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#include <qpdf/QPDFAnnotationObjectHelper.hh>
#include <qpdf/QPDFMatrix.hh>
#include <qpdf/QPDFObjectHandle_private.hh>
#include <qpdf/QTC.hh>
#include <qpdf/QUtil.hh>
using namespace qpdf;
QPDFAnnotationObjectHelper::QPDFAnnotationObjectHelper(QPDFObjectHandle oh) :
QPDFObjectHelper(oh)
{
}
std::string
QPDFAnnotationObjectHelper::getSubtype()
{
return oh().getKey("/Subtype").getName();
}
QPDFObjectHandle::Rectangle
QPDFAnnotationObjectHelper::getRect()
{
return oh().getKey("/Rect").getArrayAsRectangle();
}
QPDFObjectHandle
QPDFAnnotationObjectHelper::getAppearanceDictionary()
{
return oh().getKey("/AP");
}
std::string
QPDFAnnotationObjectHelper::getAppearanceState()
{
Name AS = get("/AS");
return AS ? AS.value() : "";
}
int
QPDFAnnotationObjectHelper::getFlags()
{
Integer flags_obj = get("/F");
return flags_obj ? flags_obj : 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()) {
// According to the spec, Appearance State is supposed to refer to a subkey of the
// appearance stream when /AP is a dictionary, but files have been seen in the wild
// where Appearance State is `/N` and `/AP` is a stream. Therefore, if `which` points to
// a stream, disregard state and just use the stream. See qpdf issue #949 for details.
return ap_sub;
}
if (ap_sub.isDictionary() && !desired_state.empty()) {
QPDFObjectHandle ap_sub_val = ap_sub.getKey(desired_state);
if (ap_sub_val.isStream()) {
return ap_sub_val;
}
}
}
return Null::temp();
}
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 = 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 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");
}
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