///压缩图片
+ (NSData *)imageCompressToData:(UIImage *)image{
  NSData *data=UIImageJPEGRepresentation(image, 1.0);
  if (data.length>300*1024) {
    if (data.length>1024*1024) {//1M以及以上
      data=UIImageJPEGRepresentation(image, 0.1);
    }else if (data.length>512*1024) {//0.5M-1M
      data=UIImageJPEGRepresentation(image, 0.5);
    }else if (data.length>300*1024) {//0.25M-0.5M
      data=UIImageJPEGRepresentation(image, 0.9);
    }
  }
  return data;
}

/** 
 * 压缩图片到指定尺寸大小 
 * 
 * @param image 原始图片 
 * @param size 目标大小 
 * 
 * @return 生成图片 
 */ 
-(UIImage *)compressOriginalImage:(UIImage *)image toSize:(CGSize)size{ 
  UIImage * resultImage = image; 
  UIGraphicsBeginImageContext(size); 
  [resultImage drawInRect:CGRectMake(00, 0, size.width, size.height)]; 
  UIGraphicsEndImageContext(); 
  return image; 
} 

/** 
 * 压缩图片到指定文件大小 
 * 
 * @param image 目标图片 
 * @param size 目标大小（最大值） 
 * 
 * @return 返回的图片文件 
 */ 
- (NSData *)compressOriginalImage:(UIImage *)image toMaxDataSizeKBytes:(CGFloat)size{ 
  NSData * data = UIImageJPEGRepresentation(image, 1.0); 
  CGFloat dataKBytes = data.length/1000.0; 
  CGFloat maxQuality = 0.9f; 
  CGFloat lastData = dataKBytes; 
  while (dataKBytes > size && maxQuality > 0.01f) { 
    maxQuality = maxQuality - 0.01f; 
    data = UIImageJPEGRepresentation(image, maxQuality); 
    dataKBytes = data.length / 1000.0; 
    if (lastData == dataKBytes) { 
      break; 
    }else{ 
      lastData = dataKBytes; 
    } 
  } 
  return data; 
}