防止iPhoneSDK图片拉伸

代码：

    self.newsImage = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,300,130)];
    //set placeholder image or cell won't update when image is loaded
    self.newsImage.image = [UIImage imageNamed:@"newsDetail.png"];
    //load the image
    self.newsImage.imageURL = [NSURL URLWithString:imageBig];
    [imageBack addSubview:self.newsImage];

有一个40/40尺寸的图片，但是imageView的尺寸是300*130。怎么避免图片被拉伸？

谢谢

居中内容就可以了：

self.newsImage.contentMode = UIViewContentModeCenter;