How to draw contour lines into a filled 2-D patch object?

Hallo!

I have a filled 2-D patch object as a figure, for example like this one:

Now I would like to draw level lines into this image, which limits areas of different values (color values). Furthermore I would like to set the number of level lines on my own (1 line, which separates 2 areas; 2 lines, which separate 3 areas; etc...).

I know there is the 'contour' or 'contourf' commands, which deal with my issue. But in my case I have a patch image and would like to keep this image and just draw the level lines into this image.

The patch object is of this form: 'patch(X,Y,C,'PropertyName',propertyvalue...)'

Answer 1

[Jan]

What about drawing a contour plot on top of this patch?

[Paul]

The problem is:

When I use contour(Z) or contourf(Z), I need a matrix Z, which is a n-m-Matrix containing the values. Now how to transform my patch object into a matrix Z? Or how can contour be used on a patch?

[Jan]

contour cannot be used on a patch, but only in the same axes as the patch, such that the drawing appear on top of each other. You do not have to convert a patch in a matrix, but you need the values only. And these values should be available, when you create the patch object.