diff options
Diffstat (limited to 'libqpdf/QPDFPageObjectHelper.cc')
| -rw-r--r-- | libqpdf/QPDFPageObjectHelper.cc | 145 |
1 files changed, 59 insertions, 86 deletions
diff --git a/libqpdf/QPDFPageObjectHelper.cc b/libqpdf/QPDFPageObjectHelper.cc index a34ed28f..608254e4 100644 --- a/libqpdf/QPDFPageObjectHelper.cc +++ b/libqpdf/QPDFPageObjectHelper.cc @@ -110,10 +110,8 @@ InlineImageTracker::convertIIDict(QPDFObjectHandle odict) } else if (name == "/I") { name = "/Indexed"; } else { - // This is a key in the page's /Resources -> - // /ColorSpace dictionary. We need to look it up - // and use its value as the color space for the - // image. + // This is a key in the page's /Resources -> /ColorSpace dictionary. We need to + // look it up and use its value as the color space for the image. QPDFObjectHandle colorspace = resources.getKey("/ColorSpace"); if (colorspace.isDictionary() && colorspace.hasKey(name)) { QTC::TC("qpdf", "QPDFPageObjectHelper colorspace lookup"); @@ -407,8 +405,8 @@ QPDFPageObjectHelper::externalizeInlineImages(size_t min_size, bool shallow) { if (shallow) { QPDFObjectHandle resources = getAttribute("/Resources", true); - // Calling mergeResources also ensures that /XObject becomes - // direct and is not shared with other pages. + // Calling mergeResources also ensures that /XObject becomes direct and is not shared with + // other pages. resources.mergeResources("<< /XObject << >> >>"_qpdf); InlineImageTracker iit(this->oh.getOwningQPDF(), min_size, resources); Pl_Buffer b("new page content"); @@ -573,11 +571,10 @@ QPDFPageObjectHelper::removeUnreferencedResourcesHelper( return false; } - // We will 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. + // We will 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. QPDFObjectHandle resources = ph.getAttribute("/Resources", true); std::vector<QPDFObjectHandle> rdicts; std::set<std::string> known_names; @@ -605,33 +602,25 @@ QPDFPageObjectHelper::removeUnreferencedResourcesHelper( } } } - // Older versions of the PDF spec allowed form XObjects to omit - // their resources dictionaries, in which case names were resolved - // from the containing page. This behavior seems to be widely - // supported by viewers. If a form XObjects has a resources - // dictionary and has some unresolved names, some viewers fail to - // resolve them, and others allow them to be inherited from the - // page or from another form XObjects that contains them. Since - // this behavior is inconsistent across viewers, we consider an - // unresolved name when a resources dictionary is present to be - // reason not to remove unreferenced resources. An unresolved name - // in the absence of a resource dictionary is not considered a - // problem. For form XObjects, we just accumulate a list of - // unresolved names, and for page objects, we avoid removing any - // such names found in nested form XObjects. + // Older versions of the PDF spec allowed form XObjects to omit their resources dictionaries, in + // which case names were resolved from the containing page. This behavior seems to be widely + // supported by viewers. If a form XObjects has a resources dictionary and has some unresolved + // names, some viewers fail to resolve them, and others allow them to be inherited from the page + // or from another form XObjects that contains them. Since this behavior is inconsistent across + // viewers, we consider an unresolved name when a resources dictionary is present to be reason + // not to remove unreferenced resources. An unresolved name in the absence of a resource + // dictionary is not considered a problem. For form XObjects, we just accumulate a list of + // unresolved names, and for page objects, we avoid removing any such names found in nested form + // XObjects. if ((!local_unresolved.empty()) && resources.isDictionary()) { - // It's not worth issuing a warning for this case. From qpdf - // 10.3, we are hopefully only looking at names that are - // referencing fonts and XObjects, but until we're certain - // that we know the meaning of every name in a content stream, - // we don't want to give warnings that might be false - // positives. Also, this can happen in legitimate cases with - // older PDFs, and there's nothing to be done about it, so - // there's no good reason to issue a warning. The only sad - // thing is that it was a false positive that alerted me to a - // logic error in the code, and any future such errors would - // now be hidden. + // It's not worth issuing a warning for this case. From qpdf 10.3, we are hopefully only + // looking at names that are referencing fonts and XObjects, but until we're certain that we + // know the meaning of every name in a content stream, we don't want to give warnings that + // might be false positives. Also, this can happen in legitimate cases with older PDFs, and + // there's nothing to be done about it, so there's no good reason to issue a warning. The + // only sad thing is that it was a false positive that alerted me to a logic error in the + // code, and any future such errors would now be hidden. QTC::TC("qpdf", "QPDFPageObjectHelper unresolved names"); return false; } @@ -639,8 +628,7 @@ QPDFPageObjectHelper::removeUnreferencedResourcesHelper( for (auto& dict: rdicts) { for (auto const& key: dict.getKeys()) { if (is_page && unresolved.count(key)) { - // This name is referenced by some nested form - // xobject, so don't remove it. + // This name is referenced by some nested form xobject, so don't remove it. QTC::TC("qpdf", "QPDFPageObjectHelper resolving unresolved"); } else if (!rf.getNames().count(key)) { dict.removeKey(key); @@ -653,8 +641,7 @@ QPDFPageObjectHelper::removeUnreferencedResourcesHelper( void QPDFPageObjectHelper::removeUnreferencedResources() { - // Accumulate a list of unresolved names across all nested form - // XObjects. + // Accumulate a list of unresolved names across all nested form XObjects. std::set<std::string> unresolved; bool any_failures = false; forEachFormXObject( @@ -724,10 +711,9 @@ QPDFPageObjectHelper::getMatrixForTransformations(bool invert) QPDFObjectHandle QPDFPageObjectHelper::getFormXObjectForPage(bool handle_transformations) { - auto result = this->oh - .getQPDF("QPDFPageObjectHelper::getFormXObjectForPage " - "called with a direct object") - .newStream(); + auto result = + this->oh.getQPDF("QPDFPageObjectHelper::getFormXObjectForPage called with a direct object") + .newStream(); QPDFObjectHandle newdict = result.getDict(); newdict.replaceKey("/Type", QPDFObjectHandle::newName("/XObject")); newdict.replaceKey("/Subtype", QPDFObjectHandle::newName("/Form")); @@ -759,18 +745,15 @@ QPDFPageObjectHelper::getMatrixForFormXObjectPlacement( bool allow_shrink, bool allow_expand) { - // Calculate the transformation matrix that will place the given - // form XObject fully inside the given rectangle, center and - // shrinking or expanding as needed if requested. - - // 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. + // Calculate the transformation matrix that will place the given form XObject fully inside the + // given rectangle, center and shrinking or expanding as needed if requested. + + // 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"); @@ -782,37 +765,32 @@ QPDFPageObjectHelper::getMatrixForFormXObjectPlacement( 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 overlaid form - // XObject's to be absolute rather than relative to properties - // of the destination page. tmatrix is part of the computed - // transformation matrix. + // tmatrix inverts scaling and rotation of the destination page. Applying this matrix allows + // the overlaid 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 + // 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. + // 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 bounding box fit within the destination rectangle. + // Step 1: figure out what scale factor we need to make the form XObject's bounding 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. Shrink or expand if needed - // and allowed. + // Calculate a scale factor, if needed. Shrink or expand if needed and allowed. if ((T.urx == T.llx) || (T.ury == T.lly)) { // avoid division by zero return QPDFMatrix(); @@ -834,8 +812,8 @@ QPDFPageObjectHelper::getMatrixForFormXObjectPlacement( } } - // Step 2: figure out what translation is required to get the - // rectangle to the right spot: centered within the destination. + // 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); @@ -849,9 +827,8 @@ QPDFPageObjectHelper::getMatrixForFormXObjectPlacement( 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. + // 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); @@ -921,18 +898,15 @@ QPDFPageObjectHelper::flattenRotation(QPDFAcroFormDocumentHelper* afdh) auto rect = box.getArrayAsRectangle(); decltype(rect) new_rect; - // How far are the edges of our rectangle from the edges - // of the media box? + // How far are the edges of our rectangle from the edges of the media box? auto left_x = rect.llx - media_rect.llx; auto right_x = media_rect.urx - rect.urx; auto bottom_y = rect.lly - media_rect.lly; auto top_y = media_rect.ury - rect.ury; - // Rotating the page 180 degrees does not change - // /MediaBox. Rotating 90 or 270 degrees reverses llx and - // lly and also reverse urx and ury. For all the other - // boxes, we want the corners to be the correct distance - // away from the corners of the mediabox. + // Rotating the page 180 degrees does not change /MediaBox. Rotating 90 or 270 degrees + // reverses llx and lly and also reverse urx and ury. For all the other boxes, we want the + // corners to be the correct distance away from the corners of the mediabox. switch (rotate) { case 90: new_rect.llx = media_rect.lly + bottom_y; @@ -963,9 +937,8 @@ QPDFPageObjectHelper::flattenRotation(QPDFAcroFormDocumentHelper* afdh) this->oh.replaceKey(boxkey, QPDFObjectHandle::newFromRectangle(new_rect)); } - // When we rotate the page, pivot about the point 0, 0 and then - // translate so the page is visible with the origin point being - // the same offset from the lower left corner of the media box. + // When we rotate the page, pivot about the point 0, 0 and then translate so the page is visible + // with the origin point being the same offset from the lower left corner of the media box. // These calculations have been verified empirically with various // PDF readers. QPDFMatrix cm(0, 0, 0, 0, 0, 0); |