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374 lines
13 KiB
C++
374 lines
13 KiB
C++
//
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// This is an example of creating a PDF file from scratch. It illustrates use of several QPDF
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// operations for creating objects and streams. It also serves as an illustration of how to use
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// StreamDataProvider with different types of filters.
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//
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#include <qpdf/Pl_Buffer.hh>
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#include <qpdf/Pl_DCT.hh>
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#include <qpdf/Pl_RunLength.hh>
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#include <qpdf/QIntC.hh>
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#include <qpdf/QPDF.hh>
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#include <qpdf/QPDFObjectHandle.hh>
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#include <qpdf/QPDFPageDocumentHelper.hh>
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#include <qpdf/QPDFWriter.hh>
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#include <qpdf/QUtil.hh>
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#include <cstdlib>
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#include <iostream>
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#include <memory>
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static char const* whoami = nullptr;
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// This is a simple StreamDataProvider that writes image data for an orange square of the given
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// width and height.
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class ImageProvider: public QPDFObjectHandle::StreamDataProvider
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{
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public:
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ImageProvider(std::string const& color_space, std::string const& filter);
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~ImageProvider() override = default;
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void provideStreamData(QPDFObjGen const&, Pipeline* pipeline) override;
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size_t getWidth() const;
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size_t getHeight() const;
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private:
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size_t width{400};
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size_t stripe_height{80};
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std::string color_space;
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std::string filter;
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size_t n_stripes{6};
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std::vector<std::string> stripes;
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J_COLOR_SPACE j_color_space{JCS_UNKNOWN};
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};
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ImageProvider::ImageProvider(std::string const& color_space, std::string const& filter) :
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color_space(color_space),
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filter(filter)
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{
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if (color_space == "/DeviceCMYK") {
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j_color_space = JCS_CMYK;
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stripes.emplace_back("\xff\x00\x00\x00", 4);
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stripes.emplace_back("\x00\xff\x00\x00", 4);
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stripes.emplace_back("\x00\x00\xff\x00", 4);
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stripes.emplace_back("\xff\x00\xff\x00", 4);
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stripes.emplace_back("\xff\xff\x00\x00", 4);
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stripes.emplace_back("\x00\x00\x00\xff", 4);
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} else if (color_space == "/DeviceRGB") {
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j_color_space = JCS_RGB;
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stripes.emplace_back("\xff\x00\x00", 3);
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stripes.emplace_back("\x00\xff\x00", 3);
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stripes.emplace_back("\x00\x00\xff", 3);
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stripes.emplace_back("\xff\x00\xff", 3);
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stripes.emplace_back("\xff\xff\x00", 3);
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stripes.emplace_back("\x00\x00\x00", 3);
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} else if (color_space == "/DeviceGray") {
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j_color_space = JCS_GRAYSCALE;
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stripes.emplace_back("\xee", 1);
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stripes.emplace_back("\xcc", 1);
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stripes.emplace_back("\x99", 1);
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stripes.emplace_back("\x66", 1);
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stripes.emplace_back("\x33", 1);
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stripes.emplace_back("\x00", 1);
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}
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}
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size_t
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ImageProvider::getWidth() const
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{
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return width;
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}
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size_t
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ImageProvider::getHeight() const
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{
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return stripe_height * n_stripes;
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}
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void
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ImageProvider::provideStreamData(QPDFObjGen const&, Pipeline* pipeline)
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{
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std::vector<std::shared_ptr<Pipeline>> to_delete;
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Pipeline* p = pipeline;
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std::shared_ptr<Pipeline> p_new;
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if (filter == "/DCTDecode") {
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p_new = std::make_shared<Pl_DCT>(
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"image encoder",
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pipeline,
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QIntC::to_uint(width),
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QIntC::to_uint(getHeight()),
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QIntC::to_int(stripes[0].length()),
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j_color_space);
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to_delete.push_back(p_new);
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p = p_new.get();
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} else if (filter == "/RunLengthDecode") {
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p_new = std::make_shared<Pl_RunLength>("image encoder", pipeline, Pl_RunLength::a_encode);
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to_delete.push_back(p_new);
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p = p_new.get();
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}
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for (size_t i = 0; i < n_stripes; ++i) {
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for (size_t j = 0; j < width * stripe_height; ++j) {
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p->writeString(stripes[i]);
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}
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}
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p->finish();
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}
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void
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usage()
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{
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std::cerr << "Usage: " << whoami << " filename" << std::endl
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<< "Creates a simple PDF and writes it to filename" << std::endl;
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exit(2);
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}
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static QPDFObjectHandle
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createPageContents(QPDF& pdf, std::string const& text)
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{
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// Create a stream that displays our image and the given text in our font.
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std::string contents = "BT /F1 24 Tf 72 320 Td (" + text +
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") Tj ET\n"
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"q 244 0 0 144 184 100 cm /Im1 Do Q\n";
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return pdf.newStream(contents);
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}
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QPDFObjectHandle
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newName(std::string const& name)
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{
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return QPDFObjectHandle::newName(name);
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}
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QPDFObjectHandle
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newInteger(size_t val)
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{
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return QPDFObjectHandle::newInteger(QIntC::to_int(val));
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}
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void
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add_page(
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QPDFPageDocumentHelper& dh,
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QPDFObjectHandle font,
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std::string const& color_space,
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std::string const& filter)
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{
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QPDF& pdf(dh.getQPDF());
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// Create a stream to encode our image. QPDFWriter will fill in the length and will respect our
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// filters based on stream data mode. Since we are not specifying, QPDFWriter will compress with
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// /FlateDecode if we don't provide any other form of compression.
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auto* p = new ImageProvider(color_space, filter);
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std::shared_ptr<QPDFObjectHandle::StreamDataProvider> provider(p);
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size_t width = p->getWidth();
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size_t height = p->getHeight();
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QPDFObjectHandle image = pdf.newStream();
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auto image_dict =
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// line-break
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"<<"
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" /Type /XObject"
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" /Subtype /Image"
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" /BitsPerComponent 8"
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">>"_qpdf;
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image_dict.replaceKey("/ColorSpace", newName(color_space));
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image_dict.replaceKey("/Width", newInteger(width));
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image_dict.replaceKey("/Height", newInteger(height));
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image.replaceDict(image_dict);
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// Provide the stream data.
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image.replaceStreamData(provider, QPDFObjectHandle::parse(filter), QPDFObjectHandle::newNull());
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// Create direct objects as needed by the page dictionary.
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QPDFObjectHandle procset = "[/PDF /Text /ImageC]"_qpdf;
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QPDFObjectHandle rfont = QPDFObjectHandle::newDictionary();
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rfont.replaceKey("/F1", font);
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QPDFObjectHandle xobject = QPDFObjectHandle::newDictionary();
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xobject.replaceKey("/Im1", image);
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QPDFObjectHandle resources = QPDFObjectHandle::newDictionary();
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resources.replaceKey("/ProcSet", procset);
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resources.replaceKey("/Font", rfont);
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resources.replaceKey("/XObject", xobject);
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// Create the page content stream
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QPDFObjectHandle contents = createPageContents(pdf, color_space + " with filter " + filter);
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// Create the page dictionary
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QPDFObjectHandle page = pdf.makeIndirectObject("<<"
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" /Type /Page"
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" /MediaBox [0 0 612 392]"
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">>"_qpdf);
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page.replaceKey("/Contents", contents);
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page.replaceKey("/Resources", resources);
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// Add the page to the PDF file
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dh.addPage(page, false);
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}
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static void
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check(
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char const* filename,
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std::vector<std::string> const& color_spaces,
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std::vector<std::string> const& filters)
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{
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// Each stream is compressed the way it is supposed to be. We will add additional tests in
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// qpdf.test to exercise QPDFWriter more fully. In this case, we want to make sure that we
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// actually have RunLengthDecode and DCTDecode where we are supposed to and FlateDecode where we
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// provided no filters.
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// Each image is correct. For non-lossy image compression, the uncompressed image data should
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// exactly match what ImageProvider provided. For the DCTDecode data, allow for some fuzz to
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// handle jpeg compression as well as its variance on different systems.
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// These tests should use QPDFObjectHandle's stream data retrieval methods, but don't try to
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// fully exercise them here. That is done elsewhere.
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size_t n_color_spaces = color_spaces.size();
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size_t n_filters = filters.size();
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QPDF pdf;
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pdf.processFile(filename);
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auto pages = QPDFPageDocumentHelper(pdf).getAllPages();
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if (n_color_spaces * n_filters != pages.size()) {
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throw std::logic_error("incorrect number of pages");
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}
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size_t pageno = 1;
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bool errors = false;
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for (auto& page: pages) {
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auto images = page.getImages();
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if (images.size() != 1) {
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throw std::logic_error("incorrect number of images on page");
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}
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// Check filter and color space.
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std::string desired_color_space = color_spaces[(pageno - 1) / n_color_spaces];
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std::string desired_filter = filters[(pageno - 1) % n_filters];
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// In the default mode, QPDFWriter will compress with /FlateDecode if no filters are
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// provided.
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if (desired_filter == "null") {
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desired_filter = "/FlateDecode";
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}
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QPDFObjectHandle image = images.begin()->second;
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QPDFObjectHandle image_dict = image.getDict();
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QPDFObjectHandle color_space = image_dict.getKey("/ColorSpace");
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QPDFObjectHandle filter = image_dict.getKey("/Filter");
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bool this_errors = false;
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if (!filter.isNameAndEquals(desired_filter)) {
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this_errors = errors = true;
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std::cout << "page " << pageno << ": expected filter " << desired_filter
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<< "; actual filter = " << filter.unparse() << std::endl;
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}
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if (!color_space.isNameAndEquals(desired_color_space)) {
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this_errors = errors = true;
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std::cout << "page " << pageno << ": expected color space " << desired_color_space
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<< "; actual color space = " << color_space.unparse() << std::endl;
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}
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if (!this_errors) {
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// Check image data
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auto actual_data = image.getStreamData(qpdf_dl_all);
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auto* p = new ImageProvider(desired_color_space, "null");
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std::shared_ptr<QPDFObjectHandle::StreamDataProvider> provider(p);
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Pl_Buffer b_p("get image data");
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provider->provideStreamData(QPDFObjGen(), &b_p);
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std::shared_ptr<Buffer> desired_data(b_p.getBuffer());
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if (desired_data->getSize() != actual_data->getSize()) {
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std::cout << "page " << pageno << ": image data length mismatch" << std::endl;
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this_errors = errors = true;
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} else {
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// Compare bytes. For JPEG, allow a certain number of the bytes to be off desired by
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// more than a given tolerance. Any of the samples may be a little off because of
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// lossy compression, and around sharp edges, things can be quite off. For non-lossy
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// compression, do not allow any tolerance.
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unsigned char const* actual_bytes = actual_data->getBuffer();
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unsigned char const* desired_bytes = desired_data->getBuffer();
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size_t len = actual_data->getSize();
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unsigned int mismatches = 0;
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int tolerance = (desired_filter == "/DCTDecode" ? 10 : 0);
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size_t threshold = (desired_filter == "/DCTDecode" ? len / 40U : 0);
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for (size_t i = 0; i < len; ++i) {
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int delta = actual_bytes[i] - desired_bytes[i];
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if ((delta > tolerance) || (delta < -tolerance)) {
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++mismatches;
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}
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}
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if (mismatches > threshold) {
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std::cout << "page " << pageno << ": " << desired_color_space << ", "
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<< desired_filter << ": mismatches: " << mismatches << " of " << len
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<< std::endl;
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this_errors = errors = true;
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}
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}
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}
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++pageno;
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}
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if (errors) {
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throw std::logic_error("errors found");
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} else {
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std::cout << "all checks passed" << std::endl;
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}
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}
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static void
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create_pdf(char const* filename)
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{
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QPDF pdf;
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// Start with an empty PDF that has no pages or non-required objects.
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pdf.emptyPDF();
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// Add an indirect object to contain a font descriptor for the built-in Helvetica font.
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QPDFObjectHandle font = pdf.makeIndirectObject(
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// line-break
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"<<"
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" /Type /Font"
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" /Subtype /Type1"
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" /Name /F1"
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" /BaseFont /Helvetica"
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" /Encoding /WinAnsiEncoding"
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">>"_qpdf);
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std::vector<std::string> color_spaces;
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color_spaces.emplace_back("/DeviceCMYK");
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color_spaces.emplace_back("/DeviceRGB");
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color_spaces.emplace_back("/DeviceGray");
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std::vector<std::string> filters;
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filters.emplace_back("null");
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filters.emplace_back("/DCTDecode");
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filters.emplace_back("/RunLengthDecode");
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QPDFPageDocumentHelper dh(pdf);
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for (auto const& color_space: color_spaces) {
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for (auto const& filter: filters) {
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add_page(dh, font, color_space, filter);
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}
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}
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QPDFWriter w(pdf, filename);
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w.write();
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// For test suite, verify that everything is the way it is supposed to be.
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check(filename, color_spaces, filters);
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}
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int
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main(int argc, char* argv[])
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{
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whoami = QUtil::getWhoami(argv[0]);
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if (argc != 2) {
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usage();
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}
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char const* filename = argv[1];
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try {
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create_pdf(filename);
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} catch (std::exception& e) {
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std::cerr << e.what() << std::endl;
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exit(2);
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}
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return 0;
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}
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