如何在 iOS 10.2 上使用 xamarin forms + zxing 扫描驾照 (PDF417) [英] How to scan driver's license (PDF417) using xamarin forms + zxing on iOS 10.2

问题描述

我正在使用 Xamarin 表单编写 iOS 应用程序并使用 ZXing 库扫描条形码.我正在尝试读取驾驶执照 (PDF417) 条形码，但图书馆无法识别该条形码.

I am using Xamarin forms to write an iOS app and using the ZXing library to scan barcodes. I am trying to read a driver's license (PDF417) barcode, but the library is not able to recognize that barcode.

如果我在可能的格式中包含 UPC 或其他条形码，它们将被正确扫描.

If I include UPC or other barcodes in the PossibleFormats, they are scanned correctly.

我也确定我尝试读取的条码是 PDF417 条码，因为 Scandit 能够在仅使用 PDF417 条码时正确识别它.

I am also certain the barcode I am trying to read is PDF417 barcode because Scandit is able to recognize it correctly while using only PDF417 barcode.

这是我正在使用的代码.我需要更改什么才能正确识别 PDF417 条码?

Here is the code I am using. What do I need to change so that the PDF417 barcode is recognized correctly?

async void Handle_Clicked (object sender, System.EventArgs e)
    {
        MobileBarcodeScanningOptions options = new MobileBarcodeScanningOptions ();
        options.PossibleFormats = new List<ZXing.BarcodeFormat> () {
            ZXing.BarcodeFormat.PDF_417
        };
        options.TryHarder = true;

        var scanPage = new ZXingScannerPage (options);


        scanPage.OnScanResult += (result) => {
            // Stop scanning
            scanPage.IsScanning = false;

            // Pop the page and show the result
            Device.BeginInvokeOnMainThread (async () => {
                await Navigation.PopAsync ();
                await DisplayAlert ("Scanned Barcode", result.Text, "OK");
            });
        };

        // Navigate to our scanner page
        await Navigation.PushAsync (scanPage);
    }

推荐答案

几天前我遇到了这个完全相同的问题，并使用以下方法修复了它.在 MobileBarcodeScanningOptions 类中有一个 CameraResolutionSelectorDelegate 类型的属性，称为 CameraResolutionSelector.您可以将其设置为从可用分辨率列表中返回更高的相机分辨率.所以我的 MobileBarcodeScanningOptions 实例化看起来像这样:

I ran into this exact same issue a few days ago and fixed it with the following. In the MobileBarcodeScanningOptions class there's a property of type CameraResolutionSelectorDelegate called CameraResolutionSelector. You can set this to return a higher camera resolution from a list of available resolutions. So my instantiation of MobileBarcodeScanningOptions looks like this:

var options = new MobileBarcodeScanningOptions {
            TryHarder = true,
            CameraResolutionSelector = HandleCameraResolutionSelectorDelegate,
            PossibleFormats = new List<BarcodeFormat> { BarcodeFormat.PDF_417 }
        };

还有我的HandleCameraResolutionSelectorDelegate:

CameraResolution HandleCameraResolutionSelectorDelegate(List<CameraResolution> availableResolutions)
{
    //Don't know if this will ever be null or empty
    if (availableResolutions == null || availableResolutions.Count < 1)
        return new CameraResolution () { Width = 800, Height = 600 };

    //Debugging revealed that the last element in the list
    //expresses the highest resolution. This could probably be more thorough.
    return availableResolutions [availableResolutions.Count - 1];
}

这就是我要扫描驾驶执照 (PDF417) 条码所需的全部更改.

That's all I needed to change to get a driver's license (PDF417) barcode to scan.

这里是 MobileBarcodeScanningOptions.cs 的源代码来自 ZXing github.

Here's the source code for MobileBarcodeScanningOptions.cs from ZXing github.

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