title: Cairo Library: produce a png file with white background
body: <p>I searched in INTERNET related to the subject but I found only people that want to save png file with the background transparent.</p>
  
  <p>I report belove the source code that at the moment I use and produces png with background transparent:</p>
  
  <pre><code>cairo_surface_t *surface; // Declarations
  cairo_t *cr;
  
  // Creations of the surface
  surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,3508,2480);
  
  // Contest
  cr = cairo_create(surface);
  
  // Moving the plot to center in the page
  cairo_translate(cr, 200,200);
  
  // Scaling the plot
  cairo_scale(cr,1.8,1.8);
  
  // Make all the necessary actions to produce the plot 
  do_drawing(cr);
  
  // write the plot on the file png
  cairo_surface_write_to_png(surface, "image.png");
  
  // End
  cairo_surface_destroy(surface);
  cairo_destroy(cr);
  </code></pre>
  
  <p>I used also the surface  CAIRO_FORMAT_RGB24 but I obtain a black rectangle like plot.</p>
  
  <p>Please could you help me?
  Thank You</p>