//Decompress byte array into aBitmap with help of width, length and bitdepth
public static AccessibleBitmapBytewise Decompress(byte[] inBytes, AccessibleBitmapBytewise inBitmap, out byte[] restBytes, int byteLayer)
{
//Create a AccessibleBitmapbitwise class from the incoming AccessibleBitmapbytewise class, for better access to individual bits
AccessibleBitmapBitwise outputBitmap = new AccessibleBitmapBitwise(inBitmap);
//Create a BitStreamFIFO class from the incoming bytes, to feed into the decompression algorithms
BitStreamFIFO bitStream = new BitStreamFIFO(inBytes);
//Loop trough all bit layers of current byte layer
for (int i = byteLayer * 8; i < byteLayer * 8 + 8; i++)
{
//Read compression type as a 3-bit integer
int compressionType = bitStream.ReadInt(3);
//Decompress using the correct compression type
switch (compressionType)
{
//Uncompressed
case 0:
outputBitmap = UncompressedBitmapCompressorBitwise.Decompress(bitStream, outputBitmap, out bitStream, i);
break;
//Bit channel compressed as 8-bit integers
case 1:
outputBitmap = ByteArrayCompressorBitwise.Decompress(bitStream, outputBitmap, out bitStream, i);
break;
//Run length encoding
case 2:
outputBitmap = RunLengthEncodingCompressorBitwise.Decompress(bitStream, outputBitmap, out bitStream, i);
break;
//Run length encoding vertical
case 3:
outputBitmap = RunLengthEncodingCompressorVerticalBitwise.Decompress(bitStream, outputBitmap, out bitStream, i);
break;
//To add a decompression type add a new case like the existing ones
//Unknown compression type: error
default:
throw new Exception("Unexisting compression type");
}
}
//Remove the bytes used for this channel from the incoming byte array and pass the rest of them to the next channel
restBytes = new byte[bitStream.Length / 8];
Array.Copy(inBytes, inBytes.Length - (bitStream.Length / 8), restBytes, 0, restBytes.Length);
//Return the modified bitmap as AccessibleBitmapbytewise so the rest of the channels can be added to complete it
return(new AccessibleBitmapBytewise(outputBitmap.GetAccessibleBitmap()));
}
//Compress aBitmap into byte array
public static byte[] Compress(AccessibleBitmapBytewise source, int byteLayer)
{
//Loop trough all layers of bits, where possible at the same time
AccessibleBitmapBitwise aBitmap = new AccessibleBitmapBitwise(source);
BitStreamFIFO[] byteLayers = new BitStreamFIFO[8];
Parallel.For(byteLayer * 8, byteLayer * 8 + 8, (z, state) => //for(int z = byteLayer * 8; z < byteLayer * 8 + 8; z++)
{
//Compress image using all different compression techniques, where possible at the same time
BitStreamFIFO[] compressionTechniques = new BitStreamFIFO[4];
Parallel.For(0, compressionTechniques.Length, (i, state2) =>
{
switch (i)
{
//Uncompressed (only used if no compression technique is smaller)
case 0:
compressionTechniques[i] = UncompressedBitmapCompressorBitwise.Compress(aBitmap, z);
break;
//Compress bit channel as an integer array using several techniques, using 8-bit integers
case 1:
compressionTechniques[i] = ByteArrayCompressorBitwise.Compress(aBitmap, z);
break;
//Run length compression: save the length of a sequence of bit values instead of saving them seperately
case 2:
compressionTechniques[i] = RunLengthEncodingCompressorBitwise.Compress(aBitmap, z);
break;
//Run length compression vertical: run length compression, but scan the pixels horizontally, becouse with some images this yields better results
case 3:
compressionTechniques[i] = RunLengthEncodingCompressorVerticalBitwise.Compress(aBitmap, z);
break;
//To add a compression technique, add a new case like the existing ones and increase the length of new byte[??][]
}
});
//Choose the smallest compression type
//Initialize
int smallestID = 0; //The ID of the smallest compression type
int smallestSize = int.MaxValue; //The size ofthe smallest compression type: int.MaxValue is assigned to make sure that the first compression to be checked will be smaaller than this value
//Loop trough all saved compression techniques
for (int i = 0; i < compressionTechniques.Length; i++)
{
//If the current technique is smaller than the smallest technique which has been checked
if (compressionTechniques[i].Length < smallestSize)
{
//Mark this technique as smallest
smallestSize = compressionTechniques[i].Length;
smallestID = i;
}
}
//Merge the number of the compression type of this layer with corresponding bitStream
BitStreamFIFO tmpStream = new BitStreamFIFO();
tmpStream.Write(smallestID, 3); //This 3-bit integer indicates which technique the decompressor should use, and should be before the image data
byteLayers[z % 8] = BitStreamFIFO.Merge(tmpStream, compressionTechniques[smallestID]);
});
//Combine all bitstreams & convert the result to a byte array
byte[] outputStream = BitStreamFIFO.Merge(byteLayers).ToByteArray();
//Return the data of all the bit channels combined
return(outputStream);
}
