iOS 实现头像选取功能（可手动编辑图片裁剪） UIImageP

- (void)showUploadSheet {
    UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:@"上传" message:@"选择图片的方式" preferredStyle:UIAlertControllerStyleActionSheet];
    [alertVC addAction:[UIAlertAction actionWithTitle:@"相册" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        UIImagePickerController *pickVC = [[UIImagePickerController alloc] init];
        pickVC.delegate = self;
        pickVC.allowsEditing = YES;
        pickVC.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        [self presentViewController:pickVC animated:YES completion:nil];
    }]];
    [alertVC addAction:[UIAlertAction actionWithTitle:@"拍照" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        
    }]];
    [alertVC addAction:[UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        
    }]];
    [self presentViewController:alertVC animated:YES completion:nil];
}

上面的关键在于 pickVC.allowsEditing = YES; 这个属性
这个属性表示选了图片以后支持拖动图片，选择裁剪范围

同时要注意的是，选择完以后一定要Dismiss掉PickerViewController，否则界面会卡住不能操作。
猜测是由于点击Choose选择以后，系统自动调取了编辑页面的popViewControllerAnimated:方法，（从动画可以看出，编辑页面就是通过push的方式压入栈内的），但是编辑页VC的nav应该是由PickerViewController的上一个VC传递过来的，所以如果PickerViewController没有Dismiss掉，那就会导致界面卡在编辑页面

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info {
    DLOG(@"image:%@",info);
    UIImage *image = info[UIImagePickerControllerOriginalImage];
    [picker dismissViewControllerAnimated:YES completion:nil];
}