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Merge pull request #112 from redstarcoder/draw2dgl_fonts
Draw2dgl Font Support
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package draw2dgl | ||
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import ( | ||
"github.com/golang/freetype/truetype" | ||
"github.com/llgcode/draw2d" | ||
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"golang.org/x/image/math/fixed" | ||
) | ||
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// 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) | ||
} | ||
} | ||
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func pointToF64Point(p truetype.Point) (x, y float64) { | ||
return fUnitsToFloat64(p.X), -fUnitsToFloat64(p.Y) | ||
} | ||
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func fUnitsToFloat64(x fixed.Int26_6) float64 { | ||
scaled := x << 2 | ||
return float64(scaled/256) + float64(scaled%256)/256.0 | ||
} | ||
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// FontExtents contains font metric information. | ||
type FontExtents struct { | ||
// Ascent is the distance that the text | ||
// extends above the baseline. | ||
Ascent float64 | ||
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// Descent is the distance that the text | ||
// extends below the baseline. The descent | ||
// is given as a negative value. | ||
Descent float64 | ||
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// Height is the distance from the lowest | ||
// descending point to the highest ascending | ||
// point. | ||
Height float64 | ||
} | ||
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// 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, | ||
} | ||
} |