How to save TWAIN acquired image as JPEG file?

You can acquire image from TWAIN scanner and save image as JPEG file by 3 ways:

1. Using Native or Memory transfer mode

This method works with any TWAIN scanner.
Image is encoded using internal encoder of SDK.
JPEG quality can be set using the TwainJpegEncoderSettings.JpegQuality property.
Image is saved as JPEG file using the AcquiredImage.Save method.

Here is an example that demonstrates how to acquire not compressed image from TWAIN device and save image as JPEG file using JPEG encoder of SDK:

/// <summary>
/// Synchronously acquires not compressed images from TWAIN device and saves images to JPEG files.
/// </summary>
static void AcquireNotCompressedImagesFromTwainDeviceAndSaveImagesToJpegFiles()
{
    // create the device manager
    using (Vintasoft.Twain.DeviceManager deviceManager = new Vintasoft.Twain.DeviceManager())
    {
        // open the device manager
        deviceManager.Open();

        // get reference to the default device
        Vintasoft.Twain.Device device = deviceManager.DefaultDevice;

        // specify that device UI must not be used
        device.ShowUI = false;

        // open the device
        device.Open();

        // specify that Memory transfer mode must be used
        device.TransferMode = Vintasoft.Twain.TransferMode.Memory;

        // acquire images from device
        Vintasoft.Twain.AcquireModalState acquireModalState = Vintasoft.Twain.AcquireModalState.None;
        do
        {
            acquireModalState = device.AcquireModal();
            switch (acquireModalState)
            {
                case Vintasoft.Twain.AcquireModalState.ImageAcquired:
                    // specify JPEG encoder settings
                    Vintasoft.Twain.ImageEncoders.TwainJpegEncoderSettings jpegEncoderSettings =
                        new Vintasoft.Twain.ImageEncoders.TwainJpegEncoderSettings();
                    jpegEncoderSettings.JpegQuality = 50;

                    // save acquired image to a disk, internal SDK encoder will be used
                    device.AcquiredImage.Save("test.jpg", jpegEncoderSettings);

                    // dispose acquired image
                    device.AcquiredImage.Dispose();
                    break;
            }
        }
        while (acquireModalState != Vintasoft.Twain.AcquireModalState.None);

        // close the device
        device.Close();

        // close the device manager
        deviceManager.Close();
    }
}

VB.NET

''' <summary>
''' Synchronously acquires not compressed images from TWAIN device and saves images to JPEG files.
''' </summary>
Private Shared Sub AcquireNotCompressedImagesFromTwainDeviceAndSaveImagesToJpegFiles()
        ' create the device manager
        Using deviceManager As New Vintasoft.Twain.DeviceManager()
                ' open the device manager
                deviceManager.Open()

                ' get reference to the default device
                Dim device As Vintasoft.Twain.Device = deviceManager.DefaultDevice

                ' specify that device UI must not be used
                device.ShowUI = False

                ' open the device
                device.Open()

                ' specify that Memory transfer mode must be used
                device.TransferMode = Vintasoft.Twain.TransferMode.Memory

                ' acquire images from device
                Dim acquireModalState As Vintasoft.Twain.AcquireModalState = Vintasoft.Twain.AcquireModalState.None
                Do
                        acquireModalState = device.AcquireModal()
                        Select Case acquireModalState
                                Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                                        ' specify JPEG encoder settings
                                        Dim jpegEncoderSettings As New Vintasoft.Twain.ImageEncoders.TwainJpegEncoderSettings()
                                        jpegEncoderSettings.JpegQuality = 50

                                        ' save acquired image to a disk, internal SDK encoder will be used
                                        device.AcquiredImage.Save("test.jpg", jpegEncoderSettings)

                                        ' dispose acquired image
                                        device.AcquiredImage.Dispose()
                                        Exit Select
                        End Select
                Loop While acquireModalState <> Vintasoft.Twain.AcquireModalState.None

                ' close the device
                device.Close()

                ' close the device manager
                deviceManager.Close()
        End Using
End Sub

2. Using File transfer mode

TWAIN driver must have built-in JPEG encoder - you can check this with the Device.GetSupportedImageFileFormats method.
TWAIN driver encodes acquired image and saves directly to disk.
JPEG compression can be set using the Device.FileFormat property.
Filename of JPEG file can be set using the Device.FileName property.
Quality of JPEG file can be set using the Device.FileJpegQuality property.

Here is an example that demonstrates how to specify that TWAIN scanner should save acquired image directly as JPEG file on disk:

/// <summary>
/// Starts synchronous acquisition of image from TWAIN device and specifies that acquired JPEG compressed images must be saved directly to JPEG files on disk.
/// </summary>
static void StartSynchronousTwainScanningAndSpecifyThatJpegCompressedImagesMustBeSavedDirectlyToJpegFiles()
{
    // create the device manager
    using (Vintasoft.Twain.DeviceManager deviceManager = new Vintasoft.Twain.DeviceManager())
    {
        // open the device manager
        deviceManager.Open();

        // get reference to the default device
        Vintasoft.Twain.Device device = deviceManager.DefaultDevice;

        // specify that device UI must not be used
        device.ShowUI = false;

        // open the device
        device.Open();

        // check if device driver can save image to disk as JPEG files
        Vintasoft.Twain.TwainImageFileFormat[] supportedImageFileFormats = device.GetSupportedImageFileFormats();
        bool isJpegFileFormatSupported = false;
        for (int i = 0; i < supportedImageFileFormats.Length; i++)
        {
            if (supportedImageFileFormats[i] == Vintasoft.Twain.TwainImageFileFormat.Jpeg)
            {
                isJpegFileFormatSupported = true;
                break;
            }
        }
        //
        if (!isJpegFileFormatSupported)
        {
            // close the device
            device.Close();
            // close the device manager
            deviceManager.Close();
            //
            return;
        }

        // specify that File transfer mode must be used
        device.TransferMode = Vintasoft.Twain.TransferMode.File;
        // save images as JPEG files
        device.FileFormat = Vintasoft.Twain.TwainImageFileFormat.Jpeg;
        // set JPEG quality
        device.FileJpegQuality = 50;

        int acquiredImageCount = 0;

        // acquire images from device
        Vintasoft.Twain.AcquireModalState acquireModalState;
        do
        {
            acquireModalState = device.AcquireModal();
            switch (acquireModalState)
            {
                case Vintasoft.Twain.AcquireModalState.ImageAcquiring:
                    // set the filename for image
                    device.FileName = string.Format("test{0}.jpg", acquiredImageCount);
                    break;

                case Vintasoft.Twain.AcquireModalState.ImageAcquired:
                    // image is already saved to disk as JPEG file

                    // specify name for next acquired image
                    acquiredImageCount++;
                    break;
            }
        }
        while (acquireModalState != Vintasoft.Twain.AcquireModalState.None);

        // close the device
        device.Close();

        // close the device manager
        deviceManager.Close();
    }
}

VB.NET

''' <summary>
''' Starts synchronous acquisition of image from TWAIN device and specifies that acquired JPEG compressed images must be saved directly to JPEG files on disk.
''' </summary>
Private Shared Sub StartSynchronousTwainScanningAndSpecifyThatJpegCompressedImagesMustBeSavedDirectlyToJpegFiles()
        ' create the device manager
        Using deviceManager As New Vintasoft.Twain.DeviceManager()
                ' open the device manager
                deviceManager.Open()

                ' get reference to the default device
                Dim device As Vintasoft.Twain.Device = deviceManager.DefaultDevice

                ' specify that device UI must not be used
                device.ShowUI = False

                ' open the device
                device.Open()

                ' check if device driver can save image to disk as JPEG files
                Dim supportedImageFileFormats As Vintasoft.Twain.TwainImageFileFormat() = device.GetSupportedImageFileFormats()
                Dim isJpegFileFormatSupported As Boolean = False
                For i As Integer = 0 To supportedImageFileFormats.Length - 1
                        If supportedImageFileFormats(i) = Vintasoft.Twain.TwainImageFileFormat.Jpeg Then
                                isJpegFileFormatSupported = True
                                Exit For
                        End If
                Next
                '
                If Not isJpegFileFormatSupported Then
                        ' close the device
                        device.Close()
                        ' close the device manager
                        deviceManager.Close()
                        '
                        Return
                End If

                ' specify that File transfer mode must be used
                device.TransferMode = Vintasoft.Twain.TransferMode.File
                ' save images as JPEG files
                device.FileFormat = Vintasoft.Twain.TwainImageFileFormat.Jpeg
                ' set JPEG quality
                device.FileJpegQuality = 50

                Dim acquiredImageCount As Integer = 0

                ' acquire images from device
                Dim acquireModalState As Vintasoft.Twain.AcquireModalState
                Do
                        acquireModalState = device.AcquireModal()
                        Select Case acquireModalState
                                Case Vintasoft.Twain.AcquireModalState.ImageAcquiring
                                        ' set the filename for image
                                        device.FileName = String.Format("test{0}.jpg", acquiredImageCount)
                                        Exit Select

                                Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                                        ' image is already saved to disk as JPEG file

                                        ' specify name for next acquired image
                                        acquiredImageCount += 1
                                        Exit Select
                        End Select
                Loop While acquireModalState <> Vintasoft.Twain.AcquireModalState.None

                ' close the device
                device.Close()

                ' close the device manager
                deviceManager.Close()
        End Using
End Sub

3. Using Memory transfer mode

TWAIN driver must have built-in JPEG encoder - you can check this with the Device.GetSupportedImageCompressions method.
TWAIN driver returns acquired image as JPEG stream.
JPEG compression can be set using the Device.ImageCompression property.
Quality of JPEG file can be set using the DeviceCapabilityId.IJpegQuality capability.

Here is an example that demonstrates how to acquire JPEG compressed image from TWAIN device and save image to a JPEG file:

/// <summary>
/// Synchronously acquires JPEG compressed images from TWAIN device and saves images to JPEG files.
/// </summary>
static void AcquireJpegCompressedImagesFromTwainDeviceAndSaveImagesToJpegFiles()
{
    // create the device manager
    using (Vintasoft.Twain.DeviceManager deviceManager = new Vintasoft.Twain.DeviceManager())
    {
        // open the device manager
        deviceManager.Open();

        // get reference to the default device
        Vintasoft.Twain.Device device = deviceManager.DefaultDevice;

        // specify that device UI must not be used
        device.ShowUI = false;

        // open the device
        device.Open();

        // check if device driver can return image data as JPEG stream
        Vintasoft.Twain.TwainImageCompression[] supportedImageCompressions = device.GetSupportedImageCompressions();
        bool isJpegCompressionSupported = false;
        for (int i = 0; i < supportedImageCompressions.Length; i++)
        {
            if (supportedImageCompressions[i] == Vintasoft.Twain.TwainImageCompression.Jpeg)
            {
                isJpegCompressionSupported = true;
                break;
            }
        }
        //
        if (!isJpegCompressionSupported)
        {
            // close the device
            device.Close();
            // close the device manager
            deviceManager.Close();
            //
            return;
        }

        // specify that Memory transfer mode must be used
        device.TransferMode = Vintasoft.Twain.TransferMode.Memory;
        // set JPEG compression for image data
        device.ImageCompression = Vintasoft.Twain.TwainImageCompression.Jpeg;
        // set JPEG quality
        Vintasoft.Twain.DeviceCapability jpegQualityCap = device.Capabilities.Find(Vintasoft.Twain.DeviceCapabilityId.IJpegQuality);
        if (jpegQualityCap != null)
            jpegQualityCap.SetValue((int)50);

        // acquire images from device
        Vintasoft.Twain.AcquireModalState acquireModalState;
        do
        {
            acquireModalState = device.AcquireModal();
            switch (acquireModalState)
            {
                case Vintasoft.Twain.AcquireModalState.ImageAcquired:
                    // save acquired image to disk, SDK will save JPEG stream received from device driver
                    device.AcquiredImage.Save("test.jpg");

                    // dispose the acquired image
                    device.AcquiredImage.Dispose();
                    break;
            }
        }
        while (acquireModalState != Vintasoft.Twain.AcquireModalState.None);

        // close the device
        device.Close();

        // close the device manager
        deviceManager.Close();
    }
}

VB.NET

''' <summary>
''' Synchronously acquires JPEG compressed images from TWAIN device and saves images to JPEG files.
''' </summary>
Private Shared Sub AcquireJpegCompressedImagesFromTwainDeviceAndSaveImagesToJpegFiles()
        ' create the device manager
        Using deviceManager As New Vintasoft.Twain.DeviceManager()
                ' open the device manager
                deviceManager.Open()

                ' get reference to the default device
                Dim device As Vintasoft.Twain.Device = deviceManager.DefaultDevice

                ' specify that device UI must not be used
                device.ShowUI = False

                ' open the device
                device.Open()

                ' check if device driver can return image data as JPEG stream
                Dim supportedImageCompressions As Vintasoft.Twain.TwainImageCompression() = device.GetSupportedImageCompressions()
                Dim isJpegCompressionSupported As Boolean = False
                For i As Integer = 0 To supportedImageCompressions.Length - 1
                        If supportedImageCompressions(i) = Vintasoft.Twain.TwainImageCompression.Jpeg Then
                                isJpegCompressionSupported = True
                                Exit For
                        End If
                Next
                '
                If Not isJpegCompressionSupported Then
                        ' close the device
                        device.Close()
                        ' close the device manager
                        deviceManager.Close()
                        '
                        Return
                End If

                ' specify that Memory transfer mode must be used
                device.TransferMode = Vintasoft.Twain.TransferMode.Memory
                ' set JPEG compression for image data
                device.ImageCompression = Vintasoft.Twain.TwainImageCompression.Jpeg
                ' set JPEG quality
                Dim jpegQualityCap As Vintasoft.Twain.DeviceCapability = device.Capabilities.Find(Vintasoft.Twain.DeviceCapabilityId.IJpegQuality)
                If jpegQualityCap IsNot Nothing Then
                        jpegQualityCap.SetValue(CInt(50))
                End If

                ' acquire images from device
                Dim acquireModalState As Vintasoft.Twain.AcquireModalState
                Do
                        acquireModalState = device.AcquireModal()
                        Select Case acquireModalState
                                Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                                        ' save acquired image to disk, SDK will save JPEG stream received from device driver
                                        device.AcquiredImage.Save("test.jpg")

                                        ' dispose the acquired image
                                        device.AcquiredImage.Dispose()
                                        Exit Select
                        End Select
                Loop While acquireModalState <> Vintasoft.Twain.AcquireModalState.None

                ' close the device
                device.Close()

                ' close the device manager
                deviceManager.Close()
        End Using
End Sub

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