private static Matrix Uncompress(CompressedImage image)
{
var result = new Matrix(image.Height, image.Width);
using (var allQuantizedBytes =
new MemoryStream(HuffmanCodec.Decode(image.CompressedBytes, image.DecodeTable, image.BitsCount)))
{
for (var y = 0; y < image.Height; y += DctSize)
{
for (var x = 0; x < image.Width; x += DctSize)
{
var _y = new double[DctSize, DctSize];
var cb = new double[DctSize, DctSize];
var cr = new double[DctSize, DctSize];
foreach (var channel in new [] { _y, cb, cr })
{
var quantizedBytes = new byte[DctSize * DctSize];
allQuantizedBytes.ReadAsync(quantizedBytes, 0, quantizedBytes.Length).Wait();
var quantizedFreqs = ZigZagUnScan(quantizedBytes);
var channelFreqs = DeQuantize(quantizedFreqs);
FastDct.InverseDct(channelFreqs, channel);
ShiftMatrixValues(channel, 128);
}
SetPixels(result, _y, cb, cr, y, x);
}
}
}
return(result);
}
private static CompressedImage Compress(Matrix matrix)
{
var allQuantizedBytes = new byte[matrix.Height * matrix.Width * 3];
Parallel.For(0, matrix.Height / DctSize, h =>
{
Parallel.For(0, matrix.Width / DctSize, w =>
{
var counter = 0;
foreach (var selector in new Func <Pixel, double>[]
{
p => 16.0 + (65.738 * p.C1 + 129.057 * p.C2 + 24.064 * p.C3) / 256.0,
p => 128.0 + (-37.945 * p.C1 - 74.494 * p.C2 + 112.439 * p.C3) / 256.0,
p => 128.0 + (112.439 * p.C1 - 94.154 * p.C2 - 18.285 * p.C3) / 256.0
})
{
var subMatrix = GetSubMatrix(matrix, h * DctSize, DctSize, w * DctSize, DctSize, selector);
ShiftMatrixValues(subMatrix, -128);
var channelFreqs = FastDct.Dct(subMatrix);
var quantizedFreqs = Quantize(channelFreqs);
var quantizedBytes = ZigZagScan(quantizedFreqs);
Array.Copy(quantizedBytes, 0, allQuantizedBytes,
h * 8 * matrix.Width * 3 + w * 64 * 3 + 64 * counter++, 64);
}
});
});
var compressedBytes = HuffmanCodec.Encode(allQuantizedBytes, out var decodeTable, out var bitsCount);
return(new CompressedImage
{
Quality = CompressionQuality,
CompressedBytes = compressedBytes,
BitsCount = bitsCount,
DecodeTable = decodeTable,
Height = matrix.Height,
Width = matrix.Width
});
}