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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 BasicCopy 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