5 files changed, 29 insertions, 10 deletions
diff --git a/intern/opencolorio/fallback_impl.cc b/intern/opencolorio/fallback_impl.cc
index 4c19c454aee..37f624e1f8b 100644
--- a/intern/opencolorio/fallback_impl.cc
+++ b/intern/opencolorio/fallback_impl.cc
@@ -381,7 +381,7 @@ void FallbackImpl::matrixTransformScale(float * , float * , const float *)
 {
 }
 
-bool FallbackImpl::setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor)
+bool FallbackImpl::setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide)
 {
 	return false;
 }
diff --git a/intern/opencolorio/ocio_capi.cc b/intern/opencolorio/ocio_capi.cc
index 8e831bb0736..c8db2c2b531 100644
--- a/intern/opencolorio/ocio_capi.cc
+++ b/intern/opencolorio/ocio_capi.cc
@@ -283,9 +283,9 @@ void OCIO_matrixTransformScale(float * m44, float * offset4, const float *scale4
 	impl->matrixTransformScale(m44, offset4, scale4f);
 }
 
-int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor)
+int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, int predivide)
 {
-	return (int) impl->setupGLSLDraw(state_r, processor);
+	return (int) impl->setupGLSLDraw(state_r, processor, (bool) predivide);
 }
 
 void OCIO_finishGLSLDraw(struct OCIO_GLSLDrawState *state)
diff --git a/intern/opencolorio/ocio_capi.h b/intern/opencolorio/ocio_capi.h
index 8d8db161077..3632a0da1c6 100644
--- a/intern/opencolorio/ocio_capi.h
+++ b/intern/opencolorio/ocio_capi.h
@@ -121,7 +121,7 @@ void OCIO_matrixTransformRelease(OCIO_MatrixTransformRcPtr *mt);
 
 void OCIO_matrixTransformScale(float * m44, float * offset4, const float * scale4);
 
-int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor);
+int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, int predivide);
 void OCIO_finishGLSLDraw(struct OCIO_GLSLDrawState *state);
 void OCIO_freeOGLState(struct OCIO_GLSLDrawState *state);
 
diff --git a/intern/opencolorio/ocio_impl.h b/intern/opencolorio/ocio_impl.h
index 3a1207d0870..a328470ccb5 100644
--- a/intern/opencolorio/ocio_impl.h
+++ b/intern/opencolorio/ocio_impl.h
@@ -96,7 +96,7 @@ public:
 
 	virtual void matrixTransformScale(float * m44, float * offset4, const float * scale4) = 0;
 
-	virtual bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor) = 0;
+	virtual bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide) = 0;
 	virtual void finishGLSLDraw(struct OCIO_GLSLDrawState *state) = 0;
 	virtual void freeGLState(struct OCIO_GLSLDrawState *state_r) = 0;
 };
@@ -169,7 +169,7 @@ public:
 
 	void matrixTransformScale(float * m44, float * offset4, const float * scale4);
 
-	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor);
+	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide);
 	void finishGLSLDraw(struct OCIO_GLSLDrawState *state);
 	void freeGLState(struct OCIO_GLSLDrawState *state_r);
 };
@@ -243,7 +243,7 @@ public:
 
 	void matrixTransformScale(float * m44, float * offset4, const float * scale4);
 
-	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor);
+	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide);
 	void finishGLSLDraw(struct OCIO_GLSLDrawState *state);
 	void freeGLState(struct OCIO_GLSLDrawState *state_r);
 };
diff --git a/intern/opencolorio/ocio_impl_glsl.cc b/intern/opencolorio/ocio_impl_glsl.cc
index 59845abca33..9343a13e888 100644
--- a/intern/opencolorio/ocio_impl_glsl.cc
+++ b/intern/opencolorio/ocio_impl_glsl.cc
@@ -77,15 +77,33 @@ typedef struct OCIO_GLSLDrawState {
 	GLint last_texture, last_texture_unit;
 } OCIO_GLSLDrawState;
 
-static const char * g_fragShaderText = ""
+/* Hardcoded to do alpha predivide before color space conversion */
+static const char *g_fragShaderText = ""
 "\n"
 "uniform sampler2D tex1;\n"
 "uniform sampler3D tex2;\n"
+"uniform bool predivide;\n"
 "\n"
 "void main()\n"
 "{\n"
 "    vec4 col = texture2D(tex1, gl_TexCoord[0].st);\n"
-"    gl_FragColor = OCIODisplay(col, tex2);\n"
+"    if (predivide == false || col[3] == 1.0f || col[3] == 0.0f) {\n"
+"      gl_FragColor = OCIODisplay(col, tex2);\n"
+"    } else {\n"
+"      float alpha = col[3];\n"
+"      float inv_alpha = 1.0f / alpha;\n"
+"\n"
+"      col[0] *= inv_alpha;\n"
+"      col[1] *= inv_alpha;\n"
+"      col[2] *= inv_alpha;\n"
+"\n"
+"      gl_FragColor = OCIODisplay(col, tex2);\n"
+"\n"
+"      col[0] *= alpha;\n"
+"      col[1] *= alpha;\n"
+"      col[2] *= alpha;\n"
+"    }\n"
+"\n"
 "}\n";
 
 static GLuint compileShaderText(GLenum shaderType, const char *text)
@@ -187,7 +205,7 @@ static void ensureLUT3DAllocated(OCIO_GLSLDrawState *state)
  * When all drawing is finished, finishGLSLDraw shall be called to
  * restore OpenGL context to it's pre-GLSL draw state.
  */
-bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor)
+bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide)
 {
 	ConstProcessorRcPtr ocio_processor = *(ConstProcessorRcPtr *) processor;
 
@@ -252,6 +270,7 @@ bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRc
 		glUseProgram(state->program);
 		glUniform1i(glGetUniformLocation(state->program, "tex1"), 0);
 		glUniform1i(glGetUniformLocation(state->program, "tex2"), 1);
+		glUniform1i(glGetUniformLocation(state->program, "predivide"), predivide);
 
 		return true;
 	}