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);
}