# x,y coordinates in .txt to points on image

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Stijn Senhorst on 9 Jun 2021
Commented: Image Analyst on 10 Jun 2021
Hi there,
I need some help with loading coordinates in a .txt to points in an image. In the attached .txt are all the coordinates. What is the best approache to do this?
thanks,
Scott MacKenzie on 9 Jun 2021
What do you mean by "to points in an image"? The x-y coordinates are in the range -10 to +10 (approximately), so if you intend to map them to an image (e.g., 1000x2000), then some scaling will be necessary. Explain your objective, if you can, please.

Adam Danz on 10 Jun 2021
2. Plot the values using the plot command where x is the first column of A and y is the second column of A. Use indexing A(:,i)
Image Analyst on 10 Jun 2021
And make sure you scale the (x,y) values
[rows, columns, numColors] = size(yourImage);
imshow(yourImage);
impixelinfo;
x = rescale(A(:, 1), 1, columns);
y = rescale(A(:, 2), 1, rows); % Or however you need to do it.
and make sure you call
hold on;
after you call imshow() but before you call plot() or else the plot will blow away your image.
And remember images are indexed (row, column) which is (y, x) -- not (x,y) like plot() uses. So don't call yourImage(x, y) and expect that the gray level will match the gray level under that coordinate. You'd need to use yourImage(y, x).

R2021a

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