Delete redundant on_color.py

[tburrows13]

Both on_color.py and VideoClip.on_color() were added in v0.2 (fdc51d2), but only VideoClip.on_color() has been maintained/updated since.

Somewhat related: is there a better name for on_color and/or its argument col_opacity? (-> background_opacity?)

[coveralls]

Coverage increased (+0.3%) to 77.6% when pulling 8b7442a on tburrows13:remove-redundant-on_color into ebfe16c on Zulko:master.

[mondeja]

I'm not a native English speaker, but perhaps VideoClip.over_color and color_opacity?

[mondeja]

Should the block after line 757 be moved to ImageClip calling VideoClip.on_color before this block using super()?

        if (
            isinstance(self, ImageClip)
            and (not hasattr(pos, "__call__"))
            and ((self.mask is None) or isinstance(self.mask, ImageClip))
        ):
            new_result = result.to_ImageClip()
            if result.mask is not None:
                new_result.mask = result.mask.to_ImageClip()
            return new_result.with_duration(result.duration)

[keikoro]

Somewhat related: is there a better name for on_color and/or its argument col_opacity? (-> background_opacity?)

I agree, on_color is not very clear. Would color_underlay (equivalent to overlay) make sense? I don't know if "background" is unambiguous enough considering that photo + film images have foregrounds and backgrounds as well. The other one could then be underlay_opacity.

Also, there is no real consistency in the naming of functions – actions vs. nouns – is there? (Though some could be either, I suppose.) -> color_underlay vs underlay_color...

[mondeja]

We can change the name later, I'm going to merge this as is. Thank you @tburrows13 👍