点击图片查看大图，再次点击还原原始尺寸
显示效果 ＜/br＞
使用方法：
1.导入XWScanImageClass ＜/br＞
2.为UIImageView增加点击事件，并且开始用户交互属性＜/br＞
// - 浏览大图点击事件
//为UIImageView1添加点击事件
UITapGestureRecognizer *tapGestureRecognizer1 = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(scanBigImageClick1:)];
[_ImageView1 addGestureRecognizer:tapGestureRecognizer1];
//让UIImageView和它的父类开启用户交互属性
[_ImageView1 setUserInteractionEnabled:YES];
// - 浏览大图点击事件
-(void)scanBigImageClick1:(UITapGestureRecognizer *)tap{
NSLog(@"点击图片");
UIImageView *clickedImageView = (UIImageView *)tap.view;
[XWScanImage scanBigImageWithImageView:clickedImageView];
}