Support adding optional metadata to images about image HOT 2 OPEN

Image metadata handling is an area of this crate that I'd certainly like to improve. Our lack of support for image orientation and color profiles have both been longstanding issues.

Exactly what belongs in an ImageMetadata struct will take some design. EXIF data and color metadata / ICC profiles should probably both be represented in some form, but I don't know exactly what that would look like. For instance, should they be binary blobs or further parsed?

I'd be a bit hesitant about transparently bundling the metadata into DynamicImage and ImageBuffer. It seems too likely for people accidentally write images containing out-of-date or sensitive information without realizing it. But I think it would be very workable for certain decoding methods to return a tuple of the image and the metadata, or for encoders to accept both the pixel data and image metadata separately

from image.

I can stand behind separating the image and the metadata, and instead providing the information to the encoders/decoders optionally. As for what is contained, we can probably take inspiration from existing formats and innovate in this space since there is no history of image crate supporting metadata.

from image.