pdfGetDeviceNBitmap
Get a bitmap for one DeviceN color channel.
int pdfGetDeviceNBitmap(PDFHandle pdf, int channelIdx, int rowPad, int upsideDown, PDFImageHeader *imgHdr, char **bits)
This function retrieves the bitmap for the specified channel
generated by the last call to
pdfConvertPageToDeviceNImage.
The bitmap will be an 8-bit grayscale bitmap, indicating the level of
the specific colorant at each pixel. The bitmap is handled in the
same way as for pdfConvertPageToBitmap2
in pdfImageGray mode:
rowPad= each row will be padded out to a multiple of this number of bytes (typically 1 for no padding, or 4 to pad to a 32-bit boundary)upsideDown= non-zero to store the bitmap with the bottom row firstimgHdr= a struct describing the output bitmap, with the following fields:width= image widthheight= image heightcolor=pdfImageGray
bits= pointer to the returned bitmap data
pdfGetDeviceNBitmap will
all have the same width and height.
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);
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 pdfConvertPageToBitmap2 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 pdfConvertPageToDeviceNImage */
pdfClearDeviceNImage(pdf);