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