public static void EncodeAsync(byte[] dataRgba, int stride, Action <Exception, byte[]> callback)
{
ThreadPool.QueueUserWorkItem((state) =>
{
try
{
byte[] png = PngEncoder.Encode(dataRgba, stride);
callback(null, png);
}
catch (Exception ex)
{
callback(ex, null);
throw;
}
}, null);
}
private void EncodeCallback(object state)
{
byte[] byteData = this.NativeData.ToArray();
int downsampledStride;
byteData = Downsampler.Downsample(byteData, this.Width * 4, this.MaximumWidth, this.MaximumHeight, out downsampledStride);
if (this.Type == ScreenshotType.Png)
{
byteData = PngEncoder.Encode(byteData, downsampledStride);
}
if (this.Callback != null)
{
this.Callback(byteData, this.State);
}
this.NativeData.Dispose();
this.IsInUse = false;
}
public static byte[] Encode(byte[] dataRgba, int stride)
{
// Preconditions
if (dataRgba == null)
{
throw new ArgumentNullException("dataRgba");
}
if (dataRgba.Length == 0)
{
throw new ArgumentException("The data length must be greater than 0.");
}
if (stride == 0)
{
throw new ArgumentException("The stride must be greater than 0.");
}
if (stride % 4 != 0)
{
throw new ArgumentException("The stride must be evenly divisible by 4.");
}
if (dataRgba.Length % 4 != 0)
{
throw new ArgumentException("The data must be evenly divisible by 4.");
}
if (dataRgba.Length % stride != 0)
{
throw new ArgumentException("The data must be evenly divisible by the stride.");
}
// Dimensions
int pixels = dataRgba.Length / 4;
int width = stride / 4;
int height = pixels / width;
// IHDR Chunk
byte[] ihdrData = new byte[13];
int ihdrPosition = 0;
ihdrData.AppendInt(ref ihdrPosition, width);
ihdrData.AppendInt(ref ihdrPosition, height);
ihdrData.AppendByte(ref ihdrPosition, 8); // Bit depth
ihdrData.AppendByte(ref ihdrPosition, 6); // Color type (color + alpha)
ihdrData.AppendByte(ref ihdrPosition, 0); // Compression method (always 0)
ihdrData.AppendByte(ref ihdrPosition, 0); // Filter method (always 0)
ihdrData.AppendByte(ref ihdrPosition, 0); // Interlace method (no interlacing)
// IDAT Chunk
byte[] scanlineData = new byte[dataRgba.Length + height];
int scanlineDataPosition = 0;
int scanlinePosition = 0;
for (int i = 0; i < dataRgba.Length; i++)
{
if (scanlinePosition >= stride)
{
scanlinePosition = 0;
}
if (scanlinePosition == 0)
{
scanlineData.AppendByte(ref scanlineDataPosition, 0);
}
scanlineData.AppendByte(ref scanlineDataPosition, dataRgba[i]);
scanlinePosition++;
}
byte[] compressedScanlineData = PngEncoder.Compress(scanlineData);
byte[] idatData = new byte[1 + 1 + compressedScanlineData.Length + 4];
int idatPosition = 0;
idatData.AppendByte(ref idatPosition, 0x78); // Zlib header
idatData.AppendByte(ref idatPosition, 0x9C); // Zlib header
idatData.AppendBytes(ref idatPosition, compressedScanlineData); // Data
idatData.AppendUInt(ref idatPosition, PngEncoder.Adler32(scanlineData)); // Adler32 checksum
// Png
byte[] png = new byte[8 + ihdrData.Length + 12 + idatData.Length + 12 + 12];
// Position
int position = 0;
// Signature
png.AppendByte(ref position, 0x89); // High bit set
png.AppendByte(ref position, 0x50); // P
png.AppendByte(ref position, 0x4E); // N
png.AppendByte(ref position, 0x47); // G
png.AppendByte(ref position, 0x0D); // DOS line ending
png.AppendByte(ref position, 0x0A); // DOS line ending
png.AppendByte(ref position, 0x1A); // DOS end of file
png.AppendByte(ref position, 0x0A); // Unix line ending
// Assemble
png.AppendChunk(ref position, "IHDR", ihdrData);
png.AppendChunk(ref position, "IDAT", idatData);
png.AppendChunk(ref position, "IEND", new byte[0]);
// Return
return(png);
}
