Implement GPU-side display transform for clip editor

Implemented using GLSL API from OpenColorIO library and
some general functions were added to it's c-api:

- OCIO_setupGLSLDraw prepares OpenGL context for GPU-based
  transformation for a giver processor.

  This function compiles and links shader, sets  up it's
  argument. After this transformation would be applied
  on an image displaying as a 2D texture.

  So, glaDrawPixelsTex called after OCIO_setupGLSLDraw will
  do a proper color space transform.

- OCIO_finishGLSLDraw restores OpenGL context after all
  color-managed display is over.

- OCIO_freeOGLState frees allocated state structure used
  for cacheing some GLSL-related stuff.

There're some utility functions in IMB_colormanagent which
are basically proxies to lower level OCIO functions but
which could be used from any place in blender.

Chacheing of movie clip frame on GPU is also removed now,
and either glaDrawPixelsTex or glaDrawPixelsAuto are used
for display now. This is so no code duplication happens
now and no large textures are lurking around in GPU memory.

Known issues:
- Texture buffer and GLSL are no longer checking for
  video card capabilities, possibly could lead to some
  artifacts on crappy drivers/cards.

- Only float buffers are displaying using GLSL, byte
  buffers will still use fallback display method.

  This is to be addressed later.

- If RGB curves are used as a part of display transform,
  GLSL display will also be disabled. This is also thing
  to be solved later.

Additional changes:

- glaDrawPixelsTexScaled will now use RGBA16F as an
  internal format of storing textures when it's used
  to draw float buffer. This is needed so LUT are
  applied without precision loss.

1 files changed, 8 insertions, 0 deletions

diff --git a/source/blender/imbuf/IMB_colormanagement.h b/source/blender/imbuf/IMB_colormanagement.h
index b981390582e..473bd7d0c7a 100644
--- a/source/blender/imbuf/IMB_colormanagement.h
+++ b/source/blender/imbuf/IMB_colormanagement.h
@@ -148,6 +148,14 @@ void IMB_colormanagement_processor_apply(struct ColormanageProcessor *cm_process
                                          int channels, int predivide);
 void IMB_colormanagement_processor_free(struct ColormanageProcessor *cm_processor);
 
+/* ** OpenGL drawing routines using GLSL for color space transform ** */
+
+int IMB_coloemanagement_setup_glsl_draw(const struct ColorManagedViewSettings *view_settings,
+                                        const struct ColorManagedDisplaySettings *display_settings);
+
+int IMB_coloemanagement_setup_glsl_draw_from_ctx(const struct bContext *C);
+void IMB_coloemanagement_finish_glsl_draw(void);
+
 /* Roles */
 enum {
 	COLOR_ROLE_SCENE_LINEAR = 0,