有时候从网络请求的图片分辨率高，缩小显示反而变模糊，主要是因为手机显示scale，导致图片锐化，可以
- (UIImage *)imageCompressWithSimple:(UIImage*)image scaledToSize:(CGSize)size {
//Determine whether the screen is retina
if([[UIScreen mainScreen] scale] == 2.0){
UIGraphicsBeginImageContextWithOptions(size, NO, 2.0);
}else if([[UIScreen mainScreen] scale] == 3.0) {
UIGraphicsBeginImageContextWithOptions(size, NO, 3.0);
}else{
UIGraphicsBeginImageContext(size);
}
[image drawInRect:CGRectMake(0,0,size.width,size.height)];
UIImage*newImage=UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
