Affine transform and intrinsic matrix

# affine transform for feature extraction

img, trans, mask, bbox = self.affine_transform_and_masking(img, mask, cfg.render_img_shape, mask, expand_ratio=cfg.render_bbox_expand_ratio)

K[0, 0] = K[0, 0] * cfg.render_img_shape[1] / bbox[2]

K[1, 1] = K[1, 1] * cfg.render_img_shape[0] / bbox[3]

K[0, 2] = (K[0, 2] - bbox[0]) * cfg.render_img_shape[1] / bbox[2]

K[1, 2] = (K[1, 2] - bbox[1]) * cfg.render_img_shape[0] / bbox[3]