Question

我正在使用ZXing.net创建一个UserControl，用于使用相机将条形码扫描到Windows Phone 8.1 RT应用程序中。

条形码解码得很好，但是当调用CapturePhotoToStreamAsync方法时，我已经冻结了UI，即使是等待它。执行大约需要600毫秒。

我正在将应用程序测试到模拟器中。

以下代码以异步方式执行：

// Preview of the camera    
await _mediaCapture.InitializeAsync(settings);
VideoCapture.Source = _mediaCapture;
VideoCapture.FlowDirection = Windows.UI.Xaml.FlowDirection.LeftToRight;
await _mediaCapture.StartPreviewAsync();

VideoEncodingProperties res = _mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview) as VideoEncodingProperties;
ImageEncodingProperties iep = ImageEncodingProperties.CreateBmp();

iep.Height = res.Height;
iep.Width = res.Width;

var barcodeReader = new BarcodeReader
{
     TryHarder = true,
     AutoRotate = true
};

WriteableBitmap wB = new WriteableBitmap((int)res.Width, (int)res.Height);
while (_result == null)
{
     using (var stream = new InMemoryRandomAccessStream())
     {
        await _mediaCapture.CapturePhotoToStreamAsync(iep, stream);

        stream.Seek(0);
        await wB.SetSourceAsync(stream);

        _result = barcodeReader.Decode(wB);
      }
 }

 await _mediaCapture.StopPreviewAsync();
 //callback to handle result
 ScanCallback(_result.Text);

如何防止用户界面冻结？

Answer 1

幸运的是，您无需在Windows Phone 8.1 Runtime上捕获照片来解码QRCode /条形码。实际上这是一个非常新的解决方案，但它有效：https://github.com/mmaitre314/VideoEffect#realtime-video-analysis-and-qr-code-detection 在使用nuget包后，您可以轻松实时解码条形码，而无需调用CapturePhotoToStreamAsync。唯一的缺点是你只能针对ARM。您可以在网站上找到示例代码。或者您可以联系我，我可以将项目的一部分发送给您。

Answer 2

当我使用相机首先拍摄照片（让您将焦点放在条形码所在的正确位置）时，我总能得到更好的效果，然后发送照片进行条形码识别。

导致口吃是因为您试图继续检查CPU上的条形码的实时馈送（特别是对于ARM设备）

var dialog = new CameraCaptureUI();
StorageFile file = await dialog.CaptureFileAsync(CameraCaptureUIMode.Photo);
var stream = await file.OpenReadAsync();
// initialize with 1,1 to get the current size of the image
var writeableBmp = new WriteableBitmap(1, 1);
writeableBmp.SetSource(stream);
// and create it again because otherwise the WB isn't fully initialized and decoding
// results in a IndexOutOfRange
writeableBmp = new WriteableBitmap(writeableBmp.PixelWidth, writeableBmp.PixelHeight);
stream.Seek(0);
writeableBmp.SetSource(stream);

var result = ScanBitmap(writeableBmp);
string barcode = "";
if (result != null)
{
    barcode = result.Text;
}

这里是ScanBitmap方法：

    private Result ScanBitmap(WriteableBitmap writeableBmp)
    {
        var barcodeReader = new BarcodeReader
        {
            Options = new ZXing.Common.DecodingOptions()
            {
                TryHarder = true
            },
            AutoRotate = true
        };
        var result = barcodeReader.Decode(writeableBmp);

        if (result != null)
        {
            CaptureImage.Source = writeableBmp;
        }

        return result;
    }

windows phone 8.1 RT Zxing.net实现：CapturePhotoToStreamAsync问题

2 个答案: