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font.go
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font.go
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// Copyright 2016 The G3N Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package text
import (
"github.com/g3n/engine/math32"
"github.com/golang/freetype/truetype"
"golang.org/x/image/font"
"golang.org/x/image/math/fixed"
"image"
"image/color"
"image/draw"
"io/ioutil"
"math"
"strings"
)
type Font struct {
ttf *truetype.Font
face font.Face
fgColor math32.Color4
bgColor math32.Color4
fontSize float64
fontDPI float64
lineSpacing float64
fg *image.Uniform
bg *image.Uniform
hinting font.Hinting
changed bool
}
const (
HintingNone = font.HintingNone
HintingVertical = font.HintingVertical
HintingFull = font.HintingFull
)
// NewFont creates and returns a new font object using the specified
// truetype font file
func NewFont(fontfile string) (*Font, error) {
// Reads font bytes
fontBytes, err := ioutil.ReadFile(fontfile)
if err != nil {
return nil, err
}
return NewFontFromData(fontBytes)
}
// NewFontFromData creates and returns a new font object from the
// specified data
func NewFontFromData(fontData []byte) (*Font, error) {
// Parses the font data
ff, err := truetype.Parse(fontData)
if err != nil {
return nil, err
}
f := new(Font)
f.ttf = ff
f.fontSize = 12
f.fontDPI = 72
f.lineSpacing = 1.0
f.hinting = font.HintingNone
f.SetFgColor4(math32.NewColor4(0, 0, 0, 1))
f.SetBgColor4(math32.NewColor4(1, 1, 1, 0))
f.changed = false
// Creates font face
f.face = truetype.NewFace(f.ttf, &truetype.Options{
Size: f.fontSize,
DPI: f.fontDPI,
Hinting: f.hinting,
})
return f, nil
}
// SetDPI sets the current DPI for the font
func (f *Font) SetDPI(dpi float64) {
if dpi == f.fontDPI {
return
}
f.fontDPI = dpi
f.changed = true
}
// SetSize sets the size of the font
func (f *Font) SetSize(size float64) {
if size == f.fontSize {
return
}
f.fontSize = size
f.changed = true
}
// SetHinting sets the hinting type
func (f *Font) SetHinting(hinting font.Hinting) {
if hinting == f.hinting {
return
}
f.hinting = hinting
f.changed = true
}
// Size returns the current font size
func (f *Font) Size() float64 {
return f.fontSize
}
// DPI returns the current font DPI
func (f *Font) DPI() float64 {
return f.fontDPI
}
// SetFgColor sets the current foreground color of the font
// The alpha value is set to 1 (opaque)
func (f *Font) SetFgColor(color *math32.Color) {
f.fgColor.R = color.R
f.fgColor.G = color.G
f.fgColor.B = color.B
f.fgColor.A = 1.0
f.fg = image.NewUniform(Color4NRGBA(&f.fgColor))
}
// SetFgColor4 sets the current foreground color of the font
func (f *Font) SetFgColor4(color *math32.Color4) {
f.fgColor = *color
f.fg = image.NewUniform(Color4NRGBA(color))
}
// FgColor returns the current foreground color
func (f *Font) FgColor4() math32.Color4 {
return f.fgColor
}
// SetBgColor sets the current foreground color of the font
// The alpha value is set to 1 (opaque)
func (f *Font) SetBgColor(color *math32.Color) {
f.bgColor.R = color.R
f.bgColor.G = color.G
f.bgColor.B = color.B
f.bgColor.A = 1.0
f.bg = image.NewUniform(Color4NRGBA(&f.fgColor))
}
// SetBgColor sets the current background color of the font
func (f *Font) SetBgColor4(color *math32.Color4) {
f.bgColor = *color
f.bg = image.NewUniform(Color4NRGBA(color))
}
// BgColor returns the current background color
func (f *Font) BgColor4() math32.Color4 {
return f.bgColor
}
// SetLineSpacing sets the spacing between lines
func (f *Font) SetLineSpacing(spacing float64) {
f.lineSpacing = spacing
}
// MeasureText returns the maximum width and height in pixels
// necessary for an image to contain the specified text.
// The supplied text string can contain line break escape sequences (\n).
func (f *Font) MeasureText(text string) (int, int) {
// Creates drawer
f.updateFace()
d := &font.Drawer{Dst: nil, Src: f.fg, Face: f.face}
// Draw text
width := 0
py := int(math.Ceil(f.fontSize * f.fontDPI / 72))
dy := int(math.Ceil(f.fontSize * f.lineSpacing * f.fontDPI / 72))
lines := strings.Split(text, "\n")
for _, s := range lines {
d.Dot = fixed.P(0, py)
lfixed := d.MeasureString(s)
lw := int(lfixed >> 6)
if lw > width {
width = lw
}
py += dy
}
height := py - dy/2
return width, height
}
func (f *Font) Metrics() font.Metrics {
f.updateFace()
return f.face.Metrics()
}
// Canvas is an image to draw text
type Canvas struct {
RGBA *image.RGBA
bgColor *image.Uniform
}
// Update font face if font parameters changed
func (f *Font) updateFace() {
if f.changed {
f.face = truetype.NewFace(f.ttf, &truetype.Options{
Size: f.fontSize,
DPI: f.fontDPI,
Hinting: f.hinting,
})
f.changed = false
}
}
// NewCanvas creates and returns a pointer to a new canvas with the
// specified width and height in pixels and background color
func NewCanvas(width, height int, bgColor *math32.Color4) *Canvas {
c := new(Canvas)
c.RGBA = image.NewRGBA(image.Rect(0, 0, width, height))
// Creates the image.Uniform for the background color
c.bgColor = image.NewUniform(Color4NRGBA(bgColor))
// Draw image
draw.Draw(c.RGBA, c.RGBA.Bounds(), c.bgColor, image.ZP, draw.Src)
return c
}
// DrawText draws text at the specified position (in pixels)
// of this canvas, using the specified font.
// The supplied text string can contain line break escape sequences (\n).
func (c Canvas) DrawText(x, y int, text string, f *Font) {
// Creates drawer
f.updateFace()
d := &font.Drawer{Dst: c.RGBA, Src: f.fg, Face: f.face}
// Draw text
py := y + int(math.Ceil(f.fontSize*f.fontDPI/72))
dy := int(math.Ceil(f.fontSize * f.lineSpacing * f.fontDPI / 72))
lines := strings.Split(text, "\n")
for _, s := range lines {
d.Dot = fixed.P(x, py)
d.DrawString(s)
py += dy
}
}
// DrawTextCaret draws text at the specified position (in pixels)
// of this canvas, using the specified font, and also a caret at
// the specified line and column.
// The supplied text string can contain line break escape sequences (\n).
func (c Canvas) DrawTextCaret(x, y int, text string, f *Font, line, col int) error {
// Creates drawer
f.updateFace()
d := &font.Drawer{Dst: c.RGBA, Src: f.fg, Face: f.face}
py := y + int(math.Ceil(f.fontSize*f.fontDPI/72))
dy := int(math.Ceil(f.fontSize * f.lineSpacing * f.fontDPI / 72))
lines := strings.Split(text, "\n")
for l, s := range lines {
d.Dot = fixed.P(x, py)
d.DrawString(s)
// Checks for caret position
if l == line && col <= StrCount(s) {
width, _ := f.MeasureText(StrPrefix(s, col))
// Draw caret vertical line
caretH := int(f.fontSize) + 2
//caretY := int(pt.Y>>6) - int(f.fontSize) + 2
caretY := int(d.Dot.Y>>6) - int(f.fontSize) + 2
color := Color4NRGBA(&math32.Color4{0, 0, 0, 1})
for j := caretY; j < caretY+caretH; j++ {
c.RGBA.Set(x+width, j, color)
}
}
py += dy
}
// pt := freetype.Pt(font.marginX+x, font.marginY+y+int(font.ctx.PointToFixed(font.fontSize)>>6))
// for l, s := range lines {
// // Draw string
// _, err := font.ctx.DrawString(s, pt)
// if err != nil {
// return err
// }
// // Checks for caret position
// if l == line && col <= StrCount(s) {
// width, _, err := font.MeasureText(StrPrefix(s, col))
// if err != nil {
// return err
// }
// // Draw caret vertical line
// caretH := int(font.fontSize) + 2
// caretY := int(pt.Y>>6) - int(font.fontSize) + 2
// color := Color4NRGBA(&math32.Color4{0, 0, 0, 1})
// for j := caretY; j < caretY+caretH; j++ {
// c.RGBA.Set(x+width, j, color)
// }
// }
// // Increment y coordinate
// pt.Y += font.ctx.PointToFixed(font.fontSize * font.lineSpacing)
// }
return nil
}
// Color4NRGBA converts a math32.Color4 to Go's image/color.NRGBA
// NON pre-multiplied alpha.
func Color4NRGBA(c *math32.Color4) color.NRGBA {
red := uint8(c.R * 0xFF)
green := uint8(c.G * 0xFF)
blue := uint8(c.B * 0xFF)
al := uint8(c.A * 0xFF)
return color.NRGBA{red, green, blue, al}
}