With contour of image how to change x and y axis?

I am plotting an contour of a matrix (image). How do I change the number of x and y axis to display angle values instead of pixel number?

If I know that 1 pixel is 0.135 mrad.

contour(imageslice)

with x-axis showing 1-30 pixel and y acis showing 1-70ish pixel.

Matrix consist of zeros and ones.

[DGM]

Steven's answer is probably the core of what you need, but I'm going to throw this out there.

This may or may not be relevant, but given that you're describing the data as an "image", bear in mind that representing the data with contour() will display it with a different YDir than might be expected of an image as displayed using image(), imagesc(), or imshow().

inpict = imread('cameraman.tif'); % a visually recognizable image
inpict = imgaussfilt(inpict,5); % make it smooth for a cleaner demo
inpict = im2double(inpict)*10 + 100; % put it on some arbitrary scale

imagesc(inpict) % origin is in the NW corner

figure
contour(inpict) % origin is in the SW corner

If you find that you need to also reorient the visualization so that they match, you can use some combination of setting the 'YDir' property of the parent axes, and using flip(..., 1) or flipud() on the data.

[Steven Lord]

The easiest way to reorient the visualization is probably to use the axis function.

inpict = imread('cameraman.tif'); % a visually recognizable image
inpict = imgaussfilt(inpict,5); % make it smooth for a cleaner demo
inpict = im2double(inpict)*10 + 100; % put it on some arbitrary scale

imagesc(inpict)
axis ij
title("With axis option ij")

figure
contour(inpict)
axis xy
title("With axis option xy")

[Happy PhD]

Ok, thanks. the "axis xy" help flip the axes so origo is at the lower corner. I decided to use "imagesc" since it gives me the crosssection image i needed. Thanks.

[DGM]

That works too.

Answer 1

[Steven Lord]

As written you're using the contour(Z) syntax shown in the Syntax section on the contour function documentation page. The Description of that syntax states "The column and row indices of Z are the x and y coordinates in the plane, respectively."

Instead it sounds like you want to use the contour(X, Y, Z) syntax, which is described as "contour(X,Y,Z) specifies the x and y coordinates for the values in Z."