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CreateAlphaImage Method

Summary
Creates a grayscale image from this RasterImage alpha channel data.
Syntax
C#
VB
Objective-C
C++
Java
public RasterImage CreateAlphaImage() 
Public Function CreateAlphaImage() As RasterImage 
- (nullable LTRasterImage *)createAlphaImage:(NSError **)error 
public RasterImage createAlphaImage() 
public: 
RasterImage^ CreateAlphaImage();  

Return Value

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

Remarks

Only 16-bit, 32-bit, 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
C#
VB
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Core; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Dicom; 
using Leadtools.Drawing; 
using Leadtools.Controls; 
using Leadtools.Svg; 
 
 
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:\LEADTOOLS21\Resources\Images"; 
} 
Imports Leadtools 
Imports Leadtools.Codecs 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Core 
Imports Leadtools.ImageProcessing.Color 
Imports Leadtools.Controls 
Imports Leadtools.Dicom 
Imports Leadtools.Drawing 
Imports Leadtools.Svg 
 
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:\LEADTOOLS21\Resources\Images" 
End Class 
Requirements

Target Platforms

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