Pre-Process Image (Brightness, Contrast, Greyscale)

I am working on a project which will detect custom shapes

Code Snippet below
ObjectDetection.ModelInput modelInput = new ObjectDetection.ModelInput
{
Image = MLImage.CreateFromFile(selectedFilePath) // selectedFilePath is the image file path
};
var modelOutput = ObjectDetection.Predict(modelInput);

I want to preprocess the image and feed it to the input model.
Preprocess means adjusting Brightness, Contrast or Greyscale

so how do we convert System.Drawing.Image to MLImage

simple workflow
Capture Image -> Adjust Brightness, Contrast -> Feed the image to input image -> We get prediction boxes -> Process the Box area