public ImmutableArray <ImageTile> DetectChanges(ImageGrid grid)
{
using var enumerator = grid.GetEnumerator();
var index = 0;
if (_lastFrame is null)
{
_lastFrame = GC.AllocateUninitializedArray <RgbColor>(grid.Tiles);
while (enumerator.MoveNext())
{
_lastFrame[index++] = enumerator.Current.Average();
}
return(ImmutableArray <ImageTile> .Empty);
}
if (_lastFrame.Length != grid.Tiles)
{
throw new InvalidOperationException("Last frame's tile count does not match the currents.");
}
var builder = ImmutableArray.CreateBuilder <ImageTile>();
while (enumerator.MoveNext())
{
var previousColor = _lastFrame[index];
var currentColor = enumerator.Current.Average();
_lastFrame[index++] = currentColor;
if (RgbComparer.Compare(previousColor, currentColor) > 0.4)
{
builder.Add(enumerator.Current);
}
}
return(builder.ToImmutable());
}
