Below you can find a link to the MATLAB code that computes the L2 bitmap projection using the adaptive finite element method. In particular, this code has an implementation of the h-adaptation algorithm in MATLAB.

The code execution is also possible in the free Octave environment.
Download code or see Appendix 6.

In order to run the codes, we save them in the Octave working directory.
We set the variables with the path to the input file in tif format
\( filename = 'C://Users/Maciej/Dropbox/bitmapa.tif' \)
then we give the number of mesh elements in the x and y directions, and the degrees of B-spline in these directions
\( elementsx=4 \), \( elementsy=4 \) are the size of the initial grid.
We enter the maximum approximation error
\( maxerror=0.5 \),
and indicate whether the mesh edges are to be drawn \( maxlevel=4 \)
and indicate whether the mesh edges are to be drawn
\( edges=1 \).
Then we start the first procedure
\( bitmap\_h(filename,elementsx,elementsy,maxerror,maxlevel,edges) \).
After executing the adaptation sequence, the code draws the bitmap in the open window.