draw2d/draw2dsvg/gc.go

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// Copyright 2015 The draw2d Authors. All rights reserved.
// created: 16/12/2017 by Drahoslav Bednář
package draw2dsvg
import (
"bytes"
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"fmt"
"github.com/llgcode/draw2d"
"github.com/llgcode/draw2d/draw2dbase"
"image"
"image/color"
"math"
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"strings"
)
const ()
var ()
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type drawType int
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const (
filled drawType = 1 << iota
stroked
)
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type SVG bytes.Buffer
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func NewSvg() *Svg {
return &Svg{Xmlns: "http://www.w3.org/2000/svg"}
}
// GraphicContext implements the draw2d.GraphicContext interface
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// It provides draw2d with a svg backend
type GraphicContext struct {
*draw2dbase.StackGraphicContext
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svg *Svg
}
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func NewGraphicContext(svg *Svg) *GraphicContext {
gc := &GraphicContext{draw2dbase.NewStackGraphicContext(), svg}
return gc
}
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// 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?
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})
}
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// 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()
}
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// 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()
}
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// FillStroke first fills the paths and than strokes them
func (gc *GraphicContext) FillStroke(paths ...*draw2d.Path) {
gc.drawPaths(filled|stroked, paths...)
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gc.Current.Path.Clear()
}
func (gc *GraphicContext) drawPaths(drawType drawType, paths ...*draw2d.Path) {
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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 {
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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"
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}
if drawType&filled == filled {
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svgPaths[i].Fill = toSvgRGBA(gc.Current.FillColor)
} else {
svgPaths[i].Fill = "none"
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}
}
gc.svg.Groups = append(gc.svg.Groups, Group{
Paths: svgPaths,
})
}
func toSvgRGBA(c color.Color) string { // TODO move elsewhere
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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)
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}
func toSvgPathDesc(p *draw2d.Path) string { // TODO move elsewhere
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parts := make([]string, len(p.Components))
ps := p.Points
for i, cmp := range p.Components {
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switch cmp {
case draw2d.MoveToCmp:
parts[i] = fmt.Sprintf("M %.4f,%.4f", ps[0], ps[1])
ps = ps[2:]
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case draw2d.LineToCmp:
parts[i] = fmt.Sprintf("L %.4f,%.4f", ps[0], ps[1])
ps = ps[2:]
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case draw2d.QuadCurveToCmp:
parts[i] = fmt.Sprintf("Q %.4f,%.4f %.4f,%.4f", ps[0], ps[1], ps[2], ps[3])
ps = ps[4:]
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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:]
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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
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large := 0
sweep := 0
if math.Abs(ps[5]) > math.Pi {
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large = 1
}
if !math.Signbit(ps[5]) {
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sweep = 1
}
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// 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,
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)
ps = ps[6:]
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case draw2d.CloseCmp:
parts[i] = "Z"
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}
}
return strings.Join(parts, " ")
}
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///////////////////////////////////////
// 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
}