private int CalculateScanlineStep(PngColorTypeInformation colorTypeInformation) { int scanlineStep = 1; if (_header.BitDepth >= 8) { scanlineStep = (colorTypeInformation.ChannelsPerColor * _header.BitDepth) / 8; } return(scanlineStep); }
private int CalculateScanlineLength(PngColorTypeInformation colorTypeInformation) { int scanlineLength = (_header.Width * _header.BitDepth * colorTypeInformation.ChannelsPerColor); int amount = scanlineLength % 8; if (amount != 0) { scanlineLength += 8 - amount; } return(scanlineLength / 8); }
public Image Decode(Stream stream) { _stream = stream; _stream.Seek(8, SeekOrigin.Current); bool isEndChunckReached = false; PngChunk currentChunk = null; byte[] palette = null; byte[] paletteAlpha = null; using (MemoryStream dataStream = new MemoryStream()) { while ((currentChunk = ReadChunk()) != null) { if (isEndChunckReached) { throw new ImageFormatException("Image does not end with end chunk."); } if (currentChunk.Type == PngChunkTypes.Header) { ReadHeaderChunk(currentChunk.Data); ValidateHeader(); } else if (currentChunk.Type == PngChunkTypes.Data) { dataStream.Write(currentChunk.Data, 0, currentChunk.Data.Length); } else if (currentChunk.Type == PngChunkTypes.Palette) { palette = currentChunk.Data; } else if (currentChunk.Type == PngChunkTypes.PaletteAlpha) { paletteAlpha = currentChunk.Data; } else if (currentChunk.Type == PngChunkTypes.End) { isEndChunckReached = true; } } if (_header.Width > Image.MaxWidth || _header.Height > Image.MaxHeight) { throw new ArgumentOutOfRangeException( $"The input png '{ _header.Width }x{ _header.Height }' is bigger then the max allowed size '{ Image.MaxWidth }x{ Image.MaxHeight }'"); } byte[] pixels = new byte[_header.Width * _header.Height * 4]; PngColorTypeInformation colorTypeInformation = _colorTypes[_header.ColorType]; if (colorTypeInformation != null) { IColorReader colorReader = colorTypeInformation.CreateColorReader(palette, paletteAlpha); ReadScanlines(dataStream, pixels, colorReader, colorTypeInformation); } return(new Image(_header.Width, _header.Height, pixels)); } }
private void ReadScanlines(MemoryStream dataStream, byte[] pixels, IColorReader colorReader, PngColorTypeInformation colorTypeInformation) { dataStream.Position = 0; int scanlineLength = CalculateScanlineLength(colorTypeInformation); int scanlineStep = CalculateScanlineStep(colorTypeInformation); byte[] lastScanline = new byte[scanlineLength]; byte[] currScanline = new byte[scanlineLength]; byte a = 0; byte b = 0; byte c = 0; int row = 0, filter = 0, column = -1; using (var compressedStream = new ZlibInflateStream(dataStream)) { int readByte = 0; while ((readByte = compressedStream.ReadByte()) >= 0) { if (column == -1) { filter = readByte; column++; } else { currScanline[column] = (byte)readByte; if (column >= scanlineStep) { a = currScanline[column - scanlineStep]; c = lastScanline[column - scanlineStep]; } else { a = 0; c = 0; } b = lastScanline[column]; if (filter == 1) { currScanline[column] = (byte)(currScanline[column] + a); } else if (filter == 2) { currScanline[column] = (byte)(currScanline[column] + b); } else if (filter == 3) { currScanline[column] = (byte)(currScanline[column] + (byte)((a + b) / 2)); } else if (filter == 4) { currScanline[column] = (byte)(currScanline[column] + PaethPredicator(a, b, c)); } column++; if (column == scanlineLength) { colorReader.ReadScanline(currScanline, pixels, _header); column = -1; row++; var tmp = currScanline; currScanline = lastScanline; lastScanline = tmp; } } } } }
private void ReadScanlines(MemoryStream dataStream, byte[] pixels, IColorReader colorReader, PngColorTypeInformation colorTypeInformation) { dataStream.Position = 0; int scanlineLength = CalculateScanlineLength(colorTypeInformation); int scanlineStep = CalculateScanlineStep(colorTypeInformation); byte[] lastScanline = new byte[scanlineLength]; byte[] currScanline = new byte[scanlineLength]; byte a = 0; byte b = 0; byte c = 0; int row = 0, filter = 0, column = -1; using (var compressedStream = new ZlibInflateStream(dataStream)) { int readByte = 0; while ((readByte = compressedStream.ReadByte()) >= 0) { if (column == -1) { filter = readByte; column++; } else { currScanline[column] = (byte)readByte; if (column >= scanlineStep) { a = currScanline[column - scanlineStep]; c = lastScanline[column - scanlineStep]; } else { a = 0; c = 0; } b = lastScanline[column]; if (filter == 1) { currScanline[column] = (byte)(currScanline[column] + a); } else if (filter == 2) { currScanline[column] = (byte)(currScanline[column] + b); } else if (filter == 3) { currScanline[column] = (byte)(currScanline[column] + (byte)((a + b) / 2)); } else if (filter == 4) { currScanline[column] = (byte)(currScanline[column] + PaethPredicator(a, b, c)); } column++; if (column == scanlineLength) { colorReader.ReadScanline(currScanline, pixels, _header); column = -1; row++; var tmp = currScanline; currScanline = lastScanline; lastScanline = tmp; } } } } }
private int CalculateScanlineStep(PngColorTypeInformation colorTypeInformation) { int scanlineStep = 1; if (_header.BitDepth >= 8) { scanlineStep = (colorTypeInformation.ChannelsPerColor * _header.BitDepth) / 8; } return scanlineStep; }
private int CalculateScanlineLength(PngColorTypeInformation colorTypeInformation) { int scanlineLength = (_header.Width * _header.BitDepth * colorTypeInformation.ChannelsPerColor); int amount = scanlineLength % 8; if (amount != 0) { scanlineLength += 8 - amount; } return scanlineLength / 8; }