Create rectangle annotation with appearance stream

pdf/annotator/annotator.go

@@ -5,6 +5,7 @@ import (
 	pdf "github.com/unidoc/unidoc/pdf/model"
 )
 
+// The currently supported line ending styles are None, Arrow (ClosedArrow) and Butt.
 type LineEndingStyle int
 
 const (
@@ -13,16 +14,18 @@ const (
 	LineEndingStyleButt  LineEndingStyle = 2
 )
 
+// Defines a line between point 1 (X1,Y1) and point 2 (X2,Y2).  The line ending styles can be none (regular line),
+// or arrows at either end.  The line also has a specified width, color and opacity.
 type LineAnnotationDef struct {
 	X1               float64
 	Y1               float64
 	X2               float64
 	Y2               float64
 	LineColor        *pdf.PdfColorDeviceRGB
-	Opacity          float64
+	Opacity          float64 // Alpha value (0-1).
 	LineWidth        float64
-	LineEndingStyle1 LineEndingStyle
-	LineEndingStyle2 LineEndingStyle
+	LineEndingStyle1 LineEndingStyle // Line ending style of point 1.
+	LineEndingStyle2 LineEndingStyle // Line ending style of point 2.
 }
 
 // Creates a line annotation object that can be added to page PDF annotations.
@@ -69,3 +72,58 @@ func CreateLineAnnotation(lineDef LineAnnotationDef) (*pdf.PdfAnnotation, error)
 
 	return lineAnnotation.PdfAnnotation, nil
 }
+
+// A rectangle defined with a specified Width and Height and a lower left corner at (X,Y).  The rectangle can
+// optionally have a border and a filling color.
+// The Width/Height includes the border (if any specified).
+type RectangleAnnotationDef struct {
+	X             float64
+	Y             float64
+	Width         float64
+	Height        float64
+	FillEnabled   bool // Show fill?
+	FillColor     *pdf.PdfColorDeviceRGB
+	BorderEnabled bool // Show border?
+	BorderWidth   float64
+	BorderColor   *pdf.PdfColorDeviceRGB
+	Opacity       float64 // Alpha value (0-1).
+}
+
+// Creates a rectangle annotation object that can be added to page PDF annotations.
+func CreateRectangleAnnotation(rectDef RectangleAnnotationDef) (*pdf.PdfAnnotation, error) {
+	rectAnnotation := pdf.NewPdfAnnotationSquare()
+
+	if rectDef.BorderEnabled {
+		r, g, b := rectDef.BorderColor.R(), rectDef.BorderColor.G(), rectDef.BorderColor.B()
+		rectAnnotation.C = pdfcore.MakeArrayFromFloats([]float64{r, g, b})
+		bs := pdf.NewBorderStyle()
+		bs.SetBorderWidth(rectDef.BorderWidth)
+		rectAnnotation.BS = bs.ToPdfObject()
+	}
+
+	if rectDef.FillEnabled {
+		r, g, b := rectDef.FillColor.R(), rectDef.FillColor.G(), rectDef.FillColor.B()
+		rectAnnotation.IC = pdfcore.MakeArrayFromFloats([]float64{r, g, b})
+	} else {
+		rectAnnotation.IC = pdfcore.MakeArrayFromIntegers([]int{}) // No fill.
+	}
+
+	if rectDef.Opacity < 1.0 {
+		rectAnnotation.CA = pdfcore.MakeFloat(rectDef.Opacity)
+	}
+
+	// Make the appearance stream (for uniform appearance).
+	apDict, bbox, err := makeRectangleAnnotationAppearanceStream(rectDef)
+	if err != nil {
+		return nil, err
+	}
+
+	rectAnnotation.AP = apDict
+	rectAnnotation.Rect = pdfcore.MakeArrayFromFloats([]float64{bbox.Llx, bbox.Lly, bbox.Urx, bbox.Ury})
+
+	return rectAnnotation.PdfAnnotation, nil
+
+}
+
+type CircleAnnotationDef struct {
+}

pdf/annotator/rectangle.go

@@ -0,0 +1,99 @@
+package annotator
+
+import (
+	"github.com/unidoc/unidoc/common"
+
+	pdfcontent "github.com/unidoc/unidoc/pdf/contentstream"
+	"github.com/unidoc/unidoc/pdf/contentstream/draw"
+	pdfcore "github.com/unidoc/unidoc/pdf/core"
+	pdf "github.com/unidoc/unidoc/pdf/model"
+)
+
+func makeRectangleAnnotationAppearanceStream(rectDef RectangleAnnotationDef) (*pdfcore.PdfObjectDictionary, *pdf.PdfRectangle, error) {
+	form := pdf.NewXObjectForm()
+	form.Resources = pdf.NewPdfPageResources()
+
+	gsName := ""
+	if rectDef.Opacity < 1.0 {
+		// Create graphics state with right opacity.
+		gsState := &pdfcore.PdfObjectDictionary{}
+		gsState.Set("ca", pdfcore.MakeFloat(rectDef.Opacity))
+		gsState.Set("CA", pdfcore.MakeFloat(rectDef.Opacity))
+		err := form.Resources.AddExtGState("gs1", gsState)
+		if err != nil {
+			common.Log.Debug("Unable to add extgstate gs1")
+			return nil, nil, err
+		}
+
+		gsName = "gs1"
+	}
+
+	content, localBbox, globalBbox, err := drawPdfRectangle(rectDef, gsName)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	err = form.SetContentStream(content, nil)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Local bounding box for the XObject Form.
+	form.BBox = localBbox.ToPdfObject()
+
+	apDict := &pdfcore.PdfObjectDictionary{}
+	apDict.Set("N", form.ToPdfObject())
+
+	return apDict, globalBbox, nil
+}
+
+func drawPdfRectangle(rectDef RectangleAnnotationDef, gsName string) ([]byte, *pdf.PdfRectangle, *pdf.PdfRectangle, error) {
+	path := draw.NewPath()
+
+	path = path.AppendPoint(draw.NewPoint(0, 0))
+	path = path.AppendPoint(draw.NewPoint(0, rectDef.Height))
+	path = path.AppendPoint(draw.NewPoint(rectDef.Width, rectDef.Height))
+	path = path.AppendPoint(draw.NewPoint(rectDef.Width, 0))
+	path = path.AppendPoint(draw.NewPoint(0, 0))
+
+	creator := pdfcontent.NewContentCreator()
+
+	creator.Add_q()
+	if rectDef.FillEnabled {
+		creator.Add_rg(rectDef.FillColor.R(), rectDef.FillColor.G(), rectDef.FillColor.B())
+	}
+	if rectDef.BorderEnabled {
+		creator.Add_RG(rectDef.BorderColor.R(), rectDef.BorderColor.G(), rectDef.BorderColor.B())
+		creator.Add_w(rectDef.BorderWidth)
+	}
+	if len(gsName) > 1 {
+		// If a graphics state is provided, use it. (Used for transparency settings here).
+		creator.Add_gs(pdfcore.PdfObjectName(gsName))
+	}
+	drawPathWithCreator(path, creator)
+	creator.Add_B() // fill and stroke.
+	creator.Add_Q()
+
+	// Offsets (needed for placement of annotations bbox).
+	offX := rectDef.X
+	offY := rectDef.Y
+
+	// Get bounding box.
+	pathBbox := path.GetBoundingBox()
+
+	// Bounding box - local coordinate system (without offset).
+	localBbox := &pdf.PdfRectangle{}
+	localBbox.Llx = pathBbox.X
+	localBbox.Lly = pathBbox.Y
+	localBbox.Urx = pathBbox.X + pathBbox.Width
+	localBbox.Ury = pathBbox.Y + pathBbox.Height
+
+	// Bounding box - global page coordinate system (with offset).
+	globalBbox := &pdf.PdfRectangle{}
+	globalBbox.Llx = offX + pathBbox.X
+	globalBbox.Lly = offY + pathBbox.Y
+	globalBbox.Urx = offX + pathBbox.X + pathBbox.Width
+	globalBbox.Ury = offY + pathBbox.Y + pathBbox.Height
+
+	return creator.Bytes(), localBbox, globalBbox, nil
+}