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 } // GetStringBounds returns the approximate points bounds of a string. // It will be required to convert points to pixels for measurement. 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() 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() { rgc.current.Scale = rgc.current.FontSizePoints * float64(rgc.DPI) * 64.0 / 72.0 } // 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 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) }