/// <summary>
/// Encodes pixel information into a Portable Networks Graphics (PNG) image file.
/// </summary>
/// <param name="bitmap">A RGB bitmap.</param>
/// <returns>A png image file</returns>
public IEnumerable <byte> Encode(IRgbBitmap bitmap)
{
// https://en.wikipedia.org/wiki/Portable_Network_Graphics
// https://tools.ietf.org/html/rfc2083
return(GetPngFileHeader()
.Concat(GetIHDRChunk(bitmap))
.Concat(GetIDATChunk(bitmap))
.Concat(GetIENDChunk()));
}
private IEnumerable <byte> GetIDATChunk(IRgbBitmap bitmap)
{
var imageData = bitmap.Pixels
.Chunk(bitmap.Width)
.Select(EncodeScanLine)
.Select(FilterImageData)
.SelectMany(x => x)
.ToList();
var compressedImageData = CompressImageData(imageData).ToList();
return(CreateChunk(ChunkType.IDAT, compressedImageData));
}
private IEnumerable <byte> GetIHDRChunk(IRgbBitmap bitmap)
{
var chunkData = GetUIntMsb((uint)bitmap.Width)
.Concat(GetUIntMsb((uint)bitmap.Height))
.Concat(new[]
{
(byte)BitDepth.BitsPerSampleIs8,
(byte)ColorType.ColorUsed,
(byte)CompressionMethod.DeflateInflateCompressionWith32KSlidingWindow,
(byte)FilterMethod.AdaptiveFilteringWithFiveBasicFilterTypes,
(byte)InterlaceMethod.NoInterlace
})
.ToList();
return(CreateChunk(ChunkType.IHDR, chunkData));
}
/// <summary>
/// Encodes pixel information into a bitmap image file.
/// </summary>
/// <param name="bitmap">A RGB bitmap.</param>
/// <returns>A bitmap image file</returns>
public IEnumerable <byte> Encode(IRgbBitmap bitmap)
{
// https://en.wikipedia.org/wiki/BMP_file_format
const int bitsPerPixel = 24;
var pixelArray = GetPixelArray(bitmap, bitsPerPixel);
var rawBitmapDataSize = (uint)pixelArray.Length;
var dibHeader = GetDibHeader(rawBitmapDataSize, (uint)bitmap.Width, (uint)bitmap.Height, bitsPerPixel).ToList();
const int bitmapHeaderSize = 14;
var bmpFileSize = (uint)(rawBitmapDataSize + dibHeader.Count + bitmapHeaderSize);
var bmpHeader = GetBmpHeader(bmpFileSize);
return(bmpHeader
.Concat(dibHeader)
.Concat(pixelArray));
}
private static byte[] GetPixelArray(IRgbBitmap bitmap, int bitsPerPixel)
{
var sourceRowSize = bitmap.Width * 3;
var sourcePixelData = bitmap.Pixels.ToRgbEncodedBytes().ToArray();
var destinationRowSize = (bitsPerPixel * bitmap.Width + 31) / 32 * 4;
var pixelArraySize = destinationRowSize * bitmap.Height;
var pixelArray = new byte[pixelArraySize];
for (var sourceRowIndex = 0; sourceRowIndex < bitmap.Height; sourceRowIndex++)
{
var sourceOffset = sourceRowIndex * bitmap.Width * 3;
var destinationOffset = (bitmap.Height - sourceRowIndex - 1) * destinationRowSize;
Buffer.BlockCopy(sourcePixelData, sourceOffset, pixelArray, destinationOffset, sourceRowSize);
}
return(pixelArray);
}
