PSD/PDF2HTML developer, who creates clean and easy to read HTML+CSS. Most important work is that separate CSS for Mpdf has to be writtten so that the look & feel .i.e. display is exactly the same as it was in design PDF ) This HTML + CSS file itself will be passed down to mPDF, which generates from this HTML file a PDF document.
You need to create us a HTML file with a separate (or embedded) CSS styles.
Both CSS and HTML have to be easily readable to other developers (they will review your work) and of course the CSS's are all commented!
The key to this is the vertical bar has 0 to 7 scale defined. The scale of 1 to 7 should show depending upon what the maximum scale ( This come from the database ) also the bar should display accordingly with code and not bar PNG .