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Then you can edit the source of that object as well as fonts/colours etc… as you need to.
Force Greyscale Image
This option will format an image as greyscale, even if the supplied image is colour by changing the specified Pixel Format. Details on the available options for this can be found here: https://msdn.microsoft.com/en-us/library/system.windows.media.pixelformats(v=vs.110).aspx
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