/// <summary>
/// Calculates the length of the scanline.
/// </summary>
/// <param name="colorTypeInformation">The color type information.</param>
/// <param name="header">The header.</param>
/// <returns>The scanline length</returns>
private static int CalculateScanlineLength(ColorTypeInformation colorTypeInformation, Header header)
{
int ScanlineLength = header.Width * header.BitDepth * colorTypeInformation.ScanlineFactor;
int Amount = ScanlineLength % 8;
if (Amount != 0)
{
ScanlineLength += 8 - Amount;
}
return(ScanlineLength / 8);
}
/// <summary>
/// Reads the scanlines.
/// </summary>
/// <param name="dataStream">The data stream.</param>
/// <param name="pixels">The pixels.</param>
/// <param name="colorReader">The color reader.</param>
/// <param name="colorTypeInformation">The color type information.</param>
/// <param name="header">The header.</param>
private void ReadScanlines(MemoryStream dataStream, Color[] pixels, IColorReader colorReader, ColorTypeInformation colorTypeInformation, Header header)
{
dataStream.Seek(0, SeekOrigin.Begin);
var ScanlineLength = CalculateScanlineLength(colorTypeInformation, header);
var ScanlineStep = CalculateScanlineStep(colorTypeInformation, header);
byte[] LastScanline = new byte[ScanlineLength];
byte[] CurrentScanline = new byte[ScanlineLength];
int Filter = 0, Column = -1, Row = 0;
using (InflateStream CompressedStream = new InflateStream(dataStream))
{
int ReadByte;
while ((ReadByte = CompressedStream.ReadByte()) >= 0)
{
if (Column == -1)
{
Filter = ReadByte;
++Column;
}
else
{
CurrentScanline[Column] = (byte)ReadByte;
byte a;
byte b;
byte c;
if (Column >= ScanlineStep)
{
a = CurrentScanline[Column - ScanlineStep];
c = LastScanline[Column - ScanlineStep];
}
else
{
a = 0;
c = 0;
}
b = LastScanline[Column];
switch (Filter)
{
case 1:
CurrentScanline[Column] = (byte)(CurrentScanline[Column] + a);
break;
case 2:
CurrentScanline[Column] = (byte)(CurrentScanline[Column] + b);
break;
case 3:
CurrentScanline[Column] = (byte)(CurrentScanline[Column] + (byte)((a + b) / 2));
break;
case 4:
CurrentScanline[Column] = (byte)(CurrentScanline[Column] + PaethPredicator(a, b, c));
break;
}
++Column;
if (Column == ScanlineLength)
{
colorReader.ReadScanline(CurrentScanline, pixels, header, Row);
++Row;
Column = -1;
var Holder = CurrentScanline;
CurrentScanline = LastScanline;
LastScanline = Holder;
}
}
}
}
//dataStream.Seek(0, SeekOrigin.Begin);
//var ScanlineLength = CalculateScanlineLength(colorTypeInformation, header);
//var ScanlineStep = CalculateScanlineStep(colorTypeInformation, header);
//byte[] LastScanline = new byte[ScanlineLength];
//byte[] CurrentScanline = new byte[ScanlineLength];
//using (InflateStream CompressedStream = new InflateStream(dataStream))
//{
// using (MemoryStream DecompressedStream = new MemoryStream())
// {
// CompressedStream.CopyTo(DecompressedStream);
// DecompressedStream.Flush();
// byte[] DecompressedArray = DecompressedStream.ToArray();
// for (int y = 0, Column = 0; y < header.Height; ++y, Column += (ScanlineLength + 1))
// {
// Array.Copy(DecompressedArray, Column + 1, CurrentScanline, 0, ScanlineLength);
// if (DecompressedArray[Column] < 0)
// break;
// byte[] Result = Filters[(FilterType)DecompressedArray[Column]].Decode(CurrentScanline, LastScanline, ScanlineStep);
// colorReader.ReadScanline(Result, pixels, header, y);
// Array.Copy(CurrentScanline, LastScanline, ScanlineLength);
// }
// }
//}
}
/// <summary>
/// Calculates the scanline step.
/// </summary>
/// <param name="colorTypeInformation">The color type information.</param>
/// <param name="header">The header.</param>
/// <returns>The scanline step</returns>
private static int CalculateScanlineStep(ColorTypeInformation colorTypeInformation, Header header)
{
return(header.BitDepth >= 8 ? (colorTypeInformation.ScanlineFactor * header.BitDepth) / 8 : 1);
}
