Transformation functionality adapted from Moritz Wagner and Andreas Würmser.

4 files changed, 128 insertions, 2 deletions

diff --git a/def.go b/def.go
index ed37f11..45ec09a 100644
--- a/def.go
+++ b/def.go
@@ -171,6 +171,7 @@ type Fpdf struct {
 	blendMap         map[string]int           // map into blendList
 	gradientList     []gradientType           // slice[idx] of gradient records
 	clipNest         int                      // Number of active clipping contexts
+	transformNest    int                      // Number of active transformation contexts
 	err              error                    // Set if error occurs during life cycle of instance
 }
 
diff --git a/doc.go b/doc.go
index 85f34d4..6f960d9 100644
--- a/doc.go
+++ b/doc.go
@@ -23,7 +23,9 @@ directly from it. Drawing support is adapted from the FPDF geometric figures
 script by David Hernández Sanz. Transparency support is adapted from the FPDF
 transparency script by Martin Hall-May. Support for gradients and clipping is
 adapted from FPDF scripts by Andreas Würmser. Support for outline bookmarks is
-adapted from Olivier Plathey by Manuel Cornes.
+adapted from Olivier Plathey by Manuel Cornes. Support for transformations is
+adapted from the FPDF transformation script by Moritz Wagner and Andreas
+Würmser.
 
 The FPDF website is http://www.fpdf.org/.
 
@@ -51,6 +53,8 @@ Features
 
 • Drawing support (lines, Bézier curves, arcs, ellipses)
 
+• Transformation support (rotation, scaling, skewing, translation, mirroring)
+
 • Clipping
 
 gofpdf has no dependencies other than the Go standard library. All tests pass
diff --git a/fpdf.go b/fpdf.go
index 50d1763..51dfad1 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -428,6 +428,8 @@ func (f *Fpdf) Close() {
 	if f.err == nil {
 		if f.clipNest > 0 {
 			f.err = fmt.Errorf("Clip procedure must be explicitly ended")
+		} else if f.transformNest > 0 {
+			f.err = fmt.Errorf("Transformation procedure must be explicitly ended")
 		}
 	}
 	if f.err != nil {
@@ -1148,7 +1150,7 @@ func (f *Fpdf) ClipEnd() {
 			f.clipNest--
 			f.out("Q")
 		} else {
-			f.err = fmt.Errorf("Error attempting to end clip operation")
+			f.err = fmt.Errorf("Error attempting to end clip operation out of sequence")
 		}
 	}
 }
diff --git a/fpdf_test.go b/fpdf_test.go
index fad67bc..ccdf1bf 100644
--- a/fpdf_test.go
+++ b/fpdf_test.go
@@ -964,3 +964,122 @@ func ExampleFpdf_tutorial16() {
 	// Output:
 	// Successfully generated pdf/tutorial16.pdf
 }
+
+// Transformation test adapted from an example script by Moritz Wagner and
+// Andreas Würmser.
+func ExampleFpdf_tutorial17() {
+	const (
+		light = 200
+		dark  = 0
+	)
+	var refX, refY float64
+	var refStr string
+	pdf := gofpdf.New("P", "mm", "A4", FONT_DIR)
+	pdf.AddPage()
+	color := func(val int) {
+		pdf.SetDrawColor(val, val, val)
+		pdf.SetTextColor(val, val, val)
+	}
+	reference := func(str string, x, y float64, val int) {
+		color(val)
+		pdf.Rect(x, y, 40, 10, "D")
+		pdf.Text(x, y-1, str)
+	}
+	refDraw := func(str string, x, y float64) {
+		refStr = str
+		refX = x
+		refY = y
+		reference(str, x, y, light)
+	}
+	refDupe := func() {
+		reference(refStr, refX, refY, dark)
+	}
+
+	titleStr := "Transformations"
+	titlePt := 36.0
+	titleHt := titlePt * 25.4 / 72.0
+	pdf.SetFont("Helvetica", "", titlePt)
+	titleWd := pdf.GetStringWidth(titleStr)
+	titleX := (210 - titleWd) / 2
+	pdf.Text(titleX, 10+titleHt, titleStr)
+	pdf.TransformBegin()
+	pdf.TransformMirrorVertical(10 + titleHt + 0.5)
+	pdf.ClipText(titleX, 10+titleHt, titleStr, false)
+	// Remember that the transform will mirror the gradient box too
+	pdf.LinearGradient(titleX, 10, titleWd, titleHt+4, 120, 120, 120, 255, 255, 255, 0, 0, 0, 0.6)
+	pdf.ClipEnd()
+	pdf.TransformEnd()
+
+	pdf.SetFont("Helvetica", "", 12)
+
+	// Scale by 150% centered by lower left corner of the rectangle
+	refDraw("Scale", 50, 60)
+	pdf.TransformBegin()
+	pdf.TransformScaleXY(150, 50, 70)
+	refDupe()
+	pdf.TransformEnd()
+
+	// Translate 7 to the right, 5 to the bottom
+	refDraw("Translate", 125, 60)
+	pdf.TransformBegin()
+	pdf.TransformTranslate(7, 5)
+	refDupe()
+	pdf.TransformEnd()
+
+	// Rotate 20 degrees counter-clockwise centered by the lower left corner of
+	// the rectangle
+	refDraw("Rotate", 50, 110)
+	pdf.TransformBegin()
+	pdf.TransformRotate(20, 50, 120)
+	refDupe()
+	pdf.TransformEnd()
+
+	// Skew 30 degrees along the x-axis centered by the lower left corner of the
+	// rectangle
+	refDraw("Skew", 125, 110)
+	pdf.TransformBegin()
+	pdf.TransformSkewX(30, 125, 110)
+	refDupe()
+	pdf.TransformEnd()
+
+	// Mirror horizontally with axis of reflection at left side of the rectangle
+	refDraw("Mirror horizontal", 50, 160)
+	pdf.TransformBegin()
+	pdf.TransformMirrorHorizontal(50)
+	refDupe()
+	pdf.TransformEnd()
+
+	// Mirror vertically with axis of reflection at bottom side of the rectangle
+	refDraw("Mirror vertical", 125, 160)
+	pdf.TransformBegin()
+	pdf.TransformMirrorVertical(170)
+	refDupe()
+	pdf.TransformEnd()
+
+	// Reflect against a point at the lower left point of rectangle
+	refDraw("Mirror point", 50, 210)
+	pdf.TransformBegin()
+	pdf.TransformMirrorPoint(50, 220)
+	refDupe()
+	pdf.TransformEnd()
+
+	// Mirror against a straight line described by a point and an angle
+	angle := -20.0
+	px := 120.0
+	py := 220.0
+	refDraw("Mirror line", 125, 210)
+	pdf.TransformBegin()
+	pdf.TransformRotate(angle, px, py)
+	pdf.Line(px-1, py-1, px+1, py+1)
+	pdf.Line(px-1, py+1, px+1, py-1)
+	pdf.Line(px-5, py, px+60, py)
+	pdf.TransformEnd()
+	pdf.TransformBegin()
+	pdf.TransformMirrorLine(angle, px, py)
+	refDupe()
+	pdf.TransformEnd()
+
+	pdf.OutputAndClose(docWriter(pdf, 17))
+	// Output:
+	// Successfully generated pdf/tutorial17.pdf
+}