Clarify (a bit) byte ordering for RGBA frames.

5 files changed, 27 insertions, 23 deletions

diff --git a/src/rgba_frame.cc b/src/argb_frame.cc
index 36157cd3..7a9ad2b9 100644
--- a/src/rgba_frame.cc
+++ b/src/argb_frame.cc
@@ -17,11 +17,11 @@
 
 */
 
-#include "rgba_frame.h"
+#include "argb_frame.h"
 
 using namespace libdcp;
 
-RGBAFrame::RGBAFrame (int width, int height)
+ARGBFrame::ARGBFrame (int width, int height)
 	: _width (width)
 	, _height (height)
 {
@@ -29,13 +29,13 @@ RGBAFrame::RGBAFrame (int width, int height)
 }
 
 
-RGBAFrame::~RGBAFrame ()
+ARGBFrame::~ARGBFrame ()
 {
 	delete[] _data;
 }
 
 int
-RGBAFrame::stride () const
+ARGBFrame::stride () const
 {
 	return _width * 4;
 }
diff --git a/src/rgba_frame.h b/src/argb_frame.h
index ef1fbaae..bc78b8fb 100644
--- a/src/rgba_frame.h
+++ b/src/argb_frame.h
@@ -22,11 +22,11 @@
 namespace libdcp
 {
 
-class RGBAFrame
+class ARGBFrame
 {
 public:
-	RGBAFrame (int width, int height);
-	~RGBAFrame ();
+	ARGBFrame (int width, int height);
+	~ARGBFrame ();
 
 	uint8_t* data () const {
 		return _data;
diff --git a/src/picture_frame.cc b/src/picture_frame.cc
index 844f0183..09ef4ae4 100644
--- a/src/picture_frame.cc
+++ b/src/picture_frame.cc
@@ -22,7 +22,7 @@
 #include "KM_fileio.h"
 #include "picture_frame.h"
 #include "exceptions.h"
-#include "rgba_frame.h"
+#include "argb_frame.h"
 #include "lut.h"
 
 using namespace std;
@@ -61,8 +61,12 @@ PictureFrame::size () const
 	return _buffer->Size ();
 }
 
-shared_ptr<RGBAFrame>
-PictureFrame::rgba_frame () const
+/** @return An ARGB representation of this frame.  This is ARGB in the
+ *  Cairo sense, so that each pixel takes up 4 bytes; the first byte
+ *  is blue, second green, third red and fourth alpha (always 255).
+ */
+shared_ptr<ARGBFrame>
+PictureFrame::argb_frame () const
 {
 	/* JPEG2000 -> decompressed XYZ */
 	
@@ -94,12 +98,12 @@ PictureFrame::rgba_frame () const
 	int* xyz_y = xyz_frame->comps[1].data;
 	int* xyz_z = xyz_frame->comps[2].data;
 
-	shared_ptr<RGBAFrame> rgba_frame (new RGBAFrame (xyz_frame->x1, xyz_frame->y1));
+	shared_ptr<ARGBFrame> argb_frame (new ARGBFrame (xyz_frame->x1, xyz_frame->y1));
 	
-	uint8_t* rgba = rgba_frame->data ();
+	uint8_t* argb = argb_frame->data ();
 	
 	for (int y = 0; y < xyz_frame->y1; ++y) {
-		uint8_t* rgba_line = rgba;
+		uint8_t* argb_line = argb;
 		for (int x = 0; x < xyz_frame->x1; ++x) {
 			
 			assert (*xyz_x >= 0 && *xyz_y >= 0 && *xyz_z >= 0 && *xyz_x < 4096 && *xyz_x < 4096 && *xyz_z < 4096);
@@ -129,17 +133,17 @@ PictureFrame::rgba_frame () const
 			d.b = max (d.b, 0.0);
 			
 			/* Out gamma LUT */
-			*rgba_line++ = lut_out[(int) (d.r * COLOR_DEPTH)];
-			*rgba_line++ = lut_out[(int) (d.g * COLOR_DEPTH)];
-			*rgba_line++ = lut_out[(int) (d.b * COLOR_DEPTH)];
-			*rgba_line++ = 0xff;
+			*argb_line++ = lut_out[(int) (d.b * COLOR_DEPTH)];
+			*argb_line++ = lut_out[(int) (d.g * COLOR_DEPTH)];
+			*argb_line++ = lut_out[(int) (d.r * COLOR_DEPTH)];
+			*argb_line++ = 0xff;
 		}
 		
-		rgba += rgba_frame->stride ();
+		argb += argb_frame->stride ();
 	}
 	
 	opj_cio_close (cio);
 	opj_image_destroy (xyz_frame);
 
-	return rgba_frame;
+	return argb_frame;
 }
diff --git a/src/picture_frame.h b/src/picture_frame.h
index bb347294..76891d9f 100644
--- a/src/picture_frame.h
+++ b/src/picture_frame.h
@@ -29,7 +29,7 @@ namespace ASDCP {
 
 namespace libdcp {
 
-class RGBAFrame;	
+class ARGBFrame;	
 
 class PictureFrame
 {
@@ -40,7 +40,7 @@ public:
 	uint8_t const * data () const;
 	int size () const;
 
-	boost::shared_ptr<RGBAFrame> rgba_frame () const;
+	boost::shared_ptr<ARGBFrame> argb_frame () const;
 
 private:
 	ASDCP::JP2K::FrameBuffer* _buffer;
diff --git a/src/wscript b/src/wscript
index bef62a93..1ca88bc6 100644
--- a/src/wscript
+++ b/src/wscript
@@ -18,7 +18,7 @@ def build(bld):
                  picture_frame.cc
                  pkl.cc
                  reel.cc
-                 rgba_frame.cc
+                 argb_frame.cc
                  sound_asset.cc
                  sound_frame.cc
                  subtitle_asset.cc
@@ -39,7 +39,7 @@ def build(bld):
               picture_asset.h
               picture_frame.h
               reel.h
-              rgba_frame.h
+              argb_frame.h
               sound_asset.h
               sound_frame.h
               subtitle_asset.h