go-chart/raster_renderer.go

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package chart
import (
"image"
"image/png"
"io"
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"math"
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"github.com/golang/freetype/truetype"
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"github.com/wcharczuk/go-chart/drawing"
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)
// PNG returns a new png/raster renderer.
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func PNG(width, height int) (Renderer, error) {
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i := image.NewRGBA(image.Rect(0, 0, width, height))
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gc, err := drawing.NewRasterGraphicContext(i)
if err == nil {
return &rasterRenderer{
i: i,
gc: gc,
}, nil
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}
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return nil, err
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}
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// rasterRenderer renders chart commands to a bitmap.
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type rasterRenderer struct {
i *image.RGBA
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gc *drawing.RasterGraphicContext
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s Style
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}
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// GetDPI returns the dpi.
func (rr *rasterRenderer) GetDPI() float64 {
return rr.gc.GetDPI()
}
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// SetDPI implements the interface method.
func (rr *rasterRenderer) SetDPI(dpi float64) {
rr.gc.SetDPI(dpi)
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}
// SetStrokeColor implements the interface method.
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func (rr *rasterRenderer) SetStrokeColor(c drawing.Color) {
rr.s.StrokeColor = c
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}
// SetLineWidth implements the interface method.
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func (rr *rasterRenderer) SetStrokeWidth(width float64) {
rr.s.StrokeWidth = width
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}
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// StrokeDashArray sets the stroke dash array.
func (rr *rasterRenderer) SetStrokeDashArray(dashArray []float64) {
rr.s.StrokeDashArray = dashArray
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}
// SetFillColor implements the interface method.
func (rr *rasterRenderer) SetFillColor(c drawing.Color) {
rr.s.FillColor = c
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}
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// MoveTo implements the interface method.
func (rr *rasterRenderer) MoveTo(x, y int) {
rr.gc.MoveTo(float64(x), float64(y))
}
// LineTo implements the interface method.
func (rr *rasterRenderer) LineTo(x, y int) {
rr.gc.LineTo(float64(x), float64(y))
}
// Close implements the interface method.
func (rr *rasterRenderer) Close() {
rr.gc.Close()
}
// Stroke implements the interface method.
func (rr *rasterRenderer) Stroke() {
rr.gc.SetStrokeColor(rr.s.StrokeColor)
rr.gc.SetLineWidth(rr.s.StrokeWidth)
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rr.gc.SetLineDash(rr.s.StrokeDashArray, 0)
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rr.gc.Stroke()
}
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// Fill implements the interface method.
func (rr *rasterRenderer) Fill() {
rr.gc.SetFillColor(rr.s.FillColor)
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rr.gc.Fill()
}
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// FillStroke implements the interface method.
func (rr *rasterRenderer) FillStroke() {
rr.gc.SetFillColor(rr.s.FillColor)
rr.gc.SetStrokeColor(rr.s.StrokeColor)
rr.gc.SetLineWidth(rr.s.StrokeWidth)
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rr.gc.SetLineDash(rr.s.StrokeDashArray, 0)
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rr.gc.FillStroke()
}
// Circle implements the interface method.
func (rr *rasterRenderer) Circle(radius float64, x, y int) {
xf := float64(x)
yf := float64(y)
rr.gc.MoveTo(xf-radius, yf) //9
rr.gc.QuadCurveTo(xf, yf, xf, yf-radius) //12
rr.gc.QuadCurveTo(xf, yf, xf+radius, yf) //3
rr.gc.QuadCurveTo(xf, yf, xf, yf+radius) //6
rr.gc.QuadCurveTo(xf, yf, xf-radius, yf) //9
rr.gc.Close()
rr.gc.FillStroke()
}
// SetFont implements the interface method.
func (rr *rasterRenderer) SetFont(f *truetype.Font) {
rr.s.Font = f
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}
// SetFontSize implements the interface method.
func (rr *rasterRenderer) SetFontSize(size float64) {
rr.s.FontSize = size
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}
// SetFontColor implements the interface method.
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func (rr *rasterRenderer) SetFontColor(c drawing.Color) {
rr.s.FontColor = c
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}
// Text implements the interface method.
func (rr *rasterRenderer) Text(body string, x, y int) {
rr.gc.SetFont(rr.s.Font)
rr.gc.SetFontSize(rr.s.FontSize)
rr.gc.SetFillColor(rr.s.FontColor)
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rr.gc.CreateStringPath(body, float64(x), float64(y))
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rr.gc.Fill()
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}
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// MeasureText returns the height and width in pixels of a string.
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func (rr *rasterRenderer) MeasureText(body string) Box {
rr.gc.SetFont(rr.s.Font)
rr.gc.SetFontSize(rr.s.FontSize)
rr.gc.SetFillColor(rr.s.FontColor)
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l, t, r, b, err := rr.gc.GetStringBounds(body)
if err != nil {
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return Box{}
}
if l < 0 {
r = r - l // equivalent to r+(-1*l)
l = 0
}
if t < 0 {
b = b - t
t = 0
}
if l > 0 {
r = r + l
l = 0
}
if t > 0 {
b = b + t
t = 0
}
return Box{
Top: int(math.Ceil(t)),
Left: int(math.Ceil(l)),
Right: int(math.Ceil(r)),
Bottom: int(math.Ceil(b)),
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}
}
// Save implements the interface method.
func (rr *rasterRenderer) Save(w io.Writer) error {
return png.Encode(w, rr.i)
}