Whitespace cleanup - no real code changes.
Add jpgQuality member datum.

Allows future expansion of saving jpg images as user-specified quality levels.
Modify all calls to ->getMimeType() to use temp image file name.

Similar change for getImagePixels().

Those functions, or the ones that call them, are all invoked when handling an
image upload *before* the uploaded image is saved to a final location. The
only valid file on the server at that point is the temp one.