pdfRemoveDeviceNChannel
Remove a DeviceN color channel.
void pdfRemoveDeviceNChannel(PDFHandle pdf, int channelIdx)
This function removes (sets to zero) one color channel of the DeviceN
image generated by the last call to
pdfConvertPageToDeviceNImage.
This is useful to remove one or more channels before calling
pdfGetDeviceNToRGBBitmap.
The channel mask functions, pdfResetDeviceNChannelMask and
pdfSetDeviceNChannelMask, provide equivalent functionality and are
more efficient.
C:
int nChannels, i;
char *channelName;
unsigned int channelCMYK;
PDFImageHeader hdr;
char *bits;
int err;
err = pdfConvertPageToDeviceNImage(pdf, pageNum, dpi);
if (err != pdfOk) {
/* handle the error */
...
}
nChannels = pdfGetNumDeviceNChannels(pdf);
for (i = 0; i < nChannels; ++i) {
channelName = pdfGetDeviceNChannelName(pdf, i);
if ( ... ) {
pdfRemoveDeviceNChannel(pdf, i);
}
}
pdfGetDeviceNToRGBBitmap(pdf, 4, &hdr, &bits);
... use the bitmap ...
/* the bitmap memory must be freed when you are finished */
pdfFreeMemory(bits);
/* free the internal storage used by pdfConvertPageToDeviceNImage */
pdfClearDeviceNImage(pdf);