Convert alpha channel to mask

I’m getting icons for extensions and then use this image as drag image. The icon image has an alpha channel but the drag image needs a picture with a mask (bug?). How do I convert an alpha channel to a mask?

First part for getting an icon for an extension:

[code] const extension = “gz”
const ScaleFactor = 1
const size = 256

dim theIcon as IconMBS = new IconMBS("", “”, extension, “”)
dim pic as new Picture(size * ScaleFactor, size * ScaleFactor)
dim thePictureContext as CGBitmapContextMBS = CGBitmapContextMBS.CreateWithPicture(pic)
const DrawNormal = 0
const DrawNoImage = 2
const DrawNoMask = 4
const DrawSelected = &h8000
if theIcon = nil or thePictureContext = nil then
'Return nil
end if
thePictureContext.ClearRect CGRectMBS.Make(0, 0, size * ScaleFactor, size * ScaleFactor)
theIcon.DrawIconCGContext(thePictureContext.Handle, 0, 0, size * ScaleFactor, size * ScaleFactor, 0, 0, DrawNormal, &c000000)

If I use the following code for converting the alpha channel to a mask:

Dim surf As RGBSurface = pic.RGBSurface dim MaskPicture as new Picture(pic.Width, pic.Height) dim masksurf as RGBSurface = MaskPicture.RGBSurface Dim lastX As Integer = pic.Width - 1 Dim lastY As Integer = pic.Height - 1 For y As Integer = 0 To lastY For x As Integer = 0 To lastX dim i as Integer = surf.Pixel(x, y).Alpha masksurf.Pixel(x, y) = RGB(i, i, i) Next Next

then I get a white ring on black. What is wrong here?

Xojo 2016r11. Mac OS 10.11.4.

You don’t need to scan the rgbsurface. Just draw the image and copy the mask

dim MaskPicture As new Picture(pic.Width, pic.Height, 32) //32 for mask MaskPicture.Graphics.DrawPicture(pic, 0, 0) MaskPicture.ApplyMask(pic.CopyMask)

Thanks, Will. CopyMask for Alpha pictures could have a better name.