CreateAlphaImage Method

Creates a grayscale image from this RasterImage alpha channel data.

Syntax

Visual Basic
C#
WinRT C#
WinRT JavaScript
C++

public RasterImage CreateAlphaImage()

'Declaration
 
Public Function CreateAlphaImage() As RasterImage

'Usage
 
Dim instance As RasterImage
Dim value As RasterImage
 
value = instance.CreateAlphaImage()

public RasterImage CreateAlphaImage()

 function Leadtools.RasterImage.CreateAlphaImage()

public:
RasterImage^ CreateAlphaImage();

Return Value

The newly create image, which contains the source image alpha channel data.

Remarks

Only 16-, 32-, and 64-bit images can have an alpha channel. If the source image has another color resolution, the result is an image filled with zeros.

Typically, the alpha channel contains a mask that is used for transparency.

For more information, refer to Implementing Transparency.

For more information, refer to Grayscale Images.

For more information, refer to Saving A Region.

Example

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Public Sub CreateAlphaImageExample()
      Dim codecs As RasterCodecs = New RasterCodecs()
      ' Load the image, at 16 bit per pixel.
      Dim image As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP"), 16, CodecsLoadByteOrder.Bgr, 1, 1)

      ' Specify a rectangle to define the region.
      Dim EllipseRectangle As LeadRect = New LeadRect(image.Width \ 8, image.Height \ 8, image.Width \ 2, image.Height \ 2)

      ' Create an elliptical region in the AlphaImage.
      image.AddEllipseToRegion(Nothing, EllipseRectangle, RasterRegionCombineMode.Set)

      ' Create a mask image from the region.
      Dim alphaImage As RasterImage = image.CreateMaskFromRegion()

      ' Update the alpha channel in the main image.
      image.SetAlphaImage(alphaImage)

      ' Save the image at 16 bits per pixel to keep the alpha channel.
      codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "TestAlpha.TIF"), RasterImageFormat.Tif, 24, 1, 1, 1, CodecsSavePageMode.Overwrite)

      ' Load the bitmap that we just saved and get its alpha channel.
      image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "TestAlpha.TIF"), 16, CodecsLoadByteOrder.Bgr, 1, 1)

      alphaImage = image.CreateAlphaImage()

      ' Use the AlphaBitmap as a mask to set the region in the MainBitmap.
      image.AddMaskToRegion(Nothing, alphaImage, RasterRegionCombineMode.Set)

      image.Dispose()
      codecs.Dispose()
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

public void CreateAlphaImageExample()
   {
      RasterCodecs codecs = new RasterCodecs();
      // Load the image, at 16 bit per pixel.
      RasterImage image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "IMAGE1.CMP"), 16, CodecsLoadByteOrder.Bgr, 1, 1);

      // Specify a rectangle to define the region.
      LeadRect ellipseRectangle = new LeadRect(image.Width / 8, image.Height / 8, image.Width / 2, image.Height / 2);

      // Create an elliptical region in the AlphaImage.
      image.AddEllipseToRegion(null, ellipseRectangle, RasterRegionCombineMode.Set);

      // Create a mask image from the region.
      RasterImage alphaImage = image.CreateMaskFromRegion();

      // Update the alpha channel in the main image.
      image.SetAlphaImage(alphaImage);

      // Save the image at 16 bits per pixel to keep the alpha channel.
      codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "TestAlpha.TIF"), RasterImageFormat.Tif, 24, 1, 1, 1, CodecsSavePageMode.Overwrite);

      // Load the bitmap that we just saved and get its alpha channel.
      image = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir,"TestAlpha.TIF"), 16, CodecsLoadByteOrder.Bgr, 1, 1);

      alphaImage = image.CreateAlphaImage();

      // Use the AlphaBitmap as a mask to set the region in the MainBitmap.
      image.AddMaskToRegion(null, alphaImage, RasterRegionCombineMode.Set);

      image.Dispose();
      codecs.Dispose();
   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

RasterImageExamples.prototype.CreateAlphaImageExample = function ( )
{
   Tools.SetLicense ( ) ;
   with (Leadtools) {
      with (Leadtools.Codecs) {

         var codecs = new RasterCodecs();
         // Load the image, at 16 bit per pixel.
         var srcFileName = "Assets\\Image1.cmp";
         var image;

         return Tools.AppInstallFolder().getFileAsync(srcFileName).then(function (loadFile) {
            return codecs.loadAsync(LeadStreamFactory.create(loadFile), 16, CodecsLoadByteOrder.bgr, 1, 1)
         })
            .then(function (img) {
               image = img;

               // Specify a rectangle to define the region.
               var ellipseRectangle = LeadRectHelper.create(image.width / 8, image.height / 8, image.width / 2, image.height / 2);

               // Create an elliptical region in the AlphaImage.
               image.addEllipseToRegion(null, ellipseRectangle, RasterRegionCombineMode.set);

               // Create a mask image from the region.
               var alphaImage = image.createMaskFromRegion();

               // Update the alpha channel in the main image.
               image.setAlphaImage(alphaImage);

               // Save the image at 16 bits per pixel to keep the alpha channel.
               return Tools.AppLocalFolder().createFileAsync("TestAlpha.TIF")
            })
            .then(function (saveFile) {

               var saveStream = LeadStreamFactory.create(saveFile);
               return codecs.saveAsync(image, saveStream, RasterImageFormat.tif, 24, 1, 1, 1, CodecsSavePageMode.overwrite)
            })
            .then(function () {

               image.close();

               // Load the bitmap that we just saved and get its alpha channel.
               srcFileName = "TestAlpha.TIF";
               return Tools.AppLocalFolder().getFileAsync(srcFileName)
            })
            .then(function (loadFile) {
               return codecs.loadAsync(LeadStreamFactory.create(loadFile), 16, CodecsLoadByteOrder.bgr, 1, 1)
            })
            .then(function (img) {
               image = img;

               alphaImage = image.createAlphaImage();

               // Use the AlphaBitmap as a mask to set the region in the MainBitmap.
               image.addMaskToRegion(null, alphaImage, RasterRegionCombineMode.set);
               console.assert(image.hasRegion, "image.HasRegion");

               image.close();
               codecs.close();
            });
      }
   }
}

[TestMethod]
public async Task CreateAlphaImageExample()
{
   RasterCodecs codecs = new RasterCodecs();
   // Load the image, at 16 bit per pixel.
   string srcFileName = @"Assets\Image1.cmp";
   StorageFile loadFile = await Tools.AppInstallFolder.GetFileAsync(srcFileName);
   RasterImage image = await codecs.LoadAsync(LeadStreamFactory.Create(loadFile), 16, CodecsLoadByteOrder.Bgr, 1, 1);
   // Specify a rectangle to define the region.
   LeadRect ellipseRectangle = LeadRectHelper.Create(image.Width / 8, image.Height / 8, image.Width / 2, image.Height / 2);

   // Create an elliptical region in the AlphaImage.
   image.AddEllipseToRegion(null, ellipseRectangle, RasterRegionCombineMode.Set);

   // Create a mask image from the region.
   RasterImage alphaImage = image.CreateMaskFromRegion();

   // Update the alpha channel in the main image.
   image.SetAlphaImage(alphaImage);

   // Save the image at 16 bits per pixel to keep the alpha channel.
   StorageFile saveFile = await Tools.AppLocalFolder.CreateFileAsync("TestAlpha.TIF");
   ILeadStream saveStream = LeadStreamFactory.Create(saveFile);
   await codecs.SaveAsync(image, saveStream, RasterImageFormat.Tif, 24, 1, 1, 1, CodecsSavePageMode.Overwrite);

   image.Dispose();

   // Load the bitmap that we just saved and get its alpha channel.
   srcFileName = @"TestAlpha.TIF";
   image = await codecs.LoadAsync(saveStream, 16, CodecsLoadByteOrder.Bgr, 1, 1);

   alphaImage = image.CreateAlphaImage();

   // Use the AlphaBitmap as a mask to set the region in the MainBitmap.
   image.AddMaskToRegion(null, alphaImage, RasterRegionCombineMode.Set);
   Assert.IsTrue(image.HasRegion);

   image.Dispose();
   codecs.Dispose();
}

public void CreateAlphaImageExample(RasterImage image, Stream destStream)
{
   RasterCodecs codecs = new RasterCodecs();
   // Specify a rectangle to define the region.
   LeadRect EllipseRectangle = new LeadRect(image.Width / 8, image.Height / 8, image.Width / 2, image.Height / 2);

   // Create a region in the AlphaImage.
   image.AddRectangleToRegion(null, EllipseRectangle, RasterRegionCombineMode.Set);

   // Create a mask image from the region.
   RasterImage alphaImage = image.CreateMaskFromRegion();

   // Update the alpha channel in the main image.
   image.SetAlphaImage(alphaImage);

   // Save the image at 16 bits per pixel to keep the alpha channel.
   codecs.Save(image, destStream, RasterImageFormat.Tif, 24, 1, 1, 1, CodecsSavePageMode.Overwrite);

   // Load the bitmap that we just saved and get its alpha channel.
   image = codecs.Load(destStream, 16, CodecsLoadByteOrder.Bgr, 1, 1);

   alphaImage = image.CreateAlphaImage();

   // Use the AlphaBitmap as a mask to set the region in the MainBitmap.
   image.AddMaskToRegion(null, alphaImage, RasterRegionCombineMode.Set);

   image.Dispose();
}

Public Sub CreateAlphaImageExample(ByVal image As RasterImage, ByVal destStream As Stream)
   Dim codecs As RasterCodecs = New RasterCodecs()
   ' Specify a rectangle to define the region.
   Dim EllipseRectangle As LeadRect = New LeadRect(image.Width / 8, image.Height / 8, image.Width / 2, image.Height / 2)

   ' Create a region in the AlphaImage.
   image.AddRectangleToRegion(Nothing, EllipseRectangle, RasterRegionCombineMode.Set)

   ' Create a mask image from the region.
   Dim alphaImage As RasterImage = image.CreateMaskFromRegion()

   ' Update the alpha channel in the main image.
   image.SetAlphaImage(alphaImage)

   ' Save the image at 16 bits per pixel to keep the alpha channel.
   codecs.Save(image, destStream, RasterImageFormat.Tif, 24, 1, 1, 1, CodecsSavePageMode.Overwrite)

   ' Load the bitmap that we just saved and get its alpha channel.
   image = codecs.Load(destStream, 16, CodecsLoadByteOrder.Bgr, 1, 1)

   alphaImage = image.CreateAlphaImage()

   ' Use the AlphaBitmap as a mask to set the region in the MainBitmap.
   image.AddMaskToRegion(Nothing, alphaImage, RasterRegionCombineMode.Set)

   image.Dispose()
End Sub

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

RasterImage Class
RasterImage Members