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Diffstat (limited to 'vendor/github.com/golang/freetype/truetype/face.go')
| -rw-r--r-- | vendor/github.com/golang/freetype/truetype/face.go | 507 |
1 files changed, 507 insertions, 0 deletions
diff --git a/vendor/github.com/golang/freetype/truetype/face.go b/vendor/github.com/golang/freetype/truetype/face.go new file mode 100644 index 000000000..099006f05 --- /dev/null +++ b/vendor/github.com/golang/freetype/truetype/face.go @@ -0,0 +1,507 @@ +// Copyright 2015 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. + +package truetype + +import ( + "image" + "math" + + "github.com/golang/freetype/raster" + "golang.org/x/image/font" + "golang.org/x/image/math/fixed" +) + +func powerOf2(i int) bool { + return i != 0 && (i&(i-1)) == 0 +} + +// Options are optional arguments to NewFace. +type Options struct { + // Size is the font size in points, as in "a 10 point font size". + // + // A zero value means to use a 12 point font size. + Size float64 + + // DPI is the dots-per-inch resolution. + // + // A zero value means to use 72 DPI. + DPI float64 + + // Hinting is how to quantize the glyph nodes. + // + // A zero value means to use no hinting. + Hinting font.Hinting + + // GlyphCacheEntries is the number of entries in the glyph mask image + // cache. + // + // If non-zero, it must be a power of 2. + // + // A zero value means to use 512 entries. + GlyphCacheEntries int + + // SubPixelsX is the number of sub-pixel locations a glyph's dot is + // quantized to, in the horizontal direction. For example, a value of 8 + // means that the dot is quantized to 1/8th of a pixel. This quantization + // only affects the glyph mask image, not its bounding box or advance + // width. A higher value gives a more faithful glyph image, but reduces the + // effectiveness of the glyph cache. + // + // If non-zero, it must be a power of 2, and be between 1 and 64 inclusive. + // + // A zero value means to use 4 sub-pixel locations. + SubPixelsX int + + // SubPixelsY is the number of sub-pixel locations a glyph's dot is + // quantized to, in the vertical direction. For example, a value of 8 + // means that the dot is quantized to 1/8th of a pixel. This quantization + // only affects the glyph mask image, not its bounding box or advance + // width. A higher value gives a more faithful glyph image, but reduces the + // effectiveness of the glyph cache. + // + // If non-zero, it must be a power of 2, and be between 1 and 64 inclusive. + // + // A zero value means to use 1 sub-pixel location. + SubPixelsY int +} + +func (o *Options) size() float64 { + if o != nil && o.Size > 0 { + return o.Size + } + return 12 +} + +func (o *Options) dpi() float64 { + if o != nil && o.DPI > 0 { + return o.DPI + } + return 72 +} + +func (o *Options) hinting() font.Hinting { + if o != nil { + switch o.Hinting { + case font.HintingVertical, font.HintingFull: + // TODO: support vertical hinting. + return font.HintingFull + } + } + return font.HintingNone +} + +func (o *Options) glyphCacheEntries() int { + if o != nil && powerOf2(o.GlyphCacheEntries) { + return o.GlyphCacheEntries + } + // 512 is 128 * 4 * 1, which lets us cache 128 glyphs at 4 * 1 subpixel + // locations in the X and Y direction. + return 512 +} + +func (o *Options) subPixelsX() (value uint32, halfQuantum, mask fixed.Int26_6) { + if o != nil { + switch o.SubPixelsX { + case 1, 2, 4, 8, 16, 32, 64: + return subPixels(o.SubPixelsX) + } + } + // This default value of 4 isn't based on anything scientific, merely as + // small a number as possible that looks almost as good as no quantization, + // or returning subPixels(64). + return subPixels(4) +} + +func (o *Options) subPixelsY() (value uint32, halfQuantum, mask fixed.Int26_6) { + if o != nil { + switch o.SubPixelsX { + case 1, 2, 4, 8, 16, 32, 64: + return subPixels(o.SubPixelsX) + } + } + // This default value of 1 isn't based on anything scientific, merely that + // vertical sub-pixel glyph rendering is pretty rare. Baseline locations + // can usually afford to snap to the pixel grid, so the vertical direction + // doesn't have the deal with the horizontal's fractional advance widths. + return subPixels(1) +} + +// subPixels returns q and the bias and mask that leads to q quantized +// sub-pixel locations per full pixel. +// +// For example, q == 4 leads to a bias of 8 and a mask of 0xfffffff0, or -16, +// because we want to round fractions of fixed.Int26_6 as: +// - 0 to 7 rounds to 0. +// - 8 to 23 rounds to 16. +// - 24 to 39 rounds to 32. +// - 40 to 55 rounds to 48. +// - 56 to 63 rounds to 64. +// which means to add 8 and then bitwise-and with -16, in two's complement +// representation. +// +// When q == 1, we want bias == 32 and mask == -64. +// When q == 2, we want bias == 16 and mask == -32. +// When q == 4, we want bias == 8 and mask == -16. +// ... +// When q == 64, we want bias == 0 and mask == -1. (The no-op case). +// The pattern is clear. +func subPixels(q int) (value uint32, bias, mask fixed.Int26_6) { + return uint32(q), 32 / fixed.Int26_6(q), -64 / fixed.Int26_6(q) +} + +// glyphCacheEntry caches the arguments and return values of rasterize. +type glyphCacheEntry struct { + key glyphCacheKey + val glyphCacheVal +} + +type glyphCacheKey struct { + index Index + fx, fy uint8 +} + +type glyphCacheVal struct { + advanceWidth fixed.Int26_6 + offset image.Point + gw int + gh int +} + +type indexCacheEntry struct { + rune rune + index Index +} + +// NewFace returns a new font.Face for the given Font. +func NewFace(f *Font, opts *Options) font.Face { + a := &face{ + f: f, + hinting: opts.hinting(), + scale: fixed.Int26_6(0.5 + (opts.size() * opts.dpi() * 64 / 72)), + glyphCache: make([]glyphCacheEntry, opts.glyphCacheEntries()), + } + a.subPixelX, a.subPixelBiasX, a.subPixelMaskX = opts.subPixelsX() + a.subPixelY, a.subPixelBiasY, a.subPixelMaskY = opts.subPixelsY() + + // Fill the cache with invalid entries. Valid glyph cache entries have fx + // and fy in the range [0, 64). Valid index cache entries have rune >= 0. + for i := range a.glyphCache { + a.glyphCache[i].key.fy = 0xff + } + for i := range a.indexCache { + a.indexCache[i].rune = -1 + } + + // Set the rasterizer's bounds to be big enough to handle the largest glyph. + b := f.Bounds(a.scale) + xmin := +int(b.Min.X) >> 6 + ymin := -int(b.Max.Y) >> 6 + xmax := +int(b.Max.X+63) >> 6 + ymax := -int(b.Min.Y-63) >> 6 + a.maxw = xmax - xmin + a.maxh = ymax - ymin + a.masks = image.NewAlpha(image.Rect(0, 0, a.maxw, a.maxh*len(a.glyphCache))) + a.r.SetBounds(a.maxw, a.maxh) + a.p = facePainter{a} + + return a +} + +type face struct { + f *Font + hinting font.Hinting + scale fixed.Int26_6 + subPixelX uint32 + subPixelBiasX fixed.Int26_6 + subPixelMaskX fixed.Int26_6 + subPixelY uint32 + subPixelBiasY fixed.Int26_6 + subPixelMaskY fixed.Int26_6 + masks *image.Alpha + glyphCache []glyphCacheEntry + r raster.Rasterizer + p raster.Painter + paintOffset int + maxw int + maxh int + glyphBuf GlyphBuf + indexCache [indexCacheLen]indexCacheEntry + + // TODO: clip rectangle? +} + +const indexCacheLen = 256 + +func (a *face) index(r rune) Index { + const mask = indexCacheLen - 1 + c := &a.indexCache[r&mask] + if c.rune == r { + return c.index + } + i := a.f.Index(r) + c.rune = r + c.index = i + return i +} + +// Close satisfies the font.Face interface. +func (a *face) Close() error { return nil } + +// Metrics satisfies the font.Face interface. +func (a *face) Metrics() font.Metrics { + scale := float64(a.scale) + fupe := float64(a.f.FUnitsPerEm()) + return font.Metrics{ + Height: a.scale, + Ascent: fixed.Int26_6(math.Ceil(scale * float64(+a.f.ascent) / fupe)), + Descent: fixed.Int26_6(math.Ceil(scale * float64(-a.f.descent) / fupe)), + } +} + +// Kern satisfies the font.Face interface. +func (a *face) Kern(r0, r1 rune) fixed.Int26_6 { + i0 := a.index(r0) + i1 := a.index(r1) + kern := a.f.Kern(a.scale, i0, i1) + if a.hinting != font.HintingNone { + kern = (kern + 32) &^ 63 + } + return kern +} + +// Glyph satisfies the font.Face interface. +func (a *face) Glyph(dot fixed.Point26_6, r rune) ( + dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) { + + // Quantize to the sub-pixel granularity. + dotX := (dot.X + a.subPixelBiasX) & a.subPixelMaskX + dotY := (dot.Y + a.subPixelBiasY) & a.subPixelMaskY + + // Split the coordinates into their integer and fractional parts. + ix, fx := int(dotX>>6), dotX&0x3f + iy, fy := int(dotY>>6), dotY&0x3f + + index := a.index(r) + cIndex := uint32(index) + cIndex = cIndex*a.subPixelX - uint32(fx/a.subPixelMaskX) + cIndex = cIndex*a.subPixelY - uint32(fy/a.subPixelMaskY) + cIndex &= uint32(len(a.glyphCache) - 1) + a.paintOffset = a.maxh * int(cIndex) + k := glyphCacheKey{ + index: index, + fx: uint8(fx), + fy: uint8(fy), + } + var v glyphCacheVal + if a.glyphCache[cIndex].key != k { + var ok bool + v, ok = a.rasterize(index, fx, fy) + if !ok { + return image.Rectangle{}, nil, image.Point{}, 0, false + } + a.glyphCache[cIndex] = glyphCacheEntry{k, v} + } else { + v = a.glyphCache[cIndex].val + } + + dr.Min = image.Point{ + X: ix + v.offset.X, + Y: iy + v.offset.Y, + } + dr.Max = image.Point{ + X: dr.Min.X + v.gw, + Y: dr.Min.Y + v.gh, + } + return dr, a.masks, image.Point{Y: a.paintOffset}, v.advanceWidth, true +} + +func (a *face) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) { + if err := a.glyphBuf.Load(a.f, a.scale, a.index(r), a.hinting); err != nil { + return fixed.Rectangle26_6{}, 0, false + } + xmin := +a.glyphBuf.Bounds.Min.X + ymin := -a.glyphBuf.Bounds.Max.Y + xmax := +a.glyphBuf.Bounds.Max.X + ymax := -a.glyphBuf.Bounds.Min.Y + if xmin > xmax || ymin > ymax { + return fixed.Rectangle26_6{}, 0, false + } + return fixed.Rectangle26_6{ + Min: fixed.Point26_6{ + X: xmin, + Y: ymin, + }, + Max: fixed.Point26_6{ + X: xmax, + Y: ymax, + }, + }, a.glyphBuf.AdvanceWidth, true +} + +func (a *face) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) { + if err := a.glyphBuf.Load(a.f, a.scale, a.index(r), a.hinting); err != nil { + return 0, false + } + return a.glyphBuf.AdvanceWidth, true +} + +// rasterize returns the advance width, integer-pixel offset to render at, and +// the width and height of the given glyph at the given sub-pixel offsets. +// +// The 26.6 fixed point arguments fx and fy must be in the range [0, 1). +func (a *face) rasterize(index Index, fx, fy fixed.Int26_6) (v glyphCacheVal, ok bool) { + if err := a.glyphBuf.Load(a.f, a.scale, index, a.hinting); err != nil { + return glyphCacheVal{}, false + } + // Calculate the integer-pixel bounds for the glyph. + xmin := int(fx+a.glyphBuf.Bounds.Min.X) >> 6 + ymin := int(fy-a.glyphBuf.Bounds.Max.Y) >> 6 + xmax := int(fx+a.glyphBuf.Bounds.Max.X+0x3f) >> 6 + ymax := int(fy-a.glyphBuf.Bounds.Min.Y+0x3f) >> 6 + if xmin > xmax || ymin > ymax { + return glyphCacheVal{}, false + } + // 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 -= fixed.Int26_6(xmin << 6) + fy -= fixed.Int26_6(ymin << 6) + // Rasterize the glyph's vectors. + a.r.Clear() + pixOffset := a.paintOffset * a.maxw + clear(a.masks.Pix[pixOffset : pixOffset+a.maxw*a.maxh]) + e0 := 0 + for _, e1 := range a.glyphBuf.Ends { + a.drawContour(a.glyphBuf.Points[e0:e1], fx, fy) + e0 = e1 + } + a.r.Rasterize(a.p) + return glyphCacheVal{ + a.glyphBuf.AdvanceWidth, + image.Point{xmin, ymin}, + xmax - xmin, + ymax - ymin, + }, true +} + +func clear(pix []byte) { + for i := range pix { + pix[i] = 0 + } +} + +// drawContour draws the given closed contour with the given offset. +func (a *face) drawContour(ps []Point, dx, dy fixed.Int26_6) { + 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 := fixed.Point26_6{ + X: dx + ps[0].X, + Y: dy - ps[0].Y, + } + var others []Point + if ps[0].Flags&0x01 != 0 { + others = ps[1:] + } else { + last := fixed.Point26_6{ + X: dx + ps[len(ps)-1].X, + Y: dy - ps[len(ps)-1].Y, + } + if ps[len(ps)-1].Flags&0x01 != 0 { + start = last + others = ps[:len(ps)-1] + } else { + start = fixed.Point26_6{ + X: (start.X + last.X) / 2, + Y: (start.Y + last.Y) / 2, + } + others = ps + } + } + a.r.Start(start) + q0, on0 := start, true + for _, p := range others { + q := fixed.Point26_6{ + X: dx + p.X, + Y: dy - p.Y, + } + on := p.Flags&0x01 != 0 + if on { + if on0 { + a.r.Add1(q) + } else { + a.r.Add2(q0, q) + } + } else { + if on0 { + // No-op. + } else { + mid := fixed.Point26_6{ + X: (q0.X + q.X) / 2, + Y: (q0.Y + q.Y) / 2, + } + a.r.Add2(q0, mid) + } + } + q0, on0 = q, on + } + // Close the curve. + if on0 { + a.r.Add1(start) + } else { + a.r.Add2(q0, start) + } +} + +// facePainter is like a raster.AlphaSrcPainter, with an additional Y offset +// (face.paintOffset) to the painted spans. +type facePainter struct { + a *face +} + +func (p facePainter) Paint(ss []raster.Span, done bool) { + m := p.a.masks + b := m.Bounds() + b.Min.Y = p.a.paintOffset + b.Max.Y = p.a.paintOffset + p.a.maxh + for _, s := range ss { + s.Y += p.a.paintOffset + if s.Y < b.Min.Y { + continue + } + if s.Y >= b.Max.Y { + return + } + if s.X0 < b.Min.X { + s.X0 = b.Min.X + } + if s.X1 > b.Max.X { + s.X1 = b.Max.X + } + if s.X0 >= s.X1 { + continue + } + base := (s.Y-m.Rect.Min.Y)*m.Stride - m.Rect.Min.X + p := m.Pix[base+s.X0 : base+s.X1] + color := uint8(s.Alpha >> 8) + for i := range p { + p[i] = color + } + } +} |