private static async Task<FrameProperties> GetFramePropertiesAsync(BitmapFrame frame)
{
const string leftProperty = "/imgdesc/Left";
const string topProperty = "/imgdesc/Top";
const string widthProperty = "/imgdesc/Width";
const string heightProperty = "/imgdesc/Height";
const string delayProperty = "/grctlext/Delay";
const string disposalProperty = "/grctlext/Disposal";
var propertiesView = frame.BitmapProperties;
var requiredProperties = new[] { leftProperty, topProperty, widthProperty, heightProperty };
var properties = await propertiesView.GetPropertiesAsync(requiredProperties);
var left = (ushort)properties[leftProperty].Value;
var top = (ushort)properties[topProperty].Value;
var width = (ushort)properties[widthProperty].Value;
var height = (ushort)properties[heightProperty].Value;
var delayMilliseconds = 30.0;
var shouldDispose = false;
try
{
var extensionProperties = new[] { delayProperty, disposalProperty };
properties = await propertiesView.GetPropertiesAsync(extensionProperties);
if (properties.ContainsKey(delayProperty) && properties[delayProperty].Type == PropertyType.UInt16)
{
var delayInHundredths = (ushort)properties[delayProperty].Value;
if (delayInHundredths >= 3u) // Prevent degenerate frames with no delay time
{
delayMilliseconds = 10.0 * delayInHundredths;
}
}
if (properties.ContainsKey(disposalProperty) && properties[disposalProperty].Type == PropertyType.UInt8)
{
var disposal = (byte)properties[disposalProperty].Value;
if (disposal == 2)
{
// 0 = undefined
// 1 = none (compose next frame on top of this one, default)
// 2 = dispose
// 3 = revert to previous (not supported)
shouldDispose = true;
}
}
}
catch
{
// These properties are not required, so it's okay to ignore failure.
}
return new FrameProperties(
new Rect(left, top, width, height),
delayMilliseconds,
shouldDispose
);
}
private static async Task<byte[]> GetPixelsAsync(BitmapFrame frame)
{
var pixelData = await frame.GetPixelDataAsync(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Premultiplied, new BitmapTransform(), ExifOrientationMode.RespectExifOrientation, ColorManagementMode.DoNotColorManage);
return pixelData.DetachPixelData();
}