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Working with Images with the Script Task

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A database of products or users frequently includes images in addition to text and numeric data. The System.Drawing namespace in the Microsoft .NET Framework provides classes for manipulating images.

Example 1: Convert Images to JPEG Format

Example 2: Create and Save Thumbnail Images

[!참고] If you want to create a task that you can more easily reuse across multiple packages, consider using the code in this Script task sample as the starting point for a custom task. For more information, see Developing a Custom Task.

Example 1 Description: Convert Images to JPEG Format

The following example opens an image file specified by a variable and saves it as a compressed JPEG file by using an encoder. The code to retrieve encoder information is encapsulated in a private function.

To configure this Script Task example for use with a single image file

  1. Create a string variable named CurrentImageFile and set its value to the path and file name of an existing image file.

  2. On the Script page of the Script Task Editor, add the CurrentImageFile variable to the ReadOnlyVariables property.

  3. In the script project, set a reference to the System.Drawing namespace.

  4. In your code, use Imports statements to import the System.Drawing and System.IO namespaces.

To configure this Script Task example for use with multiple image files

  1. Place the Script task within a Foreach Loop container.

  2. On the Collection page of the Foreach Loop Editor, select the Foreach File Enumerator as the enumerator, and specify the path and file mask of the source files, such as "*.bmp."

  3. On the Variable Mappings page, map the CurrentImageFile variable to Index 0. This variable passes the current file name to the Script task on each iteration of the enumerator.

    [!참고] These steps are in addition to the steps listed in the procedure for use with a single image file.

Example 1 Code

Public Sub Main()

    'Create and initialize variables.
    Dim currentFile As String
    Dim newFile As String
    Dim bmp As Bitmap
    Dim eps As New Imaging.EncoderParameters(1)
    Dim ici As Imaging.ImageCodecInfo
    Dim supportedExtensions() As String = _
        {".BMP", ".GIF", ".JPG", ".JPEG", ".EXIF", ".PNG", _
        ".TIFF", ".TIF", ".ICO", ".ICON"}

    Try
        'Store the variable in a string for local manipulation.
        currentFile = Dts.Variables("CurrentImageFile").Value.ToString
        'Check the extension of the file against a list of
        'files that the Bitmap class supports.
        If Array.IndexOf(supportedExtensions, _
            Path.GetExtension(currentFile).ToUpper) > -1 Then

            'Load the file.
            bmp = New Bitmap(currentFile)

            'Calculate the new name for the compressed image.
            'Note: This will overwrite existing JPEGs.
            newFile = Path.Combine( _
                Path.GetDirectoryName(currentFile), _
                String.Concat(Path.GetFileNameWithoutExtension(currentFile), _
                ".jpg"))

            'Specify the compression ratio (0=worst quality, 100=best quality).
            eps.Param(0) = New Imaging.EncoderParameter( _
                Imaging.Encoder.Quality, 75)

            'Retrieve the ImageCodecInfo associated with the jpeg format.
            ici = GetEncoderInfo("image/jpeg")

            'Save the file, compressing it into the jpeg encoding.
            bmp.Save(newFile, ici, eps)
        Else
            'The file is not supported by the Bitmap class.
            Dts.Events.FireWarning(0, "Image Resampling Sample", _
                "File " & currentFile & " is not a supported format.", _
                "", 0)
         End If
        Dts.TaskResult = Dts.Results.Success
    Catch ex As Exception
        'An error occurred.
        Dts.Events.FireError(0, "Image Resampling Sample", _
            ex.Message & ControlChars.CrLf & ex.StackTrace, _
            String.Empty, 0)
        Dts.TaskResult = Dts.Results.Failure
    End Try

End Sub

Private Function GetEncoderInfo(ByVal mimeType As String) As Imaging.ImageCodecInfo

    'The available image codecs are returned as an array,
    'which requires code to iterate until the specified codec is found.

    Dim count As Integer
    Dim encoders() As Imaging.ImageCodecInfo

    encoders = Imaging.ImageCodecInfo.GetImageEncoders()

    For count = 0 To encoders.Length
        If encoders(count).MimeType = mimeType Then
            Return encoders(count)
        End If
    Next

    'This point is only reached if a codec is not found.
    Err.Raise(513, "Image Resampling Sample", String.Format( _
        "The {0} codec is not available. Unable to compress file.", _
            mimeType))
    Return Nothing

End Function

Example 2 Description: Create and Save Thumbnail Images

The following example opens an image file specified by a variable, creates a thumbnail of the image while maintaining a constant aspect ratio, and saves the thumbnail with a modified file name. The code that calculates the height and width of the thumbnail while maintaining a constant aspect ratio is encapsulated in a private subroutine.

To configure this Script Task example for use with a single image file

  1. Create a string variable named CurrentImageFile and set its value to the path and file name of an existing image file.

  2. Also create the MaxThumbSize integer variable and assign a value in pixels, such as 100.

  3. On the Script page of the Script Task Editor, add both variables to the ReadOnlyVariables property.

  4. In the script project, set a reference to the System.Drawing namespace.

  5. In your code, use Imports statements to import the System.Drawing and System.IO namespaces.

To configure this Script Task example for use with multiple image files

  1. Place the Script task within a Foreach Loop container.

  2. On the Collection page of the Foreach Loop Editor, select the Foreach File Enumerator as the Enumerator, and specify the path and file mask of the source files, such as "*.jpg."

  3. On the Variable Mappings page, map the CurrentImageFile variable to Index 0. This variable passes the current file name to the Script task on each iteration of the enumerator.

    [!참고] These steps are in addition to the steps listed in the procedure for use with a single image file.

Example 2 Code

Public Sub Main()

    Dim currentImageFile As String
    Dim currentImage As Image
    Dim maxThumbSize As Integer
    Dim thumbnailImage As Image
    Dim thumbnailFile As String
    Dim thumbnailHeight As Integer
    Dim thumbnailWidth As Integer

    currentImageFile = Dts.Variables("CurrentImageFile").Value.ToString
    thumbnailFile = Path.Combine( _
        Path.GetDirectoryName(currentImageFile), _
        String.Concat(Path.GetFileNameWithoutExtension(currentImageFile), _
        "_thumbnail.jpg"))

    Try
        currentImage = Image.FromFile(currentImageFile)

        maxThumbSize = CType(Dts.Variables("MaxThumbSize").Value, Integer)
        CalculateThumbnailSize( _
            maxThumbSize, currentImage, thumbnailWidth, thumbnailHeight)

        thumbnailImage = currentImage.GetThumbnailImage( _
           thumbnailWidth, thumbnailHeight, Nothing, Nothing)
        thumbnailImage.Save(thumbnailFile)
        Dts.TaskResult = Dts.Results.Success
    Catch ex As Exception
        Dts.Events.FireError(0, "Script Task Example", _
        ex.Message & ControlChars.CrLf & ex.StackTrace, _
        String.Empty, 0)
        Dts.TaskResult = Dts.Results.Failure
    End Try

End Sub

Private Sub CalculateThumbnailSize( _
    ByVal maxSize As Integer, ByVal sourceImage As Image, _
    ByRef thumbWidth As Integer, ByRef thumbHeight As Integer)

    If sourceImage.Width > sourceImage.Height Then
        thumbWidth = maxSize
        thumbHeight = CInt((maxSize / sourceImage.Width) * sourceImage.Height)
    Else
        thumbHeight = maxSize
        thumbWidth = CInt((maxSize / sourceImage.Height) * sourceImage.Width)
    End If

End Sub