Free rotate enhancement

[jemiljan]

Would it be possible to enhance the 90 degree rotation feature, ProjectMirador/mirador#375, currently under development for the 2.1 release
so that it can rotate it freely to any degree, not just 90 degrees? Ideally, this could be done freehand by clicking, and freely dragging and rotate the image clockwise or counter-clockwise. This would be done with a mouse, but even better on a device or hand-held tablet.

My primary motivation for this proposal is due to the significant challenge of reading documentary inscriptions and marginalia that are so often not written at neat, straight, 90 degree angles. In many cases, the inscriptions curve and undulate, so while using 90 degree rotations is better than nothing, it can still be quite limiting and therefore frustrating to read. In the end, I wind up tilting my head one way or another, which after a while, isn't terribly pleasant for my neck.

Diagrams with accompanying commentary can be particularly challenging to read. Unfortunately, this image of an Arabic manuscript from the Doris Duke estate isn't very clear, but you can see that there are many inscriptions written not only written at different angles, but also in circles and curves. Ideally, one would be able to zoom, pan, and freely "wiggle around" in order to facilitate reading all of the inscriptions without straining one's neck.

This artistic genealogy of calligraphers is also written in many different directions.

Another significant challenge is reading the legends of seal impressions, as they are so often stamped at an odd angle, or even bear circular or ringed inscriptions that require you to fully rotate the image to read them properly.

This image captures all of the problems that I am describing, as it bears a plethora of ownership inscriptions, library accession statements, and seals.

[camillevilla]

This issue was originally filed for Mirador 2. In Mirador 3, image rotation and other image manipulation options have been moved out of core into ProjectMirador/mirador-image-tools. These are some great examples, so I'm transferring this suggestion for free rotation to that repo.