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| -rw-r--r-- | fpdftrans.go | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/fpdftrans.go b/fpdftrans.go new file mode 100644 index 0000000..8c4e48c --- /dev/null +++ b/fpdftrans.go @@ -0,0 +1,178 @@ +package gofpdf + +import ( + "fmt" + "math" +) + +// Routines in this file are translated from the work of Moritz Wagner and +// Andreas Würmser. + +// The matrix used for generalized transformations of text, drawings and images. +type TransformMatrix struct { + a, b, c, d, e, f float64 +} + +// Set up a transformation context for subsequent text, drawings and images. +// The typical usage is to immediately follow a call to this method with a call +// to one or more of the transformation methods such as TransformScale(), +// TransformSkew(), etc. This is followed by text, drawing or image output and +// finally a call to TransformEnd(). All transformation contexts must be +// properly ended prior to outputting the document. +// +// See tutorial 17 for a transformation examples. +func (f *Fpdf) TransformBegin() { + f.transformNest++ + f.out("q") +} + +// Scale the width of the following text, drawings and images. scaleWd is the +// percentage scaling factor. (x, y) is center of scaling. +func (f *Fpdf) TransformScaleX(scaleWd, x, y float64) { + f.TransformScale(scaleWd, 100, x, y) +} + +// Scale the height of the following text, drawings and images. scaleHt is the +// percentage scaling factor. (x, y) is center of scaling. +func (f *Fpdf) TransformScaleY(scaleHt, x, y float64) { + f.TransformScale(100, scaleHt, x, y) +} + +// Uniformly scale the width and height of the following text, drawings and +// images. s is the percentage scaling factor for both width and height. (x, y) +// is center of scaling. +func (f *Fpdf) TransformScaleXY(s, x, y float64) { + f.TransformScale(s, s, x, y) +} + +// Generally scale the following text, drawings and images. scaleWd and scaleHt +// are the percentage scaling factors for width and height. (x, y) is center of +// scaling. +func (f *Fpdf) TransformScale(scaleWd, scaleHt, x, y float64) { + if scaleWd == 0 || scaleHt == 0 { + f.err = fmt.Errorf("Scale factor cannot be zero") + return + } + y = (f.h - y) * f.k + x *= f.k + scaleWd /= 100 + scaleHt /= 100 + f.Transform(TransformMatrix{scaleWd, 0, 0, scaleHt, x * (1 - scaleWd), y * (1 - scaleHt)}) +} + +// Horizontally mirror the following text, drawings and images. x is the axis +// of reflection. +func (f *Fpdf) TransformMirrorHorizontal(x float64) { + f.TransformScale(-100, 100, x, f.y) +} + +// Vertically mirror the following text, drawings and images. y is the axis +// of reflection. +func (f *Fpdf) TransformMirrorVertical(y float64) { + f.TransformScale(100, -100, f.x, y) +} + +// Symmetrically mirror the following text, drawings and images on the point +// specified by (x, y). +func (f *Fpdf) TransformMirrorPoint(x, y float64) { + f.TransformScale(-100, -100, x, y) +} + +// Symmetrically mirror the following text, drawings and images on the line +// defined by angle and the point (x, y). angles is specified in degrees and +// measured counter-clockwise from the 3 o'clock position. +func (f *Fpdf) TransformMirrorLine(angle, x, y float64) { + f.TransformScale(-100, 100, x, y) + f.TransformRotate(-2*(angle-90), x, y) +} + +// Move the following text, drawings and images horizontally by the amount +// specified by tx. +func (f *Fpdf) TransformTranslateX(tx float64) { + f.TransformTranslate(tx, 0) +} + +// Move the following text, drawings and images vertically by the amount +// specified by ty. +func (f *Fpdf) TransformTranslateY(ty float64) { + f.TransformTranslate(0, ty) +} + +// Move the following text, drawings and images horizontally and vertically by +// the amounts specified by tx and ty. +func (f *Fpdf) TransformTranslate(tx, ty float64) { + f.Transform(TransformMatrix{1, 0, 0, 1, tx - f.k, -ty * f.k}) +} + +// Rotate the following text, drawings and images around the center point (x, +// y). angle is specified in degrees and measured counter-clockwise from the 3 +// o'clock position. +func (f *Fpdf) TransformRotate(angle, x, y float64) { + y = (f.h - y) * f.k + x *= f.k + angle = angle * math.Pi / 180 + var tm TransformMatrix + tm.a = math.Cos(angle) + tm.b = math.Sin(angle) + tm.c = -tm.b + tm.d = tm.a + tm.e = x + tm.b*y - tm.a*x + tm.f = y - tm.a*y - tm.b*x + f.Transform(tm) +} + +// Horizontally skew the following text, drawings and images keeping the point +// (x, y) stationary. angleX ranges from -90 degrees (skew to the left) to 90 +// degrees (skew to the right). +func (f *Fpdf) TransformSkewX(angleX, x, y float64) { + f.TransformSkew(angleX, 0, x, y) +} + +// Vertically skew the following text, drawings and images keeping the point +// (x, y) stationary. angleY ranges from -90 degrees (skew to the bottom) to 90 +// degrees (skew to the right). +func (f *Fpdf) TransformSkewY(angleY, x, y float64) { + f.TransformSkew(0, angleY, x, y) +} + +// Generally skew the following text, drawings and images keeping the point (x, +// y) stationary. angleX ranges from -90 degrees (skew to the left) to 90 +// degrees (skew to the right). angleY ranges from -90 degrees (skew to the +// bottom) to 90 degrees (skew to the right). +func (f *Fpdf) TransformSkew(angleX, angleY, x, y float64) { + if angleX <= -90 || angleX >= 90 || angleY <= -90 || angleY >= 90 { + f.err = fmt.Errorf("Skew values must be between -90° and 90°") + return + } + x *= f.k + y = (f.h - y) * f.k + var tm TransformMatrix + tm.a = 1 + tm.b = math.Tan(angleY * math.Pi / 180) + tm.c = math.Tan(angleX * math.Pi / 180) + tm.d = 1 + tm.e = -tm.c * y + tm.f = -tm.b * x + f.Transform(tm) +} + +// Generally transform the following text, drawings and images according to the +// specified matrix. It is typically easier to use the various methods such as +// TransformRotate() and TransformMirrorVertical() instead. +func (f *Fpdf) Transform(tm TransformMatrix) { + if f.transformNest > 0 { + f.outf("%.3f %.3f %.3f %.3f %.3f %.3f cm", tm.a, tm.b, tm.c, tm.d, tm.e, tm.f) + } else if f.err == nil { + f.err = fmt.Errorf("Transformation context is not active") + } +} + +// Apply a transformation that was begun with a call to TransformBegin(). +func (f *Fpdf) TransformEnd() { + if f.transformNest > 0 { + f.transformNest-- + f.out("Q") + } else { + f.err = fmt.Errorf("Error attempting to end transformation operation out of sequence") + } +} |