iOS - 图片拉伸

- (UIButton *)_createToolbarButton {
    UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
    btn.exclusiveTouch = YES;
    btn.size = CGSizeMake(kScreenWidth / _emoticonGroups.count, kToolbarHeight);
    btn.titleLabel.font = [UIFont systemFontOfSize:14];
    [btn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
    [btn setTitleColor:UIColorHex(5D5C5A) forState:UIControlStateSelected];
    
    UIImage *img;
    img = [YHExpressionHelper imageNamed:@"compose_emotion_table_left_normal"];
    img = [img resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, img.size.width - 1) resizingMode:UIImageResizingModeStretch];
    [btn setBackgroundImage:img forState:UIControlStateNormal];
    
    img = [YHExpressionHelper imageNamed:@"compose_emotion_table_left_selected"];
    img = [img resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, img.size.width - 1) resizingMode:UIImageResizingModeStretch];
    [btn setBackgroundImage:img forState:UIControlStateSelected];
    
    [btn addTarget:self action:@selector(_toolbarBtnDidTapped:) forControlEvents:UIControlEventTouchUpInside];
    return btn;
}