From dc31a371a7f5c66e32226698999f345e350f3049 Mon Sep 17 00:00:00 2001
From: Folkert Bleichrodt <F.Bleichrodt@cwi.nl>
Date: Wed, 8 Apr 2015 16:03:41 +0200
Subject: Added ASTRA-Spot operator opTomo

A Spot operator for the ASTRA projectors. Wraps the forward and
backprojection operation into a Spot operator, which can be used
with matrix-vector syntax in Matlab.
---
 samples/matlab/s017_opTomo.m | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 samples/matlab/s017_opTomo.m

(limited to 'samples')

diff --git a/samples/matlab/s017_opTomo.m b/samples/matlab/s017_opTomo.m
new file mode 100644
index 0000000..4886cc5
--- /dev/null
+++ b/samples/matlab/s017_opTomo.m
@@ -0,0 +1,44 @@
+% load a phantom image
+im = phantom(256);
+% and flatten it to a vector
+x = im(:);
+
+%% Setting up the geometry
+% projection geometry
+proj_geom = astra_create_proj_geom('parallel', 1, 256, linspace2(0,pi,180));
+% object dimensions
+vol_geom  = astra_create_vol_geom(256,256);
+
+%% Generate projection data
+% Create the Spot operator for ASTRA using the GPU.
+W = opTomo('cuda', proj_geom, vol_geom);
+
+p = W*x;
+
+% reshape the vector into a sinogram
+sinogram = reshape(p, W.proj_size);
+imshow(sinogram, []);
+
+
+%% Reconstruction
+% We use a least squares solver lsqr from Matlab to solve the 
+% equation W*x = p.
+% Max number of iterations is 100, convergence tolerance of 1e-6.
+y = lsqr(W, p, 1e-6, 100);
+
+% the output is a vector, so we reshape it into an image
+reconstruction = reshape(y, W.vol_size);
+
+subplot(1,3,1);
+imshow(reconstruction, []);
+title('Reconstruction');
+
+subplot(1,3,2);
+imshow(im, []);
+title('Ground truth');
+
+% The transpose of the operator corresponds to the backprojection.
+backProjection = W'*p;
+subplot(1,3,3);
+imshow(reshape(backProjection, W.vol_size), []);
+title('Backprojection');
-- 
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