Thresholding an image based on part of a histogram's values

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Teshan Rezel 2020-6-12

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https://ww2.mathworks.cn/matlabcentral/answers/547374-thresholding-an-image-based-on-part-of-a-histogram-s-values

评论： Teshan Rezel 2020-6-18

采纳的回答： Ameer Hamza

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Hi folks,

I'm trying to get the parts of an image that fall between 2 values of its grayscale histogram, the revert the image back to its colour form. So far, I am struggling to get anything but a black image! Any ideas on what I'm doing wrong please? Below is my code.

baseGray = rgb2gray(I);
isoLower = 135;
isoUpper = 155;
lessThan = baseGray < isoLower;
greaterThan = baseGray > isoUpper;
baseGray(lessThan) = 0;
baseGray(greaterThan) = 0;
grayThresh = imbinarize(baseGray);
grayThresh = bwareaopen(grayThresh, 3000);
grayThresh = imfill(grayThresh, 'holes');
grayThresh = bwperim(grayThresh);
grayThresh = imdilate(grayThresh, ones(5));
grayThresh = imerode(grayThresh, ones(3));
grayThresh = imfill(grayThresh, 'holes');
refigure = img.*repmat(uint8(grayThresh),[1 1 3]);
imshow(refigure);

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采纳的回答

Ameer Hamza 2020-6-13

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https://ww2.mathworks.cn/matlabcentral/answers/547374-thresholding-an-image-based-on-part-of-a-histogram-s-values#answer_450471

编辑：Ameer Hamza 2020-6-13

在 MATLAB Online 中打开

Try something like this

img = im2double(imread('pears.png'));
img_gray = rgb2gray(img);
isoLower = 135/255; % double image, pixel intensity between 0 and 1
isoUpper = 155/255;
mask = (isoLower < img_gray) & (img_gray < isoUpper);
refigure = img;
refigure(~mask(:,:,[1 1 1])) = 0;
imshow(refigure)

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Image Analyst 2020-6-18

Why not just try the Color Thresholder on the Apps tab of the tool ribbon and interactively set your thresholds???

Teshan Rezel 2020-6-18

Hi Image Analyst, I've tried the tool and found it useful to a degree. But my issue is that I will need to analyse several batches of 900 images each, so doing them individually in the app would not be efficient. Furthermore, I need to analyse them in grayscale, which isn't an option on the app as far as I can see. Thanks for your suggestion!

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