Fix Image::alpha_blend for 48-bit RGB.

1 files changed, 60 insertions, 26 deletions

diff --git a/src/lib/image.cc b/src/lib/image.cc
index bc64ba3b8..3c6769068 100644
--- a/src/lib/image.cc
+++ b/src/lib/image.cc
@@ -364,19 +364,6 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
 	assert (other->pixel_format() == PIX_FMT_RGBA);
 	int const other_bpp = 4;
 
-	int this_bpp = 0;
-	switch (_pixel_format) {
-	case PIX_FMT_BGRA:
-	case PIX_FMT_RGBA:
-		this_bpp = 4;
-		break;
-	case PIX_FMT_RGB24:
-		this_bpp = 3;
-		break;
-	default:
-		assert (false);
-	}
-
 	int start_tx = position.x;
 	int start_ox = 0;
 
@@ -393,22 +380,69 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
 		start_ty = 0;
 	}
 
-	for (int ty = start_ty, oy = start_oy; ty < size().height && oy < other->size().height; ++ty, ++oy) {
-		uint8_t* tp = data()[0] + ty * stride()[0] + start_tx * this_bpp;
-		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] + (tp[0] * (1 - alpha));
-			tp[1] = op[1] + (tp[1] * (1 - alpha));
-			tp[2] = op[2] + (tp[2] * (1 - alpha));
-			tp[3] = op[3] + (tp[3] * (1 - alpha));
-			
-			tp += this_bpp;
-			op += other_bpp;
+	switch (_pixel_format) {
+	case PIX_FMT_RGB24:
+	{
+		int const this_bpp = 3;
+		for (int ty = start_ty, oy = start_oy; ty < size().height && oy < other->size().height; ++ty, ++oy) {
+			uint8_t* tp = data()[0] + ty * stride()[0] + start_tx * this_bpp;
+			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] + (tp[0] * (1 - alpha));
+				tp[1] = op[1] + (tp[1] * (1 - alpha));
+				tp[2] = op[2] + (tp[2] * (1 - alpha));
+				
+				tp += this_bpp;
+				op += other_bpp;
+			}
 		}
+		break;
+	}
+	case PIX_FMT_BGRA:
+	case PIX_FMT_RGBA:
+	{
+		int const this_bpp = 4;
+		for (int ty = start_ty, oy = start_oy; ty < size().height && oy < other->size().height; ++ty, ++oy) {
+			uint8_t* tp = data()[0] + ty * stride()[0] + start_tx * this_bpp;
+			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] + (tp[0] * (1 - alpha));
+				tp[1] = op[1] + (tp[1] * (1 - alpha));
+				tp[2] = op[2] + (tp[2] * (1 - alpha));
+				tp[3] = op[3] + (tp[3] * (1 - alpha));
+				
+				tp += this_bpp;
+				op += other_bpp;
+			}
+		}
+		break;
+	}
+	case PIX_FMT_RGB48LE:
+	{
+		int const this_bpp = 6;
+		for (int ty = start_ty, oy = start_oy; ty < size().height && oy < other->size().height; ++ty, ++oy) {
+			uint8_t* tp = data()[0] + ty * stride()[0] + start_tx * this_bpp;
+			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;
+				/* Blend high bytes */
+				tp[1] = op[0] + (tp[1] * (1 - alpha));
+				tp[3] = op[1] + (tp[3] * (1 - alpha));
+				tp[5] = op[2] + (tp[5] * (1 - alpha));
+				
+				tp += this_bpp;
+				op += other_bpp;
+			}
+		}
+		break;
+	}
+	default:
+		assert (false);
 	}
 }
-
+	
 void
 Image::copy (shared_ptr<const Image> other, Position<int> position)
 {