/// <summary>
/// Identifies the chunk type from the chunk.
/// </summary>
/// <param name="chunk">The chunk.</param>
/// <returns>
/// The <see cref="T:byte[]"/> containing identifying information.
/// </returns>
/// <exception cref="ImageFormatException">
/// Thrown if the input stream is not valid.
/// </exception>
private byte[] ReadChunkType(PngChunk chunk)
{
byte[] typeBuffer = new byte[4];
int numBytes = this.currentStream.Read(typeBuffer, 0, 4);
if (numBytes >= 1 && numBytes <= 3)
{
throw new ImageFormatException("Image stream is not valid!");
}
char[] chars = new char[4];
chars[0] = (char)typeBuffer[0];
chars[1] = (char)typeBuffer[1];
chars[2] = (char)typeBuffer[2];
chars[3] = (char)typeBuffer[3];
chunk.Type = new string(chars);
return(typeBuffer);
}
/// <summary>
/// Reads a chunk from the stream.
/// </summary>
/// <returns>
/// The <see cref="PngChunk"/>.
/// </returns>
private PngChunk ReadChunk()
{
PngChunk chunk = new PngChunk();
if (this.ReadChunkLength(chunk) == 0)
{
return(null);
}
if (chunk.Length <= 0)
{
return(null);
}
byte[] typeBuffer = this.ReadChunkType(chunk);
this.ReadChunkData(chunk);
this.ReadChunkCrc(chunk, typeBuffer);
return(chunk);
}
/// <summary>
/// Reads the chunk data from the stream.
/// </summary>
/// <param name="chunk">The chunk.</param>
private void ReadChunkData(PngChunk chunk)
{
chunk.Data = new byte[chunk.Length];
this.currentStream.Read(chunk.Data, 0, chunk.Length);
}