Find edges in a single channel image.
E = edge(im, method) E = edge(im, method, thresh) E = edge(im, method, thresh, direction) E = edge(im, method, thresh, sigma) [E, thresh] = edge(im, method, ...)
E
, will have the un-thresholded gradient image.im
.
If thresh<0
, E
is a double un-thresholded image.The function edge performs edge detection on a grayscale intensity image. The user may set the method, the threshold level, the direction of the edge detection, etc.
im
, using the sobel gradient estimator.im
, using the prewitt gradient estimator.im
, using the the Laplacian of Gaussian method.
sigma
is the standard deviation of the LoG filter
and the size of the LoG filter is nxn, where n = ceil(sigma*3)*2+1.
The default value for sigma
is 2.im
, using the FFT gradient method, default sigma 1.0im
, using Canny method.
thresh
is a two-element vector, in which the fist element is the low threshold
and the seond one is the high threshold. If thresh
is a scalar,
the low threshold is 0.4*thresh
and the high one is thresh
.
Besides, thresh
can not be negative scalar.
sigma
is the Aperture parameter for Sobel operator, which must be 1, 3, 5 or 7.
default thresh 0.2; default sigma 3.Supported classes: INT8, UINT8, INT16, UINT16, INT32, DOUBLE.
"Shape Analysis and Classification", L. da F. Costa and R. M. Cesar Jr., CRC Press, section 3.3.
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