学习笔记:生成二维码

// 创建过滤镜对象
CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
// 设置相关属性
[filter setDefaults];
// 给过滤镜添加数据
NSString *dataStr = @"http://www.baidu.com";
NSData *data = [dataStr dataUsingEncoding:NSUTF8StringEncoding];
[filter setValue:data forKey:@"inputMessage"];
// 获取输出的二维码
CIImage *outputImage = [filter outputImage];
// 展示二维码
self.outputImage.image = [self createNonInterpolatedUIImageFormCIImage:outputImage withSize:200];

/**

• 根据CIImage生成指定大小的UIImage
• @param image CIImage
• @param size 图片宽度
  */

• (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size
  {
  CGRect extent = CGRectIntegral(image.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:image 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];
  }