How to plot a point 300 pixels to the right in an image?

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Sean on 23 Feb 2015
Edited: Sean on 23 Feb 2015
So I've a variable created called 'J' which is situated at a certain point in the image, how do I plot it 300 pixels to the right of the point its situated? it seems to be moving along the wrong axis when Im trying to move it rightwards.

Answers (1)

Image Analyst
Image Analyst on 23 Feb 2015
What is J? I'll assume it's a 1 by 2 array with the x (column) coordinate, followed by the y (row) coordinate. Then to plot 300 columns to the right, do
plot(J(1)+300, J(2), 'r*', 'MarkerSize', 20, 'LineWidth', 2);
Make sure you're not making the very common mistake of mixing up x,y with row, column - that's almost certainly what you're doing. Remember images take indexes of (row, column) which is (y, x) while plot() takes (x,y) which is (column, row). Make sure you get it straight - like I said, this is a very common error.
Sean on 23 Feb 2015
For example, See J plotted as the blue star. I'm looking to get the centre of the line or midpoint. Thanks also for the help!

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