how to superimpose a surface plot on a different size gray scale image

I have a grayscale image which has a size of 2448*2048.

I have a surface plot on a mesh grid of (1:110, 1:92)

Their data numbers are totally different. How can I make the grayscale image as the background and make the surface fit right onto it and transparent so that I can see the background image through the surface plot at the same I can still draw ROI on the surface plot with the roipoly function?

Answer 1

[Walter Roberson]

Look at the XData and YData parameters of image(): you can specify the coordinates of the centers of the bottom left and upper right pixels. Getting them to line up exactly with the boundaries of (for example) 1:110 is a bit of a nuisance because you have to account for the 1/2 pixel, which will be 1/2448/2 or 1/2048/2 of the image, but you can do it (but it's usually easier to just let half a pixel hang outside the surf plot.)

When you create the surf() plot, you will probably want to use 'edgecolor', 'none'. Make it transparent by passing in 'AlphaData', such as .8 .

[Huayan Wang]

Hi Walter,

Thank you for your answer. This helps me most of the part. Only one thing I didn't expect.

You can refer to the attached image.

This left one is a surface plot, the middle one is a grayscale image. I plot them into one figure and got the right one.

The problem is that I have some negative value point on the surface plot. It looks like that the grayscale image will cover the negative value. I want all surface plot is above of the background image.

Is there a way to do that?

Thank you!

[Walter Roberson]

All points in the image() are considered to have Z of 0, so Z below 0 on the surface plot would be "behind" the image.

You should consider using

surf(X, Y, ones(size(Z)), Z)

so that your Z data gets interpreted as "color" and so MATLAB thinks your surface is at 1 (and thus "above" your image.)

[Huayan Wang]

This works very well, exactly what I want.

Thank you so much!