func NewFontFace(path string, size float64, fg, bg color.Color) (fontface *FontFace, err error) {
var (
font *truetype.Font
fontbytes []byte
bounds truetype.Bounds
context *freetype.Context
scale float32
)
if fontbytes, err = ioutil.ReadFile(path); err != nil {
return
}
if font, err = freetype.ParseFont(fontbytes); err != nil {
return
}
bounds = font.Bounds(1)
fmt.Printf("bounds %v\n", bounds)
context = freetype.NewContext()
context.SetFont(font)
context.SetFontSize(size)
context.SetDPI(72)
scale = float32(context.PointToFixed(size) / 64)
fontface = &FontFace{
font: font,
charw: scale * float32(bounds.XMax-bounds.XMin),
charh: scale * float32(bounds.YMax-bounds.YMin),
fg: fg,
bg: bg,
context: context,
}
return
}
func NewFontFace(path string, pixels float32, fg, bg color.Color) (fontface *FontFace, err error) {
var (
font *truetype.Font
fontbytes []byte
bounds fixed.Rectangle26_6
context *freetype.Context
points float32
dpi float32 = 96
)
if fontbytes, err = ioutil.ReadFile(path); err != nil {
return
}
if font, err = freetype.ParseFont(fontbytes); err != nil {
return
}
points = pixels * 72 / dpi
bounds = font.Bounds(fixed.I(int(pixels)))
context = freetype.NewContext()
context.SetFont(font)
context.SetFontSize(float64(points))
context.SetDPI(float64(dpi))
fontface = &FontFace{
font: font,
charw: float32(bounds.Max.X-bounds.Min.X) / 64,
charh: float32(bounds.Max.Y-bounds.Min.Y) / 64,
offy: float32(bounds.Min.Y) / 64,
fg: fg,
bg: bg,
context: context,
}
return
}
// enumerate returns all glyphs with a valid index.
func enumerate(f *truetype.Font, fc font.Face) []*glyph {
var gs []*glyph
for r := rune(1); r < (1<<16)-1; r++ {
if r == '\uFEFF' {
continue // ignore BOM
}
if f.Index(r) != 0 {
b, a, _ := fc.GlyphBounds(r)
gs = append(gs, &glyph{r: r, b: b, a: a})
}
}
return gs
}
func createTextImage(text string, fontSize int, color color.Color, f *truetype.Font) (*image.RGBA, float32, float32, error) {
// 1 pt = 1/72 in, 72 dpi = 1 in
const dpi = 72
fg, bg := image.NewUniform(color), image.Transparent
c := freetype.NewContext()
c.SetFont(f)
c.SetDPI(dpi)
c.SetFontSize(float64(fontSize)) // points
c.SetSrc(fg)
c.SetHinting(font.HintingFull)
// 1. Figure out maximum height so all text lines are the same height.
// 2. Draw within small bounds to figure out bounds.
// 3. Draw within final bounds.
scale := c.PointToFixed(float64(fontSize)) // point to pixels
rect := f.Bounds(scale) // scale is pixels of 1 em
maxHeight := int(rect.Max.Y>>6) - int(rect.Min.Y>>6)
var rgba *image.RGBA
w, h := 10, maxHeight
for i := 0; i < 2; i++ {
rgba = image.NewRGBA(image.Rect(0, 0, w, h))
draw.Draw(rgba, rgba.Bounds(), bg, image.ZP, draw.Src)
c.SetClip(rgba.Bounds())
c.SetDst(rgba)
pt := freetype.Pt(0, int(scale>>6))
end, err := c.DrawString(text, pt)
if err != nil {
return nil, 0, 0, err
}
w = int(end.X >> 6)
}
return rgba, float32(w), float32(h), nil
}
func loadRanges(f *truetype.Font) (ret [][2]rune) {
rr := [2]rune{-1, -1}
for r := rune(0); r <= unicode.MaxRune; r++ {
if privateUseArea(r) {
continue
}
if f.Index(r) == 0 {
continue
}
if rr[1] == r {
rr[1] = r + 1
continue
}
if rr[0] != -1 {
ret = append(ret, rr)
}
rr = [2]rune{r, r + 1}
}
if rr[0] != -1 {
ret = append(ret, rr)
}
return ret
}
// 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.YMax) * scale,
Descent: float64(bounds.YMin) * scale,
Height: float64(bounds.YMax-bounds.YMin) * scale,
}
}
// https://code.google.com/p/plotinum/source/browse/vg/font.go#160
func widthOfString(font *truetype.Font, size float64, s string) float64 {
// scale converts truetype.FUnit to float64
scale := size / float64(font.FUnitsPerEm())
width := 0
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := font.Index(rune)
if hasPrev {
width += int(font.Kern(fixed.Int26_6(font.FUnitsPerEm()), prev, index))
}
width += int(font.HMetric(fixed.Int26_6(font.FUnitsPerEm()), index).AdvanceWidth)
prev, hasPrev = index, true
}
return float64(width) * scale
}
