public override void Perform(Pixmap pixmap, PreviewImageQuery query)
        {
            int desiredWidth  = query.DesiredWidth;
            int desiredHeight = query.DesiredHeight;

            PixelData layer = pixmap.MainLayer;

            if (layer == null)
            {
                query.Result = new Bitmap(1, 1);
                return;
            }
            float widthRatio = (float)layer.Width / (float)layer.Height;

            if (pixmap.Width * pixmap.Height > 4096 * 4096)
            {
                layer = layer.CloneSubImage(
                    pixmap.Width / 2 - Math.Min(desiredWidth, pixmap.Width) / 2,
                    pixmap.Height / 2 - Math.Min(desiredHeight, pixmap.Height) / 2,
                    Math.Min(desiredWidth, pixmap.Width),
                    Math.Min(desiredHeight, pixmap.Height));
                if (layer.Width != desiredWidth || layer.Height != desiredHeight)
                {
                    layer = layer.CloneRescale(desiredWidth, desiredHeight, ImageScaleFilter.Linear);
                }
            }
            else if (query.SizeMode == PreviewSizeMode.FixedBoth)
            {
                layer = layer.CloneRescale(desiredWidth, desiredHeight, ImageScaleFilter.Linear);
            }
            else if (query.SizeMode == PreviewSizeMode.FixedWidth)
            {
                layer = layer.CloneRescale(desiredWidth, MathF.RoundToInt(desiredWidth / widthRatio), ImageScaleFilter.Linear);
            }
            else if (query.SizeMode == PreviewSizeMode.FixedHeight)
            {
                layer = layer.CloneRescale(MathF.RoundToInt(widthRatio * desiredHeight), desiredHeight, ImageScaleFilter.Linear);
            }
            else
            {
                layer = layer.Clone();
            }

            query.Result = layer.ToBitmap();
        }