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

조회 수: 2 (최근 30일)
Teshan Rezel
Teshan Rezel 2020년 6월 12일
댓글: Teshan Rezel 2020년 6월 18일
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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Ameer Hamza
Ameer Hamza 2020년 6월 13일
편집: Ameer Hamza 2020년 6월 13일
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)
  댓글 수: 10
Image Analyst
Image Analyst 2020년 6월 18일
Why not just try the Color Thresholder on the Apps tab of the tool ribbon and interactively set your thresholds???
Teshan Rezel
Teshan Rezel 2020년 6월 18일
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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