freetype: add a Hinting enum in the top-level freetype package, and
hide the Hinter implementation in the freetype/truetype package. LGTM=bsiegert R=bsiegert CC=golang-codereviews https://codereview.appspot.com/58940043
This commit is contained in:
Nigel Tao
parent
51c4a7ede4
commit
49fa4a4de0
7 changed files with 91 additions and 51 deletions
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@ -23,6 +23,7 @@ import (
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var (
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dpi = flag.Float64("dpi", 72, "screen resolution in Dots Per Inch")
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fontfile = flag.String("fontfile", "../../testdata/luxisr.ttf", "filename of the ttf font")
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hinting = flag.String("hinting", "none", "none | full")
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size = flag.Float64("size", 12, "font size in points")
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spacing = flag.Float64("spacing", 1.5, "line spacing (e.g. 2 means double spaced)")
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wonb = flag.Bool("whiteonblack", false, "white text on a black background")
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@ -96,6 +97,12 @@ func main() {
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c.SetClip(rgba.Bounds())
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c.SetDst(rgba)
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c.SetSrc(fg)
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switch *hinting {
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default:
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c.SetHinting(freetype.NoHinting)
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case "full":
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c.SetHinting(freetype.FullHinting)
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}
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// Draw the guidelines.
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for i := 0; i < 200; i++ {
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@ -60,7 +60,7 @@ func main() {
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i0 := font.Index(c0)
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hm := font.HMetric(fupe, i0)
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g := truetype.NewGlyphBuf()
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err = g.Load(font, fupe, i0, nil)
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err = g.Load(font, fupe, i0, truetype.NoHinting)
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if err != nil {
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log.Println(err)
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return
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@ -54,6 +54,16 @@ func Pt(x, y int) raster.Point {
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}
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}
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// Hinting is the policy for snapping a glyph's contours to pixel boundaries.
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type Hinting int32
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const (
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// NoHinting means to not perform any hinting.
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NoHinting = Hinting(truetype.NoHinting)
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// FullHinting means to use the font's hinting instructions.
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FullHinting = Hinting(truetype.FullHinting)
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)
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// A Context holds the state for drawing text in a given font and size.
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type Context struct {
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r *raster.Rasterizer
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@ -65,9 +75,10 @@ type Context struct {
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dst draw.Image
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src image.Image
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// fontSize and dpi are used to calculate scale. scale is the number of
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// 26.6 fixed point units in 1 em.
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// 26.6 fixed point units in 1 em. hinting is the hinting policy.
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fontSize, dpi float64
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scale int32
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hinting Hinting
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// cache is the glyph cache.
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cache [nGlyphs * nXFractions * nYFractions]cacheEntry
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}
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@ -131,7 +142,7 @@ func (c *Context) drawContour(ps []truetype.Point, dx, dy raster.Fix32) {
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func (c *Context) rasterize(glyph truetype.Index, fx, fy raster.Fix32) (
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raster.Fix32, *image.Alpha, image.Point, error) {
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if err := c.glyphBuf.Load(c.font, c.scale, glyph, nil); err != nil {
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if err := c.glyphBuf.Load(c.font, c.scale, glyph, truetype.Hinting(c.hinting)); err != nil {
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return 0, nil, image.Point{}, err
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}
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// Calculate the integer-pixel bounds for the glyph.
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@ -204,8 +215,11 @@ func (c *Context) DrawString(s string, p raster.Point) (raster.Point, error) {
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for _, rune := range s {
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index := c.font.Index(rune)
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if hasPrev {
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// TODO: adjust for hinting.
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p.X += raster.Fix32(c.font.Kerning(c.scale, prev, index)) << 2
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kern := raster.Fix32(c.font.Kerning(c.scale, prev, index)) << 2
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if c.hinting != NoHinting {
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kern = (kern + 128) &^ 255
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}
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p.X += kern
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}
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advanceWidth, mask, offset, err := c.glyph(index, p)
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if err != nil {
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@ -270,6 +284,14 @@ func (c *Context) SetFontSize(fontSize float64) {
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c.recalc()
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}
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// SetHinting sets the hinting policy.
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func (c *Context) SetHinting(hinting Hinting) {
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c.hinting = hinting
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for i := range c.cache {
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c.cache[i] = cacheEntry{}
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}
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}
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// SetDst sets the destination image for draw operations.
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func (c *Context) SetDst(dst draw.Image) {
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c.dst = dst
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@ -5,6 +5,18 @@
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package truetype
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// Hinting is the policy for snapping a glyph's contours to pixel boundaries.
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type Hinting int32
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const (
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// NoHinting means to not perform any hinting.
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NoHinting Hinting = iota
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// FullHinting means to use the font's hinting instructions.
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FullHinting
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// TODO: implement VerticalHinting.
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)
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// A Point is a co-ordinate pair plus whether it is ``on'' a contour or an
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// ``off'' control point.
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type Point struct {
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@ -21,8 +33,8 @@ type GlyphBuf struct {
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AdvanceWidth int32
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// B is the glyph's bounding box.
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B Bounds
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// Point contains all Points from all contours of the glyph. If a
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// Hinter was used to load a glyph then Unhinted contains those
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// Point contains all Points from all contours of the glyph. If
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// hinting was used to load a glyph then Unhinted contains those
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// Points before they were hinted, and InFontUnits contains those
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// Points before they were hinted and scaled.
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Point, Unhinted, InFontUnits []Point
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@ -32,9 +44,10 @@ type GlyphBuf struct {
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// is interpreted to mean zero.
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End []int
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font *Font
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hinter *Hinter
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scale int32
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font *Font
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scale int32
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hinting Hinting
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hinter hinter
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// phantomPoints are the co-ordinates of the synthetic phantom points
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// used for hinting and bounding box calculations.
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phantomPoints [4]Point
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@ -73,22 +86,21 @@ const (
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// Load loads a glyph's contours from a Font, overwriting any previously
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// loaded contours for this GlyphBuf. scale is the number of 26.6 fixed point
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// units in 1 em. The Hinter is optional; if non-nil, then the resulting glyph
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// will be hinted by the Font's bytecode instructions.
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func (g *GlyphBuf) Load(f *Font, scale int32, i Index, h *Hinter) error {
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// units in 1 em, i is the glyph index, and h is the hinting policy.
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func (g *GlyphBuf) Load(f *Font, scale int32, i Index, h Hinting) error {
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g.Point = g.Point[:0]
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g.Unhinted = g.Unhinted[:0]
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g.InFontUnits = g.InFontUnits[:0]
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g.End = g.End[:0]
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g.font = f
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g.hinter = h
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g.hinting = h
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g.scale = scale
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g.pp1x = 0
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g.phantomPoints = [4]Point{}
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g.metricsSet = false
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if h != nil {
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if err := h.init(f, scale); err != nil {
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if h != NoHinting {
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if err := g.hinter.init(f, scale); err != nil {
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return err
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}
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}
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@ -99,7 +111,7 @@ func (g *GlyphBuf) Load(f *Font, scale int32, i Index, h *Hinter) error {
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// and should be cleaned up once we have all the testScaling tests passing,
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// plus additional tests for Freetype-Go's bounding boxes matching C Freetype's.
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pp1x := g.pp1x
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if h != nil {
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if h != NoHinting {
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pp1x = g.phantomPoints[0].X
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}
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if pp1x != 0 {
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@ -109,7 +121,7 @@ func (g *GlyphBuf) Load(f *Font, scale int32, i Index, h *Hinter) error {
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}
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advanceWidth := g.phantomPoints[1].X - g.phantomPoints[0].X
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if h != nil {
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if h != NoHinting {
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if len(f.hdmx) >= 8 {
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if n := u32(f.hdmx, 4); n > 3+uint32(i) {
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for hdmx := f.hdmx[8:]; uint32(len(hdmx)) >= n; hdmx = hdmx[n:] {
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@ -151,7 +163,7 @@ func (g *GlyphBuf) Load(f *Font, scale int32, i Index, h *Hinter) error {
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}
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}
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// Snap the box to the grid, if hinting is on.
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if h != nil {
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if h != NoHinting {
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g.B.XMin &^= 63
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g.B.YMin &^= 63
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g.B.XMax += 63
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@ -221,7 +233,7 @@ func (g *GlyphBuf) load(recursion int32, i Index, useMyMetrics bool) (err error)
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program := g.loadSimple(glyf, ne)
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g.addPhantomsAndScale(np0, np0, true, true)
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pp1x = g.Point[len(g.Point)-4].X
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if g.hinter != nil {
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if g.hinting != NoHinting {
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if len(program) != 0 {
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err := g.hinter.run(
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program,
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@ -425,7 +437,7 @@ func (g *GlyphBuf) loadCompound(recursion int32, uhm HMetric, i Index,
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}
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instrLen := 0
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if g.hinter != nil && offset+2 <= len(glyf) {
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if g.hinting != NoHinting && offset+2 <= len(glyf) {
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instrLen = int(u16(glyf, offset))
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offset += 2
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}
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@ -473,7 +485,7 @@ func (g *GlyphBuf) addPhantomsAndScale(np0, np1 int, simple, adjust bool) {
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// Add the four phantom points.
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g.Point = append(g.Point, g.phantomPoints[:]...)
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// Scale the points.
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if simple && g.hinter != nil {
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if simple && g.hinting != NoHinting {
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g.InFontUnits = append(g.InFontUnits, g.Point[np1:]...)
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}
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for i := np1; i < len(g.Point); i++ {
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@ -481,7 +493,7 @@ func (g *GlyphBuf) addPhantomsAndScale(np0, np1 int, simple, adjust bool) {
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p.X = g.font.scale(g.scale * p.X)
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p.Y = g.font.scale(g.scale * p.Y)
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}
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if g.hinter == nil {
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if g.hinting == NoHinting {
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return
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}
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// Round the 1st phantom point to the grid, shifting all other points equally.
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@ -35,16 +35,15 @@ type callStackEntry struct {
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loopCount int32
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}
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// Hinter implements bytecode hinting. Pass a Hinter to GlyphBuf.Load to hint
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// the resulting glyph. A Hinter can be re-used to hint a series of glyphs from
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// a Font.
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type Hinter struct {
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// hinter implements bytecode hinting. A hinter can be re-used to hint a series
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// of glyphs from a Font.
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type hinter struct {
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stack, store []int32
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// functions is a map from function number to bytecode.
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functions map[int32][]byte
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// font and scale are the font and scale last used for this Hinter.
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// font and scale are the font and scale last used for this hinter.
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// Changing the font will require running the new font's fpgm bytecode.
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// Changing either will require running the font's prep bytecode.
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font *Font
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@ -114,7 +113,7 @@ func resetTwilightPoints(f *Font, p []Point) []Point {
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return p
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}
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func (h *Hinter) init(f *Font, scale int32) error {
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func (h *hinter) init(f *Font, scale int32) error {
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h.points[twilightZone][0] = resetTwilightPoints(f, h.points[twilightZone][0])
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h.points[twilightZone][1] = resetTwilightPoints(f, h.points[twilightZone][1])
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h.points[twilightZone][2] = resetTwilightPoints(f, h.points[twilightZone][2])
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@ -171,7 +170,7 @@ func (h *Hinter) init(f *Font, scale int32) error {
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return nil
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}
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func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point, ends []int) error {
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func (h *hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point, ends []int) error {
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h.gs = h.defaultGS
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h.points[glyphZone][current] = pCurrent
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h.points[glyphZone][unhinted] = pUnhinted
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@ -1388,7 +1387,7 @@ func (h *Hinter) run(program []byte, pCurrent, pUnhinted, pInFontUnits []Point,
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return nil
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}
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func (h *Hinter) initializeScaledCVT() {
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func (h *hinter) initializeScaledCVT() {
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h.scaledCVTInitialized = true
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if n := len(h.font.cvt) / 2; n <= cap(h.scaledCVT) {
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h.scaledCVT = h.scaledCVT[:n]
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@ -1405,7 +1404,7 @@ func (h *Hinter) initializeScaledCVT() {
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}
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// getScaledCVT returns the scaled value from the font's Control Value Table.
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func (h *Hinter) getScaledCVT(i int32) f26dot6 {
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func (h *hinter) getScaledCVT(i int32) f26dot6 {
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if !h.scaledCVTInitialized {
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h.initializeScaledCVT()
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}
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@ -1416,7 +1415,7 @@ func (h *Hinter) getScaledCVT(i int32) f26dot6 {
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}
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// setScaledCVT overrides the scaled value from the font's Control Value Table.
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func (h *Hinter) setScaledCVT(i int32, v f26dot6) {
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func (h *hinter) setScaledCVT(i int32, v f26dot6) {
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if !h.scaledCVTInitialized {
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h.initializeScaledCVT()
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}
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@ -1426,7 +1425,7 @@ func (h *Hinter) setScaledCVT(i int32, v f26dot6) {
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h.scaledCVT[i] = v
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}
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func (h *Hinter) point(zonePointer uint32, pt pointType, i int32) *Point {
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func (h *hinter) point(zonePointer uint32, pt pointType, i int32) *Point {
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points := h.points[h.gs.zp[zonePointer]][pt]
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if i < 0 || len(points) <= int(i) {
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return nil
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@ -1434,7 +1433,7 @@ func (h *Hinter) point(zonePointer uint32, pt pointType, i int32) *Point {
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return &points[i]
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}
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func (h *Hinter) move(p *Point, distance f26dot6, touch bool) {
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func (h *hinter) move(p *Point, distance f26dot6, touch bool) {
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fvx := int64(h.gs.fv[0])
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pvx := int64(h.gs.pv[0])
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if fvx == 0x4000 && pvx == 0x4000 {
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@ -1472,7 +1471,7 @@ func (h *Hinter) move(p *Point, distance f26dot6, touch bool) {
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}
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}
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func (h *Hinter) iupInterp(interpY bool, p1, p2, ref1, ref2 int) {
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func (h *hinter) iupInterp(interpY bool, p1, p2, ref1, ref2 int) {
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if p1 > p2 {
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return
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}
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@ -1567,7 +1566,7 @@ func (h *Hinter) iupInterp(interpY bool, p1, p2, ref1, ref2 int) {
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}
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}
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func (h *Hinter) iupShift(interpY bool, p1, p2, p int) {
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func (h *hinter) iupShift(interpY bool, p1, p2, p int) {
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var delta int32
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if interpY {
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delta = h.points[glyphZone][current][p].Y - h.points[glyphZone][unhinted][p].Y
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@ -1589,7 +1588,7 @@ func (h *Hinter) iupShift(interpY bool, p1, p2, p int) {
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}
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}
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func (h *Hinter) displacement(useZP1 bool) (zonePointer uint32, i int32, d f26dot6, ok bool) {
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func (h *hinter) displacement(useZP1 bool) (zonePointer uint32, i int32, d f26dot6, ok bool) {
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zonePointer, i = uint32(0), h.gs.rp[1]
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if useZP1 {
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zonePointer, i = 1, h.gs.rp[2]
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@ -1726,7 +1725,7 @@ func mulDiv(x, y, z int64) int64 {
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// round rounds the given number. The rounding algorithm is described at
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// https://developer.apple.com/fonts/TTRefMan/RM02/Chap2.html#rounding
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func (h *Hinter) round(x f26dot6) f26dot6 {
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func (h *hinter) round(x f26dot6) f26dot6 {
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if h.gs.roundPeriod == 0 {
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// Rounding is off.
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return x
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@ -554,7 +554,7 @@ func TestBytecode(t *testing.T) {
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}
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for _, tc := range testCases {
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h := &Hinter{}
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h := &hinter{}
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h.init(&Font{
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maxStorage: 32,
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maxStackElements: 100,
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@ -583,10 +583,10 @@ func TestBytecode(t *testing.T) {
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}
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}
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// TestMove tests that the Hinter.move method matches the output of the C
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// TestMove tests that the hinter.move method matches the output of the C
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// Freetype implementation.
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func TestMove(t *testing.T) {
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h, p := Hinter{}, Point{}
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h, p := hinter{}, Point{}
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testCases := []struct {
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pvX, pvY, fvX, fvY f2dot14
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wantX, wantY int32
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@ -61,7 +61,7 @@ func TestParse(t *testing.T) {
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}
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g := NewGlyphBuf()
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err = g.Load(font, fupe, i0, nil)
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err = g.Load(font, fupe, i0, NoHinting)
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if err != nil {
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t.Fatalf("Load: %v", err)
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}
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@ -262,7 +262,7 @@ var scalingTestCases = []struct {
|
|||
{"x-times-new-roman", 13},
|
||||
}
|
||||
|
||||
func testScaling(t *testing.T, hinter *Hinter) {
|
||||
func testScaling(t *testing.T, h Hinting) {
|
||||
for _, tc := range scalingTestCases {
|
||||
font, testdataIsOptional, err := parseTestdataFont(tc.name)
|
||||
if err != nil {
|
||||
|
|
@ -273,12 +273,12 @@ func testScaling(t *testing.T, hinter *Hinter) {
|
|||
}
|
||||
continue
|
||||
}
|
||||
hinting := "sans"
|
||||
if hinter != nil {
|
||||
hinting = "with"
|
||||
hintingStr := "sans"
|
||||
if h != NoHinting {
|
||||
hintingStr = "with"
|
||||
}
|
||||
f, err := os.Open(fmt.Sprintf(
|
||||
"../../testdata/%s-%dpt-%s-hinting.txt", tc.name, tc.size, hinting))
|
||||
"../../testdata/%s-%dpt-%s-hinting.txt", tc.name, tc.size, hintingStr))
|
||||
if err != nil {
|
||||
t.Errorf("%s: Open: %v", tc.name, err)
|
||||
continue
|
||||
|
|
@ -314,7 +314,7 @@ func testScaling(t *testing.T, hinter *Hinter) {
|
|||
|
||||
glyphBuf := NewGlyphBuf()
|
||||
for i, want := range wants {
|
||||
if err = glyphBuf.Load(font, tc.size*64, Index(i), hinter); err != nil {
|
||||
if err = glyphBuf.Load(font, tc.size*64, Index(i), h); err != nil {
|
||||
t.Errorf("%s: glyph #%d: Load: %v", tc.name, i, err)
|
||||
continue
|
||||
}
|
||||
|
|
@ -354,9 +354,9 @@ func testScaling(t *testing.T, hinter *Hinter) {
|
|||
}
|
||||
|
||||
func TestScalingSansHinting(t *testing.T) {
|
||||
testScaling(t, nil)
|
||||
testScaling(t, NoHinting)
|
||||
}
|
||||
|
||||
func TestScalingWithHinting(t *testing.T) {
|
||||
testScaling(t, &Hinter{})
|
||||
testScaling(t, FullHinting)
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in a new issue