iOS 对图片进行压缩

- (UIImage *)compressImage:(UIImage *)image toMaxFileSize:(NSInteger)maxFileSize {
CGFloat compression = 0.9f;
CGFloat maxCompression = 0.1f;
NSData *imageData = UIImageJPEGRepresentation(image, compression);
while ([imageData length] > maxFileSize && compression > maxCompression) {
compression -= 0.1;
imageData = UIImageJPEGRepresentation(image, compression);
}

UIImage *compressedImage = [UIImage imageWithData:imageData];
return compressedImage;
}