private void loadFrame(BufferFrame frame)
{
using var srcmeta = new ComPtr <IWICMetadataQueryReader>(((WicImageFrame)ctx.ImageFrame).WicMetadataReader);
frame.Disposal = (GifDisposalMethod)srcmeta.GetValueOrDefault <byte>(Wic.Metadata.Gif.FrameDisposal) == GifDisposalMethod.RestoreBackground ? GifDisposalMethod.RestoreBackground : GifDisposalMethod.Preserve;
frame.Delay = srcmeta.GetValueOrDefault <ushort>(Wic.Metadata.Gif.FrameDelay);
frame.Trans = srcmeta.GetValueOrDefault <bool>(Wic.Metadata.Gif.TransparencyFlag);
frame.Area = ctx.Source.Area;
var buff = frame.Source;
fixed(byte *pbuff = buff.Span)
ctx.Source.CopyPixels(frame.Area, buff.Stride, buff.Span.Length, (IntPtr)pbuff);
}
public static (int Left, int Top, int Width, int Height, bool Alpha, bool FullScreen, GifDisposalMethod Disposal) GetGifFrameInfo(WicGifContainer cont, ComPtr <IWICBitmapSource> frame, ComPtr <IWICMetadataQueryReader> meta)
{
uint width, height;
HRESULT.Check(frame.Get()->GetSize(&width, &height));
int left = 0, top = 0;
var disp = ((GifDisposalMethod)meta.GetValueOrDefault <byte>(Wic.Metadata.Gif.FrameDisposal)).Clamp();
bool trans = meta.GetValueOrDefault <bool>(Wic.Metadata.Gif.TransparencyFlag);
bool full = width >= cont.ScreenWidth && height >= cont.ScreenHeight;
if (!full)
{
left = meta.GetValueOrDefault <ushort>(Wic.Metadata.Gif.FrameLeft);
top = meta.GetValueOrDefault <ushort>(Wic.Metadata.Gif.FrameTop);
}
width = Math.Min(width, cont.ScreenWidth - (uint)left);
height = Math.Min(height, cont.ScreenHeight - (uint)top);
return(left, top, (int)width, (int)height, trans, full, disp);
}
public static void UpdateGifAnimationContext(WicGifContainer cont, ComPtr <IWICBitmapSource> src, ComPtr <IWICMetadataQueryReader> meta)
{
Debug.Assert(cont.AnimationContext is not null);
var anictx = cont.AnimationContext;
const int bytesPerPixel = 4;
var finfo = GetGifFrameInfo(cont, src, meta);
var fbuff = anictx.FrameBufferSource ??= new FrameBufferSource(cont.ScreenWidth, cont.ScreenHeight, PixelFormat.Bgra32Bpp);
var bspan = fbuff.Span;
fbuff.ResumeTiming();
// Most GIF viewers clear the background to transparent instead of the background color when the next frame has transparency
bool ftrans = meta.GetValueOrDefault <bool>(Wic.Metadata.Gif.TransparencyFlag);
if (!finfo.FullScreen && anictx.LastDisposal == GifDisposalMethod.RestoreBackground)
{
MemoryMarshal.Cast <byte, uint>(bspan).Fill(ftrans ? 0 : cont.BackgroundColor);
}
// Similarly, they overwrite a background color with transparent pixels but overlay instead when the previous frame is preserved
var fspan = bspan.Slice(finfo.Top * fbuff.Stride + finfo.Left * bytesPerPixel);
fixed(byte *buff = fspan)
{
if (!ftrans || anictx.LastDisposal == GifDisposalMethod.RestoreBackground)
{
var rect = new WICRect {
Width = finfo.Width, Height = finfo.Height
};
HRESULT.Check(src.Get()->CopyPixels(&rect, (uint)fbuff.Stride, (uint)fspan.Length, buff));
}
else
{
using var overlay = new OverlayTransform(fbuff, src.AsPixelSource(null, nameof(IWICBitmapFrameDecode), false), finfo.Left, finfo.Top, true, true);
overlay.CopyPixels(new PixelArea(finfo.Left, finfo.Top, finfo.Width, finfo.Height), fbuff.Stride, fspan.Length, (IntPtr)buff);
}
}
fbuff.PauseTiming();
}