Exception when parameter TableA is null in "SKColorFilter.CreateTable"

[andreasfromch]

I’m currently using the following code to change the color of a signature from navy to white.

        public Stream InvertImage(Stream streamUnterschrift)
        {
            try
            {
                SKColor         outputColor = new SKColor(255, 255, 255);
                MemoryStream    stream      = new MemoryStream();

                using (SKBitmap sourceBitmap = SKBitmap.Decode(streamUnterschrift))
                {
                    SKImageInfo info = new SKImageInfo(sourceBitmap.Width,
                                                       sourceBitmap.Height,
                                                       sourceBitmap.ColorType,
                                                       sourceBitmap.AlphaType,
                                                       sourceBitmap.ColorSpace);

                    using (SKBitmap outputBitmap        = new SKBitmap(info))
                    using (SKCanvas canvas              = new SKCanvas(outputBitmap))
                    using (SKPaint  transformationBrush = new SKPaint())
                    {
                        canvas.DrawColor(SKColors.Transparent);

                        var targetColor = outputColor;

                        byte[] tableRed     = new byte[256];
                        byte[] tableGreen   = new byte[256];
                        byte[] tableBlue    = new byte[256];

                        for (int i = 0; i < 256; i++)
                        {
                            tableRed[i]     = targetColor.Red;
                            tableGreen[i]   = targetColor.Green;
                            tableBlue[i]    = targetColor.Blue;
                        }

                        // Alpha channel remains unchanged
                        transformationBrush.ColorFilter = SKColorFilter.CreateTable(null, tableRed, tableGreen, tableBlue);

                        canvas.DrawBitmap(sourceBitmap, info.Rect, transformationBrush);

                        using (var image = SKImage.FromBitmap(outputBitmap))
                        using (SKData data = image.Encode(SKEncodedImageFormat.Png, 100))

                        data.SaveTo(stream);
                        stream.Position = 0;

                        return stream;
                    }
                }
            }
            catch (Exception e)
            {
                Log.Fatal(e);
                return null;
            }
        }

In use was the version 2.88.9 of SkiaSharp. After upgrading to 3.119.0 I get the exception "System.ArgumentNullException: Value cannot be null. (Parameter 'tableA')".
Does anybody have an idea how to fill tableA that my method does the same thing as before upgrading to 3.119.0?

[mattleibow]

This may have been an accidental null check. I will check.

Can you try passing in a set if solid black or transparent or something?

[andreasfromch]

Thanks a lot for the response.
Do you mean something like that?

I tried that with 0, 127 and 255. With that it doesn't crash any more but it looks like the background color of the image changes between some gray colors.