public static List <PngDataChunk> GetChunks(byte[] imageBytes)
{
// Check for the eight-byte PNG signature
byte[] pngHeader = { 137, 80, 78, 71, 13, 10, 26, 10, };
for (int i = 0; i < 8; i++)
{
if (pngHeader[i] != imageBytes[i])
{
throw new ArgumentException("No PNG signature found");
}
}
List <PngDataChunk> chunks = new List <PngDataChunk>();
int k = 8;
while (true)
{
// get the data
UInt32 chunkLength = ByteUtils.ToUInt32(imageBytes, k);
k += 4;
ChunkType chunkType = new ChunkType(imageBytes, k);
k += 4;
byte[] chunkData = new byte[chunkLength];
for (int i = 0; i < chunkLength; i++, k++)
{
chunkData[i] = imageBytes[k];
}
UInt32 chunkCRC = ByteUtils.ToUInt32(imageBytes, k);
k += 4;
// create chunk from data and add it to list
PngDataChunk dataChunk = new PngDataChunk(chunkLength, chunkType, chunkData, chunkCRC);
chunks.Add(dataChunk);
// stop once we hit the IEND
if (chunkType.ToString() == "IEND")
{
break;
}
// TODO: proper error handling if IEND is never found
}
return(chunks);
}
/// <summary>
/// short description of given chunk type (if known)
/// </summary>
/// <param name="chunkType">chunk type to describe</param>
/// <returns>human-readable description, as string</returns>
public static string Description(ChunkType chunkType)
{
switch (chunkType.ToString())
{
// critical chunks
case "IHDR":
return("image header, the first chunk in a PNG datastream");
case "PLTE":
return("palette table");
case "IDAT":
return("image data chunk");
case "IEND":
return("image trailer, the last chunk in a PNG datastream");
// ancillary chunks
case "tRNS":
return("transparency information");
case "cHRM":
return("primary chromaticities and white point");
case "gAMA":
return("image gamma");
case "iCCP":
return("embedded ICC profile");
case "sBIT":
return("significant bits");
case "sRGB":
return("standard RGB color space");
case "tEXt":
return("textual data");
case "zTXt":
return("compressed textual data");
case "iTXt":
return("international textual data");
case "bKGD":
return("background color");
case "hIST":
return("image histogram");
case "pHYs":
return("physical pixel dimensions");
case "sPLT":
return("suggested palette");
case "tIME":
return("image last-modification time");
// ???
default:
return("unknown chunk");
}
}
