public static byte[] Decode(byte[] decompressedData, ImageHeader header, byte bytesPerPixel, byte samplesPerPixel)
{
switch (header.InterlaceMethod)
{
case InterlaceMethod.None:
{
var bytesPerScanline = BytesPerScanline(header, samplesPerPixel);
var currentRowStartByteAbsolute = 1;
for (var rowIndex = 0; rowIndex < header.Height; rowIndex++)
{
var filterType = (FilterType)decompressedData[currentRowStartByteAbsolute - 1];
var previousRowStartByteAbsolute = (rowIndex) + (bytesPerScanline * (rowIndex - 1));
var end = currentRowStartByteAbsolute + bytesPerScanline;
for (var currentByteAbsolute = currentRowStartByteAbsolute; currentByteAbsolute < end; currentByteAbsolute++)
{
ReverseFilter(decompressedData, filterType, previousRowStartByteAbsolute, currentRowStartByteAbsolute, currentByteAbsolute, currentByteAbsolute - currentRowStartByteAbsolute, bytesPerPixel);
}
currentRowStartByteAbsolute += bytesPerScanline + 1;
}
return(decompressedData);
}
case InterlaceMethod.Adam7:
{
var pixelsPerRow = header.Width * bytesPerPixel;
var newBytes = new byte[header.Height * pixelsPerRow];
var i = 0;
var previousStartRowByteAbsolute = -1;
// 7 passes
for (var pass = 0; pass < 7; pass++)
{
var numberOfScanlines = Adam7.GetNumberOfScanlinesInPass(header, pass);
var numberOfPixelsPerScanline = Adam7.GetPixelsPerScanlineInPass(header, pass);
if (numberOfScanlines <= 0 || numberOfPixelsPerScanline <= 0)
{
continue;
}
for (var scanlineIndex = 0; scanlineIndex < numberOfScanlines; scanlineIndex++)
{
var filterType = (FilterType)decompressedData[i++];
var rowStartByte = i;
for (var j = 0; j < numberOfPixelsPerScanline; j++)
{
var pixelIndex = Adam7.GetPixelIndexForScanlineInPass(header, pass, scanlineIndex, j);
for (var k = 0; k < bytesPerPixel; k++)
{
var byteLineNumber = (j * bytesPerPixel) + k;
ReverseFilter(decompressedData, filterType, previousStartRowByteAbsolute, rowStartByte, i, byteLineNumber, bytesPerPixel);
i++;
}
var start = pixelsPerRow * pixelIndex.y + pixelIndex.x * bytesPerPixel;
Array.ConstrainedCopy(decompressedData, rowStartByte + j * bytesPerPixel, newBytes, start, bytesPerPixel);
}
previousStartRowByteAbsolute = rowStartByte;
}
}
return(newBytes);
}
default:
throw new ArgumentOutOfRangeException($"Invalid interlace method: {header.InterlaceMethod}.");
}
}
public static (byte bytesPerPixel, byte samplesPerPixel) GetBytesAndSamplesPerPixel(ImageHeader header)
{
var bitDepthCorrected = (header.BitDepth + 7) / 8;
var samplesPerPixel = SamplesPerPixel(header);
return((byte)(samplesPerPixel * bitDepthCorrected), samplesPerPixel);
}
internal Png(ImageHeader header, RawPngData data)
{
Header = header;
this.data = data ?? throw new ArgumentNullException(nameof(data));
}
