生成二维码图片、扫描二维码图片

首先来看看借助苹果原生CoreImage框架如何将文字信息生成二维码图片，毫无疑问肯定要导入#import 这个头文件。
实现以下代码既可以生成二维码图片，但是图片比较模糊。

// 1.创建滤镜对象
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    
    // 2.恢复默认设置
    [filter setDefaults];
    
    // 3.设置数据
    NSString *info = @"http://www.baidu.com";
    NSData *infoData = [info dataUsingEncoding:NSUTF8StringEncoding];
    [filter setValue:infoData forKeyPath:@"inputMessage"];
    
    // 4.生成二维码
    CIImage *outputImage = [filter outputImage];
    self.imageView.image = [UIImage imageWithCIImage:outputImage];

解决二维码图片模糊问题，需要我们自己绘图。新建一个CIImage的分类，然后实现如下代码。直接调用这个分类的方法将CIImage转为UIImage即可解决问题。

- (UIImage *)createNonInterpolatedWithSize:(CGFloat)size
{
    CGRect extent = CGRectIntegral(self.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:self 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];
}

接下来看看如何扫面二维码。扫秒二维码是借助AVFoundation框架，相关注释在代码中。

#import "ViewController.h"
#import 
@interface ViewController ()
//注意这里用weak
@property (nonatomic, weak) AVCaptureSession *session;
@property (nonatomic, weak) AVCaptureVideoPreviewLayer *layer;
@end
@implementation ViewController
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    //1.获取捕捉会话
    AVCaptureSession *session = [[AVCaptureSession alloc]init];
    self.session = session;
    //2.设置输入（摄像头）
    //AVMediaTypeVideo摄像头, AVMediaTypeAudio话筒, or AVMediaTypeMuxed弹幕
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    [_session addInput:input];
    
    //3.设置输出数据
    AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc]init];
    //设置代理  
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    [_session addOutput:output];
    //设置输出类型 AVMetadataObjectTypeQRCode表示输出类型为二维码
    //注意：必须在设置代理完毕后设置
    [output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];
    
    //4.添加阅览图层
     AVCaptureVideoPreviewLayer *layer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:self.session];
    self.layer = layer;
    _layer.frame = self.view.bounds;
    [self.view.layer addSublayer:_layer];
    //5.开始扫描
    [_session startRunning];
}
#pragma mark - 
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{
    if (metadataObjects.count > 0) {
         // 1.获取扫描到的内容
        AVMetadataMachineReadableCodeObject *object = [metadataObjects lastObject];
        NSLog(@"%@", object.stringValue);
        // 2.停止会话
        [self.session stopRunning];
        // 3.移除预览图层
        [self.layer removeFromSuperlayer];
    }
}