Contourf and a background image: how set transparency ?

Hello everyone. I have a contourf plot and I need to add in the same figure, as background image, a map. The issue is enhance trasparency of contourf layers.

I try to use my own code, helped by these forum, reported here:

% plotting image and contourf
img = imread('backgroud.png');
I=imagesc(img);
hold on;
[c,h]=contourf(X,Y,griddata(x,y,z,X,Y));

% setting trasparency
set(c, 'Renderer', 'OpenGL');
alphable = findobj(h, '-property', 'FaceAlpha');
set(alphable, 'FaceAlpha',0.5);

Even though the command 'Renderer' is applied directly to countourf's handles, this error occurs:

   The name 'Renderer' is not an accessible property for an instance of class
    'matlab.graphics.GraphicsPlaceholder'.

I'm working on a Matlab 2015b.

[Lujendra Ojha]

I have the same problem. Any updates?

[Shane L]

See this answer: https://www.mathworks.com/matlabcentral/answers/250279-how-to-make-contour-plots-transparent-in-matlab-r2015a

[Thoralf Stein]

https://de.mathworks.com/matlabcentral/answers/250279-how-to-make-contour-plots-transparent-in-matlab-r2015a#comment_689862

Answer 1

[Jeff Barton]

Undocumentedmatlab.com has the solution (which involves FacePrims field):

https://undocumentedmatlab.com/blog/customizing-contour-plots

(See "Customizing the color" section)

[Alan Meier]

Link update:

http://undocumentedmatlab.com/articles/customizing-contour-plots

[Kuifeng Zhao]

This works for me, Matlab 2020b. Thanks for sharing.