/// <summary>
/// Decodes the raw pixel data row by row
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="compressedStream">The compressed pixel data stream.</param>
/// <param name="image">The image to decode to.</param>
private void DecodePixelData <TPixel>(Stream compressedStream, ImageFrame <TPixel> image)
where TPixel : struct, IPixel <TPixel>
{
while (this.currentRow < this.header.Height)
{
int bytesRead = compressedStream.Read(this.scanline.Array, this.currentRowBytesRead, this.bytesPerScanline - this.currentRowBytesRead);
this.currentRowBytesRead += bytesRead;
if (this.currentRowBytesRead < this.bytesPerScanline)
{
return;
}
this.currentRowBytesRead = 0;
var filterType = (FilterType)this.scanline[0];
switch (filterType)
{
case FilterType.None:
break;
case FilterType.Sub:
SubFilter.Decode(this.scanline, this.bytesPerPixel);
break;
case FilterType.Up:
UpFilter.Decode(this.scanline, this.previousScanline);
break;
case FilterType.Average:
AverageFilter.Decode(this.scanline, this.previousScanline, this.bytesPerPixel);
break;
case FilterType.Paeth:
PaethFilter.Decode(this.scanline, this.previousScanline, this.bytesPerPixel);
break;
default:
throw new ImageFormatException("Unknown filter type.");
}
this.ProcessDefilteredScanline(this.scanline.Array, image);
Swap(ref this.scanline, ref this.previousScanline);
this.currentRow++;
}
}
private void DecodePixelData(byte[][] pixelData)
{
// data = new Color[_width * _height];
_colors = new Color[width * height];
pixels = new int[width * height];
var previousScanline = new byte[bytesPerScanline];
for (var y = 0; y < height; ++y)
{
var scanline = pixelData[y];
byte[] defilteredScanline;
switch (scanline[0])
{
case 0:
defilteredScanline = NoneFilter.Decode(scanline);
break;
case 1:
defilteredScanline = SubFilter.Decode(scanline, bytesPerPixel);
break;
case 2:
defilteredScanline = UpFilter.Decode(scanline, previousScanline);
break;
case 3:
defilteredScanline = AverageFilter.Decode(scanline, previousScanline, bytesPerPixel);
break;
case 4:
defilteredScanline = PaethFilter.Decode(scanline, previousScanline, bytesPerPixel);
break;
default:
throw new Exception("Unknown filter type.");
}
previousScanline = defilteredScanline;
ProcessDefilteredScanline(defilteredScanline, y);
}
}
/// <summary>
/// Decodes the raw interlaced pixel data row by row
/// <see href="https://github.com/juehv/DentalImageViewer/blob/8a1a4424b15d6cc453b5de3f273daf3ff5e3a90d/DentalImageViewer/lib/jiu-0.14.3/net/sourceforge/jiu/codecs/PNGCodec.java"/>
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="compressedStream">The compressed pixel data stream.</param>
/// <param name="image">The current image.</param>
private void DecodeInterlacedPixelData <TPixel>(Stream compressedStream, ImageFrame <TPixel> image)
where TPixel : struct, IPixel <TPixel>
{
while (true)
{
int numColumns = this.ComputeColumnsAdam7(this.pass);
if (numColumns == 0)
{
this.pass++;
// This pass contains no data; skip to next pass
continue;
}
int bytesPerInterlaceScanline = this.CalculateScanlineLength(numColumns) + 1;
while (this.currentRow < this.header.Height)
{
int bytesRead = compressedStream.Read(this.scanline.Array, this.currentRowBytesRead, bytesPerInterlaceScanline - this.currentRowBytesRead);
this.currentRowBytesRead += bytesRead;
if (this.currentRowBytesRead < bytesPerInterlaceScanline)
{
return;
}
this.currentRowBytesRead = 0;
Span <byte> scanSpan = this.scanline.Slice(0, bytesPerInterlaceScanline);
Span <byte> prevSpan = this.previousScanline.Slice(0, bytesPerInterlaceScanline);
var filterType = (FilterType)scanSpan[0];
switch (filterType)
{
case FilterType.None:
break;
case FilterType.Sub:
SubFilter.Decode(scanSpan, this.bytesPerPixel);
break;
case FilterType.Up:
UpFilter.Decode(scanSpan, prevSpan);
break;
case FilterType.Average:
AverageFilter.Decode(scanSpan, prevSpan, this.bytesPerPixel);
break;
case FilterType.Paeth:
PaethFilter.Decode(scanSpan, prevSpan, this.bytesPerPixel);
break;
default:
throw new ImageFormatException("Unknown filter type.");
}
Span <TPixel> rowSpan = image.GetPixelRowSpan(this.currentRow);
this.ProcessInterlacedDefilteredScanline(this.scanline.Array, rowSpan, Adam7FirstColumn[this.pass], Adam7ColumnIncrement[this.pass]);
Swap(ref this.scanline, ref this.previousScanline);
this.currentRow += Adam7RowIncrement[this.pass];
}
this.pass++;
this.previousScanline.Clear();
if (this.pass < 7)
{
this.currentRow = Adam7FirstRow[this.pass];
}
else
{
this.pass = 0;
break;
}
}
}