Read coordinates on a txt file and plot them over an image.
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Dear all,
I made a program that reads some coordinates (x, y) of a text file and plot the points over a gray image. The problem is that the 'y' coordinates are inverted. This problem doesn't happen when I draw a regular plot (without reading from a file).
How can I fix this issue?
Thanks in advance,
3 commentaires
Image Analyst
le 4 Jan 2017
Gabriel, do you want your x axis to be at the top of your image, with rising y values going downward? Or do you want your x axis to be at the bottom of your image, with rising y values going upward? And do you like the way your image is displayed, or do you wish the top were at the bottom and vice versa?
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Stephen23
le 4 Jan 2017
Modifié(e) : Stephen23
le 4 Jan 2017
Images are referenced to the top left of the image (due to traditions related to the scanning of a CRT), so this is how all image handling programs work with them. MATLAB simply follows this standard.
People who are used to plotting data relative to an x-axis at the bottom of their plot might get a bit confused, but need to learn that images use a different standard.
A simple internet search shows many questions already dealing with this topic, e.g.:
"The high-level version of imagesc calls newplot before plotting and sets these axes properties: ... YDir to 'reverse'. Values along the y-axis increase from top to bottom."
4 commentaires
Guillaume
le 4 Jan 2017
plot(x, size(img, 1) - y, 'r*')
would solve the problem quickly
Stelios Fanourakis
le 1 Mai 2018
Hey I am doing something similar but I cannot take anything as a result. I use
filePatternu = fullfile(destinationFolder, '*.dcm'); allFiles = dir(filePatternu);
for k= 2: 1: length(allFiles) baseFileName = allFiles(k).name; % e.g. "1.png" fullFileName = fullfile(destinationFolder, baseFileName); I = dicomread(fullFileName); % img respresents input image. pause(2) [x, y] = textread('imgpositions.txt', '%f , %f'); figure imshow(I, [x y]) drawnow; end
Although, I get no error still I get no image
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