1 files changed, 24 insertions, 0 deletions

diff --git a/SD-VBS/common/toolbox/toolbox_basic/affine/grad.m b/SD-VBS/common/toolbox/toolbox_basic/affine/grad.m
new file mode 100755
index 0000000..53bab55
--- /dev/null
+++ b/SD-VBS/common/toolbox/toolbox_basic/affine/grad.m
@@ -0,0 +1,24 @@
+% gradient of an image
+% coordinates (r, c) follow matrix convention;
+% the gaussian is truncated at x = +- tail, and there are samples samples
+% inbetween, where samples = hsamples * 2 + 1
+
+function[gr,gc] = gradient(image, hsamples)
+
+tail=4;
+samples = hsamples * 2 + 1;
+
+x = linspace(-tail, tail, samples);
+gauss = exp(-x.^2);
+n = gauss * ones(samples,1);
+gauss = gauss/n;
+
+gaussderiv = -x.*gauss;
+n = -gaussderiv*linspace(1,samples,samples)';
+gaussderiv = gaussderiv/n;
+
+gr = conv2(conv2(image, gaussderiv','valid'), gauss,'valid');
+gc = conv2(conv2(image, gaussderiv,'valid'), gauss','valid');
+
+%gr = conv2(conv2(image, gaussderiv','same'), gauss,'same');
+%gc = conv2(conv2(image, gaussderiv,'same'), gauss','same');