ios – 如何从静态图像中读取QR码

我知道您可以使用AVFoundation使用设备的相机扫描QR码.现在问题来了,如何从静态UI Image对象中执行此操作？

解决方法

iOS API提供CoreImage框架中的CIDetector类.
CIDetector可让您在图像中找到特定的图案,如面部,微笑,眼睛,或者在我们的案例中：QRCodes.

以下是在Objective-C中从UIImage检测QRCode的代码：

-(NSArray *)detectQRCode:(UIImage *) image
{
    @autoreleasepool {
        NSLog(@"%@ :: %@",NSStringFromClass([self class]),NSStringFromSelector(_cmd));
        NSCAssert(image != nil,@"**Assertion Error** detectQRCode : image is nil");

        CIImage* ciImage = UIImage.CIImage; // assuming underlying data is a CIImage
        //CIImage* ciImage = [CIImage initWithCGImage: UIImage.CGImage]; // to use if the underlying data is a CGImage

        NSDictionary* options;
        CIContext* context = [CIContext context];
        options = @{ CIDetectorAccuracy : CIDetectorAccuracyHigh }; // Slow but thorough
        //options = @{ CIDetectorAccuracy : CIDetectorAccuracyLow}; // Fast but superficial

        CIDetector* qrDetector = [CIDetector detectorOfType:CIDetectorTypeQRCode
                                                    context:context
                                                    options:options];
        if ([[ciImage properties] valueForKey:(NSString*) kCGImagePropertyOrientation] == nil) {
            options = @{ CIDetectorImageOrientation : @1};
        } else {
            options = @{ CIDetectorImageOrientation : [[ciImage properties] valueForKey:(NSString*) kCGImagePropertyOrientation]};
        }

        NSArray * features = [qrDetector featuresInImage:ciImage
                                                 options:options];

        return features;

    }
}

如果存在并检测到QRCode,则返回的NSArray *将包含CIFeature *.如果没有QRCode,NSArray *将为零.如果QRCode解码失败,NSArray *将没有元素.

要获取编码的字符串：

if (features != nil && features.count > 0) {
    for (CIQRCodeFeature* qrFeature in features) {
        NSLog(@"QRFeature.messageString : %@ ",qrFeature.messageString);
    }
}

在@ Duncan-C的答案中,您可以提取QRCode角并在图像上绘制QRCode的封闭边界框.

注意 ：
在iOS10.0 beta 6下,当使用来自cameraSampleBuffer的图像时,调用[qrDetector featuresInImage：ciImage选项：选项]会记录此内部警告(它运行顺利但是垃圾邮件控制台带有此消息,我找不到办法现在摆脱它)：

Finalizing CVPixelBuffer 0x170133e20 while lock count is 1.

资源 ：

Apple Dev API Reference – CIDetector

Apple Dev API Programming guide – Face detection