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using System;
using System.IO;
namespace Tango.AnimatedGif.Decoding
{
internal class GifImageDescriptor
{
public int Left { get; private set; }
public int Top { get; private set; }
public int Width { get; private set; }
public int Height { get; private set; }
public bool HasLocalColorTable { get; private set; }
public bool Interlace { get; private set; }
public bool IsLocalColorTableSorted { get; private set; }
public int LocalColorTableSize { get; private set; }
private GifImageDescriptor()
{
}
internal static GifImageDescriptor ReadImageDescriptor(Stream stream)
{
var descriptor = new GifImageDescriptor();
descriptor.Read(stream);
return descriptor;
}
private void Read(Stream stream)
{
byte[] bytes = new byte[9];
stream.ReadAll(bytes, 0, bytes.Length);
Left = BitConverter.ToUInt16(bytes, 0);
Top = BitConverter.ToUInt16(bytes, 2);
Width = BitConverter.ToUInt16(bytes, 4);
Height = BitConverter.ToUInt16(bytes, 6);
byte packedFields = bytes[8];
HasLocalColorTable = (packedFields & 0x80) != 0;
Interlace = (packedFields & 0x40) != 0;
IsLocalColorTableSorted = (packedFields & 0x20) != 0;
LocalColorTableSize = 1 << ((packedFields & 0x07) + 1);
}
}
}
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