I cannot make an image transparent, what should I do?

[ddyakovsyndy]

Hello community,

I am trying to convert the image below to Png with a transparent background but without success.
https://syndy-assetversions.azureedge.net/a3cc7292-b195-4333-ba37-88d541b074bb

using var ms = new MemoryStream();
var image = await imageTransformation.Url.LoadImageFromUrlAsync(ctx);

try
  {
      image.Transform(imageTransformation);

      var encoder = new PngEncoder
      {
          ColorType = PngColorType.RgbWithAlpha,
          TransparentColorMode = PngTransparentColorMode.Preserve,
          BitDepth = PngBitDepth.Bit8,
          CompressionLevel = PngCompressionLevel.BestSpeed
      };

      await image.SaveAsPngAsync(ms, encoder, ctx);

      return ms.ToArray();
  }
  catch (Exception ex)
  {
      return Array.Empty<byte>();
  }

public static void Transform(this Image image, ImageTransformationDto imageTransformation)
      => image.Mutate(context =>
      {
          context.Resize(imageTransformation.ToResizeOptions(image.Size));
          context.BackgroundColor(Color.ParseHex(imageTransformation.BackgroundColor));

          context.SetGraphicsOptions(options =>
          {
              options.AlphaCompositionMode = PixelAlphaCompositionMode.Clear;
          });

          float threshold = 0.1F;
          Color sourceColor = Color.White;
          Color targetColor = Color.Transparent;
          RecolorBrush brush = new RecolorBrush(sourceColor, targetColor, threshold);

          context.Fill(brush);
      });

  public static ResizeOptions ToResizeOptions(this ImageTransformationDto? imageResize, Size imageSize)
  {
      var resizeOptions = new ResizeOptions()
      {
          Compand = imageResize?.Compand ?? default,
          Mode = imageResize?.ResizeMode ?? default,
          Position = imageResize?.AnchorPositionMode ?? default,
          PremultiplyAlpha = imageResize?.PremultiplyAlpha ?? default,
          Size = imageSize
      };

      if (imageResize is null)
          return resizeOptions;

      if (imageResize.Width.HasValue && imageResize.Height.HasValue)
          resizeOptions.Size = new Size(imageResize.Width.Value, imageResize.Height.Value);


      if (imageResize.Resampler.HasValue && Enum.IsDefined(imageResize.Resampler.Value))
          resizeOptions.Sampler = ImageHelper.GetResampler(imageResize.Resampler.Value)!;

      if (!string.IsNullOrEmpty(imageResize.PadColor))
          resizeOptions.PadColor = Color.ParseHex(imageResize.PadColor);

      return resizeOptions;
  }

The imageTransformation.BackgroundColor defaults to #000000 if I don't pass anything. And this is the body of my request that I send:
{ "compand": false, "premultiplyAlpha": true, "resizeMode": 1, "anchorPositionMode": 0, "resampler": 1, "outputFileFormat": 4, "padColor": "", "backgroundColor": "", "url": "https://syndy-assetversions.azureedge.net/861fb087-546d-498d-84f8-f99271124f09" }

This is the result

What am I doing wrong?

[JimBobSquarePants]

I suspect the pixel format of your image lacks an alpha channel. If you require transparency, you must ensure that you use a formal that supports on like Rgba32