GdPictureImaging.SetAlphaChannel Method

Sets the Alpha channel of a GdPicture image.

public GdPictureStatus SetAlphaChannel(
    int ImageID, 
    ref Byte arPixels, 
    int SrcLeft, 
    int SrcTop, 
    int Width, 
    int Height
);

Visual Basic

Public Function SetAlphaChannel(
    ByVal ImageID As Integer, 
    ByRef arPixels() As Byte, 
    ByVal SrcLeft As Integer, 
    ByVal SrcTop As Integer, 
    ByVal Width As Integer, 
    ByVal Height As Integer
) As GdPictureStatus

Parameters

Parameters	Description
ImageID	GdPicture Image Identifier.
arPixels	Array of alpha components.
SrcLeft	The left source pixel of the area.
SrcTop	The top source pixel of the area.
Width	The width of the area in pixel.
Height	The height of the area in pixel.

Returns

A member of the GdPictureStatus enumeration.

Related Topics

GetAlphaChannel

Example

Applying a vertical transparent gradient to an image

Copy Code

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim Alpha() As Byte
    Dim PixelCount As Integer
    Dim oGdPictureImaging As New GdPictureImaging
    Dim ImageID As Integer
    Dim ImageHeight As Integer
    Dim ImageWidth As Integer
 
 
    oGdPictureImaging.SetLicenseNumber("XXXX")  'Please, replace XXXX by a valid demo or commercial license key.
    'Go to http://evaluation-gdpicture.com to get a 1 month trial key unlocking all features of the toolkit.
 
    ImageID = oGdPictureImaging.CreateGdPictureImageFromFile("")
    ImageHeight = oGdPictureImaging.GetHeight(ImageID)
    ImageWidth = oGdPictureImaging.GetWidth(ImageID)
    PixelCount = ImageHeight * ImageWidth
 
    ReDim Alpha(PixelCount)
 
    For i As Integer = 0 To PixelCount - 1
        Alpha(i) = CByte(255 / PixelCount * (i + 1))
    Next
    oGdPictureImaging.SetAlphaChannel(ImageID, Alpha, 0, 0, ImageWidth, ImageHeight)
 
 
    oGdPictureImaging.SaveAsPNG(ImageID, "c:test.png")
    oGdPictureImaging.ReleaseGdPictureImage(ImageID)
End Sub