Generate your own DMC with free data matrix code generator.
Input the desired sequence in text field and press button generate DMC code. Data matrix code generator lets you generate codes of different sizes. Generator will output .png image file of desired size.
After creating DMC codes double check them if they can be read properly with your telephone or other kind of DMC scanner. In your data matrix code sequence you should use a minimal amount of characters possible. This will reflect in smaller sizes of data matrix code (14×14 size is smaller than 16×16) and consistently such codes on the same size are easily readable due to bigger module size.
Below you can see two sample DMC codes that were compiled with my data matrix code generator. Rendered DMC can be simply downloaded as .png files and used in your application. My proposal is that you use sufficient size in pixels for rendering and that you avoid any later re-sizing to bigger scale.