MATLAB Answers

Radon transform and Prewitt filters for hair removal

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hamed abdulaziz
hamed abdulaziz on 29 Sep 2013
Commented: Walter Roberson on 9 May 2017
Hi All,
I'm working on dermoscopic images (skin cancer images)that contains a light and thick hair,how can detect the predominant orientation of hairs in the image by using Radon transform, followed by filtering the image by Prewitt filters using the orientation of existing hairs I tried to write this code :
if true
% %%Radon transform and Prewitt filters
rgbImage = imread('hair.bmp');
redChannel =rgbImage(:, :, 1);
greenChannel =rgbImage(:, :, 2);
blueChannel =rgbImage(:, :, 3);
theta = 0:180;
[R,xp] = radon(rgbImage,theta);
BW = edge(rgbImage,'prewitt',[],xp);
but I've got this error message :
Error using edge>parse_inputs (line 607) Invalid input arguments.
Error in edge (line 190) [a,method,thresh,sigma,thinning,H,kx,ky] = parse_inputs(varargin{:});
Error in Untitled2 (line 12) BW = edge(rgbImage,'prewitt',[],xp);
I attached a bitmap image contains hair called (hair.bmp),could any one guid me please because I'm really stuck in my project,thanks in advance. Hamed

Answers (3)

Image Analyst
Image Analyst on 29 Sep 2013
The documentation for edge() says:
Class Support
I is a nonsparse 2-D numeric array.
BW isa 2-D array of class logical.
rgbImage is not a 2D image - it's a 3D color image. You need to pass one of the color channels you extracted into edge(), not the full RGB image.
BW = edge(greenChannel,'prewitt',[],xp);


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Image Analyst
Image Analyst on 29 Sep 2013
The help for edge() says this:
BW = edge(I,'prewitt',thresh,direction) specifiesthe direction of detection for the Prewitt method. direction is a string specifying whether to look for 'horizontal' or 'vertical' edges or 'both' (default).
The help for radon() says this:
[R,xp] = radon(...) returns a vector xp containing the radial coordinates correspondingto each row of R.
So edge() wants a string and you're passing in a double vector. Do you think that might cause problems?
hamed abdulaziz
hamed abdulaziz on 29 Sep 2013
my be ? how can I deal with a vector xp as a string?is that possible?
hamed abdulaziz
hamed abdulaziz on 29 Sep 2013
but I've got the same error !!! what the disappointed I have?!please guide me

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asma arafat
asma arafat on 9 May 2017
how i can remove eyebrows from an image to use edge detectors after that and i don't need eyebrows to detect as edge. any help!!?