Comments on: Image overlay using transparency

By: Steve

Steve — Fri, 13 Nov 2009 18:21:24 +0000

Amina—I don’t understand. Can you be more specific? Do you mean superimpose plotted 2-D graphics over an image?

By: amina

amina — Fri, 13 Nov 2009 17:21:22 +0000

Hello!
i want to ask you that how can I add a small figure on a particular pixel(as its center) of another large image?

Thanks!

By: Steve

Steve — Thu, 08 Oct 2009 12:32:35 +0000

Kai—You can control the size of the figure explicity by setting the figure properties. You can also control the size of the axes object in which the image is drawn by setting the axes properties. See the MATLAB Graphics doc for information about the ‘Units’ and ‘Position’ properties for figure and axes objects.

By: Kai

Kai — Thu, 08 Oct 2009 12:29:36 +0000

Hallo Steve,

thanks for your help. The problem was, that my images are imported as rgb colored pics. After converting with rgb2gray, the program run perfectly.

Another question. If I use print to save the current figure, the image will be saved bigger than I need. At the moment I reload the picture cut it and save it again. How can I replace this second step. Can I set a size for my figure. Or is there an option to save the overlayed axes without margin.

Thanks for help
Kai

By: Steve

Steve — Mon, 05 Oct 2009 14:44:14 +0000

Kai—Use dbstop if error to get MATLAB to stop when the error occurs. Then examine the variables in your code to see what might be the problem. For example, look at the size of the variable green in the call to imshow. Also, I encourage you to use the "Get the MATLAB code" link at the bottom of the blog post to make sure you are using the same code that I posted. Regarding saving a figure without it appearing on screen—create an invisible figure:

fig = figure('Visible', 'off')

Then plot into the figure and use print -dpng to print the figure.

By: Kai

Kai — Wed, 30 Sep 2009 09:01:34 +0000

Hello Steve,

I’ve got another problem concerning the first example.
After processing the line “set(h, ‘AlphaData’, alpha_data);” my figure shows only the a few rows of the image. The Alpha_data and the image have the same dimension. This problem will also appear, if I run the script as shown in this article.
Is there an opportunity to overlay some picture, add text and save the “figure” as png or jpg without displaying it on the screen?

By: Kai

Kai — Tue, 22 Sep 2009 14:08:45 +0000

I tried to use your second example to overlay a picture with a transparent box. But I get an unknow mistake:”??? Error using ==> imageDisplayParseInputs>validateCData at 249
Unsupported dimension

Error in ==> imageDisplayParseInputs at 202
common_args.CData = validateCData(common_args.CData,image_type);

Error in ==> imshow at 173
[common_args,specific_args] = …

Error in ==> plot at 84
h = imshow(green);” What is the Problem. I use Matlab 7.5.0

By: Steve

Steve — Mon, 27 Jul 2009 13:53:03 +0000

Jay—Set the figure to have the desired size and units, set the figure’s PaperPositionMode to ‘auto’, and then use the -r switch with print.

By: Jay

Jay — Sun, 26 Jul 2009 18:30:03 +0000

I am trying to do something similar to this, but I want to overlay a plot onto the image. When I try to save it with the print command, I get a new image that is a different resolution. Do you know of a way to print to a specified resolution (say 1600×1200 pixels)?
Thanks

By: Steve

Steve — Thu, 04 Jun 2009 01:29:29 +0000

Zhenghui—Click on the “Get the MATLAB code” link at the bottom of the post.