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Implement CreateStringPath and GetStringBounds in svg context

This commit is contained in:
Drahoslav 2018-01-07 17:47:54 +01:00
parent 6f03f106f6
commit c1e5edea41
4 changed files with 244 additions and 29 deletions
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2
draw2dgl/gc.go
View File

@ -124,7 +124,7 @@ type GraphicContext struct {
painter *Painter
fillRasterizer *raster.Rasterizer
strokeRasterizer *raster.Rasterizer
FontCache draw2d.FontCache
FontCache draw2d.FontCache
glyphCache draw2dbase.GlyphCache
glyphBuf *truetype.GlyphBuf
DPI int

185
draw2dsvg/gc.go
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@ -4,11 +4,17 @@
package draw2dsvg
import (
"bytes"
"github.com/llgcode/draw2d"
"github.com/llgcode/draw2d/draw2dbase"
"image"
"log"
"strings"
"math"
"github.com/golang/freetype/truetype"
"golang.org/x/image/math/fixed"
"golang.org/x/image/font"
"strconv"
"fmt"
)
type drawType int
@ -22,11 +28,22 @@ const (
// It provides draw2d with a svg backend
type GraphicContext struct {
*draw2dbase.StackGraphicContext
svg *Svg
FontCache draw2d.FontCache
glyphCache draw2dbase.GlyphCache
glyphBuf *truetype.GlyphBuf
svg *Svg
DPI int
}
func NewGraphicContext(svg *Svg) *GraphicContext {
gc := &GraphicContext{draw2dbase.NewStackGraphicContext(), svg}
gc := &GraphicContext{
draw2dbase.NewStackGraphicContext(),
draw2d.GetGlobalFontCache(),
draw2dbase.NewGlyphCache(),
&truetype.GlyphBuf{},
svg,
92,
}
return gc
}
@ -120,7 +137,8 @@ func (gc *GraphicContext) drawString(text string, drawType drawType, x, y float6
// link to group
group.Texts = []*Text{&svgText}
return 0
left, _, right, _ := gc.GetStringBounds(text)
return right-left
}
// Creates new group from current context
@ -165,37 +183,150 @@ func (gc *GraphicContext) GetFontData() draw2d.FontData {
return draw2d.FontData{}
}
// NOTE following functions copied from dwra2d{img|gl}
// TODO move them all to common draw2dbase?
// 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 (gc *GraphicContext) CreateStringPath(s string, x, y float64) (cursor float64) {
f, err := gc.loadCurrentFont()
if err != nil {
log.Println(err)
return 0.0
}
startx := x
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := f.Index(rune)
if hasPrev {
x += fUnitsToFloat64(f.Kern(fixed.Int26_6(gc.Current.Scale), prev, index))
}
err := gc.drawGlyph(index, x, y)
if err != nil {
log.Println(err)
return startx - x
}
x += fUnitsToFloat64(f.HMetric(fixed.Int26_6(gc.Current.Scale), index).AdvanceWidth)
prev, hasPrev = index, true
}
return x - startx
}
// GetStringBounds returns the approximate pixel bounds of the string s at x, y.
// The the left edge of the em square of the first character of s
// and the baseline intersect at 0, 0 in the returned coordinates.
// Therefore the top and left coordinates may well be negative.
func (gc *GraphicContext) GetStringBounds(s string) (left, top, right, bottom float64) {
f, err := gc.loadCurrentFont()
if err != nil {
log.Println(err)
return 0, 0, 0, 0
}
if gc.Current.Scale == 0 {
panic("zero scale")
}
top, left, bottom, right = 10e6, 10e6, -10e6, -10e6
cursor := 0.0
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := f.Index(rune)
if hasPrev {
cursor += fUnitsToFloat64(f.Kern(fixed.Int26_6(gc.Current.Scale), prev, index))
}
if err := gc.glyphBuf.Load(gc.Current.Font, fixed.Int26_6(gc.Current.Scale), index, font.HintingNone); err != nil {
log.Println(err)
return 0, 0, 0, 0
}
e0 := 0
for _, e1 := range gc.glyphBuf.Ends {
ps := gc.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)
}
}
cursor += fUnitsToFloat64(f.HMetric(fixed.Int26_6(gc.Current.Scale), index).AdvanceWidth)
prev, hasPrev = index, true
}
return left, top, right, bottom
}
func (gc *GraphicContext) loadCurrentFont() (*truetype.Font, error) {
font, err := gc.FontCache.Load(gc.Current.FontData)
if err != nil {
font, err = gc.FontCache.Load(draw2dbase.DefaultFontData)
}
if font != nil {
gc.SetFont(font)
gc.SetFontSize(gc.Current.FontSize)
}
return font, err
}
func (gc *GraphicContext) drawGlyph(glyph truetype.Index, dx, dy float64) error {
if err := gc.glyphBuf.Load(gc.Current.Font, fixed.Int26_6(gc.Current.Scale), glyph, font.HintingNone); err != nil {
return err
}
e0 := 0
for _, e1 := range gc.glyphBuf.Ends {
DrawContour(gc, gc.glyphBuf.Points[e0:e1], dx, dy)
e0 = e1
}
return nil
}
// recalc recalculates scale and bounds values from the font size, screen
// resolution and font metrics, and invalidates the glyph cache.
func (gc *GraphicContext) recalc() {
gc.Current.Scale = gc.Current.FontSize * float64(gc.DPI) * (64.0 / 72.0)
}
func (gc *GraphicContext) SetDPI(dpi int) {
gc.DPI = dpi
gc.recalc()
}
func (gc *GraphicContext) GetDPI() int {
return gc.DPI
}
// SetFont sets the font used to draw text.
func (gc *GraphicContext) SetFont(font *truetype.Font) {
gc.Current.Font = font
}
// SetFontSize sets the font size in points (as in “a 12 point font”).
func (gc *GraphicContext) SetFontSize(fontSize float64) {
gc.Current.FontSize = fontSize
gc.recalc()
}
///////////////////////////////////////
// TODO implement following methods (or remove if not neccesary)
// GetFontName gets the current FontData as a string
func (gc *GraphicContext) GetFontName() string {
return ""
fontData := gc.Current.FontData
return fmt.Sprintf("%s:%d:%d:%d", fontData.Name, fontData.Family, fontData.Style, gc.Current.FontSize)
}
// DrawImage draws the raster image in the current canvas
func (gc *GraphicContext) DrawImage(image image.Image) {
// panic("not implemented")
}
// 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 // TODO use glyphCache for creating string path
// panic("not implemented")
}

83
draw2dsvg/text.go Normal file
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@ -0,0 +1,83 @@
// NOTE that this is identical copy of draw2dgl/text.go and draw2dimg/text.go
package draw2dsvg
import (
"github.com/golang/freetype/truetype"
"github.com/llgcode/draw2d"
"golang.org/x/image/math/fixed"
)
// DrawContour draws the given closed contour at the given sub-pixel offset.
func DrawContour(path draw2d.PathBuilder, ps []truetype.Point, dx, dy float64) {
if len(ps) == 0 {
return
}
startX, startY := pointToF64Point(ps[0])
path.MoveTo(startX+dx, startY+dy)
q0X, q0Y, on0 := startX, startY, true
for _, p := range ps[1:] {
qX, qY := pointToF64Point(p)
on := p.Flags&0x01 != 0
if on {
if on0 {
path.LineTo(qX+dx, qY+dy)
} else {
path.QuadCurveTo(q0X+dx, q0Y+dy, qX+dx, qY+dy)
}
} else {
if on0 {
// No-op.
} else {
midX := (q0X + qX) / 2
midY := (q0Y + qY) / 2
path.QuadCurveTo(q0X+dx, q0Y+dy, midX+dx, midY+dy)
}
}
q0X, q0Y, on0 = qX, qY, on
}
// Close the curve.
if on0 {
path.LineTo(startX+dx, startY+dy)
} else {
path.QuadCurveTo(q0X+dx, q0Y+dy, startX+dx, startY+dy)
}
}
func pointToF64Point(p truetype.Point) (x, y float64) {
return fUnitsToFloat64(p.X), -fUnitsToFloat64(p.Y)
}
func fUnitsToFloat64(x fixed.Int26_6) float64 {
scaled := x << 2
return float64(scaled/256) + float64(scaled%256)/256.0
}
// FontExtents contains font metric information.
type FontExtents struct {
// Ascent is the distance that the text
// extends above the baseline.
Ascent float64
// Descent is the distance that the text
// extends below the baseline. The descent
// is given as a negative value.
Descent float64
// Height is the distance from the lowest
// descending point to the highest ascending
// point.
Height float64
}
// Extents returns the FontExtents for a font.
// TODO needs to read this https://developer.apple.com/fonts/TrueType-Reference-Manual/RM02/Chap2.html#intro
func Extents(font *truetype.Font, size float64) FontExtents {
bounds := font.Bounds(fixed.Int26_6(font.FUnitsPerEm()))
scale := size / float64(font.FUnitsPerEm())
return FontExtents{
Ascent: float64(bounds.Max.Y) * scale,
Descent: float64(bounds.Min.Y) * scale,
Height: float64(bounds.Max.Y-bounds.Min.Y) * scale,
}
}

3
samples/geometry/geometry.go
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@ -202,7 +202,8 @@ func FillString(gc draw2d.GraphicContext, x, y, width, height float64) {
gc.SetFontData(draw2d.FontData{
Name: "luxi",
Family: draw2d.FontFamilyMono,
Style: draw2d.FontStyleBold | draw2d.FontStyleItalic})
Style: draw2d.FontStyleBold | draw2d.FontStyleItalic,
})
w := gc.FillString("Hug")
gc.Translate(w+sx, 0)
left, top, right, bottom := gc.GetStringBounds("cou")