title: How to set DPI in cairographics?
body: <p>When creating vector graphics for PDFs, I use one of the "create" functions for PDF rendering, for instance <code>cairo_pdf_surface_create_for_stream</code>. The signature of that function is:</p>
  
  <pre><code>cairo_surface_t *   cairo_pdf_surface_create_for_stream (cairo_write_func_t write_func,
                                                           void *closure,
                                                           double width_in_points,
                                                           double height_in_points);
  </code></pre>
  
  <p>Now, I can set the size of the surface in points, but the size of one point is seemingly hardcoded. in the description it says:</p>
  
  <blockquote>
    <p>width_in_points: width of the surface, in points (1 point == 1/72.0 inch)<br>
    height_in_points: height of the surface, in points (1 point == 1/72.0 inch)</p>
  </blockquote>
  
  <p>As you can see, 1pt = 1/72" (72 dpi). But how do I change that setting?</p>
  
  <p>I could factor something into the size, when using a different resolution and compensate that way, but this seems to me like worst practice ever.</p>