/// <summary>
/// Verifies that a JPEG File Interchange Format image falls inside the
/// AOL-required dimensions: between 48x48 and 50x50
/// </summary>
/// <param name="fs">
/// An opened <see cref="FileStream"/> two bytes into the JFIF.
/// </param>
/// <returns>
/// <c>true</c> if the JFIF fits in the required dimensions,
/// <c>false</c> otherwise.
/// </returns>
private static bool VerifyJFIF(FileStream fs)
{
// Scroll to the Start Frame 0 position in the image
bool foundframe0 = false;
while (!foundframe0 && fs.Position < fs.Length)
{
if (fs.ReadByte() == 0xFF && fs.ReadByte() == 0xC0)
{
break;
}
}
if (fs.Position == fs.Length)
{
return(false);
}
// Three skip bytes, then the next four are the width and height (in NBO format)
byte[] size = new byte[7];
if (fs.Read(size, 0, size.Length) != size.Length)
{
return(false);
}
ushort height = 0, width = 0;
using (ByteStream bstream = new ByteStream(size))
{
bstream.AdvanceToPosition(3);
height = bstream.ReadUshort();
width = bstream.ReadUshort();
}
return((width >= 48 && width <= 50) && (height >= 48 && height <= 50));
}