1.需要导入

import <CoreImage/CoreImage.h>

import <AVFoundation/AVFoundation.h>

两个库。
2.生成二维码

#pragma mark 清晰二维码
- (void)MakeQRCode2{
    CIFilter * filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    [filter setDefaults];
    NSString *dataString = @"http://w.url.cn/s/A6zf4SV";
    NSData * data = [dataString dataUsingEncoding:NSUTF8StringEncoding];
    [filter setValue:data forKey:@"inputMessage"];
    CIImage * outputImage = [filter outputImage];
    ErWeiMa.image = [self creatClearImageFromCIImage:outputImage withSize:200];
}
- (UIImage *)creatClearImageFromCIImage:(CIImage *)image withSize:(CGFloat) size
{
    CGRect extent = CGRectIntegral(image.extent);
    CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
    
    size_t width = CGRectGetWidth(extent) * scale;
    size_t height = CGRectGetHeight(extent) * scale;
    // 创建灰度色调空间
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceGray();
    CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, colorSpaceRef, (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);
    
    // 保存图片
    CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
    CGContextRelease(bitmapRef);
    CGImageRelease(bitmapImage);
    return [UIImage imageWithCGImage:scaledImage];
}

3.扫描二维码

#pragma mark 扫描二维码
- (void)MakeQRCode3{
    //创建拍摄会话
    Session = [[AVCaptureSession alloc] init];
    //添加输入设备
    AVCaptureDevice * device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput * input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    [Session addInput:input];
    
    //添加输出数据
    AVCaptureMetadataOutput * output = [[AVCaptureMetadataOutput alloc] init];
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    [Session addOutput:output];
    
    //设置输入元数据的类型
    [output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];
    
    //添加扫描图层
    Layer = [AVCaptureVideoPreviewLayer layerWithSession:Session];
    Layer.frame = self.view.bounds;
    [self.view.layer addSublayer:Layer];
    
    //启动会话
    [Session startRunning];
}
#pragma mark - 扫描到数据就会执行该代理方法
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
    if (metadataObjects.count > 0) {
        // 提示：如果需要对url或者文本等信息进行扫描，可以在此进行扩展
        AVMetadataMachineReadableCodeObject *object = [metadataObjects lastObject];
        NSLog(@"%@", object.stringValue);
        
        // 如果扫描完成，停止会话
        [Session stopRunning];
        
        // 删除预览图层
        [Layer removeFromSuperlayer];
    } else {
        NSLog(@"没有扫描到数据");
    }
}