public static double[,] UncompressWithDCT(this CompressedImage image, int DCTSize)
{
var result = new double[image.Height, image.Width];
var freqNum = 0;
for (var y = 0; y < image.Height; y += DCTSize)
{
for (var x = 0; x < image.Width; x += DCTSize)
{
var channelFreqs = new double[DCTSize, DCTSize];
for (var i = 0; i < DCTSize; i++)
{
for (var j = 0; j < DCTSize; j++)
{
if (i + j < image.CompressionLevel)
{
channelFreqs[i, j] = image.Frequences[freqNum++];
}
}
}
var processedSubmatrix = DCTTransformer.IDCT2D(channelFreqs);
processedSubmatrix.ShiftMatrixValues(128);
result.SetSubmatrix(processedSubmatrix, y, x);
}
}
return(result);
}
public static double[,] ParallelUncompressWithDCT(this CompressedImage image, Options options)
{
const int DCTSize = 8;
var result = new double[image.Height, image.Width];
var blocksCount = image.Width * image.Height / (DCTSize * DCTSize);
var freqsCount = Enumerable.Range(1, image.CompressionLevel).Sum();
Parallel.For(0, blocksCount, new ParallelOptions {
MaxDegreeOfParallelism = options.Threads
},
blockIndex =>
{
var y = blockIndex / (image.Width / DCTSize);
var x = blockIndex % (image.Width / DCTSize);
var channelFreqs = new double[DCTSize, DCTSize];
var freqNum = blockIndex * freqsCount;
for (var i = 0; i < DCTSize; i++)
{
for (var j = 0; j < DCTSize; j++)
{
if (i + j < image.CompressionLevel)
{
channelFreqs[i, j] = image.Frequences[freqNum++];
}
}
}
var processedSubmatrix = DCTTransformer.IDCT2D(channelFreqs);
processedSubmatrix.ShiftMatrixValues(128);
result.SetSubmatrix(processedSubmatrix, y * DCTSize, x * DCTSize);
});
return(result);
}
public static CompressedImage CompressWithDCT(this double[,] channelPixels, int DCTSize, int compressionLevel = 4)
{
var frequencesPerBlock = -1;
var height = channelPixels.GetLength(0);
var width = channelPixels.GetLength(1);
var result = new List <double>();
for (var y = 0; y < height; y += DCTSize)
{
for (var x = 0; x < width; x += DCTSize)
{
var subMatrix = channelPixels.GetSubMatrix(y, DCTSize, x, DCTSize, DCTSize);
subMatrix.ShiftMatrixValues(-128);
var channelFreqs = DCTTransformer.DCT2D(subMatrix);
frequencesPerBlock = DCTSize * DCTSize;
for (var i = 0; i < DCTSize; i++)
{
for (var j = 0; j < DCTSize; j++)
{
if (i + j < compressionLevel)
{
result.Add(channelFreqs[i, j]);
continue;
}
channelFreqs[i, j] = 0;
frequencesPerBlock--;
}
}
}
}
return(new CompressedImage {
CompressionLevel = compressionLevel, FrequencesPerBlock = frequencesPerBlock, Frequences = result, Height = height, Width = width
});
}
private static List <double> GetFrequencesFromSubmatrix(double[,] channelPixels,
int DCTSize, int compressionLevel, int y, int x)
{
var subMatrix = channelPixels.GetSubMatrix(y, DCTSize, x, DCTSize, DCTSize);
subMatrix.ShiftMatrixValues(-128);
var localResult = new List <double>();
var channelFreqs = DCTTransformer.DCT2D(subMatrix);
for (var i = 0; i < DCTSize; i++)
{
for (var j = 0; j < DCTSize; j++)
{
if (i + j < compressionLevel)
{
localResult.Add(channelFreqs[i, j]);
continue;
}
channelFreqs[i, j] = 0;
}
}
return(localResult);
}