Fixes #634 and fixes #746 by making the fields of Image private, adding the safe constructor from #637 (EDIT: Image::gen_image_color already does that) and adding unsafe functions to modify the fields.

This is still work in progress and a breaking change.

New methods

• Image::from_raw_parts: method for creating an image from width, height and bytes while checking if the amount of bytes is correct
• Image::bytes: returns an immutable slice of all bytes in the image
• Image::width_mut, Image::height_mut, Image::bytes_mut: unsafe methods that return a mutable reference to the respective field, allowing for unchecked manipulation
• Image::pixel_amount: returns the amount of pixels this image has according to its dimensions
• Image::from_color: creates an image filled with one color, previously called Image::gen_image_color

Breaking changes

• Image.width, Image.height and Image.bytes are private now
• Return type of Image::width and Image::height is u16 now instead of usize
• Image::set_pixel and Image::get_pixel take u16 instead of u32 as x and y arguments now

Bugfixes

• Reading an out-of-bounds pixel with Image::get_pixel correctly panics now
• Image::blend and Image::overlay panic now if the two images have the same amount of pixels, but different width and height

Other non-breaking changes

• Some Into implementations for Color are now From implementations (should give Into automatically)
• Image::from_color / Image::gen_image_color is 2-3 times faster now
• Image::empty, Image::width, Image::height are const fns now
• Image::gen_image_color is a deprecated alias of Image::from_color now

TODO:

• Should the width and height be u16, u32 or usize?
• How large is the impact of this breakage?
• Should this be split into breaking and non-breaking changes, to merge the non-breaking changes now and the breaking changes in 0.5?