public async Task CreateThumbnailAsync(Stream source, string mimeType, Stream destination, ResizeOptions options,
CancellationToken ct = default)
{
Guard.NotNull(source, nameof(source));
Guard.NotNull(destination, nameof(destination));
Guard.NotNull(options, nameof(options));
if (!options.IsValid)
{
await source.CopyToAsync(destination, ct);
return;
}
var w = options.TargetWidth ?? 0;
var h = options.TargetHeight ?? 0;
using (var image = Image.Load(source, out var format))
{
image.Mutate(x => x.AutoOrient());
if (w > 0 || h > 0)
{
var isCropUpsize = options.Mode == ResizeMode.CropUpsize;
if (!Enum.TryParse <ISResizeMode>(options.Mode.ToString(), true, out var resizeMode))
{
resizeMode = ISResizeMode.Max;
}
if (isCropUpsize)
{
resizeMode = ISResizeMode.Crop;
}
if (w >= image.Width && h >= image.Height && resizeMode == ISResizeMode.Crop && !isCropUpsize)
{
resizeMode = ISResizeMode.BoxPad;
}
var resizeOptions = new ISResizeOptions {
Size = new Size(w, h), Mode = resizeMode, PremultiplyAlpha = true
};
if (options.FocusX.HasValue && options.FocusY.HasValue)
{
resizeOptions.CenterCoordinates = new PointF(
+(options.FocusX.Value / 2f) + 0.5f,
-(options.FocusY.Value / 2f) + 0.5f
);
}
image.Mutate(operation =>
{
operation.Resize(resizeOptions);
if (Color.TryParse(options.Background, out var color))
{
operation.BackgroundColor(color);
}
else
{
operation.BackgroundColor(Color.Transparent);
}
});
}
var encoder = options.GetEncoder(format);
await image.SaveAsync(destination, encoder, ct);
}
}
