/**
 生成二维码
 QRStering：字符串
 imageFloat：二维码图片大小
 */
+ (UIImage *)createQRCodeWithString:(NSString *)QRString withImgSize:(CGFloat)imageFloat{
  CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
  [filter setDefaults];
  NSString *getString = QRString;
  NSData *dataString = [getString dataUsingEncoding:NSUTF8StringEncoding];
  [filter setValue:dataString forKey:@"inputMessage"];
  ///获取滤镜输出的图像
  CIImage *outImage = [filter outputImage];
  UIImage *imageV = [self imageWithImageSize:imageFloat withCIIImage:outImage];
  //返回二维码图像
  return imageV;
}

/** 将CIImage转换成UIImage 并放大(内部转换使用)*/
+ (UIImage *)imageWithImageSize:(CGFloat)size withCIIImage:(CIImage *)ciiImage{
  CGRect extent = CGRectIntegral(ciiImage.extent);
  CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
  // 1.创建bitmap;
  size_t width = CGRectGetWidth(extent) * scale;
  size_t height = CGRectGetHeight(extent) * scale;
  CGColorSpaceRef cs = CGColorSpaceCreateDeviceGray();
  CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, cs, (CGBitmapInfo)kCGImageAlphaNone);
  CIContext *context = [CIContext contextWithOptions:nil];
  CGImageRef bitmapImage = [context createCGImage:ciiImage fromRect:extent];
  CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);
  CGContextScaleCTM(bitmapRef, scale, scale);
  CGContextDrawImage(bitmapRef, extent, bitmapImage);
  // 2.保存bitmap到图片
  CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
  CGContextRelease(bitmapRef);
  CGImageRelease(bitmapImage);
  return [UIImage imageWithCGImage:scaledImage];
}