How to acquire black-white images from TWAIN scanner?

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If you want to acquire black-white images from TWAIN scanner, you should set the pixel type of scanned images using WebTwainDeviceJS.set_PixelType function.

If you want to acquire black-white images from SANE scanner, you should set the scan mode that allows to get black-white images. The WebTwainDeviceJS.set_SaneScanMode function allows to set the scan mode for SANE scanner. SANE API does not provide the standard name for scan mode, which allows to acquire black-white images from SANE scanner, and scanner vendors use different names for this scan mode. For example, Canon, HP, Kodak and Samsung use "Lineart" name, Brother uses "Black & White" name, Kyocera uses "Mono" name. Names of scan modes, which are supported by SANE device, can be obtained using WebTwainDeviceJS.getSupportedSaneScanModes function.

Here is JavaScript code that demonstrates how to acquire black-white images from TWAIN/SANE scanner:

JavaScript

// acquire black-white images from TWAIN/SANE scanner
__acquireBlackWhiteImagesFromTwainScanner();



/**
 * Acquires black-white images from TWAIN/SANE scanner.
 */
function __acquireBlackWhiteImagesFromTwainScanner() {
    // register the evaluation version of VintaSoft Web TWAIN service
    // please read how to get evaluation license in documentation: https://www.vintasoft.com/docs/vstwain-dotnet-web/Licensing-Twain_Web-Evaluation.html
    Vintasoft.Twain.WebTwainGlobalSettingsJS.register('REG_USER', 'REG_URL', 'REG_CODE', 'EXPIRATION_DATE');

    // URL to the VintaSoft Web TWAIN service
    var serviceUrl = 'https://localhost:25329/api/VintasoftTwainApi';
    // a Web API controller that allows to work with TWAIN and SANE devices
    var twainService = new Vintasoft.Shared.WebServiceControllerJS(serviceUrl);

    // TWAIN/SANE device manager
    var deviceManager = new Vintasoft.Twain.WebTwainDeviceManagerJS(twainService);

    // the default settings of device manager
    var deviceManagerInitSetting = new Vintasoft.Twain.WebTwainDeviceManagerInitSettingsJS();

    var device = null;
    try {
        // open device manager
        deviceManager.open(deviceManagerInitSetting);

        // get the default TWAIN/SANE device
        device = deviceManager.get_DefaultDevice();

        // open device without UI
        device.open(false);

        // if device is SANE device
        if (device.get_DeviceName().substring(0, 4) == "Sane") {
            // specify that images must be acquired in "Lineart" mode
            device.set_SaneScanMode("Lineart");
        }
        // if device is TWAIN device
        else {
            // specify that black-white images must be acquired from TWAIN scanner
            device.set_PixelType(new Vintasoft.Twain.WebPixelTypeEnumJS("BW"));
        }

        var acquireModalState;
        do {
            // do one step of modal image acquisition process
            var acquireModalResult = device.acquireModalSync();
            // get state of image acquisition
            acquireModalState = acquireModalResult.get_AcquireModalState().valueOf();

            switch (acquireModalState) {
                case 2:   // image is acquired
                    // get acquired image
                    var acquiredImage = acquireModalResult.get_AcquiredImage();
                    // get image as Base64 string
                    var bitmapAsBase64String = acquiredImage.getAsBase64String();
                    // update image preview
                    var previewImageElement = document.getElementById('previewImage');
                    previewImageElement.src = bitmapAsBase64String;
                    break;
                case 4:   // image scan is failed
                    alert(acquireModalResult.get_ErrorMessage());
                    break;
                case 9:   // image scan is finished
                    break;
            }
        }
        while (acquireModalState !== 0);
    }
    catch (ex) {
        alert(ex);
    }
    finally {
        if (device != null) {
            // close the device
            device.close();
        }
        // close the device manager
        deviceManager.close();
    }
}

Here is TypeScript code that demonstrates how to acquire black-white images from TWAIN/SANE scanner:

TYPESCRIPT

import { Component } from '@angular/core';

@Component({
  selector: 'twain-scanning-demo',
  templateUrl: './twain-scanning-demo.component.html'
})
export class TwainScanningDemoComponent {

  ngOnInit() {
    // acquire images from TWAIN/SANE scanner
    this.__acquireImageFromTwainScanner();
  }


  /**
   * Acquires images from TWAIN/SANE scanner.
   */
  __acquireImageFromTwainScanner() {
    // register the evaluation version of VintaSoft Web TWAIN service
    // please read how to get evaluation license in documentation: https://www.vintasoft.com/docs/vstwain-dotnet-web/Licensing-Twain_Web-Evaluation.html
    Vintasoft.Twain.WebTwainGlobalSettingsJS.register('REG_USER', 'REG_URL', 'REG_CODE', 'EXPIRATION_DATE');

    // URL to the VintaSoft Web TWAIN service
    let serviceUrl: string = 'https://localhost:25329/api/VintasoftTwainApi';
    // a Web API controller that allows to work with TWAIN and SANE devices
    let twainService: Vintasoft.Shared.WebServiceControllerJS = new Vintasoft.Shared.WebServiceControllerJS(serviceUrl);

    // TWAIN/SANE device manager
    let deviceManager: Vintasoft.Twain.WebTwainDeviceManagerJS = new Vintasoft.Twain.WebTwainDeviceManagerJS(twainService);

    // the default settings of device manager
    let deviceManagerInitSetting: Vintasoft.Twain.WebTwainDeviceManagerInitSettingsJS = new Vintasoft.Twain.WebTwainDeviceManagerInitSettingsJS();

    try {
      // open device manager
      deviceManager.open(deviceManagerInitSetting);
    }
    catch (ex) {
      alert(ex);
      return;
    }

    let device: Vintasoft.Twain.WebTwainDeviceJS = null;
    try {
      // get the default TWAIN/SANE device
      device = deviceManager.get_DefaultDevice();

      // open device without UI
      device.open(false);

      // if device is SANE device
      if (device.get_DeviceName().substring(0, 4) == "Sane") {
          // specify that images must be acquired in "Lineart" mode
          device.set_SaneScanMode("Lineart");
      }
      // if device is TWAIN device
      else {
          // specify that black-white images must be acquired from TWAIN scanner
          device.set_PixelType(new Vintasoft.Twain.WebPixelTypeEnumJS("BW"));
      }

      let acquireModalState: number;
      do {
        // do one step of modal image acquisition process
        let acquireModalResult: Vintasoft.Twain.WebTwainDeviceAcquireModalResultJS = device.acquireModalSync();
        // get state of image acquisition
        acquireModalState = acquireModalResult.get_AcquireModalState().valueOf() as number;

        switch (acquireModalState) {
          case 2:   // image is acquired
            // get acquired image
            let acquiredImage: Vintasoft.Twain.WebAcquiredImageJS = acquireModalResult.get_AcquiredImage();
            // get image as Base64 string
            let bitmapAsBase64String: string = acquiredImage.getAsBase64String();
            // update image preview
            let previewImageElement: HTMLImageElement = document.getElementById('previewImage') as HTMLImageElement;
            previewImageElement.src = bitmapAsBase64String;
            break;
          case 4:   // image scan is failed
            alert(acquireModalResult.get_ErrorMessage());
            break;
          case 9:   // image scan is finished
            break;
        }
      }
      while (acquireModalState !== 0);
    }
    catch (ex) {
      alert(ex);
    }
    finally {
      if (device != null) {
        // close the device
        device.close();
      }
      // close the device manager
      deviceManager.close();
    }
  }

}

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