[fix] correct scaling

[rvalitov]

Fixes #13
I added code to fix all the problems from there, except the last line about exporting in function toDataURL to formats other than jpeg. There are 2 reasons for that:

• it's not a bug, but a feature
• not all browsers may support export to formats other than jpeg and png. For example, Chrome even supports webp, see the docs.
• the user (programmer) may not want to have an image in the original format. Usually when we upload an image we want to have it in a predefined format, usually jpeg. It does not matter what kind of image the user selects: it may be any format supported by the browser, but after uploading we will have always jpeg, i.e. auto conversion is performed. I think it's logical. Alternatively, we could add a new option that would define the output format in which the JS code saves the final image. But such option is beyond the current PR.

[rossturner]

The whitespacing here needs correcting