• 使用前需导入#import <CoreImage/CoreImage.h>
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- (void)touchesBegan:(NSSet *)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];
    
    // 3.二维码信息
    NSString *str = @"哎呀我去"; // 展示一串文字
//    NSString *str = @"http://www.baidu.com"; // 直接打开网页
    
    // 4.将字符串转成二进制数据
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    
    // 5.通过KVC设置滤镜inputMessage数据
    [filter setValue:data forKey:@"inputMessage"];
    
    // 6.获取滤镜输出的图像
    CIImage *outputImage = [filter outputImage];
    
    // 7.将CIImage转成UIImage
    UIImage *image = [self createNonInterpolatedUIImageFormCIImage:outputImage withSize:200];
    
    // 8.展示二维码
    self.imageView.image = image;
}
  • 系统默认获取到的二维码图片不太清晰,可以利用下面的方法,获取指定大小的二维码图片
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/**
 *  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];
}