Convert a rectangular region to a DeviceN image.
int pdfConvertRegionToDeviceNImage(PDFHandle pdf, int page, int regionX, int regionY, int regionW, int regionH, double dpi)
This function rasterizes a rectangular region of a PDF 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.

The rectangular region is specified by the x,y coordinates of its upper-left corner and its width and height - in bitmap coordinates, not PDF coordinates. That is, if the whole-page bitmap would have been 1000 pixels wide and 2000 pixels high, and you request a region with (x,y) = (0,0) and (w,h) = (1000,500), the resulting bitmap will be the top fourth of the page.

After calling pdfConvertRegionToDeviceNImage:

Finally, call pdfClearDeviceNImage to release the memory used by pdfConvertRegionToDeviceNImage.

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

pdfSetConfig("overprintPreview yes");
int nChannels, i; char *channelName; unsigned int channelCMYK; PDFImageHeader hdr; char *bits; int err; err = pdfConvertRegionToDeviceNImage(pdf, 5, 0, 0, 1000, 500, dpi); if (err != pdfOk) { /* handle the error */ ... } nChannels = pdfGetNumDeviceNChannels(pdf); for (i = 0; i < nChannels; ++i) { channelName = pdfGetDeviceNChannelName(pdf, i); channelCMYK = pdfGetDeviceNChannelCMYK(pdf, i); printf("channel %d: %s = %08x\n", channelName, channelCMYK); pdfGetDeviceNBitmap(pdf, i, 1, 0, &hdr, *bits); /* hdr and bits represent a grayscale bitmap -- similar to pdfConvertRegionToBitmap2 with pdfImageGray */ /* each channel has an 8-bit bitmap; the bitmaps for all channels will have the same width and height */ ... /* the bitmap memory must be freed when you are finished */ pdfFreeMemory(bits); } /* free the internal storage used by pdfConvertRegionToDeviceNImage */ pdfClearDeviceNImage(pdf);