qpdf/libqpdf/QPDFPageObjectHelper.cc

#include <qpdf/QPDFPageObjectHelper.hh>
#include <qpdf/QTC.hh>
#include <qpdf/QPDF.hh>
#include <qpdf/Pl_Concatenate.hh>
#include <qpdf/QUtil.hh>
#include <qpdf/QPDFExc.hh>
#include <qpdf/QPDFMatrix.hh>

class ContentProvider: public QPDFObjectHandle::StreamDataProvider
{
  public:
    ContentProvider(QPDFObjectHandle from_page) :
        from_page(from_page)
    {
    }
    virtual ~ContentProvider()
    {
    }
    virtual void provideStreamData(int objid, int generation,
                                   Pipeline* pipeline);

  private:
    QPDFObjectHandle from_page;
};

void
ContentProvider::provideStreamData(int, int, Pipeline* p)
{
    Pl_Concatenate concat("concatenate", p);
    std::string description = "contents from page object " +
        QUtil::int_to_string(from_page.getObjectID()) + " " +
        QUtil::int_to_string(from_page.getGeneration());
    std::string all_description;
    from_page.getKey("/Contents").pipeContentStreams(
        &concat, description, all_description);
    concat.manualFinish();
}

QPDFPageObjectHelper::Members::~Members()
{
}

QPDFPageObjectHelper::Members::Members()
{
}

QPDFPageObjectHelper::QPDFPageObjectHelper(QPDFObjectHandle oh) :
    QPDFObjectHelper(oh)
{
}

QPDFObjectHandle
QPDFPageObjectHelper::getAttribute(std::string const& name,
                                   bool copy_if_shared)
{
    bool inheritable = ((name == "/MediaBox") || (name == "/CropBox") ||
                        (name == "/Resources") || (name == "/Rotate"));

    QPDFObjectHandle node = this->oh;
    QPDFObjectHandle result(node.getKey(name));
    std::set<QPDFObjGen> seen;
    bool inherited = false;
    while (inheritable && result.isNull() && node.hasKey("/Parent"))
    {
        seen.insert(node.getObjGen());
        node = node.getKey("/Parent");
        if (seen.count(node.getObjGen()))
        {
            break;
        }
        result = node.getKey(name);
        if (! result.isNull())
        {
            QTC::TC("qpdf", "QPDFPageObjectHelper non-trivial inheritance");
            inherited = true;
        }
    }
    if (copy_if_shared && (inherited || result.isIndirect()))
    {
        QTC::TC("qpdf", "QPDFPageObjectHelper copy shared attribute");
        result = result.shallowCopy();
        this->oh.replaceKey(name, result);
    }
    return result;
}

QPDFObjectHandle
QPDFPageObjectHelper::getTrimBox(bool copy_if_shared)
{
    QPDFObjectHandle result = getAttribute("/TrimBox", copy_if_shared);
    if (result.isNull())
    {
        result = getCropBox(copy_if_shared);
    }
    return result;
}

QPDFObjectHandle
QPDFPageObjectHelper::getCropBox(bool copy_if_shared)
{
    QPDFObjectHandle result = getAttribute("/CropBox", copy_if_shared);
    if (result.isNull())
    {
        result = getMediaBox();
    }
    return result;
}

QPDFObjectHandle
QPDFPageObjectHelper::getMediaBox(bool copy_if_shared)
{
    return getAttribute("/MediaBox", copy_if_shared);
}


std::map<std::string, QPDFObjectHandle>
QPDFPageObjectHelper::getPageImages()
{
    return this->oh.getPageImages();
}

std::vector<QPDFAnnotationObjectHelper>
QPDFPageObjectHelper::getAnnotations(std::string const& only_subtype)
{
    std::vector<QPDFAnnotationObjectHelper> result;
    QPDFObjectHandle annots = this->oh.getKey("/Annots");
    if (annots.isArray())
    {
        size_t nannots = annots.getArrayNItems();
        for (size_t i = 0; i < nannots; ++i)
        {
            QPDFObjectHandle annot = annots.getArrayItem(i);
            if (only_subtype.empty() ||
                (annot.isDictionary() &&
                 annot.getKey("/Subtype").isName() &&
                 (only_subtype == annot.getKey("/Subtype").getName())))
            {
                result.push_back(QPDFAnnotationObjectHelper(annot));
            }
        }
    }
    return result;
}

std::vector<QPDFObjectHandle>
QPDFPageObjectHelper::getPageContents()
{
    return this->oh.getPageContents();
}

void
QPDFPageObjectHelper::addPageContents(QPDFObjectHandle contents, bool first)
{
    this->oh.addPageContents(contents, first);
}

void
QPDFPageObjectHelper::rotatePage(int angle, bool relative)
{
    this->oh.rotatePage(angle, relative);
}

void
QPDFPageObjectHelper::coalesceContentStreams()
{
    this->oh.coalesceContentStreams();
}

void
QPDFPageObjectHelper::parsePageContents(
    QPDFObjectHandle::ParserCallbacks* callbacks)
{
    this->oh.parsePageContents(callbacks);
}

void
QPDFPageObjectHelper::filterPageContents(
    QPDFObjectHandle::TokenFilter* filter,
    Pipeline* next)
{
    this->oh.filterPageContents(filter, next);
}

void
QPDFPageObjectHelper::pipePageContents(Pipeline* p)
{
    this->oh.pipePageContents(p);
}

void
QPDFPageObjectHelper::addContentTokenFilter(
    PointerHolder<QPDFObjectHandle::TokenFilter> token_filter)
{
    this->oh.addContentTokenFilter(token_filter);
}

class NameWatcher: public QPDFObjectHandle::TokenFilter
{
  public:
    NameWatcher() :
        saw_bad(false)
    {
    }
    virtual ~NameWatcher()
    {
    }
    virtual void handleToken(QPDFTokenizer::Token const&);
    std::set<std::string> names;
    bool saw_bad;
};

void
NameWatcher::handleToken(QPDFTokenizer::Token const& token)
{
    if (token.getType() == QPDFTokenizer::tt_name)
    {
        // Create a name object and get its name. This canonicalizes
        // the representation of the name
        this->names.insert(
            QPDFObjectHandle::newName(token.getValue()).getName());
    }
    else if (token.getType() == QPDFTokenizer::tt_bad)
    {
        saw_bad = true;
    }
    writeToken(token);
}

void
QPDFPageObjectHelper::removeUnreferencedResources()
{
    NameWatcher nw;
    try
    {
        filterPageContents(&nw);
    }
    catch (std::exception& e)
    {
        this->oh.warnIfPossible(
            std::string("Unable to parse content stream: ") + e.what() +
            "; not attempting to remove unreferenced objects from this page");
        return;
    }
    if (nw.saw_bad)
    {
        QTC::TC("qpdf", "QPDFPageObjectHelper bad token finding names");
        this->oh.warnIfPossible(
            "Bad token found while scanning content stream; "
            "not attempting to remove unreferenced objects from this page");
        return;
    }
    // Walk through /Font and /XObject dictionaries, removing any
    // resources that are not referenced. We must make copies of
    // resource dictionaries down into the dictionaries are mutating
    // to prevent mutating one dictionary from having the side effect
    // of mutating the one it was copied from.
    std::vector<std::string> to_filter;
    to_filter.push_back("/Font");
    to_filter.push_back("/XObject");
    QPDFObjectHandle resources = getAttribute("/Resources", true);
    for (std::vector<std::string>::iterator d_iter = to_filter.begin();
         d_iter != to_filter.end(); ++d_iter)
    {
        QPDFObjectHandle dict = resources.getKey(*d_iter);
        if (! dict.isDictionary())
        {
            continue;
        }
        dict = dict.shallowCopy();
        resources.replaceKey(*d_iter, dict);
        std::set<std::string> keys = dict.getKeys();
        for (std::set<std::string>::iterator k_iter = keys.begin();
             k_iter != keys.end(); ++k_iter)
        {
            if (! nw.names.count(*k_iter))
            {
                dict.removeKey(*k_iter);
            }
        }
    }
}

QPDFPageObjectHelper
QPDFPageObjectHelper::shallowCopyPage()
{
    QPDF* qpdf = this->oh.getOwningQPDF();
    if (! qpdf)
    {
        throw std::runtime_error(
            "QPDFPageObjectHelper::shallowCopyPage"
            " called with a direct objet");
    }
    QPDFObjectHandle new_page = this->oh.shallowCopy();
    return QPDFPageObjectHelper(qpdf->makeIndirectObject(new_page));
}

QPDFObjectHandle::Matrix
QPDFPageObjectHelper::getMatrixForTransformations(bool invert)
{
    QPDFObjectHandle::Matrix matrix(1, 0, 0, 1, 0, 0);
    QPDFObjectHandle bbox = getTrimBox(false);
    if (! bbox.isRectangle())
    {
        return matrix;
    }
    QPDFObjectHandle rotate_obj = getAttribute("/Rotate", false);
    QPDFObjectHandle scale_obj = getAttribute("/UserUnit", false);
    if (! (rotate_obj.isNull() && scale_obj.isNull()))
    {
        QPDFObjectHandle::Rectangle rect = bbox.getArrayAsRectangle();
        double width = rect.urx - rect.llx;
        double height = rect.ury - rect.lly;
        double scale = (scale_obj.isNumber()
                        ? scale_obj.getNumericValue()
                        : 1.0);
        int rotate = (rotate_obj.isInteger()
                      ? rotate_obj.getIntValue()
                      : 0);
        if (invert)
        {
            if (scale == 0.0)
            {
                return matrix;
            }
            scale = 1.0 / scale;
            rotate = 360 - rotate;
        }

        // Ignore invalid rotation angle
        switch (rotate)
        {
          case 90:
            matrix = QPDFObjectHandle::Matrix(
                0, -scale, scale, 0, 0, width * scale);
            break;
          case 180:
            matrix = QPDFObjectHandle::Matrix(
                -scale, 0, 0, -scale, width * scale, height * scale);
            break;
          case 270:
            matrix = QPDFObjectHandle::Matrix(
                0, scale, -scale, 0, height * scale, 0);
            break;
          default:
            matrix = QPDFObjectHandle::Matrix(
                scale, 0, 0, scale, 0, 0);
            break;
        }
    }
    return matrix;
}

QPDFObjectHandle
QPDFPageObjectHelper::getFormXObjectForPage(bool handle_transformations)
{
    QPDF* qpdf = this->oh.getOwningQPDF();
    if (! qpdf)
    {
        throw std::runtime_error(
            "QPDFPageObjectHelper::getFormXObjectForPage"
            " called with a direct objet");
    }
    QPDFObjectHandle result = QPDFObjectHandle::newStream(qpdf);
    QPDFObjectHandle newdict = result.getDict();
    newdict.replaceKey("/Type", QPDFObjectHandle::newName("/XObject"));
    newdict.replaceKey("/Subtype", QPDFObjectHandle::newName("/Form"));
    newdict.replaceKey("/Resources",
                       getAttribute("/Resources", false).shallowCopy());
    newdict.replaceKey("/Group",
                       getAttribute("/Group", false).shallowCopy());
    QPDFObjectHandle bbox = getTrimBox(false).shallowCopy();
    if (! bbox.isRectangle())
    {
        this->oh.warnIfPossible(
            "bounding box is invalid; form"
            " XObject created from page will not work");
    }
    newdict.replaceKey("/BBox", bbox);
    PointerHolder<QPDFObjectHandle::StreamDataProvider> provider =
        new ContentProvider(this->oh);
    result.replaceStreamData(
        provider, QPDFObjectHandle::newNull(), QPDFObjectHandle::newNull());
    QPDFObjectHandle rotate_obj = getAttribute("/Rotate", false);
    QPDFObjectHandle scale_obj = getAttribute("/UserUnit", false);
    if (handle_transformations &&
        (! (rotate_obj.isNull() && scale_obj.isNull())))
    {
        newdict.replaceKey("/Matrix",
                           QPDFObjectHandle::newArray(
                               getMatrixForTransformations()));
    }

    return result;
}

std::string
QPDFPageObjectHelper::placeFormXObject(
    QPDFObjectHandle fo, std::string name,
    QPDFObjectHandle::Rectangle rect,
    bool invert_transformations)
{
    // Calculate the transformation matrix that will place the given
    // form XObject fully inside the given rectangle, shrinking and
    // centering if needed.

    // When rendering a form XObject, the transformation in the
    // graphics state (cm) is applied first (of course -- when it is
    // applied, the PDF interpreter doesn't even know we're going to
    // be drawing a form XObject yet), and then the object's matrix
    // (M) is applied. The resulting matrix, when applied to the form
    // XObject's bounding box, will generate a new rectangle. We want
    // to create a transformation matrix that make the form XObject's
    // bounding box land in exactly the right spot.

    QPDFObjectHandle fdict = fo.getDict();
    QPDFObjectHandle bbox_obj = fdict.getKey("/BBox");
    if (! bbox_obj.isRectangle())
    {
        return "";
    }

    QPDFMatrix wmatrix;         // work matrix
    QPDFMatrix tmatrix;         // "to" matrix
    QPDFMatrix fmatrix;         // "from" matrix
    if (invert_transformations)
    {
        // tmatrix inverts scaling and rotation of the destination
        // page. Applying this matrix allows the overlayed form
        // XObject's to be absolute rather than relative to properties
        // of the destination page. tmatrix is part of the computed
        // transformation matrix.
        tmatrix = QPDFMatrix(getMatrixForTransformations(true));
        wmatrix.concat(tmatrix);
    }
    if (fdict.getKey("/Matrix").isMatrix())
    {
        // fmatrix is the transformation matrix that is applied to the
        // form XObject itself. We need this for calculations, but we
        // don't explicitly use it in the final result because the PDF
        // rendering system automatically applies this last before
        // drawing the form XObject.
        fmatrix = QPDFMatrix(fdict.getKey("/Matrix").getArrayAsMatrix());
        wmatrix.concat(fmatrix);
    }

    // The current wmatrix handles transformation from the form
    // xobject and, if requested, the destination page. Next, we have
    // to adjust this for scale and position.

    // Step 1: figure out what scale factor we need to make the form
    // XObject's bnounding box fit within the destination rectangle.

    // Transform bounding box
    QPDFObjectHandle::Rectangle bbox = bbox_obj.getArrayAsRectangle();
    QPDFObjectHandle::Rectangle T = wmatrix.transformRectangle(bbox);

    // Calculate a scale factor, if needed. If the transformed
    // rectangle is too big, shrink it. Never expand it.
    if ((T.urx == T.llx) || (T.ury == T.lly))
    {
        // avoid division by zero
        return "";
    }
    double rect_w = rect.urx - rect.llx;
    double rect_h = rect.ury - rect.lly;
    double t_w = T.urx - T.llx;
    double t_h = T.ury - T.lly;
    double xscale = rect_w / t_w;
    double yscale = rect_h / t_h;
    double scale = (xscale < yscale ? xscale : yscale);
    if (scale > 1.0)
    {
        scale = 1.0;
    }

    // Step 2: figure out what translation is required to get the
    // rectangle to the right spot: centered within the destination.
    wmatrix = QPDFMatrix();
    wmatrix.scale(scale, scale);
    wmatrix.concat(tmatrix);
    wmatrix.concat(fmatrix);

    T = wmatrix.transformRectangle(bbox);
    double t_cx = (T.llx + T.urx) / 2.0;
    double t_cy = (T.lly + T.ury) / 2.0;
    double r_cx = (rect.llx + rect.urx) / 2.0;
    double r_cy = (rect.lly + rect.ury) / 2.0;
    double tx = r_cx - t_cx;
    double ty = r_cy - t_cy;

    // Now we can calculate the final matrix. The final matrix does
    // not include fmatrix because that is applied automatically by
    // the PDF interpreter.
    QPDFMatrix cm;
    cm.translate(tx, ty);
    cm.scale(scale, scale);
    cm.concat(tmatrix);
    return (
        "q\n" +
        cm.unparse() + " cm\n" +
        name + " Do\n" +
        "Q\n");
}