二维码的生成

#import <CoreImage/CoreImage.h>

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
   // 1. 实例化二维码滤镜
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    // 2. 恢复滤镜的默认属性
    [filter setDefaults];
    
    // 3. 将字符串转换成NSData
    NSString *dataStr = @"你想添加的数据";
    NSData *data = [dataStr dataUsingEncoding:NSUTF8StringEncoding];
    
    // 4. 通过KVO设置滤镜inputMessage数据
    [filter setValue:data forKey:@"inputMessage"];
    
    // 5. 获得滤镜输出的图像
    CIImage *outputImage = [filter outputImage];
    
    // 6. 将CIImage转换成UIImage，并放大显示
    self.imageView.image = [self createNonInterpolatedUIImageFormCIImage:outputImage withSize:200];
    
}
/**
 *  根据CIImage生成指定大小的UIImage(高清的二维码图片)
 *
 *  @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];
}