Convert a PNG image to grayscale and preserving the transparency

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C#

WPF

image-processing

Hi,

I'm having trouble in converting a PNG image to a grayscale image and preserving the existing transparency in the image.

Currently the conversion is done but all transparent pixels are converted to black (as clearly stated in documentation).

When searching about the subject, I found examples that convert the image pixel by pixel but I'm curious if there's more elegant ways.

Please note that I'm quite new to imaging.

Current conversion

System.Windows.Media.Imaging.BitmapImage original = new System.Windows.Media.Imaging.BitmapImage();
System.Windows.Media.Imaging.FormatConvertedBitmap converted = new System.Windows.Media.Imaging.FormatConvertedBitmap();

original.BeginInit();
original.UriSource = new System.Uri("pack://application:,,,/Images/Add.png", System.UriKind.Absolute);
original.EndInit();


converted.BeginInit();
converted.Source = original;
converted.DestinationFormat = System.Windows.Media.PixelFormats.Gray32Float;
converted.AlphaThreshold = 100;
converted.EndInit();

Any help is appreciated.