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-rw-r--r--include/astra/ParallelBeamBlobKernelProjector2D.inl119
1 files changed, 87 insertions, 32 deletions
diff --git a/include/astra/ParallelBeamBlobKernelProjector2D.inl b/include/astra/ParallelBeamBlobKernelProjector2D.inl
index 1945cdd..c2aa193 100644
--- a/include/astra/ParallelBeamBlobKernelProjector2D.inl
+++ b/include/astra/ParallelBeamBlobKernelProjector2D.inl
@@ -50,6 +50,63 @@ void CParallelBeamBlobKernelProjector2D::projectSingleRay(int _iProjection, int
//----------------------------------------------------------------------------------------
// PROJECT BLOCK - vector projection geometry
+//
+// Kernel limitations: isotropic pixels (PixelLengthX == PixelLengthY)
+//
+// For each angle/detector pair:
+//
+// Let D=(Dx,Dy) denote the centre of the detector (point) in volume coordinates, and
+// let R=(Rx,Ry) denote the direction of the ray (vector).
+//
+// For mainly vertical rays (|Rx|<=|Ry|),
+// let E=(Ex,Ey) denote the centre of the most upper left pixel:
+// E = (WindowMinX + PixelLengthX/2, WindowMaxY - PixelLengthY/2),
+// and let F=(Fx,Fy) denote a vector to the next pixel
+// F = (PixelLengthX, 0)
+//
+// The intersection of the ray (D+aR) with the centre line of the upper row of pixels (E+bF) is
+// { Dx + a*Rx = Ex + b*Fx
+// { Dy + a*Ry = Ey + b*Fy
+// Solving for (a,b) results in:
+// a = (Ey + b*Fy - Dy)/Ry
+// = (Ey - Dy)/Ry
+// b = (Dx + a*Rx - Ex)/Fx
+// = (Dx + (Ey - Dy)*Rx/Ry - Ex)/Fx
+//
+// Define c as the x-value of the intersection of the ray with the upper row in pixel coordinates.
+// c = b
+//
+// The intersection of the ray (D+aR) with the centre line of the second row of pixels (E'+bF) with
+// E'=(WindowMinX + PixelLengthX/2, WindowMaxY - 3*PixelLengthY/2)
+// expressed in x-value pixel coordinates is
+// c' = (Dx + (Ey' - Dy)*Rx/Ry - Ex)/Fx.
+// And thus:
+// deltac = c' - c = (Dx + (Ey' - Dy)*Rx/Ry - Ex)/Fx - (Dx + (Ey - Dy)*Rx/Ry - Ex)/Fx
+// = [(Ey' - Dy)*Rx/Ry - (Ey - Dy)*Rx/Ry]/Fx
+// = [Ey' - Ey]*(Rx/Ry)/Fx
+// = [Ey' - Ey]*(Rx/Ry)/Fx
+// = -PixelLengthY*(Rx/Ry)/Fx.
+//
+// Given c on a certain row, its pixel directly on its left (col), and the distance (offset) to it, can be found:
+// col = floor(c)
+// offset = c - col
+//
+// The index of this pixel is
+// volumeIndex = row * colCount + col
+//
+//
+// Mainly horizontal rays (|Rx|<=|Ry|) are handled in a similar fashion:
+//
+// E = (WindowMinX + PixelLengthX/2, WindowMaxY - PixelLengthY/2),
+// F = (0, -PixelLengthX)
+//
+// a = (Ex + b*Fx - Dx)/Rx = (Ex - Dx)/Rx
+// b = (Dy + a*Ry - Ey)/Fy = (Dy + (Ex - Dx)*Ry/Rx - Ey)/Fy
+// r = b
+// deltar = PixelLengthX*(Ry/Rx)/Fy.
+// row = floor(r+1/2)
+// offset = r - row
+//
template <typename Policy>
void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, int _iProjTo, int _iDetFrom, int _iDetTo, Policy& p)
{
@@ -62,6 +119,8 @@ void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, i
}
// precomputations
+ const float32 pixelLengthX = m_pVolumeGeometry->getPixelLengthX();
+ const float32 pixelLengthY = m_pVolumeGeometry->getPixelLengthY();
const float32 inv_pixelLengthX = 1.0f / m_pVolumeGeometry->getPixelLengthX();
const float32 inv_pixelLengthY = 1.0f / m_pVolumeGeometry->getPixelLengthY();
const int colCount = m_pVolumeGeometry->getGridColCount();
@@ -73,7 +132,7 @@ void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, i
for (int iAngle = _iProjFrom; iAngle < _iProjTo; ++iAngle) {
// variables
- float32 detX, detY, x, y, c, r, update_c, update_r, offset, invBlobExtent, weight, d;
+ float32 Dx, Dy, Ex, Ey, c, r, deltac, deltar, offset, invBlobExtent, RxOverRy, RyOverRx;
int iVolumeIndex, iRayIndex, row, col, iDetector;
int col_left, col_right, row_top, row_bottom, index;
@@ -81,15 +140,18 @@ void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, i
bool vertical = fabs(proj->fRayX) < fabs(proj->fRayY);
if (vertical) {
- update_c = -m_pVolumeGeometry->getPixelLengthY() * (proj->fRayX/proj->fRayY) * inv_pixelLengthX;
- float32 normR = sqrt(proj->fRayY*proj->fRayY + proj->fRayX*proj->fRayX);
- invBlobExtent = m_pVolumeGeometry->getPixelLengthY() / abs(m_fBlobSize * normR / proj->fRayY);
+ RxOverRy = proj->fRayX/proj->fRayY;
+ deltac = -m_pVolumeGeometry->getPixelLengthY() * (proj->fRayX/proj->fRayY) * inv_pixelLengthX;
+ invBlobExtent = m_pVolumeGeometry->getPixelLengthY() / abs(m_fBlobSize * sqrt(proj->fRayY*proj->fRayY + proj->fRayX*proj->fRayX) / proj->fRayY);
} else {
- update_r = -m_pVolumeGeometry->getPixelLengthX() * (proj->fRayY/proj->fRayX) * inv_pixelLengthY;
- float32 normR = sqrt(proj->fRayY*proj->fRayY + proj->fRayX*proj->fRayX);
- invBlobExtent = m_pVolumeGeometry->getPixelLengthX() / abs(m_fBlobSize * normR / proj->fRayX);
+ RyOverRx = proj->fRayY/proj->fRayX;
+ deltar = -m_pVolumeGeometry->getPixelLengthX() * (proj->fRayY/proj->fRayX) * inv_pixelLengthY;
+ invBlobExtent = m_pVolumeGeometry->getPixelLengthX() / abs(m_fBlobSize * sqrt(proj->fRayY*proj->fRayY + proj->fRayX*proj->fRayX) / proj->fRayX);
}
+ Ex = m_pVolumeGeometry->getWindowMinY() + pixelLengthX*0.5f;
+ Ey = m_pVolumeGeometry->getWindowMaxY() - pixelLengthY*0.5f;
+
// loop detectors
for (iDetector = _iDetFrom; iDetector < _iDetTo; ++iDetector) {
@@ -98,18 +160,17 @@ void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, i
// POLICY: RAY PRIOR
if (!p.rayPrior(iRayIndex)) continue;
- detX = proj->fDetSX + (iDetector+0.5f) * proj->fDetUX;
- detY = proj->fDetSY + (iDetector+0.5f) * proj->fDetUY;
+ Dx = proj->fDetSX + (iDetector+0.5f) * proj->fDetUX;
+ Dy = proj->fDetSY + (iDetector+0.5f) * proj->fDetUY;
// vertically
if (vertical) {
- // calculate x for row 0
- x = detX + (proj->fRayX/proj->fRayY)*(m_pVolumeGeometry->pixelRowToCenterY(0)-detY);
- c = (x - m_pVolumeGeometry->getWindowMinX()) * inv_pixelLengthX - 0.5f;
+ // calculate c for row 0
+ c = (Dx + (Ey - Dy)*RxOverRy - Ex) * inv_pixelLengthX;
- // for each row
- for (row = 0; row < rowCount; ++row, c += update_c) {
+ // loop rows
+ for (row = 0; row < rowCount; ++row, c += deltac) {
col_left = int(c - 0.5f - m_fBlobSize);
col_right = int(c + 0.5f + m_fBlobSize);
@@ -117,17 +178,15 @@ void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, i
if (col_left < 0) col_left = 0;
if (col_right > colCount-1) col_right = colCount-1;
- // for each column
+ // loop columns
for (col = col_left; col <= col_right; ++col) {
- offset = abs(c - float32(col)) * invBlobExtent;
- index = (int)(offset*m_iBlobSampleCount+0.5f);
- weight = m_pfBlobValues[min(index,m_iBlobSampleCount-1)];
-
iVolumeIndex = row * colCount + col;
// POLICY: PIXEL PRIOR + ADD + POSTERIOR
if (p.pixelPrior(iVolumeIndex)) {
- p.addWeight(iRayIndex, iVolumeIndex, weight);
+ offset = abs(c - float32(col)) * invBlobExtent;
+ index = (int)(offset*m_iBlobSampleCount+0.5f);
+ p.addWeight(iRayIndex, iVolumeIndex, m_pfBlobValues[min(index,m_iBlobSampleCount-1)]);
p.pixelPosterior(iVolumeIndex);
}
}
@@ -137,12 +196,11 @@ void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, i
// horizontally
else {
- // calculate y for col 0
- y = detY + (proj->fRayY/proj->fRayX)*(m_pVolumeGeometry->pixelColToCenterX(0)-detX);
- r = (m_pVolumeGeometry->getWindowMaxY() - y) * inv_pixelLengthY - 0.5f;
+ // calculate r for col 0
+ r = -(Dy + (Ex - Dx)*RyOverRx - Ey) * inv_pixelLengthY;
- // for each col
- for (col = 0; col < colCount; ++col, r += update_r) {
+ // loop columns
+ for (col = 0; col < colCount; ++col, r += deltar) {
row_top = int(r - 0.5f - m_fBlobSize);
row_bottom = int(r + 0.5f + m_fBlobSize);
@@ -150,21 +208,18 @@ void CParallelBeamBlobKernelProjector2D::projectBlock_internal(int _iProjFrom, i
if (row_top < 0) row_top = 0;
if (row_bottom > rowCount-1) row_bottom = rowCount-1;
- // for each column
+ // loop rows
for (row = row_top; row <= row_bottom; ++row) {
- offset = abs(r - float32(row)) * invBlobExtent;
- index = (int)(offset*m_iBlobSampleCount+0.5f);
- weight = m_pfBlobValues[min(index,m_iBlobSampleCount-1)];
-
iVolumeIndex = row * colCount + col;
// POLICY: PIXEL PRIOR + ADD + POSTERIOR
if (p.pixelPrior(iVolumeIndex)) {
- p.addWeight(iRayIndex, iVolumeIndex, weight);
+ offset = abs(r - float32(row)) * invBlobExtent;
+ index = (int)(offset*m_iBlobSampleCount+0.5f);
+ p.addWeight(iRayIndex, iVolumeIndex, m_pfBlobValues[min(index,m_iBlobSampleCount-1)]);
p.pixelPosterior(iVolumeIndex);
}
}
-
}
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-01 13:32:43 +0000