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CreateAlphaImage Method
See Also  Example
Leadtools Namespace > RasterImage Class : CreateAlphaImage Method



Creates a grayscale image from this RasterImage alpha channel data.

Syntax

Visual Basic (Declaration)  
Public Function CreateAlphaImage() As RasterImage
Visual Basic (Usage) Copy Code
Dim instance As RasterImage
Dim value As RasterImage
 
value = instance.CreateAlphaImage()
C#  
public RasterImage CreateAlphaImage()
C++/CLI  
public:
RasterImage^ CreateAlphaImage();

Return Value

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

Example

Visual Basic Copy Code
Public Sub CreateAlphaImageExample()
   RasterCodecs.Startup()
   Dim codecs As RasterCodecs = New RasterCodecs()
   ' Load the image, at 16 bit per pixel.
   Dim image As RasterImage = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "IMAGE1.CMP", 16, CodecsLoadByteOrder.Bgr, 1, 1)

   ' Specify a rectangle to define the region.
   Dim EllipseRectangle As Rectangle = New Rectangle(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, LeadtoolsExamples.Common.ImagesPath.Path + "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(LeadtoolsExamples.Common.ImagesPath.Path + "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()
   RasterCodecs.Shutdown()
End Sub
C# Copy Code
public void CreateAlphaImageExample() 
{ 
   RasterCodecs.Startup(); 
   RasterCodecs codecs = new RasterCodecs(); 
   // Load the image, at 16 bit per pixel. 
   RasterImage image = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "IMAGE1.CMP", 16, CodecsLoadByteOrder.Bgr, 1, 1); 
 
   // Specify a rectangle to define the region. 
   Rectangle EllipseRectangle = new Rectangle(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, LeadtoolsExamples.Common.ImagesPath.Path + "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(LeadtoolsExamples.Common.ImagesPath.Path + "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(); 
   RasterCodecs.Shutdown(); 
}

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.

Requirements

Target Platforms: Microsoft .NET Framework 3.0, Windows XP, Windows Server 2003 family, Windows Server 2008 family

See Also