Alpha premul pipeline cleanup

This assumptions are now made:
- Internally float buffers are always linear alpha-premul colors
- Readers should worry about delivering float buffers with that
  assumptions.
- There's an input image setting to say whether it's stored with
  straight/premul alpha on the disk.
- Byte buffers are now assumed have straight alpha, readers should
  deliver straight alpha.

Some implementation details:

- Removed scene's color unpremultiply setting, which was very
  much confusing and was wrong for default settings.
  Now all renderers assumes to deliver premultiplied alpha.

- IMB_buffer_byte_from_float will now linearize alpha when
  converting from buffer.

- Sequencer's effects were changed to assume bytes have got
  straight alpha. Most of effects will work with bytes still,
  however for glow it was more tricky to avoid data loss, so
  there's a commented out glow implementation which converts
  byte buffer to floats first, operates on floats and returns
  bytes back. It's slower and not sure if it should actually
  be used -- who're using glow on alpha anyway?

- Sequencer modifiers should also be working nice with straight
  bytes now.

- GLSL preview will predivide float textures to make nice shading,
  shading with byte textures worked nice (GLSL was assuming straight
  alpha).

- Blender Internal will set alpha=1 to the whole sky. The same
  happens in Cycles and there's no way to avoid this -- sky is
  neither straight nor premul and doesn't fit color pipeline well.

- Straight alpha mode for render result was also eliminated.

- Conversion to correct alpha need to be done before linearizing
  float buffer.

- TIFF will now load and save files with proper alpha mode setting
  in file meta data header.

- Remove Use Alpha from texture mapping and replaced with image
  datablock setting.

  Behaves much more predictable and clear from code point of view
  and solves possible regressions when non-premultiplied images were
  used as textures with ignoring alpha channel.

1 files changed, 3 insertions, 1 deletions

diff --git a/source/blender/imbuf/IMB_imbuf.h b/source/blender/imbuf/IMB_imbuf.h
index db1404813b1..850060ef4d5 100644
--- a/source/blender/imbuf/IMB_imbuf.h
+++ b/source/blender/imbuf/IMB_imbuf.h
@@ -373,7 +373,6 @@ void IMB_rect_from_float(struct ImBuf *ibuf);
  * Changed part will be stored in buffer. This is expected to be used for texture painting updates */
 void IMB_partial_rect_from_float(struct ImBuf *ibuf, float *buffer, int x, int y, int w, int h, int is_data);
 void IMB_float_from_rect(struct ImBuf *ibuf);
-void IMB_float_from_rect_simple(struct ImBuf *ibuf); /* no profile conversion */
 /* note, check that the conversion exists, only some are supported */
 float *IMB_float_profile_ensure(struct ImBuf *ibuf, int profile, int *alloc);
 void IMB_color_to_bw(struct ImBuf *ibuf);
@@ -393,6 +392,8 @@ void IMB_buffer_byte_from_byte(unsigned char *rect_to, const unsigned char *rect
 	int profile_to, int profile_from, int predivide,
 	int width, int height, int stride_to, int stride_from);
 void IMB_buffer_float_clamp(float *buf, int width, int height);
+void IMB_buffer_float_unpremultiply(float *buf, int width, int height);
+void IMB_buffer_float_premultiply(float *buf, int width, int height);
 
 /**
  * Change the ordering of the color bytes pointed to by rect from
@@ -467,6 +468,7 @@ void IMB_flipy(struct ImBuf *ibuf);
 /* Premultiply alpha */
 
 void IMB_premultiply_alpha(struct ImBuf *ibuf);
+void IMB_unpremultiply_alpha(struct ImBuf *ibuf);
 
 /**
  *