Similar to what is in the Qt frontend, this camera takes a URI to a
picture file. When the config is empty, it will open up the gallery and
ask the user to pick a picture.
The image is then read and cropped from the Java side by the Picasso library,
and sent to the native code with android NDK Bitmap API (jnigraphics).
The native code handles the format conversion with libyuv.
Image flipping is yet to be implemented.
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