Use pixel informations to create a grid on images
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Hi,
I have an picture of graph paper I have to use as a reference. To be clear I have to use the grid as calibration for an acquisition sistem wich I used also to acquire the picture.
I want to get the grid of this image and superimpose it on other images that are acquired during a measurement session. Is it possible? how to do it? I was thinking to count the pixel between two lines and get the coordinates of the central pixel and make a plot on the other images using this information
Thanks
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Accepted Answer
Image Analyst
on 23 Jan 2012
Sounds reasonable. If the image is good, threshold it and find the crossings
columns = find(grayImage(rowToExamine, :) < 100);
There are more robust ways to do it where you look at more than just one line.
2 Comments
Image Analyst
on 24 Jan 2012
% Make all white image.
grayImage = 255 * ones(256, 'uint8');
% Put dark grid into it
grayImage(8:16:256, :) = 0; % Make dark rows
grayImage(:, 8:16:256) = 0; % Make dark columns
% Display the original gray scale image.
imshow(grayImage, []);
axis on;
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off')
% Pick some line to examine
rowToExamine = 50;
% Find columns in line 50 that are dark.
columns = find(grayImage(rowToExamine, :) < 100)
msgbox('Demo done. Look in command window for results.');
More Answers (2)
Francesco
on 24 Jan 2012
2 Comments
Image Analyst
on 24 Jan 2012
You're probably mixing up row and column with x and y. Be aware that x = column, and y = row. You need to index image arrays by row and column, not x and y so it's
imageArray(row, column, colorChannel)
which is
imageArray(y, x, colorChannel)
NOT
imageArray(x, y, colorChannel)
Francesco
on 25 Jan 2012
1 Comment
Image Analyst
on 25 Jan 2012
Please provide a snapshot of the rounded grid with a radius. Post it to tinypic.com. Do you mean like some kind of polar coordinates grid?
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