Fix for half pixel offset rasterizing masks

2 files changed, 6 insertions, 2 deletions

diff --git a/source/blender/compositor/operations/COM_MaskOperation.cpp b/source/blender/compositor/operations/COM_MaskOperation.cpp
index 112b5912ad3..8c8ba93327d 100644
--- a/source/blender/compositor/operations/COM_MaskOperation.cpp
+++ b/source/blender/compositor/operations/COM_MaskOperation.cpp
@@ -129,8 +129,9 @@ void MaskOperation::determineResolution(unsigned int resolution[2], unsigned int
 
 void MaskOperation::executePixelSampled(float output[4], float x, float y, PixelSampler sampler)
 {
-	const float xy[2] = {x * this->m_maskWidthInv,
-	                     y * this->m_maskHeightInv};
+	const float xy[2] = {
+	    (x * this->m_maskWidthInv)  + this->m_mask_px_ofs[0],
+	    (y * this->m_maskHeightInv) + this->m_mask_px_ofs[1]};
 
 	if (this->m_rasterMaskHandleTot == 1) {
 		if (this->m_rasterMaskHandles[0]) {
diff --git a/source/blender/compositor/operations/COM_MaskOperation.h b/source/blender/compositor/operations/COM_MaskOperation.h
index 18d7e594104..522b873e167 100644
--- a/source/blender/compositor/operations/COM_MaskOperation.h
+++ b/source/blender/compositor/operations/COM_MaskOperation.h
@@ -43,6 +43,7 @@ protected:
 	int   m_maskHeight;
 	float m_maskWidthInv;  /* 1 / m_maskWidth  */
 	float m_maskHeightInv; /* 1 / m_maskHeight */
+	float m_mask_px_ofs[2];
 
 	float m_frame_shutter;
 	int   m_frame_number;
@@ -70,11 +71,13 @@ public:
 	{
 		this->m_maskWidth    = width;
 		this->m_maskWidthInv = 1.0f / (float)width;
+		this->m_mask_px_ofs[0] = this->m_maskWidthInv * 0.5f;
 	}
 	void setMaskHeight(int height)
 	{
 		this->m_maskHeight = height;
 		this->m_maskHeightInv = 1.0f / (float)height;
+		this->m_mask_px_ofs[1] = this->m_maskHeightInv * 0.5f;
 	}
 	void setFramenumber(int frame_number) { this->m_frame_number = frame_number; }
 	void setSmooth(bool smooth) { this->m_do_smooth = smooth; }