Merge pull request #51 from stanim/doc

Godoc improvement.

README.md

@@ -1,19 +1,20 @@
 draw2d
 ======
 
-This package (written in [go](http://golang.org)) provides an API to draw 2d vector forms on [images](http://golang.org/pkg/image).
+Package draw2d is a pure [go](http://golang.org) 2D vector graphics library with support for multiple output devices such as [images](http://golang.org/pkg/image) (draw2d), pdf documents (draw2dpdf) and opengl (draw2dopengl), which can also be used on the google app engine.
 This library is inspired by [postscript](http://www.tailrecursive.org/postscript) and [HTML5 canvas](http://www.w3.org/TR/2dcontext/).
 
+See the [documentation](http://godoc.org/github.com/llgcode/draw2d) for more details.
+
 The package depends on [freetype-go](http://code.google.com/p/freetype-go) package for its rasterization algorithm.
 
+Installation
+------------
 
-Using
------
-
-Install [golang](http://golang.org/doc/install) and get `draw2d` 
+Install [golang](http://golang.org/doc/install). To install or update the package draw2d on your system, run:
 
 ```
-go get github.com/llgcode/draw2d
+go get -u github.com/llgcode/draw2d
 ```
 
 and start coding using one of the [Samples](https://github.com/llgcode/draw2d.samples).

advanced_path.go

@@ -1,14 +1,15 @@
 // Copyright 2010 The draw2d Authors. All rights reserved.
 // created: 13/12/2010 by Laurent Le Goff
 
+//high level path creation
+
 package draw2d
 
 import (
 	"math"
 )
 
-//high level path creation
-
+// Rect draws a rectangle between (x1,y1) and (x2,y2)
 func Rect(path Path, x1, y1, x2, y2 float64) {
 	path.MoveTo(x1, y1)
 	path.LineTo(x2, y1)
@@ -17,6 +18,7 @@ func Rect(path Path, x1, y1, x2, y2 float64) {
 	path.Close()
 }
 
+// RoundRect draws a rectangle between (x1,y1) and (x2,y2) with rounded corners
 func RoundRect(path Path, x1, y1, x2, y2, arcWidth, arcHeight float64) {
 	arcWidth = arcWidth / 2
 	arcHeight = arcHeight / 2
@@ -31,12 +33,14 @@ func RoundRect(path Path, x1, y1, x2, y2, arcWidth, arcHeight float64) {
 	path.Close()
 }
 
+// Ellipse is drawn with center (cx,cy) and radius (rx,ry)
 func Ellipse(path Path, cx, cy, rx, ry float64) {
 	path.MoveTo(cx-rx, cy)
 	path.ArcTo(cx, cy, rx, ry, 0, -math.Pi*2)
 	path.Close()
 }
 
+// Circle is drawn with center (cx,cy) and radius
 func Circle(path Path, cx, cy, radius float64) {
 	path.MoveTo(cx-radius, cy)
 	path.ArcTo(cx, cy, radius, radius, 0, -math.Pi*2)

draw2d.go

@@ -1,5 +1,68 @@
 // Copyright 2010 The draw2d Authors. All rights reserved.
 // created: 13/12/2010 by Laurent Le Goff
 
-// Package draw2d provides a Graphic Context that can draw vector form on canvas.
+// Package draw2d is a pure go 2D vector graphics library with support
+// for multiple output devices such as images (draw2d), pdf documents
+// (draw2dpdf) and opengl (draw2dopengl), which can also be used on the
+// google app engine.
+//
+// Features
+//
+// Operations in draw2d include stroking and filling polygons, arcs,
+// Bézier curves, drawing images and text rendering with truetype fonts.
+// All drawing operations can be transformed by affine transformations
+// (scale, rotation, translation).
+//
+// Installation
+//
+// To install or update the package draw2d on your system, run:
+//   go get -u github.com/llgcode/draw2d
+//
+// Quick Start
+//
+// Package draw2d itself provides a graphic context that can draw vector
+// graphics and text on an image canvas. The following Go code
+// generates a simple drawing and saves it to an image file:
+//   // Initialize the graphic context on an RGBA image
+//   dest := image.NewRGBA(image.Rect(0, 0, 297, 210.0))
+//   gc := draw2d.NewGraphicContext(dest)
+//
+//   // Set some properties
+//   gc.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
+//   gc.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
+//   gc.SetLineWidth(5)
+//
+//   // Draw a closed shape
+//   gc.MoveTo(10, 10) // should always be called first for a new path
+//   gc.LineTo(100, 50)
+//   gc.QuadCurveTo(100, 10, 10, 10)
+//   gc.Close()
+//   gc.FillStroke()
+//
+//   // Save to file
+//   draw2d.SaveToPngFile(fn, dest)
+//
+// There are more examples here:
+// https://github.com/llgcode/draw2d.samples
+//
+// Drawing on pdf documents is provided by the draw2dpdf package.
+// Drawing on opengl is provided by the draw2dgl package.
+// See subdirectories at the bottom of this page.
+//
+// Acknowledgments
+//
+// Laurent Le Goff wrote this library, inspired by postscript and
+// HTML5 canvas. He implemented the image and opengl backend. Also
+// he created a pure go Postscripter interpreter which can draw to a
+// draw2d graphic context (https://github.com/llgcode/ps). Stani
+// Michiels implemented the pdf backend.
+//
+// The package depends on freetype-go package for its rasterization
+// algorithm.
+//
+// Packages using draw2d
+//
+// - https://github.com/llgcode/ps
+//
+// - https://github.com/gonum/plot
 package draw2d

draw2dgl/doc.go

@@ -0,0 +1,3 @@
+// Package draw2dgl provides a graphic context that can draw vector
+// graphics and text on OpenGL.
+package draw2dgl

draw2dpdf/doc.go

@@ -1,5 +1,39 @@
 // Copyright 2015 The draw2d Authors. All rights reserved.
 // created: 26/06/2015 by Stani Michiels
 
-// Package draw2dpdf provides a Graphic Context that can draw vector form on pdf file.
+// Package draw2dpdf provides a graphic context that can draw vector
+// graphics and text on pdf file.
+//
+// Quick Start
+//
+// The following Go code generates a simple drawing and saves it to a
+// pdf document:
+//   // Initialize the graphic context on an RGBA image
+//   dest := draw2dpdf.NewPdf("L", "mm", "A4")
+//   gc := draw2d.NewGraphicContext(dest)
+//
+//   // Set some properties
+//   gc.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
+//   gc.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
+//   gc.SetLineWidth(5)
+//
+//   // Draw a closed shape
+//   gc.MoveTo(10, 10) // should always be called first for a new path
+//   gc.LineTo(100, 50)
+//   gc.QuadCurveTo(100, 10, 10, 10)
+//   gc.Close()
+//   gc.FillStroke()
+//
+//   // Save to file
+//   draw2dpdf.SaveToPdfFile(fn, dest)
+//
+// There are more examples here:
+// https://github.com/llgcode/draw2d.samples
+//
+// Drawing on images is provided by the draw2d package.
+// Drawing on opengl is provided by the draw2dgl package.
+//
+// Acknowledgments
+//
+// The pdf backend uses https://github.com/jung-kurt/gofpdf
 package draw2dpdf

draw2dpdf/gc.go

@@ -17,14 +17,14 @@ import (
 
 	"code.google.com/p/freetype-go/freetype/truetype"
 
-	"github.com/llgcode/draw2d"
 	"github.com/jung-kurt/gofpdf"
+	"github.com/llgcode/draw2d"
 )
 
 const (
-	c255 = 255.0 / 65535.0
 	// DPI of a pdf document is fixed at 72.
 	DPI  = 72
+	c255 = 255.0 / 65535.0
 )
 
 var (
@@ -89,6 +89,7 @@ func NewGraphicContext(pdf *gofpdf.Fpdf) *GraphicContext {
 // TODO: add type (tp) as parameter to argument list?
 func (gc *GraphicContext) DrawImage(image image.Image) {
 	name := strconv.Itoa(int(imageCount))
+	imageCount += 1
 	tp := "PNG" // "JPG", "JPEG", "PNG" and "GIF"
 	b := &bytes.Buffer{}
 	png.Encode(b, image)
@@ -168,12 +169,12 @@ func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (cursor floa
 	return gc.CreateStringPath(text, x, y)
 }
 
-// Stroke strokes the paths
+// Stroke strokes the paths with the color specified by SetStrokeColor
 func (gc *GraphicContext) Stroke(paths ...*draw2d.PathStorage) {
 	gc.draw("D", paths...)
 }
 
-// Fill strokes the paths
+// Fill fills the paths with the color specified by SetFillColor
 func (gc *GraphicContext) Fill(paths ...*draw2d.PathStorage) {
 	gc.draw("F", paths...)
 }

draw2dpdf/graphiccontext_test.go

@@ -1,35 +0,0 @@
-package draw2dpdf
-
-import (
-	"fmt"
-	"image/color"
-
-	"github.com/llgcode/draw2d"
-	"github.com/jung-kurt/gofpdf"
-)
-
-func ExampleGraphicContext() {
-	// Initialize the graphic context on a pdf document
-	pdf := gofpdf.New("P", "mm", "A4", "../font")
-	pdf.AddPage()
-	gc := NewGraphicContext(pdf)
-
-	// some properties
-	gc.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
-	gc.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
-	gc.SetLineCap(draw2d.RoundCap)
-	gc.SetLineWidth(5)
-
-	// draw something
-	gc.MoveTo(10, 10) // should always be called first for a new path
-	gc.LineTo(100, 50)
-	gc.QuadCurveTo(100, 10, 10, 10)
-	gc.Close()
-	gc.FillStroke()
-	fmt.Println(gc.LastPoint())
-
-	// draw2dpdf.SaveToPdfFile("example.pdf", pdf)
-
-	// Output:
-	// 10 10
-}

draw2dpdf/test_test.go

@@ -11,12 +11,14 @@ import (
 	"github.com/llgcode/draw2d/draw2dpdf"
 )
 
-func test(t *testing.T, sample draw2d.Sample) {
+type sample func(gc draw2d.GraphicContext, ext string) (string, error)
+
+func test(t *testing.T, draw sample) {
 	// Initialize the graphic context on an pdf document
 	dest := draw2dpdf.NewPdf("L", "mm", "A4")
 	gc := draw2dpdf.NewGraphicContext(dest)
 	// Draw sample
-	fn, err := sample(gc, "pdf")
+	fn, err := draw(gc, "pdf")
 	if err != nil {
 		t.Errorf("Drawing %q failed: %v", fn, err)
 		return

gc.go

@@ -8,15 +8,17 @@ import (
 	"image/color"
 )
 
+// FillRule defines the type for fill rules
 type FillRule int
 
 const (
+	// FillRuleEvenOdd defines the even odd filling rule
 	FillRuleEvenOdd FillRule = iota
+	// FillRuleWinding defines the non zero winding rule
 	FillRuleWinding
 )
 
-type Sample func(gc GraphicContext, ext string) (string, error)
-
+// GraphicContext describes the interface for the various backends (images, pdf, opengl, ...)
 type GraphicContext interface {
 	Path
 	// Create a new path

image.go

@@ -34,9 +34,7 @@ type ImageGraphicContext struct {
 	DPI              int
 }
 
-/**
- * Create a new Graphic context from an image
- */
+// NewGraphicContext creates a new Graphic context from an image.
 func NewGraphicContext(img draw.Image) *ImageGraphicContext {
 	var painter Painter
 	switch selectImage := img.(type) {
@@ -48,7 +46,7 @@ func NewGraphicContext(img draw.Image) *ImageGraphicContext {
 	return NewGraphicContextWithPainter(img, painter)
 }
 
-// Create a new Graphic context from an image and a Painter (see Freetype-go)
+// NewGraphicContextWithPainter creates a new Graphic context from an image and a Painter (see Freetype-go)
 func NewGraphicContextWithPainter(img draw.Image, painter Painter) *ImageGraphicContext {
 	width, height := img.Bounds().Dx(), img.Bounds().Dy()
 	dpi := 92
@@ -274,7 +272,7 @@ func (gc *ImageGraphicContext) paint(rasterizer *raster.Rasterizer, color color.
 	gc.Current.Path.Clear()
 }
 
-/**** second method ****/
+// Stroke strokes the paths with the color specified by SetStrokeColor
 func (gc *ImageGraphicContext) Stroke(paths ...*PathStorage) {
 	paths = append(paths, gc.Current.Path)
 	gc.strokeRasterizer.UseNonZeroWinding = true
@@ -294,7 +292,7 @@ func (gc *ImageGraphicContext) Stroke(paths ...*PathStorage) {
 	gc.paint(gc.strokeRasterizer, gc.Current.StrokeColor)
 }
 
-/**** second method ****/
+// Fill fills the paths with the color specified by SetFillColor
 func (gc *ImageGraphicContext) Fill(paths ...*PathStorage) {
 	paths = append(paths, gc.Current.Path)
 	gc.fillRasterizer.UseNonZeroWinding = gc.Current.FillRule.UseNonZeroWinding()
@@ -307,7 +305,7 @@ func (gc *ImageGraphicContext) Fill(paths ...*PathStorage) {
 	gc.paint(gc.fillRasterizer, gc.Current.FillColor)
 }
 
-/* second method */
+// FillStroke first fills the paths and than strokes them
 func (gc *ImageGraphicContext) FillStroke(paths ...*PathStorage) {
 	gc.fillRasterizer.UseNonZeroWinding = gc.Current.FillRule.UseNonZeroWinding()
 	gc.strokeRasterizer.UseNonZeroWinding = true

path.go

@@ -3,25 +3,37 @@
 
 package draw2d
 
+// Path describes the interface for path drawing.
 type Path interface {
-	// Return the current point of the path
+	// LastPoint returns the current point of the path
 	LastPoint() (x, y float64)
-	// Create a new subpath that start at the specified point
+	// MoveTo creates a new subpath that start at the specified point
 	MoveTo(x, y float64)
-	// Create a new subpath that start at the specified point
+	// RMoveTo creates a new subpath that start at the specified point
 	// relative to the current point
 	RMoveTo(dx, dy float64)
-	// Add a line to the current subpath
+	// LineTo adds a line to the current subpath
 	LineTo(x, y float64)
-	// Add a line to the current subpath
+	// RLineTo adds a line to the current subpath
 	// relative to the current point
 	RLineTo(dx, dy float64)
-
+	// QuadCurveTo adds a quadratic Bézier curve to the current subpath
 	QuadCurveTo(cx, cy, x, y float64)
+	// QuadCurveTo adds a quadratic Bézier curve to the current subpath
+	// relative to the current point
 	RQuadCurveTo(dcx, dcy, dx, dy float64)
+	// CubicCurveTo adds a cubic Bézier curve to the current subpath
 	CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64)
+	// RCubicCurveTo adds a cubic Bézier curve to the current subpath
+	// relative to the current point
 	RCubicCurveTo(dcx1, dcy1, dcx2, dcy2, dx, dy float64)
+	// ArcTo adds an arc to the current subpath
 	ArcTo(cx, cy, rx, ry, startAngle, angle float64)
+	// RArcTo adds an arc to the current subpath
+	// relative to the current point
 	RArcTo(dcx, dcy, rx, ry, startAngle, angle float64)
+	// Close creates a line from the current point to the last MoveTo
+	// point (if not the same) and mark the path as closed so the
+	// first and last lines join nicely.
 	Close()
 }

test_test.go

@@ -9,7 +9,9 @@ import (
 	"github.com/llgcode/draw2d"
 )
 
-func test(t *testing.T, draw draw2d.Sample) {
+type sample func(gc draw2d.GraphicContext, ext string) (string, error)
+
+func test(t *testing.T, draw sample) {
 	// Initialize the graphic context on an RGBA image
 	dest := image.NewRGBA(image.Rect(0, 0, 297, 210.0))
 	gc := draw2d.NewGraphicContext(dest)