How to find the x and y coordinates of points inside a binary image M?

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Loren99
Loren99 2022-6-9
编辑： Loren99 2022-6-15
Hi everyone! I need a help with a code. On one hand, I have a binary image M (logical); on the other hand, I have vrx (2x658) and vry (2x658) where the first row of vrx is the x coordinate of the initial point of a line, the second row of vrx is the x coordinate of the final point of a line. The same reasoning is valid for vry but it is the y_coordinate.
Starting from the initial points of a line (so the elements vrx(1,:) and vry(1,:)), the code has to check, in correspondence of every single point of coordinates vrx and vry, if the binary image M in that specific point has value 1 or 0. If the value of M is 1, then I have to remove that point from the total vector. If the value of M is 0, that point can stay in the total vector. The same procedure must be done for the final points of a line (so the elements vrx(2,:) and vry(2,:); at the end I have to plot the new vectors vrx and vry obtained, after this check.
My problem is that I don't know how to make this correspondence between the vrx and vry coordinates of the current point I am analyzing and the value that the binary Image M assumes at that specific point.
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Loren99
Loren99 2022-6-9
编辑：Loren99 2022-6-10
@Matt J yes, I was thinking about the fact that for example vrx and vry coordinates like (149.5 ; 158,5) could be rounded to the pixel coordinates (149;158)
Loren99
Loren99 2022-6-9
编辑：Loren99 2022-6-9
@Image Analyst I have to check first all the initial points x1,y1 ; then all the final points x2,y2

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回答（1 个）

Image Analyst
Image Analyst 2022-6-9
Write all the endpoints to a binary image. Then use imreconstruct. I bet you can figure it out, but if you can't, write back for help.
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Loren99
Loren99 2022-6-9
@Image Analyst sorry but I don't understand how this answer is linked to my question. Then:
1) Why I have to consider only the endpoints (x2,y2) and not also (x1,y1)?
2) How can i write the endpoints to a binary image?
3) Why I have to use imreconstruct?
Image Analyst
Image Analyst 2022-6-10
@Loren99
  1. I did not say that. I said "Write all the endpoints".
  2. You can do binaryImage(round(y2(k)), round(x2(k))) = true; Iterate over all k and also do the x1 and y2 arrays.
  3. imreconstruct will tell you what regions/blobs in the mask image also contain any pixels from the marker image. So if your mask image is your M array, and your marker image is the one you created in #2 above, you'll know which blobs the xy points are in and then you can erase those from M.

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