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-rw-r--r--Godeps/_workspace/src/code.google.com/p/freetype-go/freetype/freetype.go349
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diff --git a/Godeps/_workspace/src/code.google.com/p/freetype-go/freetype/freetype.go b/Godeps/_workspace/src/code.google.com/p/freetype-go/freetype/freetype.go
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+++ b/Godeps/_workspace/src/code.google.com/p/freetype-go/freetype/freetype.go
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+// Copyright 2010 The Freetype-Go Authors. All rights reserved.
+// Use of this source code is governed by your choice of either the
+// FreeType License or the GNU General Public License version 2 (or
+// any later version), both of which can be found in the LICENSE file.
+
+// The freetype package provides a convenient API to draw text onto an image.
+// Use the freetype/raster and freetype/truetype packages for lower level
+// control over rasterization and TrueType parsing.
+package freetype
+
+import (
+ "errors"
+ "image"
+ "image/draw"
+
+ "code.google.com/p/freetype-go/freetype/raster"
+ "code.google.com/p/freetype-go/freetype/truetype"
+)
+
+// These constants determine the size of the glyph cache. The cache is keyed
+// primarily by the glyph index modulo nGlyphs, and secondarily by sub-pixel
+// position for the mask image. Sub-pixel positions are quantized to
+// nXFractions possible values in both the x and y directions.
+const (
+ nGlyphs = 256
+ nXFractions = 4
+ nYFractions = 1
+)
+
+// An entry in the glyph cache is keyed explicitly by the glyph index and
+// implicitly by the quantized x and y fractional offset. It maps to a mask
+// image and an offset.
+type cacheEntry struct {
+ valid bool
+ glyph truetype.Index
+ advanceWidth raster.Fix32
+ mask *image.Alpha
+ offset image.Point
+}
+
+// ParseFont just calls the Parse function from the freetype/truetype package.
+// It is provided here so that code that imports this package doesn't need
+// to also include the freetype/truetype package.
+func ParseFont(b []byte) (*truetype.Font, error) {
+ return truetype.Parse(b)
+}
+
+// Pt converts from a co-ordinate pair measured in pixels to a raster.Point
+// co-ordinate pair measured in raster.Fix32 units.
+func Pt(x, y int) raster.Point {
+ return raster.Point{
+ X: raster.Fix32(x << 8),
+ Y: raster.Fix32(y << 8),
+ }
+}
+
+// Hinting is the policy for snapping a glyph's contours to pixel boundaries.
+type Hinting int32
+
+const (
+ // NoHinting means to not perform any hinting.
+ NoHinting = Hinting(truetype.NoHinting)
+ // FullHinting means to use the font's hinting instructions.
+ FullHinting = Hinting(truetype.FullHinting)
+)
+
+// A Context holds the state for drawing text in a given font and size.
+type Context struct {
+ r *raster.Rasterizer
+ font *truetype.Font
+ glyphBuf *truetype.GlyphBuf
+ // clip is the clip rectangle for drawing.
+ clip image.Rectangle
+ // dst and src are the destination and source images for drawing.
+ dst draw.Image
+ src image.Image
+ // fontSize and dpi are used to calculate scale. scale is the number of
+ // 26.6 fixed point units in 1 em. hinting is the hinting policy.
+ fontSize, dpi float64
+ scale int32
+ hinting Hinting
+ // cache is the glyph cache.
+ cache [nGlyphs * nXFractions * nYFractions]cacheEntry
+}
+
+// PointToFix32 converts the given number of points (as in ``a 12 point font'')
+// into fixed point units.
+func (c *Context) PointToFix32(x float64) raster.Fix32 {
+ return raster.Fix32(x * float64(c.dpi) * (256.0 / 72.0))
+}
+
+// drawContour draws the given closed contour with the given offset.
+func (c *Context) drawContour(ps []truetype.Point, dx, dy raster.Fix32) {
+ if len(ps) == 0 {
+ return
+ }
+
+ // The low bit of each point's Flags value is whether the point is on the
+ // curve. Truetype fonts only have quadratic Bézier curves, not cubics.
+ // Thus, two consecutive off-curve points imply an on-curve point in the
+ // middle of those two.
+ //
+ // See http://chanae.walon.org/pub/ttf/ttf_glyphs.htm for more details.
+
+ // ps[0] is a truetype.Point measured in FUnits and positive Y going
+ // upwards. start is the same thing measured in fixed point units and
+ // positive Y going downwards, and offset by (dx, dy).
+ start := raster.Point{
+ X: dx + raster.Fix32(ps[0].X<<2),
+ Y: dy - raster.Fix32(ps[0].Y<<2),
+ }
+ others := []truetype.Point(nil)
+ if ps[0].Flags&0x01 != 0 {
+ others = ps[1:]
+ } else {
+ last := raster.Point{
+ X: dx + raster.Fix32(ps[len(ps)-1].X<<2),
+ Y: dy - raster.Fix32(ps[len(ps)-1].Y<<2),
+ }
+ if ps[len(ps)-1].Flags&0x01 != 0 {
+ start = last
+ others = ps[:len(ps)-1]
+ } else {
+ start = raster.Point{
+ X: (start.X + last.X) / 2,
+ Y: (start.Y + last.Y) / 2,
+ }
+ others = ps
+ }
+ }
+ c.r.Start(start)
+ q0, on0 := start, true
+ for _, p := range others {
+ q := raster.Point{
+ X: dx + raster.Fix32(p.X<<2),
+ Y: dy - raster.Fix32(p.Y<<2),
+ }
+ on := p.Flags&0x01 != 0
+ if on {
+ if on0 {
+ c.r.Add1(q)
+ } else {
+ c.r.Add2(q0, q)
+ }
+ } else {
+ if on0 {
+ // No-op.
+ } else {
+ mid := raster.Point{
+ X: (q0.X + q.X) / 2,
+ Y: (q0.Y + q.Y) / 2,
+ }
+ c.r.Add2(q0, mid)
+ }
+ }
+ q0, on0 = q, on
+ }
+ // Close the curve.
+ if on0 {
+ c.r.Add1(start)
+ } else {
+ c.r.Add2(q0, start)
+ }
+}
+
+// rasterize returns the advance width, glyph mask and integer-pixel offset
+// to render the given glyph at the given sub-pixel offsets.
+// The 24.8 fixed point arguments fx and fy must be in the range [0, 1).
+func (c *Context) rasterize(glyph truetype.Index, fx, fy raster.Fix32) (
+ raster.Fix32, *image.Alpha, image.Point, error) {
+
+ if err := c.glyphBuf.Load(c.font, c.scale, glyph, truetype.Hinting(c.hinting)); err != nil {
+ return 0, nil, image.Point{}, err
+ }
+ // Calculate the integer-pixel bounds for the glyph.
+ xmin := int(fx+raster.Fix32(c.glyphBuf.B.XMin<<2)) >> 8
+ ymin := int(fy-raster.Fix32(c.glyphBuf.B.YMax<<2)) >> 8
+ xmax := int(fx+raster.Fix32(c.glyphBuf.B.XMax<<2)+0xff) >> 8
+ ymax := int(fy-raster.Fix32(c.glyphBuf.B.YMin<<2)+0xff) >> 8
+ if xmin > xmax || ymin > ymax {
+ return 0, nil, image.Point{}, errors.New("freetype: negative sized glyph")
+ }
+ // A TrueType's glyph's nodes can have negative co-ordinates, but the
+ // rasterizer clips anything left of x=0 or above y=0. xmin and ymin
+ // are the pixel offsets, based on the font's FUnit metrics, that let
+ // a negative co-ordinate in TrueType space be non-negative in
+ // rasterizer space. xmin and ymin are typically <= 0.
+ fx += raster.Fix32(-xmin << 8)
+ fy += raster.Fix32(-ymin << 8)
+ // Rasterize the glyph's vectors.
+ c.r.Clear()
+ e0 := 0
+ for _, e1 := range c.glyphBuf.End {
+ c.drawContour(c.glyphBuf.Point[e0:e1], fx, fy)
+ e0 = e1
+ }
+ a := image.NewAlpha(image.Rect(0, 0, xmax-xmin, ymax-ymin))
+ c.r.Rasterize(raster.NewAlphaSrcPainter(a))
+ return raster.Fix32(c.glyphBuf.AdvanceWidth << 2), a, image.Point{xmin, ymin}, nil
+}
+
+// glyph returns the advance width, glyph mask and integer-pixel offset to
+// render the given glyph at the given sub-pixel point. It is a cache for the
+// rasterize method. Unlike rasterize, p's co-ordinates do not have to be in
+// the range [0, 1).
+func (c *Context) glyph(glyph truetype.Index, p raster.Point) (
+ raster.Fix32, *image.Alpha, image.Point, error) {
+
+ // Split p.X and p.Y into their integer and fractional parts.
+ ix, fx := int(p.X>>8), p.X&0xff
+ iy, fy := int(p.Y>>8), p.Y&0xff
+ // Calculate the index t into the cache array.
+ tg := int(glyph) % nGlyphs
+ tx := int(fx) / (256 / nXFractions)
+ ty := int(fy) / (256 / nYFractions)
+ t := ((tg*nXFractions)+tx)*nYFractions + ty
+ // Check for a cache hit.
+ if e := c.cache[t]; e.valid && e.glyph == glyph {
+ return e.advanceWidth, e.mask, e.offset.Add(image.Point{ix, iy}), nil
+ }
+ // Rasterize the glyph and put the result into the cache.
+ advanceWidth, mask, offset, err := c.rasterize(glyph, fx, fy)
+ if err != nil {
+ return 0, nil, image.Point{}, err
+ }
+ c.cache[t] = cacheEntry{true, glyph, advanceWidth, mask, offset}
+ return advanceWidth, mask, offset.Add(image.Point{ix, iy}), 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 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
+}
+
+// recalc recalculates scale and bounds values from the font size, screen
+// resolution and font metrics, and invalidates the glyph cache.
+func (c *Context) recalc() {
+ c.scale = int32(c.fontSize * c.dpi * (64.0 / 72.0))
+ if c.font == nil {
+ c.r.SetBounds(0, 0)
+ } else {
+ // Set the rasterizer's bounds to be big enough to handle the largest glyph.
+ b := c.font.Bounds(c.scale)
+ xmin := +int(b.XMin) >> 6
+ ymin := -int(b.YMax) >> 6
+ xmax := +int(b.XMax+63) >> 6
+ ymax := -int(b.YMin-63) >> 6
+ c.r.SetBounds(xmax-xmin, ymax-ymin)
+ }
+ for i := range c.cache {
+ c.cache[i] = cacheEntry{}
+ }
+}
+
+// SetDPI sets the screen resolution in dots per inch.
+func (c *Context) SetDPI(dpi float64) {
+ if c.dpi == dpi {
+ return
+ }
+ c.dpi = dpi
+ c.recalc()
+}
+
+// SetFont sets the font used to draw text.
+func (c *Context) SetFont(font *truetype.Font) {
+ if c.font == font {
+ return
+ }
+ c.font = font
+ c.recalc()
+}
+
+// SetFontSize sets the font size in points (as in ``a 12 point font'').
+func (c *Context) SetFontSize(fontSize float64) {
+ if c.fontSize == fontSize {
+ return
+ }
+ c.fontSize = fontSize
+ c.recalc()
+}
+
+// SetHinting sets the hinting policy.
+func (c *Context) SetHinting(hinting Hinting) {
+ c.hinting = hinting
+ for i := range c.cache {
+ c.cache[i] = cacheEntry{}
+ }
+}
+
+// SetDst sets the destination image for draw operations.
+func (c *Context) SetDst(dst draw.Image) {
+ c.dst = dst
+}
+
+// SetSrc sets the source image for draw operations. This is typically an
+// image.Uniform.
+func (c *Context) SetSrc(src image.Image) {
+ c.src = src
+}
+
+// SetClip sets the clip rectangle for drawing.
+func (c *Context) SetClip(clip image.Rectangle) {
+ c.clip = clip
+}
+
+// TODO(nigeltao): implement Context.SetGamma.
+
+// NewContext creates a new Context.
+func NewContext() *Context {
+ return &Context{
+ r: raster.NewRasterizer(0, 0),
+ glyphBuf: truetype.NewGlyphBuf(),
+ fontSize: 12,
+ dpi: 72,
+ scale: 12 << 6,
+ }
+}
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