Function WebPPictureView 

pub unsafe extern "C" fn WebPPictureView(
    src: *const WebPPicture,
    left: c_int,
    top: c_int,
    width: c_int,
    height: c_int,
    dst: *mut WebPPicture,
) -> c_int

Extracts a view from src picture into dst. The rectangle for the view is defined by the top-left corner pixel coordinates (left, top) as well as its width and height. This rectangle must be fully be comprised inside the src source picture. If the source picture uses the YUV420 colorspace, the top and left coordinates will be snapped to even values. Picture src must out-live dst picture. Self-extraction of view is allowed (src equal to dst) as a mean of fast-cropping (but note that doing so, the original dimension will be lost). Picture dst need not be initialized with WebPPictureInit() if it is different from src, since its content will be overwritten. Returns false in case of invalid parameters.