UIImageView圆角，自适应图片宽高比例,图片拉伸,缩放比例

/*
设置圆角，通过layer中的cornerRadius和masksToBounds即可。

自适应图片宽高比例。通过UIViewContentModeScaleAspectFit设置，注意这个UIImageView的frame就不是init中的数据了。

同样的UIImage图片放入不同frame中的UIImageView就可以实现比例缩放了。只是UIImageView的大小改变了，

*/
UIImage* image = [UIImage imageNamed:@"back2.jpg"];
UIImageView* imageView1 = [[[UIImageView alloc] initWithImage:image] autorelease];
imageView1.frame = CGRectMake(0, 0, 300, 200);
imageView1.center = CGPointMake(150, 200);
//设置圆角
imageView1.layer.cornerRadius = 8;
imageView1.layer.masksToBounds = YES;

//自适应图片宽高比例
imageView1.contentMode = UIViewContentModeScaleAspectFit;
[self.view addSubview:imageView1];

//拉伸图片
CGFloat capWidth = image.size.width / 2;
CGFloat capHeight = image.size.height / 2;
UIImage* stretchableImage = [image stretchableImageWithLeftCapWidth:capWidth topCapHeight:capHeight];
UIImageView* imageView3 = [[[UIImageView alloc] initWithImage:stretchableImage] autorelease];
imageView3.frame = CGRectMake(0, 0, 300, 200);
imageView3.center = CGPointMake(150, 200);
[self.view addSubview:imageView3];

//改变frame改变
UIImageView* imageView4 = [[[UIImageView alloc] initWithImage:image] autorelease];
imageView4.frame = CGRectMake(0, 0, 300/2, 200/2);
imageView4.center = CGPointMake(150, 200);
[self.view addSubview:imageView4];