[MATLAB] Retrieve data from .fig files

In MATLAB, when you saved an image into a .fig file and then want to retrieve the data from it, you can do as follows:

First, get a handle to the input .fig image by either doing

h = gcf;  % handle to the current displayed image.

or do (relate .fig format to .mat format):

h = hgload('display.fig');   % also give you the handle to the figure file

Now h is the handle to your image file. When you close the window of the displayed image, h is deleted.

Next step is to go down the hierarchy from the figure handle –> axes object –> image object (contains the data you need)

axesObjs = get(h, 'Children');       % get the axes object from the handle
imageObj = get(axesobj, 'Children')  % get the image object from the axes object

Now that you have your image object, you are able to retrieve all source of information of your .fig image file. Within this ‘imageObj’ object, some major information:

XData: the x-dimension size of your image
YData: the y-dimension size of your image
CData: this is the matrix of your image pixel intensities

There are other properties stored in the image object such as transparency, etc. But most of the time we care about the size and content of our image file. Last step is to retrieve the info you need using the ‘get’ function:

image = get(imageObj, 'CData'); % give you the image data

The second argument could be any property contained in the image object. (e.g. XData, YData, CData, etc.)


[Installation]Installing OpenCV 2.4.10 on Yosemite

Newest version of OpenCV 2.4.10 is out and ready for download!

Check if Xcode is installed

First check if Xcode is installed on your machine. To do that, open a Terminal and type:

$ xcode-select -p

This gives you the path to your installed xcode. If you see

$ /Applications/Xcode.app/Contents/Developer/

Your xcode is fully installed! You can also check the version of your xcode by typing:

$ /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -version

Download a Package Manager

Multiple package managers do the job. (e.g. Macports, Fink or Homebrew). In my case I used Macports, so everything below is based on Macports. You can check to see if it installed successfully by opening your terminal and typing:

$ port

Use Macports to get cmake

In your terminal, type in the following:

$ sudo port install cmake

This will go fetch cmake and its dependencies and install them onto your system. You can check to see if cmake is installed by typing

$ cmake

Download and Build OpenCV

Sometimes opencv.org just failed to load. I downloaded the latest OpenCV from SourceForge. (They update it so you always get the newest version!)

Download the .zip file and unzip it to a directory. We are going to build OpenCV using cmake. In terminal, go to the directory where OpenCV was extracted to. Type in the following to make a separate directory for building purpose:

mkdir build
cd build
cmake -G "Unix Makefiles" ..

Notice that there is a space before the two ending dots.

Now, we can make OpenCV. Type the following in:

make -j8
sudo make install

This should now build OpenCV into your /usr/local/ directory.

If you want to double check to ensure it is installed, go to the directory /usr/local/lib (to do this, click the ‘Go’ tab at the top of your screen and click ‘Go to folder’ to type in the directory). Clean up the files by ‘Date Modified’, you can see those **2.4.10.dylib files.

Congratulations! Now you can do a bunch of super duper cool stuff with this awesome vision tool.