Make alpha_blend support RGBA as well as BGRA.

diff --git a/src/lib/image.cc b/src/lib/image.cc
index 46c085ff2cf17943b6bd3b2b11d90779fefdfefc..f005e3f6397b2726291004cd82cbaa1dc3ef7811 100644 (file)
--- a/src/lib/image.cc
+++ b/src/lib/image.cc
@@ -479,8 +479,11 @@ Image::make_transparent ()
 void
 Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
 {
-       /* We're blending BGRA images; first byte is blue, second byte is green, third byte red, fourth byte alpha */
-       DCPOMATIC_ASSERT (other->pixel_format() == AV_PIX_FMT_BGRA);
+       /* We're blending RGBA or BGRA images */
+       DCPOMATIC_ASSERT (other->pixel_format() == AV_PIX_FMT_BGRA || other->pixel_format() == AV_PIX_FMT_RGBA);
+       int const blue = other->pixel_format() == AV_PIX_FMT_BGRA ? 0 : 2;
+       int const red = other->pixel_format() == AV_PIX_FMT_BGRA ? 2 : 0;
+
        int const other_bpp = 4;
 
        int start_tx = position.x;
@@ -509,9 +512,9 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
                        uint8_t* op = other->data()[0] + oy * other->stride()[0];
                        for (int tx = start_tx, ox = start_ox; tx < size().width && ox < other->size().width; ++tx, ++ox) {
                                float const alpha = float (op[3]) / 255;
-                               tp[0] = op[2] * alpha + tp[0] * (1 - alpha);
+                               tp[0] = op[red] * alpha + tp[0] * (1 - alpha);
                                tp[1] = op[1] * alpha + tp[1] * (1 - alpha);
-                               tp[2] = op[0] * alpha + tp[2] * (1 - alpha);
+                               tp[2] = op[blue] * alpha + tp[2] * (1 - alpha);
 
                                tp += this_bpp;
                                op += other_bpp;
@@ -527,9 +530,9 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
                        uint8_t* op = other->data()[0] + oy * other->stride()[0];
                        for (int tx = start_tx, ox = start_ox; tx < size().width && ox < other->size().width; ++tx, ++ox) {
                                float const alpha = float (op[3]) / 255;
-                               tp[0] = op[0] * alpha + tp[0] * (1 - alpha);
+                               tp[0] = op[blue] * alpha + tp[0] * (1 - alpha);
                                tp[1] = op[1] * alpha + tp[1] * (1 - alpha);
-                               tp[2] = op[2] * alpha + tp[2] * (1 - alpha);
+                               tp[2] = op[red] * alpha + tp[2] * (1 - alpha);
                                tp[3] = op[3] * alpha + tp[3] * (1 - alpha);
 
                                tp += this_bpp;
@@ -546,9 +549,9 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
                        uint8_t* op = other->data()[0] + oy * other->stride()[0];
                        for (int tx = start_tx, ox = start_ox; tx < size().width && ox < other->size().width; ++tx, ++ox) {
                                float const alpha = float (op[3]) / 255;
-                               tp[0] = op[2] * alpha + tp[0] * (1 - alpha);
+                               tp[0] = op[red] * alpha + tp[0] * (1 - alpha);
                                tp[1] = op[1] * alpha + tp[1] * (1 - alpha);
-                               tp[2] = op[0] * alpha + tp[2] * (1 - alpha);
+                               tp[2] = op[blue] * alpha + tp[2] * (1 - alpha);
                                tp[3] = op[3] * alpha + tp[3] * (1 - alpha);
 
                                tp += this_bpp;
@@ -566,9 +569,9 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
                        for (int tx = start_tx, ox = start_ox; tx < size().width && ox < other->size().width; ++tx, ++ox) {
                                float const alpha = float (op[3]) / 255;
                                /* Blend high bytes */
-                               tp[1] = op[2] * alpha + tp[1] * (1 - alpha);
+                               tp[1] = op[red] * alpha + tp[1] * (1 - alpha);
                                tp[3] = op[1] * alpha + tp[3] * (1 - alpha);
-                               tp[5] = op[0] * alpha + tp[5] * (1 - alpha);
+                               tp[5] = op[blue] * alpha + tp[5] * (1 - alpha);
 
                                tp += this_bpp;
                                op += other_bpp;
@@ -591,9 +594,9 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
                                float const alpha = float (op[3]) / 255;
 
                                /* Convert sRGB to XYZ; op is BGRA.  First, input gamma LUT */
-                               double const r = lut_in[op[2]];
+                               double const r = lut_in[op[red]];
                                double const g = lut_in[op[1]];
-                               double const b = lut_in[op[0]];
+                               double const b = lut_in[op[blue]];
 
                                /* RGB to XYZ, including Bradford transform and DCI companding */
                                double const x = max (0.0, min (65535.0, r * fast_matrix[0] + g * fast_matrix[1] + b * fast_matrix[2]));