unipdf/pdf/page.go

/*
 * This file is subject to the terms and conditions defined in
 * file 'LICENSE.md', which is part of this source code package.
 */

//
// Allow higher level manipulation of PDF files and pages.
// This can be continously expanded to support more and more features.
// Generic handling can be done by defining elements as PdfObject which
// can later be replaced and fully defined.
//

package pdf

import (
	"errors"
	"fmt"
	"regexp"
	"strconv"

	"github.com/unidoc/unidoc/common"
)

type PdfRectangle struct {
	Llx float64 // Lower left corner (ll).
	Lly float64
	Urx float64 // Upper right corner (ur).
	Ury float64
}

func getNumberAsFloat(obj PdfObject) (float64, error) {
	if fObj, ok := obj.(*PdfObjectFloat); ok {
		return float64(*fObj), nil
	}

	if iObj, ok := obj.(*PdfObjectInteger); ok {
		return float64(*iObj), nil
	}

	return 0, errors.New("Not a number")
}

// Cases where expecting an integer, but some implementations actually
// store the number in a floating point format.
func getNumberAsInt64(obj PdfObject) (int64, error) {
	if iObj, ok := obj.(*PdfObjectInteger); ok {
		return int64(*iObj), nil
	}

	if fObj, ok := obj.(*PdfObjectFloat); ok {
		common.Log.Debug("Number expected as integer was stored as float (type casting used)")
		return int64(*fObj), nil
	}

	return 0, errors.New("Not a number")
}

func getNumberAsFloatOrNull(obj PdfObject) (*float64, error) {
	if fObj, ok := obj.(*PdfObjectFloat); ok {
		num := float64(*fObj)
		return &num, nil
	}

	if iObj, ok := obj.(*PdfObjectInteger); ok {
		num := float64(*iObj)
		return &num, nil
	}
	if _, ok := obj.(*PdfObjectNull); ok {
		return nil, nil
	}

	return nil, errors.New("Not a number")
}

// Create a PDF rectangle object based on an input array of 4 integers.
// Defining the lower left (LL) and upper right (UR) corners with
// floating point numbers.
func NewPdfRectangle(arr PdfObjectArray) (*PdfRectangle, error) {
	rect := PdfRectangle{}
	if len(arr) != 4 {
		return nil, errors.New("Invalid rectangle array, len != 4")
	}

	var err error
	rect.Llx, err = getNumberAsFloat(arr[0])
	if err != nil {
		return nil, err
	}

	rect.Lly, err = getNumberAsFloat(arr[1])
	if err != nil {
		return nil, err
	}

	rect.Urx, err = getNumberAsFloat(arr[2])
	if err != nil {
		return nil, err
	}

	rect.Ury, err = getNumberAsFloat(arr[3])
	if err != nil {
		return nil, err
	}

	return &rect, nil
}

// Convert to a PDF object.
func (rect *PdfRectangle) ToPdfObject() PdfObject {
	arr := PdfObjectArray{}
	arr = append(arr, MakeFloat(rect.Llx))
	arr = append(arr, MakeFloat(rect.Lly))
	arr = append(arr, MakeFloat(rect.Urx))
	arr = append(arr, MakeFloat(rect.Ury))
	return &arr
}

// A date is a PDF string of the form:
// (D:YYYYMMDDHHmmSSOHH'mm)
type PdfDate struct {
	year          int64 // YYYY
	month         int64 // MM (01-12)
	day           int64 // DD (01-31)
	hour          int64 // HH (00-23)
	minute        int64 // mm (00-59)
	second        int64 // SS (00-59)
	utOffsetSign  byte  // O ('+' / '-' / 'Z')
	utOffsetHours int64 // HH' (00-23 followed by ')
	utOffsetMins  int64 // mm (00-59)
}

var reDate = regexp.MustCompile(`\s*D\s*:\s*(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})([+-Z])?(\d{2})?'?(\d{2})?`)

// Make a new PdfDate object from a PDF date string (see 7.9.4 Dates).
// format: "D: YYYYMMDDHHmmSSOHH'mm"
func NewPdfDate(dateStr string) (PdfDate, error) {
	d := PdfDate{}

	matches := reDate.FindAllStringSubmatch(dateStr, 1)
	if len(matches) < 1 {
		return d, fmt.Errorf("Invalid date string (%s)", dateStr)
	}
	if len(matches[0]) != 10 {
		return d, errors.New("Invalid regexp group match length != 10")
	}

	// No need to handle err from ParseInt, as pre-validated via regexp.
	d.year, _ = strconv.ParseInt(matches[0][1], 10, 32)
	d.month, _ = strconv.ParseInt(matches[0][2], 10, 32)
	d.day, _ = strconv.ParseInt(matches[0][3], 10, 32)
	d.hour, _ = strconv.ParseInt(matches[0][4], 10, 32)
	d.minute, _ = strconv.ParseInt(matches[0][5], 10, 32)
	d.second, _ = strconv.ParseInt(matches[0][6], 10, 32)
	// Some poor implementations do not include the offset.
	if len(matches[0][7]) > 0 {
		d.utOffsetSign = matches[0][7][0]
	} else {
		d.utOffsetSign = '+'
	}
	if len(matches[0][8]) > 0 {
		d.utOffsetHours, _ = strconv.ParseInt(matches[0][8], 10, 32)
	} else {
		d.utOffsetHours = 0
	}
	if len(matches[0][9]) > 0 {
		d.utOffsetMins, _ = strconv.ParseInt(matches[0][9], 10, 32)
	} else {
		d.utOffsetMins = 0
	}

	return d, nil
}

// Convert to a PDF string object.
func (date *PdfDate) ToPdfObject() PdfObject {
	str := fmt.Sprintf("D:%.4d%.2d%.2d%.2d%.2d%.2d%c%.2d'%.2d'",
		date.year, date.month, date.day, date.hour, date.minute, date.second,
		date.utOffsetSign, date.utOffsetHours, date.utOffsetMins)
	pdfStr := PdfObjectString(str)
	return &pdfStr
}

type PdfPageTreeNode struct {
	Parent *PdfPageTreeNode
	Kids   *PdfPageTreeNode
	Count  *int64
}

type PdfPages struct {
	PdfPageTreeNode
	// Inheritable attributes.
	Resources *PdfPageResources
	MediaBox  *PdfRectangle
	CropBox   *PdfRectangle
	Rotate    *PdfRectangle
}

// PDF page object (7.7.3.3 - Table 30).
type PdfPage struct {
	Parent               PdfObject
	LastModified         *PdfDate
	Resources            *PdfPageResources
	CropBox              *PdfRectangle
	MediaBox             *PdfRectangle
	BleedBox             *PdfRectangle
	TrimBox              *PdfRectangle
	ArtBox               *PdfRectangle
	BoxColorInfo         PdfObject
	Contents             PdfObject
	Rotate               *int64
	Group                PdfObject
	Thumb                PdfObject
	B                    PdfObject
	Dur                  PdfObject
	Trans                PdfObject
	Annots               PdfObject
	AA                   PdfObject
	Metadata             PdfObject
	PieceInfo            PdfObject
	StructParents        PdfObject
	ID                   PdfObject
	PZ                   PdfObject
	SeparationInfo       PdfObject
	Tabs                 PdfObject
	TemplateInstantiated PdfObject
	PresSteps            PdfObject
	UserUnit             PdfObject
	VP                   PdfObject
	pageDict             *PdfObjectDictionary
}

/*
 * Rather than storing the page tree exactly as it is kept in the PDF file, let's store it as a
 * list.  Then once we create our own PDF we can make it into a more balanced tree, depending on the
 * output.
 * For example merging pdf files, might be better to maek our own tree structure etc.
 * Maybe 20-50 pages per tree node or something, or using a balanced tree approach.
 * Makes more sense to make it when writing it out.
 */
/*
func BuildPageList() ([]*PdfPage) {
	name, ok := dict["Type"].(*PdfObjectName)
	if !ok {
		return nil, errors.New("Type not a name")
	}
	if *name == "Pages" {
		list := []*PdfPage{}
		for
		page[]
		AddPageTreeNode(...)
		BuildPageTree()
		BuildPageList(dict.Kids, )
	}

	if *name == "Page" {
		page, err := NewPdfPageFromDict(dict)...
		if err != nil {
			return err
		}

		doc.hashmap[*PdfPage]           -> *PdfIndirectObject
		doc.hashmap[*PdfIndirectObject] -> *PdfPage
		doc.pages = append(doc.pages, page)
	}
}
*/

func NewPdfPagesFromDict(dict PdfObjectDictionary) (*PdfPages, error) {
	pages := PdfPages{}

	name, ok := dict["Type"].(*PdfObjectName)
	if !ok {
		return nil, errors.New("Type not a name")
	}
	if *name != "Pages" {
		return nil, errors.New("Name != Pages")
	}

	// XXX pass in the parent object directly?
	/*
		parent, ok := dict["Parent"].(*PdfIndirectObject)
		if !ok {
			return nil, errors.New("Parent not an indirect object")
		}
		pages.Parent = parent
	*/

	// Better syntax could be:
	/*
		kids, ok := TraceToDirectObject(dict["Kids"]).(*PdfObjectArray)
		if !ok {
			return nil, errors.New("Kids not an array")
		}
		pages.Kids = kids
	*/

	count, ok := TraceToDirectObject(dict["Count"]).(*PdfObjectInteger)
	if !ok {
		return nil, errors.New("Count is not an integer")
	}
	val := int64(*count)
	pages.Count = &val

	return nil, nil
}

// Build a PdfPage based on the underlying dictionary.
// Used in loading existing PDF files.
func (reader *PdfReader) newPdfPageFromDict(p *PdfObjectDictionary) (*PdfPage, error) {
	page := PdfPage{}
	page.pageDict = &PdfObjectDictionary{}

	d := *p

	pType, ok := d["Type"].(*PdfObjectName)
	if !ok {
		return nil, errors.New("Missing/Invalid Page dictionary Type")
	}
	if *pType != "Page" {
		return nil, errors.New("Page dictionary Type != Page")
	}

	if obj, isDefined := d["Parent"]; isDefined {
		page.Parent = obj
	}

	if obj, isDefined := d["LastModified"]; isDefined {
		strObj, ok := obj.(*PdfObjectString)
		if !ok {
			return nil, errors.New("Page dictionary LastModified != string")
		}
		lastmod, err := NewPdfDate(string(*strObj))
		if err != nil {
			return nil, err
		}
		page.LastModified = &lastmod
	}

	if obj, isDefined := d["Resources"]; isDefined {
		obj, err := reader.traceToObject(obj)
		if err != nil {
			return nil, err
		}

		dict, ok := TraceToDirectObject(obj).(*PdfObjectDictionary)
		if !ok {
			return nil, fmt.Errorf("Invalid resource dictionary (%T)", obj)
		}

		page.Resources, err = NewPdfPageResourcesFromDict(dict)
		if err != nil {
			return nil, err
		}
	}

	if obj, isDefined := d["MediaBox"]; isDefined {
		boxArr, ok := obj.(*PdfObjectArray)
		if !ok {
			return nil, errors.New("Page MediaBox not an array")
		}
		var err error
		page.MediaBox, err = NewPdfRectangle(*boxArr)
		if err != nil {
			return nil, err
		}
	}
	if obj, isDefined := d["CropBox"]; isDefined {
		boxArr, ok := obj.(*PdfObjectArray)
		if !ok {
			return nil, errors.New("Page CropBox not an array")
		}
		var err error
		page.CropBox, err = NewPdfRectangle(*boxArr)
		if err != nil {
			return nil, err
		}
	}
	if obj, isDefined := d["BleedBox"]; isDefined {
		boxArr, ok := obj.(*PdfObjectArray)
		if !ok {
			return nil, errors.New("Page BleedBox not an array")
		}
		var err error
		page.BleedBox, err = NewPdfRectangle(*boxArr)
		if err != nil {
			return nil, err
		}
	}
	if obj, isDefined := d["TrimBox"]; isDefined {
		boxArr, ok := obj.(*PdfObjectArray)
		if !ok {
			return nil, errors.New("Page TrimBox not an array")
		}
		var err error
		page.TrimBox, err = NewPdfRectangle(*boxArr)
		if err != nil {
			return nil, err
		}
	}
	if obj, isDefined := d["ArtBox"]; isDefined {
		boxArr, ok := obj.(*PdfObjectArray)
		if !ok {
			return nil, errors.New("Page ArtBox not an array")
		}
		var err error
		page.ArtBox, err = NewPdfRectangle(*boxArr)
		if err != nil {
			return nil, err
		}
	}
	if obj, isDefined := d["BoxColorInfo"]; isDefined {
		page.BoxColorInfo = obj
	}
	if obj, isDefined := d["Contents"]; isDefined {
		page.Contents = obj
	}
	if obj, isDefined := d["Rotate"]; isDefined {
		iObj, ok := obj.(*PdfObjectInteger)
		if !ok {
			return nil, errors.New("Invalid Page Rotate object")
		}
		iVal := int64(*iObj)
		page.Rotate = &iVal
	}
	if obj, isDefined := d["Group"]; isDefined {
		page.Group = obj
	}
	if obj, isDefined := d["Thumb"]; isDefined {
		page.Thumb = obj
	}
	if obj, isDefined := d["B"]; isDefined {
		page.B = obj
	}
	if obj, isDefined := d["Dur"]; isDefined {
		page.Dur = obj
	}
	if obj, isDefined := d["Trans"]; isDefined {
		page.Trans = obj
	}
	if obj, isDefined := d["Annots"]; isDefined {
		page.Annots = obj
	}
	if obj, isDefined := d["AA"]; isDefined {
		page.AA = obj
	}
	if obj, isDefined := d["Metadata"]; isDefined {
		page.Metadata = obj
	}
	if obj, isDefined := d["PieceInfo"]; isDefined {
		page.PieceInfo = obj
	}
	if obj, isDefined := d["StructParents"]; isDefined {
		page.StructParents = obj
	}
	if obj, isDefined := d["ID"]; isDefined {
		page.ID = obj
	}
	if obj, isDefined := d["PZ"]; isDefined {
		page.PZ = obj
	}
	if obj, isDefined := d["SeparationInfo"]; isDefined {
		page.SeparationInfo = obj
	}
	if obj, isDefined := d["Tabs"]; isDefined {
		page.Tabs = obj
	}
	if obj, isDefined := d["TemplateInstantiated"]; isDefined {
		page.TemplateInstantiated = obj
	}
	if obj, isDefined := d["PresSteps"]; isDefined {
		page.PresSteps = obj
	}
	if obj, isDefined := d["UserUnit"]; isDefined {
		page.UserUnit = obj
	}
	if obj, isDefined := d["VP"]; isDefined {
		page.VP = obj
	}

	return &page, nil
}

// Get the inheritable media box value, either from the page
// or a higher up page/pages struct.
func (this *PdfPage) GetMediaBox() (*PdfRectangle, error) {
	if this.MediaBox != nil {
		return this.MediaBox, nil
	}

	node := this.Parent
	for node != nil {
		dictObj, ok := node.(*PdfIndirectObject)
		if !ok {
			return nil, errors.New("Invalid parent object")
		}

		dict, ok := dictObj.PdfObject.(*PdfObjectDictionary)
		if !ok {
			return nil, errors.New("Invalid parent objects dictionary")
		}

		if obj, hasMediaBox := (*dict)["MediaBox"]; hasMediaBox {
			arr, ok := obj.(*PdfObjectArray)
			if !ok {
				return nil, errors.New("Invalid media box")
			}
			rect, err := NewPdfRectangle(*arr)

			if err != nil {
				return nil, err
			}

			return rect, nil
		}

		node = (*dict)["Parent"]
	}

	return nil, errors.New("Media box not defined")
}

// Convert the Page to a PDF object dictionary.
func (this *PdfPage) GetPageDict() *PdfObjectDictionary {
	p := this.pageDict
	(*p)["Type"] = MakeName("Page")
	(*p)["Parent"] = this.Parent

	if this.LastModified != nil {
		p.Set("LastModified", this.LastModified.ToPdfObject())
	}
	if this.Resources != nil {
		p.Set("Resources", this.Resources.ToPdfObject())
	}
	if this.CropBox != nil {
		p.Set("CropBox", this.CropBox.ToPdfObject())
	}
	if this.MediaBox != nil {
		p.Set("MediaBox", this.MediaBox.ToPdfObject())
	}
	if this.BleedBox != nil {
		p.Set("BleedBox", this.BleedBox.ToPdfObject())
	}
	if this.TrimBox != nil {
		p.Set("TrimBox", this.TrimBox.ToPdfObject())
	}
	if this.ArtBox != nil {
		p.Set("ArtBox", this.ArtBox.ToPdfObject())
	}
	p.SetIfNotNil("BoxColorInfo", this.BoxColorInfo)
	p.SetIfNotNil("Contents", this.Contents)

	if this.Rotate != nil {
		p.Set("Rotate", MakeInteger(*this.Rotate))
	}

	p.SetIfNotNil("Group", this.Group)
	p.SetIfNotNil("Thumb", this.Thumb)
	p.SetIfNotNil("B", this.B)
	p.SetIfNotNil("Dur", this.Dur)
	p.SetIfNotNil("Trans", this.Trans)
	p.SetIfNotNil("Annots", this.Annots)
	p.SetIfNotNil("AA", this.AA)
	p.SetIfNotNil("Metadata", this.Metadata)
	p.SetIfNotNil("PieceInfo", this.PieceInfo)
	p.SetIfNotNil("StructParents", this.StructParents)
	p.SetIfNotNil("ID", this.ID)
	p.SetIfNotNil("PZ", this.PZ)
	p.SetIfNotNil("SeparationInfo", this.SeparationInfo)
	p.SetIfNotNil("Tabs", this.Tabs)
	p.SetIfNotNil("TemplateInstantiated", this.TemplateInstantiated)
	p.SetIfNotNil("PresSteps", this.PresSteps)
	p.SetIfNotNil("UserUnit", this.UserUnit)
	p.SetIfNotNil("VP", this.VP)

	return p
}

// Get the page object as an indirect objects.  Wraps the Page
// dictionary into an indirect object.
func (this *PdfPage) GetPageAsIndirectObject() *PdfIndirectObject {
	dict := this.GetPageDict()
	iobj := PdfIndirectObject{}
	iobj.PdfObject = dict
	return &iobj
}

// Add an image to the XObject resources.
func (this *PdfPage) AddImageResource(name PdfObjectName, ximg *XObjectImage) error {
	if this.Resources == nil {
		this.Resources = &PdfPageResources{}
	}
	var xresDict *PdfObjectDictionary
	if this.Resources.XObject == nil {
		xresDict = &PdfObjectDictionary{}
		this.Resources.XObject = xresDict
	} else {
		var ok bool
		xresDict, ok = (this.Resources.XObject).(*PdfObjectDictionary)
		if !ok {
			return errors.New("Invalid xres dict type")
		}

	}
	// Make a stream object container.
	(*xresDict)[name] = ximg.ToPdfObject()

	return nil
}

// Add a graphics state to the XObject resources.
func (this *PdfPage) AddExtGState(name PdfObjectName, egs *PdfObjectDictionary) {
	if this.Resources == nil {
		this.Resources = &PdfPageResources{}
	}

	if this.Resources.ExtGState == nil {
		this.Resources.ExtGState = &PdfObjectDictionary{}
	}

	egsDict := this.Resources.ExtGState.(*PdfObjectDictionary)
	(*egsDict)[name] = egs
}

// Add a font dictionary to the Font resources.
func (this *PdfPage) AddFont(name PdfObjectName, font *PdfObjectDictionary) {
	if this.Resources == nil {
		this.Resources = &PdfPageResources{}
	}

	if this.Resources.Font == nil {
		this.Resources.Font = &PdfObjectDictionary{}
	}

	fontDict := this.Resources.Font.(*PdfObjectDictionary)
	(*fontDict)[name] = font
}

type WatermarkImageOptions struct {
	Alpha               float64
	FitToWidth          bool
	PreserveAspectRatio bool
}

// Add a watermark to the page.
func (this *PdfPage) AddWatermarkImage(ximg *XObjectImage, opt WatermarkImageOptions) error {
	bbox, err := this.GetMediaBox()
	if err != nil {
		return err
	}
	pWidth := bbox.Urx - bbox.Llx
	pHeight := bbox.Ury - bbox.Lly

	wWidth := float64(*ximg.Width)
	xOffset := (float64(pWidth) - float64(wWidth)) / 2
	if opt.FitToWidth {
		wWidth = pWidth
		xOffset = 0
	}
	wHeight := pHeight
	yOffset := float64(0)
	if opt.PreserveAspectRatio {
		wHeight = wWidth * float64(*ximg.Height) / float64(*ximg.Width)
		yOffset = (pHeight - wHeight) / 2
	}

	imgName := PdfObjectName("Imw0")
	this.AddImageResource(imgName, ximg)

	gs0 := PdfObjectDictionary{}
	gs0["BM"] = MakeName("Normal")
	gs0["CA"] = MakeFloat(opt.Alpha)
	gs0["ca"] = MakeFloat(opt.Alpha)
	this.AddExtGState("GS0", &gs0)

	contentStr := fmt.Sprintf("q\n"+
		"/GS0 gs\n"+
		"%.0f 0 0 %.0f %.4f %.4f cm\n"+
		"/%s Do\n"+
		"Q", wWidth, wHeight, xOffset, yOffset, imgName)
	this.AddContentStreamByString(contentStr)

	return nil
}

// Add content stream by string.  Puts the content string into a stream
// object and points the content stream towards it.
func (this *PdfPage) AddContentStreamByString(contentStr string) {
	stream := PdfObjectStream{}

	sDict := PdfObjectDictionary{}
	stream.PdfObjectDictionary = &sDict

	sDict["Length"] = MakeInteger(int64(len(contentStr)))
	stream.Stream = []byte(contentStr)

	if this.Contents == nil {
		// If not set, place it directly.
		this.Contents = &stream
	} else if contArray, isArray := this.Contents.(*PdfObjectArray); isArray {
		// If an array of content streams, append it.
		*contArray = append(*contArray, &stream)
	} else {
		// Only 1 element in place. Wrap inside a new array and add the new one.
		contArray := PdfObjectArray{}
		contArray = append(contArray, this.Contents)
		contArray = append(contArray, &stream)
		this.Contents = &contArray
	}

}

// Page resources.
type PdfPageResources struct {
	ExtGState  PdfObject
	ColorSpace PdfObject
	Pattern    PdfObject
	Shading    PdfObject
	XObject    PdfObject
	Font       PdfObject
	ProcSet    PdfObject
}

func NewPdfPageResourcesFromDict(dict *PdfObjectDictionary) (*PdfPageResources, error) {
	r := PdfPageResources{}

	if obj, isDefined := (*dict)["ExtGState"]; isDefined {
		r.ExtGState = obj
	}
	if obj, isDefined := (*dict)["ColorSpace"]; isDefined {
		r.ColorSpace = obj
	}
	if obj, isDefined := (*dict)["Pattern"]; isDefined {
		r.Pattern = obj
	}
	if obj, isDefined := (*dict)["Shading"]; isDefined {
		r.Shading = obj
	}
	if obj, isDefined := (*dict)["XObject"]; isDefined {
		r.XObject = obj
	}
	if obj, isDefined := (*dict)["Font"]; isDefined {
		r.Font = obj
	}
	if obj, isDefined := (*dict)["ProcSet"]; isDefined {
		r.ProcSet = obj
	}

	return &r, nil
}

func (r *PdfPageResources) ToPdfObject() PdfObject {
	d := &PdfObjectDictionary{}
	d.SetIfNotNil("ExtGState", r.ExtGState)
	d.SetIfNotNil("ColorSpace", r.ColorSpace)
	d.SetIfNotNil("Pattern", r.Pattern)
	d.SetIfNotNil("Shading", r.Shading)
	d.SetIfNotNil("XObject", r.XObject)
	d.SetIfNotNil("Font", r.Font)
	d.SetIfNotNil("ProcSet", r.ProcSet)
	return d
}

// Image XObject (Table 89 in 8.9.5.1).
type XObjectImage struct {
	Width            *int64
	Height           *int64
	ColorSpace       PdfObject
	BitsPerComponent *int64
	Intent           PdfObject
	ImageMask        PdfObject
	Mask             PdfObject
	Decode           PdfObject
	Interpolate      PdfObject
	Alternatives     PdfObject
	SMask            PdfObject
	SMaskInData      PdfObject
	Name             PdfObject
	StructParent     PdfObject
	ID               PdfObject
	OPI              PdfObject
	Metadata         PdfObject
	OC               PdfObject
	Stream           []byte
}

// Creates a new XObject Image from an image object with default
// options.
func NewXObjectImage(name PdfObjectName, img *Image) (*XObjectImage, error) {
	xobj := XObjectImage{}

	xobj.Name = &name
	xobj.Stream = img.Data.Bytes()

	// Width and height.
	imWidth := img.Width
	imHeight := img.Height
	xobj.Width = &imWidth
	xobj.Height = &imHeight

	// Bits.
	bitDepth := int64(8)
	xobj.BitsPerComponent = &bitDepth

	xobj.ColorSpace = MakeName("DeviceRGB")

	return &xobj, nil
}

// Build the image xobject from a stream object.
func NewXObjectImageFromStream(stream PdfObjectStream) (*XObjectImage, error) {
	img := XObjectImage{}

	dict := *(stream.PdfObjectDictionary)

	if obj, isDefined := dict["Width"]; isDefined {
		iObj, ok := obj.(*PdfObjectInteger)
		if !ok {
			return nil, errors.New("Invalid image width object")
		}
		iVal := int64(*iObj)
		img.Width = &iVal
	}

	if obj, isDefined := dict["Height"]; isDefined {
		iObj, ok := obj.(*PdfObjectInteger)
		if !ok {
			return nil, errors.New("Invalid image height object")
		}
		iVal := int64(*iObj)
		img.Height = &iVal
	}

	if obj, isDefined := dict["ColorSpace"]; isDefined {
		img.ColorSpace = obj
	}

	if obj, isDefined := dict["BitsPerComponent"]; isDefined {
		iObj, ok := obj.(*PdfObjectInteger)
		if !ok {
			return nil, errors.New("Invalid image height object")
		}
		iVal := int64(*iObj)
		img.BitsPerComponent = &iVal
	}

	if obj, isDefined := dict["Intent"]; isDefined {
		img.Intent = obj
	}
	if obj, isDefined := dict["ImageMask"]; isDefined {
		img.ImageMask = obj
	}
	if obj, isDefined := dict["Mask"]; isDefined {
		img.Mask = obj
	}
	if obj, isDefined := dict["Decode"]; isDefined {
		img.Decode = obj
	}
	if obj, isDefined := dict["Interpolate"]; isDefined {
		img.Interpolate = obj
	}
	if obj, isDefined := dict["Alternatives"]; isDefined {
		img.Alternatives = obj
	}
	if obj, isDefined := dict["SMask"]; isDefined {
		img.SMask = obj
	}
	if obj, isDefined := dict["SMaskInData"]; isDefined {
		img.SMaskInData = obj
	}
	if obj, isDefined := dict["Name"]; isDefined {
		img.Name = obj
	}
	if obj, isDefined := dict["StructParent"]; isDefined {
		img.StructParent = obj
	}
	if obj, isDefined := dict["ID"]; isDefined {
		img.ID = obj
	}
	if obj, isDefined := dict["OPI"]; isDefined {
		img.OPI = obj
	}
	if obj, isDefined := dict["Metadata"]; isDefined {
		img.Metadata = obj
	}
	if obj, isDefined := dict["OC"]; isDefined {
		img.OC = obj
	}

	img.Stream = stream.Stream

	return &img, nil
}

// Return a stream object.
func (ximg *XObjectImage) ToPdfObject() PdfObject {
	stream := PdfObjectStream{}
	stream.Stream = ximg.Stream

	dict := PdfObjectDictionary{}
	stream.PdfObjectDictionary = &dict

	// XXX/FIXME: Continue defining these.
	dict["Type"] = MakeName("XObject")
	dict["Subtype"] = MakeName("Image")
	dict["Width"] = MakeInteger(*(ximg.Width))
	dict["Height"] = MakeInteger(*(ximg.Height))
	dict["Filter"] = MakeName("DCTDecode")

	if ximg.BitsPerComponent != nil {
		dict["BitsPerComponent"] = MakeInteger(*(ximg.BitsPerComponent))
	}

	dict.SetIfNotNil("ColorSpace", ximg.ColorSpace)
	dict.SetIfNotNil("Intent", ximg.Intent)
	dict.SetIfNotNil("ImageMask", ximg.ImageMask)
	dict.SetIfNotNil("Mask", ximg.Mask)
	dict.SetIfNotNil("Decode", ximg.Decode)
	dict.SetIfNotNil("Interpolate", ximg.Interpolate)
	dict.SetIfNotNil("Alternatives", ximg.Alternatives)
	dict.SetIfNotNil("SMask", ximg.SMask)
	dict.SetIfNotNil("SMaskInData", ximg.SMaskInData)
	dict.SetIfNotNil("Name", ximg.Name)
	dict.SetIfNotNil("StructParent", ximg.StructParent)
	dict.SetIfNotNil("ID", ximg.ID)
	dict.SetIfNotNil("OPI", ximg.OPI)
	dict.SetIfNotNil("Metadata", ximg.Metadata)
	dict.SetIfNotNil("OC", ximg.OC)

	dict["Length"] = MakeInteger(int64(len(ximg.Stream)))
	stream.Stream = ximg.Stream

	return &stream
}