getDeviceNAlphaPicture
Get a Picture object for the DeviceN alpha channel.
getDeviceNAlphaPicture([out, retval] IUnknown **pic)
This function retrieves the Picture object (OLE
IPicture
interface) for the alpha channel generated by the last call to
convertPageToDeviceNImageWithAlpha.
The Picture will be an 8-bit grayscale bitmap, indicating the alpha value at each pixel.
Note: this function is only useful with
convertPageToDeviceNImageWithAlpha and
convertRegionToDeviceNImageWithAlpha.
VB:
rast.convertPageToDeviceNImage(page, dpi)
nChannels = rast.getNumDeviceNChannels()
For i = 0 To nChannels-1
channelName = rast.getDeviceNChannelName(i)
channelCMYK = rast.getDeviceNChannelCMYK(i)
pic = rast.getDeviceNPicture(i)
' each channel has an 8-bit grayscale bitmap, similar to what
' is returned by convertPageToPicture in imageGray mode
...
Next i
pic = rast.getDeviceNAlphaPicture()
' the returned image is similar to the color channel images
...
rast.clearDeviceNImage()