convertPageToDeviceNImageWithAlpha

Convert a page to a DeviceN image with an alpha channel.
convertPageToDeviceNImageWithAlpha([in] int page, [in] double dpi)
This function rasterizes a page in DeviceN mode, i.e., with separate color channels for each process color (cyan, magenta, yellow, and black), and for each custom (a.k.a., spot) color.

This function differs from convertPageToDeviceNImage in that it skips the final page compositing step, and maintains an alpha bitmap. The alpha bitmap can be retrieved with getDeviceNAlphaPicture.

Note: The alpha bitmap is only useful with PDF files that have been constructed with a transparent background.

After calling convertPageToDeviceNImageWithAlpha:

Finally, call clearDeviceNImage to release the memory used by convertPageToDeviceNImageWithAlpha.

To enable an overprint preview rasterization, call setConfig to set the overprintPreview parameter before calling convertPageToDeviceNImage:

pdf.setConfig "overprintPreview yes"
VB6:
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
convertRegionToDeviceNImageWithAlpha
getNumDeviceNChannels
getDeviceNChannelName
getDeviceNChannelCMYK
getDeviceNPicture
getDeviceNAlphaPicture
clearDeviceNImage