QPDFAnnotationObjectHelper.cc
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#include <qpdf/QPDFAnnotationObjectHelper.hh>
#include <qpdf/QPDF.hh>
#include <qpdf/QPDFMatrix.hh>
#include <qpdf/QTC.hh>
#include <qpdf/QUtil.hh>
QPDFAnnotationObjectHelper::QPDFAnnotationObjectHelper(QPDFObjectHandle oh) :
QPDFObjectHelper(oh)
{
}
std::string
QPDFAnnotationObjectHelper::getSubtype()
{
return this->oh.getKey("/Subtype").getName();
}
QPDFObjectHandle::Rectangle
QPDFAnnotationObjectHelper::getRect()
{
return this->oh.getKey("/Rect").getArrayAsRectangle();
}
QPDFObjectHandle
QPDFAnnotationObjectHelper::getAppearanceDictionary()
{
return this->oh.getKey("/AP");
}
std::string
QPDFAnnotationObjectHelper::getAppearanceState()
{
if (this->oh.getKey("/AS").isName()) {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper AS present");
return this->oh.getKey("/AS").getName();
}
QTC::TC("qpdf", "QPDFAnnotationObjectHelper AS absent");
return "";
}
int
QPDFAnnotationObjectHelper::getFlags()
{
QPDFObjectHandle flags_obj = this->oh.getKey("/F");
return flags_obj.isInteger() ? flags_obj.getIntValueAsInt() : 0;
}
QPDFObjectHandle
QPDFAnnotationObjectHelper::getAppearanceStream(
std::string const& which, std::string const& state)
{
QPDFObjectHandle ap = getAppearanceDictionary();
std::string desired_state = state.empty() ? getAppearanceState() : state;
if (ap.isDictionary()) {
QPDFObjectHandle ap_sub = ap.getKey(which);
if (ap_sub.isStream() && desired_state.empty()) {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP stream");
return ap_sub;
}
if (ap_sub.isDictionary() && (!desired_state.empty())) {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP dictionary");
QPDFObjectHandle ap_sub_val = ap_sub.getKey(desired_state);
if (ap_sub_val.isStream()) {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP sub stream");
return ap_sub_val;
}
}
}
QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP null");
return QPDFObjectHandle::newNull();
}
std::string
QPDFAnnotationObjectHelper::getPageContentForAppearance(
std::string const& name,
int rotate,
int required_flags,
int forbidden_flags)
{
if (!getAppearanceStream("/N").isStream()) {
return "";
}
// The appearance matrix computed by this method is the
// transformation matrix that needs to be in effect when drawing
// this annotation's appearance stream on the page. The algorithm
// for computing the appearance matrix described in section 12.5.5
// of the ISO-32000 PDF spec is similar but not identical to what
// we are doing here.
// When rendering an appearance stream associated with an
// annotation, there are four relevant components:
//
// * The appearance stream's bounding box (/BBox)
// * The appearance stream's matrix (/Matrix)
// * The annotation's rectangle (/Rect)
// * In the case of form fields with the NoRotate flag, the
// page's rotation
// When rendering a form xobject in isolation, just drawn with a
// /Do operator, there is no form field, so page rotation is not
// relevant, and there is no annotation, so /Rect is not relevant,
// so only /BBox and /Matrix are relevant. The effect of these are
// as follows:
// * /BBox is treated as a clipping region
// * /Matrix is applied as a transformation prior to rendering the
// appearance stream.
// There is no relationship between /BBox and /Matrix in this
// case.
// When rendering a form xobject in the context of an annotation,
// things are a little different. In particular, a matrix is
// established such that /BBox, when transformed by /Matrix, would
// fit completely inside of /Rect. /BBox is no longer a clipping
// region. To illustrate the difference, consider a /Matrix of
// [2 0 0 2 0 0], which is scaling by a factor of two along both
// axes. If the appearance stream drew a rectangle equal to /BBox,
// in the case of the form xobject in isolation, this matrix would
// cause only the lower-left quadrant of the rectangle to be
// visible since the scaling would cause the rest of it to fall
// outside of the clipping region. In the case of the form xobject
// displayed in the context of an annotation, such a matrix would
// have no effect at all because it would be applied to the
// bounding box first, and then when the resulting enclosing
// quadrilateral was transformed to fit into /Rect, the effect of
// the scaling would be undone.
// Our job is to create a transformation matrix that compensates
// for these differences so that the appearance stream of an
// annotation can be drawn as a regular form xobject.
// To do this, we perform the following steps, which overlap
// significantly with the algorithm in 12.5.5:
// 1. Transform the four corners of /BBox by applying /Matrix to
// them, creating an arbitrarily transformed quadrilateral.
// 2. Find the minimum upright rectangle that encompasses the
// resulting quadrilateral. This is the "transformed appearance
// box", T.
// 3. Compute matrix A that maps the lower left and upper right
// corners of T to the annotation's /Rect. This can be done by
// scaling so that the sizes match and translating so that the
// scaled T exactly overlaps /Rect.
// If the annotation's /F flag has bit 4 set, this means that
// annotation is to be rotated about its upper left corner to
// counteract any rotation of the page so it remains upright. To
// achieve this effect, we do the following extra steps:
// 1. Perform the rotation on /BBox box prior to transforming it
// with /Matrix (by replacing matrix with concatenation of
// matrix onto the rotation)
// 2. Rotate the destination rectangle by the specified amount
// 3. Apply the rotation to A as computed above to get the final
// appearance matrix.
QPDFObjectHandle rect_obj = this->oh.getKey("/Rect");
QPDFObjectHandle as = getAppearanceStream("/N").getDict();
QPDFObjectHandle bbox_obj = as.getKey("/BBox");
QPDFObjectHandle matrix_obj = as.getKey("/Matrix");
int flags = getFlags();
if (flags & forbidden_flags) {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper forbidden flags");
return "";
}
if ((flags & required_flags) != required_flags) {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper missing required flags");
return "";
}
if (!(bbox_obj.isRectangle() && rect_obj.isRectangle())) {
return "";
}
QPDFMatrix matrix;
if (matrix_obj.isMatrix()) {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper explicit matrix");
matrix = QPDFMatrix(matrix_obj.getArrayAsMatrix());
} else {
QTC::TC("qpdf", "QPDFAnnotationObjectHelper default matrix");
}
QPDFObjectHandle::Rectangle rect = rect_obj.getArrayAsRectangle();
bool do_rotate = (rotate && (flags & an_no_rotate));
if (do_rotate) {
// If the the annotation flags include the NoRotate bit and
// the page is rotated, we have to rotate the annotation about
// its upper left corner by the same amount in the opposite
// direction so that it will remain upright in absolute
// coordinates. Since the semantics of /Rotate for a page are
// to rotate the page, while the effect of rotating using a
// transformation matrix is to rotate the coordinate system,
// the opposite directionality is explicit in the code.
QPDFMatrix mr;
mr.rotatex90(rotate);
mr.concat(matrix);
matrix = mr;
double rect_w = rect.urx - rect.llx;
double rect_h = rect.ury - rect.lly;
switch (rotate) {
case 90:
QTC::TC("qpdf", "QPDFAnnotationObjectHelper rotate 90");
rect = QPDFObjectHandle::Rectangle(
rect.llx, rect.ury, rect.llx + rect_h, rect.ury + rect_w);
break;
case 180:
QTC::TC("qpdf", "QPDFAnnotationObjectHelper rotate 180");
rect = QPDFObjectHandle::Rectangle(
rect.llx - rect_w, rect.ury, rect.llx, rect.ury + rect_h);
break;
case 270:
QTC::TC("qpdf", "QPDFAnnotationObjectHelper rotate 270");
rect = QPDFObjectHandle::Rectangle(
rect.llx - rect_h, rect.ury - rect_w, rect.llx, rect.ury);
break;
default:
// ignore
break;
}
}
// Transform bounding box by matrix to get T
QPDFObjectHandle::Rectangle bbox = bbox_obj.getArrayAsRectangle();
QPDFObjectHandle::Rectangle T = matrix.transformRectangle(bbox);
if ((T.urx == T.llx) || (T.ury == T.lly)) {
// avoid division by zero
return "";
}
// Compute a matrix to transform the appearance box to the rectangle
QPDFMatrix AA;
AA.translate(rect.llx, rect.lly);
AA.scale(
(rect.urx - rect.llx) / (T.urx - T.llx),
(rect.ury - rect.lly) / (T.ury - T.lly));
AA.translate(-T.llx, -T.lly);
if (do_rotate) {
AA.rotatex90(rotate);
}
as.replaceKey("/Subtype", QPDFObjectHandle::newName("/Form"));
return ("q\n" + AA.unparse() + " cm\n" + name + " Do\n" + "Q\n");
}