bw_complemented = ~bw;

Second, imoverlay always uses the foreground (white pixels) to do the overlay. It sounds like you expected it to use foreground pixels sometimes and to use background pixels sometimes.

I want to overlay perimeters of two objects on top of each other. I used the function bwperim for the same. The output of bwperim is a white outline in a black background. I reverse this using a for loop to give me a black outline in a white background. imoverlay works perfectly in the first case. However it fails in the latter case. All I get is the outline of one object and background is the colour that I specify in the input of imoverlay. Can you please help me in this regard.

Thank you
Nancy

thicker_mask = imdilate(mask, ones(3, 3));

Can you please tell me how can I make imoverlay output line thicker?

So you need to do little extra work. One approach is to display the image as you already do, using imagesc and the desired colormap. Call imagesc with an output argument so you can save the handle to the created image object. Then call colorbar. Finally, set the CData of the image object to the overlay image created using the code shown in this post.

This overlay looks to be just about what I need.
I have a grayscale image that I currently use imagesc to display, using a stock colormap (jet). The values vary from 0 to perhaps 0.010 across the image. However, my object does not fill the entire image. All pixels outside the object are set to 0 using a mask. The data displayed is an error signal at each pixel.

Now, the issue is that as my object improves, the error at some (many, I hope) pixels approaches 0, and so those pixels are indistinguishable form the background or masked-off areas outside the object. I could set the masked areas to -1, and use CLIMS 0 to 0.010, but this still sets the masked areas to the 0 color.

Your overlay should do exactly what I need for the image. However, how do I now display a colorbar to indicate the original scaled colormap?

Thanks
Chuck

Yes, that is what I am looking to do but My “Mask” is not an image, it is a contour of densities (from the contourf function)so is there any way I can adapt what you had showed in “Image overlay using transparency” to suit my task?

Thank you for your help.

Rushil