Inserts one canvas into a color or alpha channel on another.

[VBScript]
Canvas.SetChannel inChannel, inImage

This allows you to insert a color channel using another Canvas as an intensity map. Most commonly you will want to use this method to insert an alpha channel using another Canvas as a matte. You can use then use blends and transparencies (both are specified using alpha channels).

The depth of the Canvas will be set to 'millions' as soon as you insert a channel. If the sizes of the two Canvases do not match the intensity map Canvas will be stretched to the correct size.

The channel names you can use are:

• "red"
• "green"
• "blue"
• "alpha"

Canvas Image property.
Canvas DrawCanvas function.
Mode parameter.
Alpha Channels.

[VBScript]
Set bg = Server.CreateObject("ImageGlue7.Canvas")
Set stamp = Server.CreateObject("ImageGlue7.Canvas")
Set mask = Server.CreateObject("ImageGlue7.Canvas")
' create canvas
bg.Color = "blue"
bg.Width = 100
bg.Height = 90
mask.DrawFile Server.MapPath("cloud.gif"), ""
stamp.Width = mask.Width
stamp.Height = mask.Height
' first draw white cloud
stamp.Color = "white"
stamp.Erase
stamp.SetChannel "alpha", mask.Image
bg.DrawCanvas stamp.Image, "Pos=10,10 Mode=Transparent"
' ... then light gray cloud
stamp.Color = "lightgray"
stamp.Erase
stamp.SetChannel "alpha", mask.Image
bg.DrawCanvas stamp.Image, "Pos=60,10 Mode=Transparent"
' ... then dark gray cloud
stamp.Color = "darkgray"
stamp.Erase
stamp.SetChannel "alpha", mask.Image
bg.DrawCanvas stamp.Image, "Pos=10,60 Mode=Transparent"
' ... then black cloud
stamp.Color = "black"
stamp.Erase
stamp.SetChannel "alpha", mask.Image
bg.DrawCanvas stamp.Image, "Pos=60,60 Mode=Transparent"
' finally save image
bg.SaveAs Server.MapPath("setchannel.jpg"), "Quality=high"

The above draws four solid blocks of color using an alpha channel as a matte. The input and output files are shown below.

cloud.gif

setchannel.jpg