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authorWillem Jan Palenstijn <Willem.Jan.Palenstijn@cwi.nl>2019-03-29 10:57:16 +0100
committerWillem Jan Palenstijn <Willem.Jan.Palenstijn@cwi.nl>2019-03-29 14:16:28 +0100
commit667a390d94ad3b3ee706f9598a707376d9604810 (patch)
tree2538526dff4f3da594df2f8f426a641c1d9fc23d /tests
parent0f7c3261f159882316429d8a13009a8c1f858cbc (diff)
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Fix scaling for fan/strip projector
The strip model for a fan beam geometry wasn't taking pixel magnification into account. Among other things, this resulted in diagonals through rectangles being weighted the same as hor/ver lines. This commit fixes this by scaling each pixel contribution by its magnification on the detector. This is only an approximation (since the magnification isn't constant inside the pixel), but since pixels are usually small, the error is also small. Unfortunately, computing this scaling factor is relatively expensive because it introduces a square root in the inner loop.
Diffstat (limited to 'tests')
-rw-r--r--tests/python/test_line2d.py27
1 files changed, 26 insertions, 1 deletions
diff --git a/tests/python/test_line2d.py b/tests/python/test_line2d.py
index e7bca98..d04ffb8 100644
--- a/tests/python/test_line2d.py
+++ b/tests/python/test_line2d.py
@@ -556,11 +556,36 @@ class Test2DKernel(unittest.TestCase):
if DISPLAY and x > TOL:
display_mismatch(data, sinogram, a)
self.assertFalse(x > TOL)
+ elif proj_type == 'strip' and 'fan' in type:
+ a = np.zeros(np.prod(astra.functions.geom_size(pg)), dtype=np.float32)
+ for i, (center, edge1, edge2) in enumerate(gen_lines(pg)):
+ (src, det) = center
+ det_dist = np.linalg.norm(src-det, ord=2)
+ l = 0.0
+ for j in range(rect_min[0], rect_max[0]):
+ xmin = origin[0] + (-0.5 * shape[0] + j) * pixsize[0]
+ xmax = origin[0] + (-0.5 * shape[0] + j + 1) * pixsize[0]
+ xcen = 0.5 * (xmin + xmax)
+ for k in range(rect_min[1], rect_max[1]):
+ ymin = origin[1] + (+0.5 * shape[1] - k - 1) * pixsize[1]
+ ymax = origin[1] + (+0.5 * shape[1] - k) * pixsize[1]
+ ycen = 0.5 * (ymin + ymax)
+ scale = det_dist / np.linalg.norm( src - np.array((xcen,ycen)), ord=2 )
+ w = intersect_ray_rect(edge1, edge2, xmin, xmax, ymin, ymax)
+ l += w * scale
+ a[i] = l
+ a = a.reshape(astra.functions.geom_size(pg))
+ if not np.all(np.isfinite(a)):
+ raise RuntimeError("Invalid value in reference sinogram")
+ x = np.max(np.abs(sinogram-a))
+ TOL = 8e-3
+ if DISPLAY and x > TOL:
+ display_mismatch(data, sinogram, a)
+ self.assertFalse(x > TOL)
elif proj_type == 'strip':
a = np.zeros(np.prod(astra.functions.geom_size(pg)), dtype=np.float32)
for i, (center, edge1, edge2) in enumerate(gen_lines(pg)):
a[i] = intersect_ray_rect(edge1, edge2, xmin, xmax, ymin, ymax)
-
a = a.reshape(astra.functions.geom_size(pg))
if not np.all(np.isfinite(a)):
raise RuntimeError("Invalid value in reference sinogram")