Image content-type to file extension.

image_ext_map.rb

{
  'image/bmp' => '.bmp',
  'image/cgm' => '.cgm',
  'image/gif' => '.gif',
  'image/ief' => '.ief',
  'image/jpeg' => '.jpg',
  'image/png' => '.png',
  'image/svg+xml' => '.svg',
  'image/tiff' => '.tif',
  'image/vnd.djvu' => '.djv',
  'image/vnd.wap.wbmp' => '.wbmp',
  'image/x-cmu-raster' => '.ras',
  'image/x-icon' => '.ico',
  'image/x-portable-anymap' => '.pnm',
  'image/x-portable-bitmap' => '.pbm',
  'image/x-portable-graymap' => '.pgm',
  'image/x-portable-pixmap' => '.ppm',
  'image/x-rgb' => '.rgb',
  'image/x-xbitmap' => '.xbm',
  'image/x-xpixmap' => '.xpm',
  'image/x-xwindowdump' => '.xwd'
}