Beralih daripada .NET MAUI Blazor kepada Kawalan WebView untuk Pengimbasan Dokumen

Dalam pembangunan .NET MAUI, kedua-dua BlazorWebView dan WebView digunakan untuk memaparkan kandungan web, tetapi ia mempunyai tujuan yang berbeza dan direka untuk senario yang berbeza. BlazorWebView direka khusus untuk mengehoskan komponen Blazor dalam aplikasi .NET MAUI, membolehkan anda menggunakan semula komponen Blazor dan berkongsi kod antara aplikasi web dan asli. WebView ialah kawalan tujuan umum untuk memaparkan kandungan web, termasuk halaman web, rentetan HTML dan fail HTML tempatan. Dalam artikel ini, kami akan meneroka cara untuk mengalihkan aplikasi pengimbas dokumen .NET MAUI Blazor kepada aplikasi .NET MAUI menggunakan kawalan WebView, melaksanakan logik pengimbasan dokumen dalam JavaScript dan HTML, dan membolehkan interoperasi antara C# dan JavaScript untuk mengimbas dokumen dan simpan imej.

Prasyarat

1. Pasang Perkhidmatan Dynamsoft: Perkhidmatan ini diperlukan untuk berkomunikasi dengan pengimbas TWAIN, SANE, ICA, ESCL dan WIA pada Windows dan macOS.
   • Windows: Dynamsoft-Service-Setup.msi
   • macOS: Dynamsoft-Service-Setup.pkg
2. Minta Lesen Percubaan Percuma: Dapatkan lesen percubaan percuma selama 30 hari untuk Dynamic Web TWAIN untuk bermula.

Langkah 1: Cipta Projek .NET MAUI Baharu dengan Kawalan WebView

1. Dalam Visual Studio atau Visual Studio Code, buat projek .NET MAUI baharu.

2. Buka fail MainPage.xaml dan gantikan kod sedia ada dengan XAML berikut untuk menambah kawalan WebView:
   

   <?xml version="1.0" encoding="utf-8" ?>
   <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                x:Class="MauiWebView.MainPage">
   
       <ScrollView>
           <StackLayout
               VerticalOptions="FillAndExpand"
   HorizontalOptions="FillAndExpand">
               <WebView
       x:Name="WebView"
       VerticalOptions="FillAndExpand"
       HorizontalOptions="FillAndExpand" Navigating="OnWebViewNavigated"/>
   
           </StackLayout>
       </ScrollView>
   
   </ContentPage>
   

3. Buka fail MainPage.xaml.cs dan tambah kod berikut untuk menetapkan sumber WebView dan mengendalikan acara Navigasi:
   

   namespace MauiWebView
   {
       public partial class MainPage : ContentPage
       {
           public MainPage()
           {
               InitializeComponent();
               LoadHtmlFile();
           }
   
           private void LoadHtmlFile()
           {
               WebView.Source = "index.html";
   
           }
   
           private async void OnWebViewNavigated(object sender, WebNavigatingEventArgs e)
           {
               if (e.Url.StartsWith("invoke://callcsharpfunction"))
               {
                   // TODO: Implement interop between C# and JavaScript
               }
           }
       }
   
   }
   
   

   Penjelasan:

   • Kaedah LoadHtmlFile menetapkan sifat Sumber kawalan WebView untuk memuatkan fail index.html.
   • Kaedah OnWebViewNavigated dicetuskan apabila WebView menavigasi ke URL baharu. Ia menyemak sama ada URL bermula dengan invoke://callcsharpfunction dan, jika ya, membenarkan interop C# dan JavaScript.

Langkah 2: Muatkan Fail HTML, JavaScript dan CSS Statik ke dalam Kawalan WebView

Dalam projek .NET MAUI, anda boleh memuatkan fail HTML, JavaScript dan CSS statik yang terletak dalam folder Sumber/Mentah ke dalam WebView. Pastikan tindakan bina MauiAsset disertakan dalam fail .csproj:

d0fd252dd0536d593a865b1b7d180310
    a6b6999ef84f0df9dca4c12a06340421
6e5ad26193226e804779ce3cd902f2c9

Kami mencipta reka letak UI yang serupa seperti aplikasi pengimbas dokumen Blazor sebelumnya dalam fail index.html.

8b05045a5be5764f313ed5b9168a17e6
49099650ebdc5f3125501fa170048923

93f0f5c25f18dab9d176bd4f6de5d30e
    1fc2df4564f5324148703df3b6ed50c1
    4f2fb0231f24e8aef524fc9bf9b9874f

    b2386ffb911b14667cb8f0f91ea547a7Dynamsoft RESTful API Example6e916e0f7d1e588d4f442bf645aedb2f
    ea507197563fe9808580cd58ff5dae83
9c3bca370b5104690d9ef395f2c5f8d1

6c04bd5ca3fcae76e30b72ad730ca86d
    38b885ab7897934b555c67b94cd711e2
        0a6bb94971119ee328f517322c66980c16b28748ea4df4d9c2150843fecfba68
    16b28748ea4df4d9c2150843fecfba68

    c1a436a314ed609750bd7c7d319db4daDocument Scanner2e9b454fa8428549ca2e64dfac4625cd
    39bbc163833ae4e036fa5108a4263823
        dc6dce4a544fdca2df29d5ac0ea9906b
            2e1cf0710519d5598b1f0f14c36ba674
                Get a License key from e854f899d6c08fe1c619c9c20acd0fd7here5db79b134e9f6b82c0b36e0489ee08ed.
            8c1ecd4bb896b2264e0711597d40766c
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        16b28748ea4df4d9c2150843fecfba68

    16b28748ea4df4d9c2150843fecfba68

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        b91e30dda1382ac7285aae3f45407cef
            684271ed9684bde649abda8831d4d355Acquire Image39528cedfa926ea0c01e69ef5b2ea9b0
            b6f796d82ff1b4e710c079542e89e182Get Devices65281c5ac262bf6d81768915a4a77ac0

            dc6dce4a544fdca2df29d5ac0ea9906b
                6870baf322929e763a5a4dd5b95638a2Source: 8c1ecd4bb896b2264e0711597d40766c
                4e4da74db0fbe784cd1a8c486f2d663a18bb6ffaf0152bbe49cd8a3620346341
            16b28748ea4df4d9c2150843fecfba68

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                5eeb331c51742deae3114e4956cc1be1
                    5a07473c87748fb1bf73f23d45547ab8B & W4afa15d3069109ac30911f04c56f3338
                    5a07473c87748fb1bf73f23d45547ab8Gray4afa15d3069109ac30911f04c56f3338
                    5a07473c87748fb1bf73f23d45547ab8Color4afa15d3069109ac30911f04c56f3338
                18bb6ffaf0152bbe49cd8a3620346341
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            dc6dce4a544fdca2df29d5ac0ea9906b
                045b2ead8e25645fdd0c39f585f1e5bfResolution: 8c1ecd4bb896b2264e0711597d40766c
                c0e226d2d22b2a84209a20e9fa5db602
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                    5a07473c87748fb1bf73f23d45547ab82004afa15d3069109ac30911f04c56f3338
                    5a07473c87748fb1bf73f23d45547ab83004afa15d3069109ac30911f04c56f3338
                18bb6ffaf0152bbe49cd8a3620346341
            16b28748ea4df4d9c2150843fecfba68


            dc6dce4a544fdca2df29d5ac0ea9906b
                1ee9335f254f79d03a6febbcf5d3d46b
                2c55b6d296473c35276f4ed5dfe2cf7dShow UI8c1ecd4bb896b2264e0711597d40766c
            16b28748ea4df4d9c2150843fecfba68
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            16b28748ea4df4d9c2150843fecfba68

            ebf9f28c318eafce2dd4c8e1bb2c253cScan Now65281c5ac262bf6d81768915a4a77ac0
            6d9fd183d333544e9d5fe06824808c81Save65281c5ac262bf6d81768915a4a77ac0

            684271ed9684bde649abda8831d4d355Image Tools39528cedfa926ea0c01e69ef5b2ea9b0
            2326325328cfb1510e6119c7566a1325
                679019de3d0cfbcca4676917ab8cd4f0
                    803a9dc7ffbcccf77de190935b40089a
                65281c5ac262bf6d81768915a4a77ac0
                becd6db3ab50097bcb2036771f348f01
                    b411ae39fbc39f0429a39ad945dcd511
                65281c5ac262bf6d81768915a4a77ac0
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                65281c5ac262bf6d81768915a4a77ac0
            16b28748ea4df4d9c2150843fecfba68
        16b28748ea4df4d9c2150843fecfba68

        b3be3238529c3d77b69b7fd150fd938b
            46c5d3aad1e47bee946e6355bc5143b4
                ec6b4fd79f2415f29f0b734dcd571fb5
            16b28748ea4df4d9c2150843fecfba68

            39bbc163833ae4e036fa5108a4263823
                b7c1222a61bcb1861cf5c6bfedb3b7cd
                    a1e9e9b21d1fae6be88debb6fb09c6cc 
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                16b28748ea4df4d9c2150843fecfba68
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        16b28748ea4df4d9c2150843fecfba68
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    e803653d6fd93b3996ebf69dd59af1622cacc6d41bbb37262a98f745aa00fbf0
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73a6ac4ed44ffec12cee46588e518a5e

Langkah 3: Laksanakan Pengimbasan Dokumen dalam JavaScript

Dengan persekitaran sedia, langkah seterusnya ialah melaksanakan fungsi yang berkaitan dalam JavaScript.

Dapatkan Peranti

Jumlah pengimbas yang tersedia.

const ScannerType = {
    // TWAIN scanner type, represented by the value 0x10
    TWAINSCANNER: 0x10,

    // WIA scanner type, represented by the value 0x20
    WIASCANNER: 0x20,

    // 64-bit TWAIN scanner type, represented by the value 0x40
    TWAINX64SCANNER: 0x40,

    // ICA scanner type, represented by the value 0x80
    ICASCANNER: 0x80,

    // SANE scanner type, represented by the value 0x100
    SANESCANNER: 0x100,

    // eSCL scanner type, represented by the value 0x200
    ESCLSCANNER: 0x200,

    // WiFi Direct scanner type, represented by the value 0x400
    WIFIDIRECTSCANNER: 0x400,

    // WIA-TWAIN scanner type, represented by the value 0x800
    WIATWAINSCANNER: 0x800
};

let queryDevicesButton = document.getElementById("query-devices-button");
queryDevicesButton.onclick = async () => {
    let scannerType = ScannerType.TWAINSCANNER | ScannerType.TWAINX64SCANNER;
    let devices = await getDevices(host, scannerType);
    let select = document.getElementById("sources");
    select.innerHTML = '';
    for (let i = 0; i f5a6af4b681417349ece19c3f7d9d681 {
    let select = document.getElementById("sources");
    let device = select.value;

    if (device == null || device.length == 0) {
        alert('Please select a scanner.');
        return;
    }

    let inputText = document.getElementById("inputText").value;
    let license = inputText.trim();

    if (license == null || license.length == 0) {
        alert('Please input a valid license key.');
    }

    let parameters = {
        license: license,
        device: JSON.parse(device)['device'],
    };

    let showUICheck = document.getElementById("showUICheckId");

    let pixelTypeSelect = document.getElementById("pixelTypeSelectId");

    let resolutionSelect = document.getElementById("resolutionSelectId");

    let adfCheck = document.getElementById("adfCheckId");

    let duplexCheck = document.getElementById("duplexCheckId");

    parameters.config = {
        IfShowUI: showUICheck.checked,
        PixelType: pixelTypeSelect.selectedIndex,
        Resolution: parseInt(resolutionSelect.value),
        IfFeederEnabled: adfCheck.checked,
        IfDuplexEnabled: duplexCheck.checked,
    };


    let jobId = await scanDocument(host, parameters);
    let images = await getImages(host, jobId);

    for (let i = 0; i 30f38ec796a9a4f3b797e10c6aa42e38 {
                if (e != null && e.target != null) {
                    let target = e.target;
                    img.src = target.src;
                    selectedThumbnail = target;
                }
            });
        }

        selectedThumbnail = newImage;
    }

}

async function scanDocument(host, parameters, timeout = 30) {
    let url = host + '/DWTAPI/ScanJobs?timeout=' + timeout;

    try {
        let response = await fetch(url, {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json'
            },
            body: JSON.stringify(parameters)
        });

        if (response.ok) {
            let jobId = await response.text();
            return jobId;
        }
        else {
            return '';
        }
    } catch (error) {
        alert(error);
        return '';
    }
}

async function getImages(host, jobId) {
    let images = [];
    let url = host + '/DWTAPI/ScanJobs/' + jobId + '/NextDocument';

    while (true) {
        try {

            let response = await fetch(url);

            if (response.status == 200) {
                const arrayBuffer = await response.arrayBuffer();
                const blob = new Blob([arrayBuffer], { type: response.type });
                const imageUrl = URL.createObjectURL(blob);

                images.push(imageUrl);
            }
            else {
                break;
            }

        } catch (error) {
            console.error('No more images.');
            break;
        }
    }

    return images;
}

Penjelasan

• Fungsi scanDocument menghantar permintaan POST ke titik akhir API RESTful /DWTAPI/ScanJobs untuk memulakan kerja pengimbasan. Parameter termasuk kunci lesen, nama peranti dan tetapan pengimbasan.
• Fungsi getImages menghantar permintaan GET ke titik akhir API RESTful /DWTAPI/ScanJobs/{jobId}/NextDocument untuk mengambil imej yang diimbas. Imej disimpan dalam objek gumpalan dan dipaparkan dalam kawasan paparan imej.

Putar Imej

Putar imej yang diimbas sebanyak -90 atau 90 darjah.

let rotateLeftButton = document.getElementById("rotate-left-button");
rotateLeftButton.onclick = () => {
    let img = document.getElementById('document-image');
    img.src = rotateImage('document-image', -90);
    selectedThumbnail.src = img.src;
}

let rotateRightButton = document.getElementById("rotate-right-button");
rotateRightButton.onclick = () => {
    let img = document.getElementById('document-image');
    img.src = rotateImage('document-image', 90);
    selectedThumbnail.src = img.src;
}

    function rotateImage (imageId, angle) {
    const image = document.getElementById(imageId);
    const canvas = document.createElement('canvas');
    const context = canvas.getContext('2d');
    const imageWidth = image.naturalWidth;
    const imageHeight = image.naturalHeight;

    // Calculate the new rotation
    let rotation = 0;
    rotation = (rotation + angle) % 360;

    // Adjust canvas size for rotation
    if (rotation === 90 || rotation === -270 || rotation === 270) {
        canvas.width = imageHeight;
        canvas.height = imageWidth;
    } else if (rotation === 180 || rotation === -180) {
        canvas.width = imageWidth;
        canvas.height = imageHeight;
    } else if (rotation === 270 || rotation === -90) {
        canvas.width = imageHeight;
        canvas.height = imageWidth;
    } else {
        canvas.width = imageWidth;
        canvas.height = imageHeight;
    }

    // Clear the canvas
    context.clearRect(0, 0, canvas.width, canvas.height);

    // Draw the rotated image on the canvas
    context.save();
    if (rotation === 90 || rotation === -270) {
        context.translate(canvas.width, 0);
        context.rotate(90 * Math.PI / 180);
    } else if (rotation === 180 || rotation === -180) {
        context.translate(canvas.width, canvas.height);
        context.rotate(180 * Math.PI / 180);
    } else if (rotation === 270 || rotation === -90) {
        context.translate(0, canvas.height);
        context.rotate(270 * Math.PI / 180);
    }
    context.drawImage(image, 0, 0);
    context.restore();

    return canvas.toDataURL();
}

Padam Imej

Padam semua imej yang diimbas, termasuk imej utama dan lakaran kecil, dan tetapkan semula tatasusunan data.

let deleteButton = document.getElementById("delete-button");
deleteButton.onclick = async () => {
    let img = document.getElementById('document-image');
    img.src = 'images/default.png';
    data = [];
    let thumbnails = document.getElementById("thumb-box");
    thumbnails.innerHTML = '';
}

Langkah 4: Interop Antara C# dan JavaScript untuk Menyimpan Imej

Menyimpan imej secara terus dalam JavaScript adalah terhad kerana kebimbangan keselamatan. Oleh itu, kita perlu beroperasi antara C# dan JavaScript untuk menyelesaikan tugas ini.

1. Buat fungsi JavaScript untuk menukar imej yang diimbas kepada rentetan base64.
   

   function getBase64Image() {
       var img = document.getElementById('document-image');
       var canvas = document.createElement('canvas');
       canvas.width = img.naturalWidth;
       canvas.height = img.naturalHeight;
       var ctx = canvas.getContext('2d');
       ctx.drawImage(img, 0, 0);
   
       var dataURL = canvas.toDataURL('image/png'); 
       var base64 = dataURL.split(',')[1]; 
       return base64;
   }
   

2. Apabila mengklik butang simpan, tetapkan window.location.href untuk mencetuskan pengendali acara OnWebViewNavigated bagi kawalan WebView.
   

   let saveButton = document.getElementById("save-button");
   saveButton.onclick = async () => {
       window.location.href = 'invoke://CallCSharpFunction';    
   }
   

3. Dalam pengendali acara OnWebViewNavigated, panggil EvaluateJavaScriptAsync untuk mendapatkan semula data imej base64 daripada JavaScript dan menyimpannya pada fail.
   

   private async void OnWebViewNavigated(object sender, WebNavigatingEventArgs e)
   {
       if (e.Url.StartsWith("invoke://callcsharpfunction"))
       {
           var base64String = await WebView.EvaluateJavaScriptAsync("getBase64Image()");
           CallCSharpFunction(base64String);
       }
   }
   
   private void CallCSharpFunction(string base64String)
   {
       if (!string.IsNullOrEmpty(base64String))
       {
   
           try
           {
               byte[] imageBytes = Convert.FromBase64String(base64String);
   
               var filePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), GenerateFilename());
               File.WriteAllBytes(filePath, imageBytes);
               DisplayAlert("Success", "Image saved to: " + filePath, "OK");
   
           }
           catch (Exception ex)
           {
               DisplayAlert("Error", ex.Message, "OK");
           }
       }
       else
       {
           DisplayAlert("Failure", "No image data found", "OK");
       }
   }
   
   private string GenerateFilename()
   {
       DateTime now = DateTime.Now;
       string timestamp = now.ToString("yyyyMMdd_HHmmss");
       return $"image_{timestamp}.png";
   }
   

Note: Do not pass the base64 string directly to the C# function via window.location.href, as the string may be too long and cause an error. Instead, return the base64 string when calling EvaluateJavaScriptAsync from the C# function.

Step 5: Run the .NET MAUI Document Scanner Application

Press F5 in Visual Studio or Visual Studio Code to run the .NET document scanner application on Windows or macOS.

Source Code

https://github.com/yushulx/dotnet-twain-wia-sane-scanner/tree/main/examples/MauiWebView

Atas ialah kandungan terperinci Beralih daripada .NET MAUI Blazor kepada Kawalan WebView untuk Pengimbasan Dokumen. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!