.h文件

#import <UIKit/UIKit.h>
@interface QRCoreViewController : UIViewController

@property (nonatomic, copy) NSString *url;//转为二维码的URL

@end

.m文件

#import "QRCoreViewController.h"
@import AVFoundation;
@import Photos;
@interface QRCoreViewController ()<AVCaptureMetadataOutputObjectsDelegate>
@property (nonatomic, strong) AVCaptureSession *session;//管道
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *layer;//在屏幕上输出摄像头图像
@property (nonatomic, strong) UIImage *image;//二维码图片
@end

@implementation QRCoreViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor whiteColor];
    
    UIImageView *imageView = [[UIImageView alloc] init];
    [self.view addSubview:imageView];
    [imageView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.center.equalTo(self.view);
        make.size.equalTo(200);
    }];

    CIImage *ciImage = [self getImageByString:_url];
    imageView.image = [self excludeFuzzyImageFromCIImage:ciImage size:200];
    self.image = imageView.image;
    
    imageView.userInteractionEnabled = YES;
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(saveQR)];
    [imageView addGestureRecognizer:tap];
    
    UIButton *saveBtn = [[UIButton alloc] init];
    saveBtn.titleLabel.font = [UIFont systemFontOfSize:17];
    saveBtn.titleLabel.textAlignment = NSTextAlignmentCenter;
    [saveBtn setTitle:@"保存二维码" forState:UIControlStateNormal];
    [saveBtn setTitleColor:TEXT_COLOR forState:UIControlStateNormal];
    [self.view addSubview:saveBtn];
    [saveBtn mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(imageView.mas_bottom).offset(20);
        make.centerX.equalTo(self.view);
        make.size.equalTo(CGSizeMake(100, 40));
    }];
    
    [saveBtn addTarget:self action:@selector(saveQR) forControlEvents:UIControlEventTouchUpInside];
}

#pragma mark -- 使用给定的字符串获得CIImage类型的对象
- (CIImage *)getImageByString:(NSString *)dataString
{
    //首先判断字符串是否合理！
    if (!dataString || dataString == nil || [dataString isEqualToString:@""])
    {
        return nil;
    }
    //实例化一个滤镜对象
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    //1、设置filter的默认值，防止之前的设置对本次转化有影响
    [filter setDefaults];
    
    //2、将传入的字符串转换为NSData
    NSData *data = [dataString dataUsingEncoding:NSUTF8StringEncoding];
    
    //3、将NSData传递给滤镜（通过KVC的方式，设置inputMessage）
    [filter setValue:data forKey:@"inputMessage"];
    
    //4、由filter对象输出图像
    CIImage *outputImage = [filter outputImage];
    
    //5、返回二维码图像
    return outputImage;
}

#pragma mark -- 对图像进行清晰处理
- (UIImage *)excludeFuzzyImageFromCIImage: (CIImage *)image size: (CGFloat)size
{
    
    CGRect extent = CGRectIntegral(image.extent);
    
    //通过比例计算，让最终的图像大小合理（正方形是我们想要的）
    CGFloat scale = MIN(size / CGRectGetWidth(extent), size / CGRectGetHeight(extent));
    
    size_t width = CGRectGetWidth(extent) * scale;
    size_t height = CGRectGetHeight(extent) * scale;
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, colorSpace, (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);
    CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
    
    UIImage *clearImage = [UIImage imageWithCGImage:scaledImage];

    //切记ARC模式下是不会对CoreFoundation框架的对象进行自动释放的，所以要我们手动释放
    CGContextRelease(bitmapRef);
    CGImageRelease(bitmapImage);
    CGColorSpaceRelease(colorSpace);
    CGImageRelease(scaledImage);

    return clearImage;
}

- (void)saveQR {//保存二维码按钮触发
    [self loadImageFinished:self.image];
}

// 图片保存到系统相册(无法保存到自定义相册)
- (void)loadImageFinished:(UIImage *)image
{
    UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), (__bridge void *)self);
}

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
    NSLog(@"image = %@, error = %@, contextInfo = %@", image, error, contextInfo);
    if (error == nil) {
        [self.view showMsg:@"二维码保存成功"];
    }
}