eg. VImage::width() is now int VImage::width() const; ie. it does not alter the image objects. In factr we can mark almost all members const. see https://github.com/jcupitt/libvips/issues/983
eg. VImage::width() is now int VImage::width() const; ie. it does not alter the image objects. In factr we can mark almost all members const. see https://github.com/jcupitt/libvips/issues/983