public static CompressedImage Load(string path)
{
var result = new CompressedImage();
using (var sr = new FileStream(path, FileMode.Open))
{
var buffer = new byte[8];
sr.Read(buffer, 0, 4);
result.Width = BitConverter.ToInt32(buffer, 0);
sr.Read(buffer, 0, 4);
result.Height = BitConverter.ToInt32(buffer, 0);
sr.Read(buffer, 0, 4);
result.Quality = BitConverter.ToInt32(buffer, 0);
sr.Read(buffer, 0, 4);
var decodeTableSize = BitConverter.ToInt32(buffer, 0);
result.DecodeTable = new ConcurrentDictionary <BitsWithLength, byte>(new BitsWithLength.Comparer());
for (var i = 0; i < decodeTableSize; i++)
{
sr.Read(buffer, 0, 4);
var bits = BitConverter.ToInt32(buffer, 0);
sr.Read(buffer, 0, 4);
var bitsCount = BitConverter.ToInt32(buffer, 0);
var mappedByte = (byte)sr.ReadByte();
result.DecodeTable[new BitsWithLength {
Bits = bits, BitsCount = bitsCount
}] = mappedByte;
}
sr.Read(buffer, 0, 8);
result.BitsCount = BitConverter.ToInt64(buffer, 0);
sr.Read(buffer, 0, 4);
var compressedBytesCount = BitConverter.ToInt32(buffer, 0);
result.CompressedBytes = new byte[compressedBytesCount];
var totalRead = 0;
while (totalRead < compressedBytesCount)
{
totalRead += sr.Read(result.CompressedBytes, totalRead, compressedBytesCount - totalRead);
}
}
return(result);
}
public static void Decompress(string inputFile, int threadsCount, int compressionQuality)
{
try
{
var uncompressedFileName = inputFile + ".uncompressed." + compressionQuality + ".bmp";
var compressedImage = CompressedImage.Load(inputFile);
var uncompressedImage = Uncompress(compressedImage, threadsCount);
var grayscaleBmp = GrayscaleMatrixToBitmap(uncompressedImage);
grayscaleBmp.Save(uncompressedFileName, ImageFormat.Bmp);
}
catch (Exception e)
{
Console.WriteLine(e);
}
}
private static double[,] Uncompress(CompressedImage image, int degreeOfParallelism)
{
var allQuantizedBytes = HuffmanCodec.HuffmanCodec.Decode(image.CompressedBytes, image.DecodeTable, image.BitsCount, degreeOfParallelism);
var result = new double[image.Height, image.Width];
for (var y = 0; y < image.Height; y += DCTSize)
{
for (var x = 0; x < image.Width; x += DCTSize)
{
var quantizedBytes = new byte[DCTSize * DCTSize];
Array.Copy(allQuantizedBytes, y * image.Width + x * DCTSize, quantizedBytes, 0, quantizedBytes.Length);
var quantizedFreqs = ZigZagUnScan(quantizedBytes);
var channelFreqs = DeQuantize(quantizedFreqs, image.Quality);
var subMatrix = DCT.IDCT2D(channelFreqs, degreeOfParallelism);
subMatrix.ShiftMatrixValues(128);
result.SetSubmatrix(subMatrix, y, x);
}
}
return(result);
}
