2
1
mirror of https://github.com/qpdf/qpdf.git synced 2024-12-22 19:08:59 +00:00
qpdf/examples/pdf-invert-images.cc
Jay Berkenbilt 9744414c66 Enable finer grained control of stream decoding
This commit adds several API methods that enable control over which
types of filters QPDF will attempt to decode. It also adds support for
/RunLengthDecode and /DCTDecode filters for both encoding and
decoding.
2017-08-21 17:44:22 -04:00

181 lines
5.3 KiB
C++

#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <qpdf/QPDF.hh>
#include <qpdf/QUtil.hh>
#include <qpdf/Buffer.hh>
#include <qpdf/QPDFWriter.hh>
static char const* whoami = 0;
void usage()
{
std::cerr << "Usage: " << whoami << " infile.pdf outfile.pdf [in-password]"
<< std::endl
<< "Invert some images in infile.pdf;"
<< " write output to outfile.pdf" << std::endl;
exit(2);
}
// Derive a class from StreamDataProvider to provide updated stream
// data. The main purpose of using this object is to avoid having to
// allocate memory up front for the objects. A real application might
// use temporary files in order to avoid having to allocate all the
// memory. Here, we're not going to worry about that since the goal
// is really to show how to use this facility rather than to show the
// best possible way to write an image inverter. This class still
// illustrates dynamic creation of the new stream data.
class ImageInverter: public QPDFObjectHandle::StreamDataProvider
{
public:
virtual ~ImageInverter()
{
}
virtual void provideStreamData(int objid, int generation,
Pipeline* pipeline);
// Map [og] = image object
std::map<QPDFObjGen, QPDFObjectHandle> image_objects;
// Map [og] = image data
std::map<QPDFObjGen, PointerHolder<Buffer> > image_data;
};
void
ImageInverter::provideStreamData(int objid, int generation,
Pipeline* pipeline)
{
// Use the object and generation number supplied to look up the
// image data. Then invert the image data and write the inverted
// data to the pipeline.
PointerHolder<Buffer> data =
this->image_data[QPDFObjGen(objid, generation)];
size_t size = data->getSize();
unsigned char* buf = data->getBuffer();
unsigned char ch;
for (size_t i = 0; i < size; ++i)
{
ch = static_cast<unsigned char>(0xff) - buf[i];
pipeline->write(&ch, 1);
}
pipeline->finish();
}
int main(int argc, char* argv[])
{
whoami = QUtil::getWhoami(argv[0]);
// For libtool's sake....
if (strncmp(whoami, "lt-", 3) == 0)
{
whoami += 3;
}
// For test suite
bool static_id = false;
if ((argc > 1) && (strcmp(argv[1], " --static-id") == 0))
{
static_id = true;
--argc;
++argv;
}
if (! ((argc == 3) || (argc == 4)))
{
usage();
}
char const* infilename = argv[1];
char const* outfilename = argv[2];
char const* password = (argc == 4) ? argv[3] : "";
try
{
QPDF qpdf;
qpdf.processFile(infilename, password);
ImageInverter* inv = new ImageInverter;
PointerHolder<QPDFObjectHandle::StreamDataProvider> p = inv;
// For each page...
std::vector<QPDFObjectHandle> pages = qpdf.getAllPages();
for (std::vector<QPDFObjectHandle>::iterator iter = pages.begin();
iter != pages.end(); ++iter)
{
QPDFObjectHandle& page = *iter;
// Get all images on the page.
std::map<std::string, QPDFObjectHandle> images =
page.getPageImages();
for (std::map<std::string, QPDFObjectHandle>::iterator iter =
images.begin();
iter != images.end(); ++iter)
{
QPDFObjectHandle& image = (*iter).second;
QPDFObjectHandle image_dict = image.getDict();
QPDFObjectHandle color_space =
image_dict.getKey("/ColorSpace");
QPDFObjectHandle bits_per_component =
image_dict.getKey("/BitsPerComponent");
// For our example, we can only work with images 8-bit
// grayscale images that we can fully decode. Use
// pipeStreamData with a null pipeline to determine
// whether the image is filterable. Directly inspect
// keys to determine the image type.
if (image.pipeStreamData(0, qpdf_ef_compress,
qpdf_dl_generalized) &&
color_space.isName() &&
bits_per_component.isInteger() &&
(color_space.getName() == "/DeviceGray") &&
(bits_per_component.getIntValue() == 8))
{
// Store information about the images based on the
// object and generation number. Recall that a single
// image object may be used more than once.
QPDFObjGen og = image.getObjGen();
if (inv->image_objects.count(og) == 0)
{
inv->image_objects[og] = image;
inv->image_data[og] = image.getStreamData();
// Register our stream data provider for this
// stream. Future calls to getStreamData or
// pipeStreamData will use the new
// information. Provide null for both filter
// and decode parameters. Note that this does
// not mean the image data will be
// uncompressed when we write the file. By
// default, QPDFWriter will use /FlateDecode
// for anything that is uncompressed or
// filterable in the input QPDF object, so we
// don't have to deal with it explicitly here.
image.replaceStreamData(
p,
QPDFObjectHandle::newNull(),
QPDFObjectHandle::newNull());
}
}
}
}
// Write out a new file
QPDFWriter w(qpdf, outfilename);
if (static_id)
{
// For the test suite, uncompress streams and use static
// IDs.
w.setStaticID(true); // for testing only
}
w.write();
std::cout << whoami << ": new file written to " << outfilename
<< std::endl;
}
catch (std::exception &e)
{
std::cerr << whoami << " processing file " << infilename << ": "
<< e.what() << std::endl;
exit(2);
}
return 0;
}