// AddFrame
public void AddFrame(SKPixmap frame, SKGifEncoderFrameInfo frameInfo = default)
{
using var bmp = new SKBitmap();
bmp.InstallPixels(frame);
AddFrame(bmp, frameInfo);
}
// Write*
private void WriteGraphicControlExtension(SKQuantizedFrame quantizedFrame, SKGifEncoderFrameInfo frameInfo)
{
stream.WriteByte(0x21); // extension introducer
stream.WriteByte(0xf9); // GCE label
stream.WriteByte(4); // data block size
int transp, disp;
if (frameInfo.TransparentColor != SKColor.Empty)
{
transp = 1;
disp = 2;
}
else
{
transp = 0;
disp = 0;
}
if (frameInfo.DisposalMethod >= 0)
{
disp = ((int)frameInfo.DisposalMethod) & 7; // user override
}
disp <<= 2;
// packed fields
stream.WriteByte(Convert.ToByte(
0 | // 1:3 reserved
disp | // 4:6 disposal
0 | // 7 user input - 0 = none
transp)); // 8 transparency flag
WriteShort(frameInfo.Duration / 10); // delay x 1/100 sec
// transparent color index
if (frameInfo.TransparentColor != SKColor.Empty)
{
stream.WriteByte(quantizer.GetColorIndex(frameInfo.TransparentColor));
}
else
{
stream.WriteByte(0);
}
stream.WriteByte(0); // block terminator
}
public void AddFrame(SKImage frame, SKGifEncoderFrameInfo frameInfo = default)
{
// make sure we have the pixels
var raster = frame.ToRasterImage(true);
try
{
using var pixmap = raster.PeekPixels();
AddFrame(pixmap, frameInfo);
}
finally
{
if (raster != frame)
{
raster.Dispose();
}
}
}
public void AddFrame(SKBitmap frame, SKGifEncoderFrameInfo frameInfo = default)
{
if (stream == null)
{
throw new InvalidOperationException("File is already completed.");
}
if (frame == null)
{
throw new ArgumentNullException(nameof(frame));
}
if (!firstFrame && frame.Info.Size != frameSize)
{
throw new InvalidOperationException("Image size does not match the first frame.");
}
var quantizedFrame = quantizer.Quantize(frame.Pixels);
if (firstFrame)
{
WriteString("GIF89a"); // header
frameSize = frame.Info.Size;
WriteLogicalScreenDescriptor(quantizedFrame);
WritePalette(quantizedFrame);
WriteNetscapeExtension();
}
WriteGraphicControlExtension(quantizedFrame, frameInfo);
WriteImageDescriptor(quantizedFrame);
if (!firstFrame)
{
WritePalette(quantizedFrame);
}
WritePixels(quantizedFrame);
firstFrame = false;
}
