 16] / 65535.f;
float value = smoothstep_float(weight, softness + weight, field_pos[field]);
mix_a = calculate_mix(1.0f - value, q[3]);
mix_b = calculate_mix(value, p[3]);
if (invert) {
float mix2 = mix_b + mix_a;
q[3] = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
} else {
float mix2 = mix_b + mix_a;
q[3] = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
if (alpha_over) {
// Alpha over-blending, source alpha will be passed to dest
mix_a = calculate_mix(1.0f - value, q[3]);
if (invert) {
float mix2 = mix_b + mix_a;
q[3] = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
} else {
float mix2 = mix_b + mix_a;
q[3] = 255 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
}
}
q[0] = sample_mix(q[0], p[0], mix_b);
q[1] = sample_mix(q[1], p[1], mix_b);
Expand Down Expand Up @@ -591,7 +599,8 @@ static int luma_composite_rgba64(mlt_frame a_frame,
int field_order,
int width,
int height,
int invert)
int invert,
int alpha_over)
{
if (mlt_properties_get(&a_frame->parent, "distort"))
mlt_properties_set(&b_frame->parent,
Expand Down Expand Up @@ -652,18 +661,21 @@ static int luma_composite_rgba64(mlt_frame a_frame,
while (j--) {
float weight = l[x_offset >> 16] / 65535.f;
float value = smoothstep_float(weight, softness + weight, field_pos[field]);
mix_a = calculate_mix_16(1.0f - value, q[3]);
mix_b = calculate_mix_16(value, p[3]);
if (invert) {
float mix2 = mix_b + mix_a;
q[3] = 65535 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
} else {
float mix2 = mix_b + mix_a;
q[3] = 65535 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
if (alpha_over) {
// Alpha over-blending, source alpha will be passed to dest
mix_a = calculate_mix_16(1.0f - value, q[3]);
if (invert) {
float mix2 = mix_b + mix_a;
q[3] = 65535 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
} else {
float mix2 = mix_b + mix_a;
q[3] = 65535 * mix2;
if (mix2 != 0.f)
mix_b /= mix2;
}
}
q[0] = sample_mix_16(q[0], p[0], mix_b);
q[1] = sample_mix_16(q[1], p[1], mix_b);
Expand Down Expand Up @@ -958,7 +970,8 @@ static int transition_get_image(mlt_frame a_frame,
progressive ? -1 : top_field_first,
*width,
*height,
invert);
invert,
alpha_over);
} else if (*format == mlt_image_rgba64) {
ret = luma_composite_rgba64(!invert ? a_frame : b_frame,
!invert ? b_frame : a_frame,
Expand All @@ -971,7 +984,8 @@ static int transition_get_image(mlt_frame a_frame,
progressive ? -1 : top_field_first,
*width,
*height,
invert);
invert,
alpha_over);
} else {
*format = mlt_image_yuv422;
luma_composite_yuv422(!invert ? a_frame : b_frame,
Expand All @@ -986,7 +1000,8 @@ static int transition_get_image(mlt_frame a_frame,
width,
height,
invert,
fix_background_alpha);
fix_background_alpha,
alpha_over);
}
} else {
if (mlt_properties_get(&a_frame->parent, "distort"))
Expand Down
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