How to render text in .NET in the same size as browsers does given CSS for the text

Question

I am trying to create a \"save webpage as bitmap\"-function on a website and i have some problems rendering the text in the correct size on the server side.

The font

Answer 1

Actually, the docs say "em-size", not "em-point" ("The em-size, in points, of the new font"). It's asking you to specify the size in points. There are 72 points per inch. You need to figure out the DPI of the user's screen and the DPI of the canvas you're drawing on and multiply the 16px size by the difference in that ratio.

e.g.

(CSS_Font_Size_Pixels * Canvas_DPI) / (User_Screen_DPI * 72) = Equivalent_Point_Size

You could save yourself a mathematical operation by using the Font constructor overload that takes a GraphicUnit and specify Pixels. This way, the appropriate size would be:

(CSS_Font_Size_Pixels  / User_Screen_DPI) * Canvas_DPI