图像裁剪的实现

#pragma mark 根据指定的大小来裁剪图片
+(UIImage *)returnClicpImageFromBottomBaseOnSize:(CGSize)Newsize OldImage:(UIImage *)imageOld
{
    CGImageRef imgRef=imageOld.CGImage;
    //从图片的上方开始裁剪图片
    CGRect rect1 = CGRectMake(0,0,Newsize.width,Newsize.height);
    NSLog(@"指定的宽度 %f 高度 %f",rect1.size.width,rect1.size.height);
    CGImageRef img=CGImageCreateWithImageInRect(imgRef,rect1);    
    UIImage *subImage=[UIImage imageWithCGImage:img];
    NSLog(@"宽度：%f 高度%f",subImage.size.width,subImage.size.height);
  
    CGImageRelease(img);
    
    return subImage;
}