draw2d/draw2dsvg/gc.go

// Copyright 2015 The draw2d Authors. All rights reserved.
// created: 16/12/2017 by Drahoslav Bednář

package draw2dsvg

import (
	"bytes"
	"fmt"
	"github.com/llgcode/draw2d"
	"github.com/llgcode/draw2d/draw2dbase"
	"image"
	"image/color"
	"math"
	"strings"
)

const ()

var ()

type drawType int

const (
	filled drawType = 1 << iota
	stroked
)

type SVG bytes.Buffer

func NewSvg() *Svg {
	return &Svg{Xmlns: "http://www.w3.org/2000/svg"}
}

// GraphicContext implements the draw2d.GraphicContext interface
// It provides draw2d with a svg backend
type GraphicContext struct {
	*draw2dbase.StackGraphicContext
	svg *Svg
}

func NewGraphicContext(svg *Svg) *GraphicContext {
	gc := &GraphicContext{draw2dbase.NewStackGraphicContext(), svg}
	return gc
}

// Clear fills the current canvas with a default transparent color
func (gc *GraphicContext) Clear() {
	gc.svg.Groups = nil
	gc.svg.Groups = append(gc.svg.Groups, Group{
	// TODO add background color?
	})
}

// Stroke strokes the paths with the color specified by SetStrokeColor
func (gc *GraphicContext) Stroke(paths ...*draw2d.Path) {
	gc.drawPaths(stroked, paths...)
	gc.Current.Path.Clear()
}

// Fill fills the paths with the color specified by SetFillColor
func (gc *GraphicContext) Fill(paths ...*draw2d.Path) {
	gc.drawPaths(filled, paths...)
	gc.Current.Path.Clear()
}

// FillStroke first fills the paths and than strokes them
func (gc *GraphicContext) FillStroke(paths ...*draw2d.Path) {
	gc.drawPaths(filled|stroked, paths...)
	gc.Current.Path.Clear()
}

func (gc *GraphicContext) drawPaths(drawType drawType, paths ...*draw2d.Path) {
	paths = append(paths, gc.Current.Path)

	svgPaths := make([]Path, len(paths))

	for i, path := range paths {
		svgPaths[i].Desc = toSvgPathDesc(path)
		if drawType&stroked == stroked {
			svgPaths[i].Stroke = toSvgRGBA(gc.Current.StrokeColor)
			svgPaths[i].StrokeWidth = toSvgLength(gc.Current.LineWidth)
			svgPaths[i].StrokeLinecap = gc.Current.Cap.String()
			svgPaths[i].StrokeLinejoin = gc.Current.Join.String()
		} else {
			svgPaths[i].Stroke = "none"
		}
		if drawType&filled == filled {
			svgPaths[i].Fill = toSvgRGBA(gc.Current.FillColor)
		} else {
			svgPaths[i].Fill = "none"
		}
	}

	gc.svg.Groups = append(gc.svg.Groups, Group{
		Paths: svgPaths,
	})
}

func toSvgRGBA(c color.Color) string { // TODO move elsewhere
	r, g, b, a := c.RGBA()
	return fmt.Sprintf("rgba(%v, %v, %v, %.3f)", r>>8, g>>8, b>>8, float64(a>>8)/255)
}

func toSvgLength(l float64) string {
	return fmt.Sprintf("%.4f", l)
}

func toSvgPathDesc(p *draw2d.Path) string { // TODO move elsewhere
	parts := make([]string, len(p.Components))
	ps := p.Points
	for i, cmp := range p.Components {
		switch cmp {
		case draw2d.MoveToCmp:
			parts[i] = fmt.Sprintf("M %.4f,%.4f", ps[0], ps[1])
			ps = ps[2:]
		case draw2d.LineToCmp:
			parts[i] = fmt.Sprintf("L %.4f,%.4f", ps[0], ps[1])
			ps = ps[2:]
		case draw2d.QuadCurveToCmp:
			parts[i] = fmt.Sprintf("Q %.4f,%.4f %.4f,%.4f", ps[0], ps[1], ps[2], ps[3])
			ps = ps[4:]
		case draw2d.CubicCurveToCmp:
			parts[i] = fmt.Sprintf("C %.4f,%.4f %.4f,%.4f %.4f,%.4f", ps[0], ps[1], ps[2], ps[3], ps[4], ps[5])
			ps = ps[6:]
		case draw2d.ArcToCmp:
			cx, cy := ps[0], ps[1] // center
			rx, ry := ps[2], ps[3] // radii
			fi := ps[4] + ps[5]    // startAngle + angle

			// compute endpoint
			sinfi, cosfi := math.Sincos(fi)
			nom := math.Hypot(ry*cosfi, rx*sinfi)
			x := cx + (rx*ry*cosfi)/nom
			y := cy + (rx*ry*sinfi)/nom
			x += 0.001 // dirty hack to ensure whole arc is drawn if start point equals endpoint
			y += 0.001

			// compute large and sweep flags
			large := 0
			sweep := 0
			if math.Abs(ps[5]) > math.Pi {
				large = 1
			}
			if !math.Signbit(ps[5]) {
				sweep = 1
			}

			// rx ry x-axis-rotation large-arc-flag sweep-flag x y
			parts[i] = fmt.Sprintf("A %.4f %.4f %v %v %v %.4f %.4f",
				rx, ry,
				0,
				large, sweep,
				x, y,
			)
			ps = ps[6:]
		case draw2d.CloseCmp:
			parts[i] = "Z"
		}
	}
	return strings.Join(parts, " ")
}

///////////////////////////////////////
// TODO implement following methods (or remove if not neccesary)

// SetFontData sets the current FontData
func (gc *GraphicContext) SetFontData(fontData draw2d.FontData) {

}

// GetFontData gets the current FontData
func (gc *GraphicContext) GetFontData() draw2d.FontData {
	return draw2d.FontData{}
}

// GetFontName gets the current FontData as a string
func (gc *GraphicContext) GetFontName() string {
	return ""
}

// DrawImage draws the raster image in the current canvas
func (gc *GraphicContext) DrawImage(image image.Image) {

}

// Save the context and push it to the context stack
func (gc *GraphicContext) Save() {

}

// Restore remove the current context and restore the last one
func (gc *GraphicContext) Restore() {

}

// ClearRect fills the specified rectangle with a default transparent color
func (gc *GraphicContext) ClearRect(x1, y1, x2, y2 int) {

}

// SetDPI sets the current DPI
func (gc *GraphicContext) SetDPI(dpi int) {

}

// GetDPI gets the current DPI
func (gc *GraphicContext) GetDPI() int {
	return 0
}

// GetStringBounds gets pixel bounds(dimensions) of given string
func (gc *GraphicContext) GetStringBounds(s string) (left, top, right, bottom float64) {
	return 0, 0, 0, 0
}

// CreateStringPath creates a path from the string s at x, y
func (gc *GraphicContext) CreateStringPath(text string, x, y float64) (cursor float64) {
	return 0
}

// FillString draws the text at point (0, 0)
func (gc *GraphicContext) FillString(text string) (cursor float64) {
	return 0
}

// FillStringAt draws the text at the specified point (x, y)
func (gc *GraphicContext) FillStringAt(text string, x, y float64) (cursor float64) {
	return 0
}

// StrokeString draws the contour of the text at point (0, 0)
func (gc *GraphicContext) StrokeString(text string) (cursor float64) {
	return 0
}

// StrokeStringAt draws the contour of the text at point (x, y)
func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (cursor float64) {
	return 0
}