/// <summary>
/// Write the PNG file bytes to the provided stream.
/// </summary>
public void Save(Stream outputStream, SaveOptions options = null)
{
options = options ?? new SaveOptions();
byte[] palette = null;
var dataLength = rawData.Length;
var bitDepth = 8;
if (!hasTooManyColorsForPalette)
{
var paletteColors = colorCounts.OrderByDescending(x => x.Value).Select(x => x.Key).ToList();
bitDepth = paletteColors.Count >= 128 ? 8 : 4;
var samplesPerByte = bitDepth == 8 ? 1 : 2;
var applyShift = samplesPerByte == 2;
palette = new byte[3 * paletteColors.Count];
for (var i = 0; i < paletteColors.Count; i++)
{
var color = ColorIntToPixel(paletteColors[i]);
var startIndex = i * 3;
palette[startIndex++] = color.r;
palette[startIndex++] = color.g;
palette[startIndex] = color.b;
}
var rawDataIndex = 0;
for (var y = 0; y < height; y++)
{
// None filter - we don't use filtering for palette images.
rawData[rawDataIndex++] = 0;
for (var x = 0; x < width; x++)
{
var index = ((y * width * bytesPerPixel) + y + 1) + (x * bytesPerPixel);
var r = rawData[index++];
var g = rawData[index++];
var b = rawData[index];
var colorInt = PixelToColorInt(r, g, b);
var value = (byte)paletteColors.IndexOf(colorInt);
if (applyShift)
{
// apply mask and shift
var withinByteIndex = x % 2;
if (withinByteIndex == 1)
{
rawData[rawDataIndex] = (byte)(rawData[rawDataIndex] + value);
rawDataIndex++;
}
else
{
rawData[rawDataIndex] = (byte)(value << 4);
}
}
else
{
rawData[rawDataIndex++] = value;
}
}
}
dataLength = rawDataIndex;
File.WriteAllBytes(@"C:\temp\mycompressed.bin", rawData.Take(dataLength).ToArray());
}
else
{
AttemptCompressionOfRawData(rawData, options);
}
outputStream.Write(HeaderValidationResult.ExpectedHeader, 0, HeaderValidationResult.ExpectedHeader.Length);
var stream = new PngStreamWriteHelper(outputStream);
stream.WriteChunkLength(13);
stream.WriteChunkHeader(ImageHeader.HeaderBytes);
StreamHelper.WriteBigEndianInt32(stream, width);
StreamHelper.WriteBigEndianInt32(stream, height);
stream.WriteByte((byte)bitDepth);
var colorType = ColorType.ColorUsed;
if (hasAlphaChannel)
{
colorType |= ColorType.AlphaChannelUsed;
}
if (palette != null)
{
colorType |= ColorType.PaletteUsed;
}
stream.WriteByte((byte)colorType);
stream.WriteByte((byte)CompressionMethod.DeflateWithSlidingWindow);
stream.WriteByte((byte)FilterMethod.AdaptiveFiltering);
stream.WriteByte((byte)InterlaceMethod.None);
stream.WriteCrc();
if (palette != null)
{
stream.WriteChunkLength(palette.Length);
stream.WriteChunkHeader(Encoding.ASCII.GetBytes("PLTE"));
stream.Write(palette, 0, palette.Length);
stream.WriteCrc();
}
var imageData = Compress(rawData, dataLength, options);
stream.WriteChunkLength(imageData.Length);
stream.WriteChunkHeader(Encoding.ASCII.GetBytes("IDAT"));
stream.Write(imageData, 0, imageData.Length);
stream.WriteCrc();
stream.WriteChunkLength(0);
stream.WriteChunkHeader(Encoding.ASCII.GetBytes("IEND"));
stream.WriteCrc();
}