go-chart/drawing/raster_graphic_context.go

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package drawing
import (
"errors"
"image"
"image/color"
"math"
"github.com/golang/freetype/raster"
"github.com/golang/freetype/truetype"
"golang.org/x/image/draw"
"golang.org/x/image/font"
"golang.org/x/image/math/fixed"
)
// NewRasterGraphicContext creates a new Graphic context from an image.
func NewRasterGraphicContext(img draw.Image) (*RasterGraphicContext, error) {
var painter Painter
switch selectImage := img.(type) {
case *image.RGBA:
painter = raster.NewRGBAPainter(selectImage)
default:
return nil, errors.New("NewRasterGraphicContext() :: invalid image type")
}
return NewRasterGraphicContextWithPainter(img, painter), nil
}
// NewRasterGraphicContextWithPainter creates a new Graphic context from an image and a Painter (see Freetype-go)
func NewRasterGraphicContextWithPainter(img draw.Image, painter Painter) *RasterGraphicContext {
width, height := img.Bounds().Dx(), img.Bounds().Dy()
return &RasterGraphicContext{
NewStackGraphicContext(),
img,
painter,
raster.NewRasterizer(width, height),
raster.NewRasterizer(width, height),
&truetype.GlyphBuf{},
DefaultDPI,
}
}
// RasterGraphicContext is the implementation of GraphicContext for a raster image
type RasterGraphicContext struct {
*StackGraphicContext
img draw.Image
painter Painter
fillRasterizer *raster.Rasterizer
strokeRasterizer *raster.Rasterizer
glyphBuf *truetype.GlyphBuf
DPI float64
}
// SetDPI sets the screen resolution in dots per inch.
func (rgc *RasterGraphicContext) SetDPI(dpi float64) {
rgc.DPI = dpi
rgc.recalc()
}
// GetDPI returns the resolution of the Image GraphicContext
func (rgc *RasterGraphicContext) GetDPI() float64 {
return rgc.DPI
}
// Clear fills the current canvas with a default transparent color
func (rgc *RasterGraphicContext) Clear() {
width, height := rgc.img.Bounds().Dx(), rgc.img.Bounds().Dy()
rgc.ClearRect(0, 0, width, height)
}
// ClearRect fills the current canvas with a default transparent color at the specified rectangle
func (rgc *RasterGraphicContext) ClearRect(x1, y1, x2, y2 int) {
imageColor := image.NewUniform(rgc.current.FillColor)
draw.Draw(rgc.img, image.Rect(x1, y1, x2, y2), imageColor, image.ZP, draw.Over)
}
// DrawImage draws the raster image in the current canvas
func (rgc *RasterGraphicContext) DrawImage(img image.Image) {
DrawImage(img, rgc.img, rgc.current.Tr, draw.Over, BilinearFilter)
}
// FillString draws the text at point (0, 0)
func (rgc *RasterGraphicContext) FillString(text string) (cursor float64, err error) {
cursor, err = rgc.FillStringAt(text, 0, 0)
return
}
// FillStringAt draws the text at the specified point (x, y)
func (rgc *RasterGraphicContext) FillStringAt(text string, x, y float64) (cursor float64, err error) {
cursor, err = rgc.CreateStringPath(text, x, y)
rgc.Fill()
return
}
// StrokeString draws the contour of the text at point (0, 0)
func (rgc *RasterGraphicContext) StrokeString(text string) (cursor float64, err error) {
cursor, err = rgc.StrokeStringAt(text, 0, 0)
return
}
// StrokeStringAt draws the contour of the text at point (x, y)
func (rgc *RasterGraphicContext) StrokeStringAt(text string, x, y float64) (cursor float64, err error) {
cursor, err = rgc.CreateStringPath(text, x, y)
rgc.Stroke()
return
}
func (rgc *RasterGraphicContext) drawGlyph(glyph truetype.Index, dx, dy float64) error {
if err := rgc.glyphBuf.Load(rgc.current.Font, fixed.Int26_6(rgc.current.Scale), glyph, font.HintingNone); err != nil {
return err
}
e0 := 0
for _, e1 := range rgc.glyphBuf.Ends {
DrawContour(rgc, rgc.glyphBuf.Points[e0:e1], dx, dy)
e0 = e1
}
return nil
}
// CreateStringPath creates a path from the string s at x, y, and returns the string width.
// The text is placed so that the left edge of the em square of the first character of s
// and the baseline intersect at x, y. The majority of the affected pixels will be
// above and to the right of the point, but some may be below or to the left.
// For example, drawing a string that starts with a 'J' in an italic font may
// affect pixels below and left of the point.
func (rgc *RasterGraphicContext) CreateStringPath(s string, x, y float64) (cursor float64, err error) {
f := rgc.GetFont()
if f == nil {
err = errors.New("No font loaded, cannot continue")
return
}
rgc.recalc()
startx := x
prev, hasPrev := truetype.Index(0), false
for _, rc := range s {
index := f.Index(rc)
if hasPrev {
x += fUnitsToFloat64(f.Kern(fixed.Int26_6(rgc.current.Scale), prev, index))
}
err = rgc.drawGlyph(index, x, y)
if err != nil {
cursor = x - startx
return
}
x += fUnitsToFloat64(f.HMetric(fixed.Int26_6(rgc.current.Scale), index).AdvanceWidth)
prev, hasPrev = index, true
}
cursor = x - startx
return
}
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// GetStringBounds returns the approximate pixel bounds of a string.
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func (rgc *RasterGraphicContext) GetStringBounds(s string) (left, top, right, bottom float64, err error) {
f := rgc.GetFont()
if f == nil {
err = errors.New("No font loaded, cannot continue")
return
}
rgc.recalc()
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left = math.MaxFloat64
top = math.MaxFloat64
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cursor := 0.0
prev, hasPrev := truetype.Index(0), false
for _, rc := range s {
index := f.Index(rc)
if hasPrev {
cursor += fUnitsToFloat64(f.Kern(fixed.Int26_6(rgc.current.Scale), prev, index))
}
if err = rgc.glyphBuf.Load(rgc.current.Font, fixed.Int26_6(rgc.current.Scale), index, font.HintingNone); err != nil {
return
}
e0 := 0
for _, e1 := range rgc.glyphBuf.Ends {
ps := rgc.glyphBuf.Points[e0:e1]
for _, p := range ps {
x, y := pointToF64Point(p)
top = math.Min(top, y)
bottom = math.Max(bottom, y)
left = math.Min(left, x+cursor)
right = math.Max(right, x+cursor)
}
e0 = e1
}
cursor += fUnitsToFloat64(f.HMetric(fixed.Int26_6(rgc.current.Scale), index).AdvanceWidth)
prev, hasPrev = index, true
}
return
}
// recalc recalculates scale and bounds values from the font size, screen
// resolution and font metrics, and invalidates the glyph cache.
func (rgc *RasterGraphicContext) recalc() {
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rgc.current.Scale = rgc.current.FontSizePoints * float64(rgc.DPI)
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}
// SetFont sets the font used to draw text.
func (rgc *RasterGraphicContext) SetFont(font *truetype.Font) {
rgc.current.Font = font
}
// GetFont returns the font used to draw text.
func (rgc *RasterGraphicContext) GetFont() *truetype.Font {
return rgc.current.Font
}
// SetFontSize sets the font size in points (as in ``a 12 point font'').
func (rgc *RasterGraphicContext) SetFontSize(fontSizePoints float64) {
rgc.current.FontSizePoints = fontSizePoints
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rgc.recalc()
}
func (rgc *RasterGraphicContext) paint(rasterizer *raster.Rasterizer, color color.Color) {
rgc.painter.SetColor(color)
rasterizer.Rasterize(rgc.painter)
rasterizer.Clear()
rgc.current.Path.Clear()
}
// Stroke strokes the paths with the color specified by SetStrokeColor
func (rgc *RasterGraphicContext) Stroke(paths ...*Path) {
paths = append(paths, rgc.current.Path)
rgc.strokeRasterizer.UseNonZeroWinding = true
stroker := NewLineStroker(rgc.current.Cap, rgc.current.Join, Transformer{Tr: rgc.current.Tr, Flattener: FtLineBuilder{Adder: rgc.strokeRasterizer}})
stroker.HalfLineWidth = rgc.current.LineWidth / 2
var liner Flattener
if rgc.current.Dash != nil && len(rgc.current.Dash) > 0 {
liner = NewDashVertexConverter(rgc.current.Dash, rgc.current.DashOffset, stroker)
} else {
liner = stroker
}
for _, p := range paths {
Flatten(p, liner, rgc.current.Tr.GetScale())
}
rgc.paint(rgc.strokeRasterizer, rgc.current.StrokeColor)
}
// Fill fills the paths with the color specified by SetFillColor
func (rgc *RasterGraphicContext) Fill(paths ...*Path) {
paths = append(paths, rgc.current.Path)
rgc.fillRasterizer.UseNonZeroWinding = rgc.current.FillRule == FillRuleWinding
flattener := Transformer{Tr: rgc.current.Tr, Flattener: FtLineBuilder{Adder: rgc.fillRasterizer}}
for _, p := range paths {
Flatten(p, flattener, rgc.current.Tr.GetScale())
}
rgc.paint(rgc.fillRasterizer, rgc.current.FillColor)
}
// FillStroke first fills the paths and than strokes them
func (rgc *RasterGraphicContext) FillStroke(paths ...*Path) {
paths = append(paths, rgc.current.Path)
rgc.fillRasterizer.UseNonZeroWinding = rgc.current.FillRule == FillRuleWinding
rgc.strokeRasterizer.UseNonZeroWinding = true
flattener := Transformer{Tr: rgc.current.Tr, Flattener: FtLineBuilder{Adder: rgc.fillRasterizer}}
stroker := NewLineStroker(rgc.current.Cap, rgc.current.Join, Transformer{Tr: rgc.current.Tr, Flattener: FtLineBuilder{Adder: rgc.strokeRasterizer}})
stroker.HalfLineWidth = rgc.current.LineWidth / 2
var liner Flattener
if rgc.current.Dash != nil && len(rgc.current.Dash) > 0 {
liner = NewDashVertexConverter(rgc.current.Dash, rgc.current.DashOffset, stroker)
} else {
liner = stroker
}
demux := DemuxFlattener{Flatteners: []Flattener{flattener, liner}}
for _, p := range paths {
Flatten(p, demux, rgc.current.Tr.GetScale())
}
// Fill
rgc.paint(rgc.fillRasterizer, rgc.current.FillColor)
// Stroke
rgc.paint(rgc.strokeRasterizer, rgc.current.StrokeColor)
}