Add NewOutlineFromReaderOutline

model/outline.go

@@ -6,6 +6,9 @@
 package model
 
 import (
+	"errors"
+
+	"github.com/unidoc/unipdf/v3/common"
 	"github.com/unidoc/unipdf/v3/core"
 )
 
@@ -27,6 +30,53 @@ func NewOutlineDest(page int64, x, y float64) OutlineDest {
 	}
 }
 
+// newOutlineDestFromPdfObject creates a new outline destination from the
+// specified PDF object.
+func newOutlineDestFromPdfObject(o core.PdfObject, r *PdfReader) OutlineDest {
+	dest := OutlineDest{}
+
+	destArr, ok := core.GetArray(o)
+	if !ok {
+		return dest
+	}
+
+	// Covered destination formats:
+	// [pageObj|pageNum /Fit]
+	// [pageObj|pageNum /FitB]
+	// [pageObj|pageNum /FitH top]
+	// [pageObj|pageNum /FitV left]
+	// [pageObj|pageNum /FitBH top]
+	// [pageObj|pageNum /XYZ x y zoom]
+	// [pageObj|pageNum /FitR left bottom right top]
+	// See section 12.3.2.2 "Explicit Destinations" (page 374).
+	destArrLen := destArr.Len()
+	if destArrLen < 2 {
+		return dest
+	}
+
+	// Extract page number.
+	pageObj := destArr.Get(0)
+	if pageInd, ok := core.GetIndirect(pageObj); ok {
+		// Page object is provided. Identify page number using the reader.
+		if _, pageNum, err := r.PageFromIndirectObject(pageInd); err == nil {
+			dest.Page = int64(pageNum - 1)
+		}
+	} else if pageNum, ok := core.GetIntVal(pageObj); ok {
+		// Page number is provided.
+		dest.Page = int64(pageNum)
+	}
+
+	// Extract destination coordinates.
+	if destArrLen == 5 {
+		if xyz, ok := core.GetName(destArr.Get(1)); ok && xyz.String() == "XYZ" {
+			dest.X, _ = core.GetFloatVal(destArr.Get(2))
+			dest.Y, _ = core.GetFloatVal(destArr.Get(3))
+		}
+	}
+
+	return dest
+}
+
 // ToPdfObject returns a PDF object representation of the outline destination.
 func (od OutlineDest) ToPdfObject() core.PdfObject {
 	return core.MakeArray(
@@ -49,7 +99,54 @@ func NewOutline() *Outline {
 	return &Outline{}
 }
 
-func NewOutlineFromOutlineTree(node *PdfOutlineTreeNode) {
+// NewOutlineFromReaderOutline returns a new outline from the outline tree of
+// the passed in reader.
+func NewOutlineFromReaderOutline(r *PdfReader) (*Outline, error) {
+	if r == nil {
+		return nil, errors.New("cannot create outline from nil reader")
+	}
+
+	outlineTree := r.GetOutlineTree()
+	if outlineTree == nil {
+		return nil, errors.New("the specified reader does not have an outline tree")
+	}
+
+	var traverseFunc func(node *PdfOutlineTreeNode, entries *[]*OutlineItem)
+	traverseFunc = func(node *PdfOutlineTreeNode, entries *[]*OutlineItem) {
+		if node == nil {
+			return
+		}
+		if node.context == nil {
+			common.Log.Debug("ERROR: missing outline entry context")
+			return
+		}
+
+		// Check if node is an outline item.
+		var entry *OutlineItem
+		if item, ok := node.context.(*PdfOutlineItem); ok {
+			entry = NewOutlineItem(item.Title.Decoded(), newOutlineDestFromPdfObject(item.Dest, r))
+			*entries = append(*entries, entry)
+
+			// Traverse next node.
+			if item.Next != nil {
+				traverseFunc(item.Next, entries)
+			}
+		}
+
+		// Check if node has children.
+		if node.First != nil {
+			if entry != nil {
+				entries = &entry.Entries
+			}
+
+			// Traverse node children.
+			traverseFunc(node.First, entries)
+		}
+	}
+
+	outline := NewOutline()
+	traverseFunc(outlineTree, &outline.Entries)
+	return outline, nil
 }
 
 // Add appends a top level outline item to the outline.