#!/usr/bin/env python
# -*- coding: utf-8 -*-
# File: geometry.py
# Author: Yuxin Wu <ppwwyyxxc@gmail.com>
from .base import ImageAugmentor
import math
import cv2
import numpy as np
__all__ = ['Rotation', 'RotationAndCropValid']
class Rotation(ImageAugmentor):
""" Random rotate the image w.r.t a random center"""
def __init__(self, max_deg, center_range=(0,1),
interp=cv2.INTER_CUBIC,
border=cv2.BORDER_REPLICATE):
"""
:param max_deg: max abs value of the rotation degree
:param center_range: the location of the rotation center
"""
super(Rotation, self).__init__()
self._init(locals())
def _get_augment_params(self, img):
center = img.shape[1::-1] * self._rand_range(
self.center_range[0], self.center_range[1], (2,))
deg = self._rand_range(-self.max_deg, self.max_deg)
return cv2.getRotationMatrix2D(tuple(center), deg, 1)
def _augment(self, img, rot_m):
ret = cv2.warpAffine(img, rot_m, img.shape[1::-1],
flags=self.interp, borderMode=self.border)
return ret
class RotationAndCropValid(ImageAugmentor):
""" Random rotate and crop the largest possible rect without the border
This will produce images of different shapes.
"""
def __init__(self, max_deg, interp=cv2.INTER_CUBIC):
super(RotationAndCropValid, self).__init__()
self._init(locals())
def _get_augment_params(self, img):
deg = self._rand_range(-self.max_deg, self.max_deg)
return deg
def _augment(self, img, deg):
center = (img.shape[1]*0.5, img.shape[0]*0.5)
rot_m = cv2.getRotationMatrix2D(center, deg, 1)
ret = cv2.warpAffine(img, rot_m, img.shape[1::-1],
flags=self.interp, borderMode=cv2.BORDER_CONSTANT)
neww, newh = RotationAndCropValid.largest_rotated_rect(ret.shape[1], ret.shape[0], deg)
neww = min(neww, ret.shape[1])
newh = min(newh, ret.shape[0])
newx = center[0] - neww * 0.5
newy = center[1] - newh * 0.5
#print(ret.shape, deg, newx, newy, neww, newh)
return ret[newy:newy+newh,newx:newx+neww]
@staticmethod
def largest_rotated_rect(w, h, angle):
""" http://stackoverflow.com/questions/16702966/rotate-image-and-crop-out-black-borders """
angle = angle / 180.0 * math.pi
if w <= 0 or h <= 0:
return 0,0
width_is_longer = w >= h
side_long, side_short = (w,h) if width_is_longer else (h,w)
# since the solutions for angle, -angle and 180-angle are all the same,
# if suffices to look at the first quadrant and the absolute values of sin,cos:
sin_a, cos_a = abs(math.sin(angle)), abs(math.cos(angle))
if side_short <= 2.*sin_a*cos_a*side_long:
# half constrained case: two crop corners touch the longer side,
# the other two corners are on the mid-line parallel to the longer line
x = 0.5*side_short
wr,hr = (x/sin_a,x/cos_a) if width_is_longer else (x/cos_a,x/sin_a)
else:
# fully constrained case: crop touches all 4 sides
cos_2a = cos_a*cos_a - sin_a*sin_a
wr,hr = (w*cos_a - h*sin_a)/cos_2a, (h*cos_a - w*sin_a)/cos_2a
return wr,hr
