// 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) {
font, err := gc.loadCurrentFont()
if err != nil {
log.Println(err)
return 0, 0, 0, 0
}
top, left, bottom, right = 10e6, 10e6, -10e6, -10e6
cursor := 0.0
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := font.Index(rune)
if hasPrev {
cursor += fUnitsToFloat64(int32(font.Kern(fixed.Int26_6(gc.Current.Scale), prev, index)))
}
if err := gc.glyphBuf.Load(gc.Current.Font, fixed.Int26_6(gc.Current.Scale), index, expfont.HintingNone); err != nil {
log.Println(err)
return 0, 0, 0, 0
}
e0 := 0
for _, e1 := range gc.glyphBuf.End {
ps := gc.glyphBuf.Point[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(int32(font.HMetric(fixed.Int26_6(gc.Current.Scale), index).AdvanceWidth))
prev, hasPrev = index, true
}
return left, top, right, bottom
}
func (t *Text) getFontMetrics(scale int) FontMetrics {
// Adapted from: https://code.google.com/p/plotinum/
// Converts truetype.FUnit to float64
fUnit2Float64 := float64(t.size) / float64(t.font.FUnitsPerEm())
width := 0
prev, hasPrev := truetype.Index(0), false
for _, rune := range t.content {
index := t.font.Index(rune)
if hasPrev {
width += int(t.font.Kerning(t.font.FUnitsPerEm(), prev, index))
}
width += int(t.font.HMetric(t.font.FUnitsPerEm(), index).AdvanceWidth)
prev, hasPrev = index, true
}
widthFloat := float64(width) * fUnit2Float64 * float64(scale)
bounds := t.font.Bounds(t.font.FUnitsPerEm())
height := float64(bounds.YMax-bounds.YMin) * fUnit2Float64 * float64(scale)
ascent := float64(bounds.YMax) * fUnit2Float64 * float64(scale)
descent := float64(bounds.YMin) * fUnit2Float64 * float64(scale)
return FontMetrics{widthFloat, height, ascent, descent}
}
// DrawString draws s at p and returns p advanced by the text extent. The text
// is placed so that the left edge of the em square of the first character of s
// and the baseline intersect at p. 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.
// p is a raster.Point and can therefore represent sub-pixel positions.
func (c *Context) DrawString(s string, p raster.Point) (raster.Point, error) {
if c.font == nil {
return raster.Point{}, errors.New("freetype: DrawText called with a nil font")
}
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := c.font.Index(rune)
if hasPrev {
kern := raster.Fix32(c.font.Kerning(c.scale, prev, index)) << 2
if c.hinting != NoHinting {
kern = (kern + 128) &^ 255
}
p.X += kern
}
advanceWidth, mask, offset, err := c.glyph(index, p)
if err != nil {
return raster.Point{}, err
}
p.X += advanceWidth
glyphRect := mask.Bounds().Add(offset)
dr := c.clip.Intersect(glyphRect)
if !dr.Empty() {
mp := image.Point{0, dr.Min.Y - glyphRect.Min.Y}
draw.DrawMask(c.dst, dr, c.src, image.ZP, mask, mp, draw.Over)
}
prev, hasPrev = index, true
}
return p, nil
}
// DrawString draws s at p and returns p advanced by the text extent. The text
// is placed so that the left edge of the em square of the first character of s
// and the baseline intersect at p. 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.
//
// p is a fixed.Point26_6 and can therefore represent sub-pixel positions.
func (c *Context) DrawString(s string, p fixed.Point26_6) (fixed.Point26_6, error) {
if c.f == nil {
return fixed.Point26_6{}, errors.New("freetype: DrawText called with a nil font")
}
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := c.f.Index(rune)
if hasPrev {
kern := c.f.Kern(c.scale, prev, index)
if c.hinting != font.HintingNone {
kern = (kern + 32) &^ 63
}
p.X += kern
}
advanceWidth, mask, offset, err := c.glyph(index, p)
if err != nil {
return fixed.Point26_6{}, err
}
p.X += advanceWidth
glyphRect := mask.Bounds().Add(offset)
dr := c.clip.Intersect(glyphRect)
if !dr.Empty() {
mp := image.Point{0, dr.Min.Y - glyphRect.Min.Y}
draw.DrawMask(c.dst, dr, c.src, image.ZP, mask, mp, draw.Over)
}
prev, hasPrev = index, true
}
return p, nil
}
// Width returns width of a string when drawn using the font.
func (f *Font) Width(s string) Length {
// scale converts truetype.FUnit to float64
scale := f.Size / Points(float64(f.font.FUnitsPerEm()))
width := 0
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := f.font.Index(rune)
if hasPrev {
width += int(f.font.Kerning(f.font.FUnitsPerEm(), prev, index))
}
width += int(f.font.HMetric(f.font.FUnitsPerEm(), index).AdvanceWidth)
prev, hasPrev = index, true
}
return Points(float64(width)) * 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
}
// 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) float64 {
font, 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 := font.Index(rune)
if hasPrev {
x += fUnitsToFloat64(int32(font.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(int32(font.HMetric(fixed.Int26_6(gc.Current.Scale), index).AdvanceWidth))
prev, hasPrev = index, true
}
return x - startx
}