added method for autoscaling

[sjbokhari]

Hey I added a method for autoscaling the pictures, since this is my first pull request Im not sure if everything is alright. Please let me know :)

[sjbokhari]

@suyashkumar what do you say about this? :)

[suyashkumar]

@sjbokhari thank you for taking a stab at this! Unfortunately, if I understand correctly, correct autoscaling of a DICOM is a bit more complicated than picking the midpoint. I think we should be applying possible lookup table values, and/or trying to see if window center tags and others are present in the dicom to initialize the values. More details here: #2 (comment)

That said, maybe there's a way we can factor out some of this into a library or top level function in a pkg/ library that makes it clear it applies a different type of default scaling. e.g. MidpointScaling(NativeFrame frame) (image.Image, error).

WDYT? You're welcome to read more about dicom scaling at the issue above if you'd like to take a try at it! We can probably implement it incrementally or something.