Extracting cartesian coordinates from a binarized image of a curved line

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Michiel Firlefyn
Michiel Firlefyn 2018-4-23
评论： Michiel Firlefyn 2018-5-1
Hi everyone
After image pre-processing, I obtained the following binarized image:
This is in a 2848x4272 array form and I would like to convert the line to a 2 column matrix with x and y coordinates. Does anyone have any idea how to achieve this?
The code I used to achieve the line is:
img = imread('G1.JPG');
background = imopen(img,strel('disk',60));
surf(double(background(1:8:end,1:8:end))),zlim([0 255]);
set(gca,'ydir','reverse');
I2 = img - background;
grayImage = I2(:, :, 1);
I3 = imadjust(grayImage);
bw = imbinarize(I3);
bw = bwareaopen(bw, 5000);
cc = bwconncomp(bw, 8);
line = false(size(bw));
line(cc.PixelIdxList{1}) = true;
imshow(line);
Thanks!

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回答（1 个）

Sigurd Askeland
Sigurd Askeland 2018-4-27
I don't have the Image Processing Toolbox, so I can't recreate your scenario exactly. However, if you have a 2D array of booleans ( true / false, or 1 / 0), this can be translated to an (Nx2) array of the x and y indices of the true pixels.
[m,n] = size(my_image); %my_image to be replaced by your image...
x = ones(m*n,1) * [1:m*n];
y = [1:m*n]' * ones(1,m*n);
coordinates = [x,y]; %All coordinates.
coordinates = coordinates(my_image(:),:); %'true' coordinates.
Note that the x and y values are the number of pixels from the top left corner. A simple transformation can make them into more traditional x- and y-coordinates.

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