Photo Grayscale Filter With XLabs Photo

I'm trying to improve the OCR Xamarin.Tesseract.
The best way to improve it is by processing the image before it's processed by the OCR, putting it at a grayscale filter and adjusting the contrast, clip and brightness. I'm using XLabs to take the photo, but I don't know any library or way to apply a filter over it... someone knows a way or library to do it?

PS: I'm using Xamarin.Forms

Thanks, Mario.