image to binary issues
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Hi,
i want to run a single image through multiple thresholds. Initially, i had separate lines of code for each threshold (im2bw(img,.1), im2bw(img,.2) and so on). Now i want to run the image between thresholds ranging from 0:.001:.5. thats a total of 500 hundred values. How do I write that in few lines rather than write 500 lines?
I have tried for loop
thld = 0 : .001 : .5
for i=1:500
a(i)=im2bw(img,thld)
end
but this doesn't work.
Thank you for the help
采纳的回答
Guillaume
2014-10-23
Nearly there. Use cell arrays for storing your images or a 3d matrix:
thld = 0 : .001 : .5;
for idx = 1:numel(thld)
a{idx} = im2bw(img, thld(idx));
end
or
thld = 0 : .001 : .5;
a = zeros([size(img), numel(thld)]); %better preallocate huge array
for idx = 1:numel(thld)
a(:,:, idx) = im2bw(img, thld(idx));
end
8 个评论
jchris14
2014-10-23
Image Analyst
2014-10-23
编辑：Image Analyst
2014-10-23
First of all, img better be a double image. If it's a uint8 image, or even a double image that was created from a uint8 image with something like imdouble(img) or img/max(img(:)) then you're not going to get more than 256 threshold, not 501. You can do this:
thld = 0 : .001 : .5;
numWhitePixels = zeros(1, length(thld));
numBlackPixels = zeros(1, length(thld));
for idx = 1:numel(thld)
thisImage = im2bw(img, thld(idx));
numWhitePixels(idx) = sum(thisImage(:));
numBlackPixels(idx) = numel(thisImage) - numWhitePixels(idx);
% Save to a cell array only if
% you need all images after the loop has exited.
a{idx} = thisImage;
end
Image Analyst
2014-10-23
Your img is a character string. Did you pass the filename to im2bw() instead of the image array? It should look like this:
img = imread(fullFileName);
binaryImage = im2bw(img,..............
jchris14
2014-10-23
Guillaume
2014-10-23
Use more descriptive name than a for your variable and you'll see where you go wrong.
You ask for a filename with uigetfile but you never load the image. In addition even if you'd loaded the image in a, you would have overwritten it in the loop since you're also using a for storing the binary image.
Your code should be something like:
imgfilename = uigetfile('*.tif');
sourceimage = imread(imgfilename);
...
binaryimage = im2bw(sourceimage, thld(idx));
binaryimages{idx} = binaryimage;
Image Analyst
2014-10-23
Yep, like I said, the badly-named "a" is the culprit. It's a string just like I said. Did you use imread() like I suggested in my prior comment? No, not in that code you just posted. Why don't you use my suggestion? It will be alright then if you do.
jchris14
2014-10-23
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