UIImageView圆角，自适应图片宽高比例,图片拉伸,缩放比例和图片缩微图

/*

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];

//缩微图

- (UIImage *)generatePhotoThumbnail:(UIImage *)image {
// Create a thumbnail version of the image for the event object.
CGSize size = image.size;
CGSize croppedSize;
CGFloat ratioX = 75.0;
CGFloat ratioY = 60.0;
CGFloat offsetX = 0.0;
CGFloat offsetY = 0.0;

// check the size of the image, we want to make it
// a square with sides the size of the smallest dimension
if (size.width > size.height) {
offsetX = (size.height - size.width) /
2;
croppedSize = CGSizeMake(size.height, size.height);
} else {
offsetY = (size.width - size.height) /
2;
croppedSize = CGSizeMake(size.width, size.width);
}

// Crop the image before resize
CGRect clippedRect = CGRectMake(offsetX * -1, offsetY * -1, croppedSize.width, croppedSize.height);
CGImageRef imageRef =
CGImageCreateWithImageInRect([image CGImage], clippedRect);
// Done cropping
// Resize the image
CGRect rect = CGRectMake(0.0,
0.0, ratioX, ratioY); // 设置图片缩微图的区域（（0，0），宽：75 高：60）
UIGraphicsBeginImageContext(rect.size);
[[UIImage imageWithCGImage:imageRef]
drawInRect:rect];
UIImage *thumbnail =
UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Done Resizing
return thumbnail;
}