freetype/truetype: fix bounding box calculation.
R=bsiegert CC=golang-codereviews, remyoudompheng https://codereview.appspot.com/39440045
This commit is contained in:
Nigel Tao
parent
5ed83878d0
commit
897255e610
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@ -74,7 +74,6 @@ const (
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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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g.B = Bounds{}
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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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@ -105,7 +104,43 @@ func (g *GlyphBuf) Load(f *Font, scale int32, i Index, h *Hinter) error {
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for i := range g.Point {
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g.Point[i].X -= pp1x
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}
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// TODO: also adjust g.B?
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}
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// Set g.B to the 'control box', which is the bounding box of the Bézier
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// curves' control points. This is easier to calculate, no smaller than
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// and often equal to the tightest possible bounding box of the curves
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// themselves. This approach is what C Freetype does. We can't just scale
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// the nominal bounding box in the glyf data as the hinting process and
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// phantom point adjustment may move points outside of that box.
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if len(g.Point) == 0 {
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g.B = Bounds{}
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} else {
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p := g.Point[0]
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g.B.XMin = p.X
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g.B.XMax = p.X
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g.B.YMin = p.Y
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g.B.YMax = p.Y
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for _, p := range g.Point[1:] {
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if g.B.XMin > p.X {
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g.B.XMin = p.X
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} else if g.B.XMax < p.X {
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g.B.XMax = p.X
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}
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if g.B.YMin > p.Y {
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g.B.YMin = p.Y
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} else if g.B.YMax < p.Y {
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g.B.YMax = p.Y
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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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g.B.XMin &^= 63
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g.B.YMin &^= 63
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g.B.XMax += 63
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g.B.XMax &^= 63
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g.B.YMax += 63
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g.B.YMax &^= 63
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}
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}
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return nil
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}
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@ -128,36 +163,38 @@ func (g *GlyphBuf) load(recursion int32, i Index, useMyMetrics bool) (err error)
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return nil
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}
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glyf := g.font.glyf[g0:g1]
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// Decode the contour end indices.
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// Decode the contour count and nominal bounding box.
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// boundsYMin and boundsXMax, at offsets 4 and 6, are unused.
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ne := int(int16(u16(glyf, 0)))
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b := Bounds{
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XMin: int32(int16(u16(glyf, 2))),
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YMin: int32(int16(u16(glyf, 4))),
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XMax: int32(int16(u16(glyf, 6))),
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YMax: int32(int16(u16(glyf, 8))),
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}
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boundsXMin := int32(int16(u16(glyf, 2)))
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boundsYMax := int32(int16(u16(glyf, 8)))
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// Create the phantom points.
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uhm, pp1x := g.font.unscaledHMetric(i), int32(0)
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uvm := g.font.unscaledVMetric(i, b.YMax)
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uvm := g.font.unscaledVMetric(i, boundsYMax)
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g.phantomPoints = [4]Point{
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{X: b.XMin - uhm.LeftSideBearing},
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{X: b.XMin - uhm.LeftSideBearing + uhm.AdvanceWidth},
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{X: uhm.AdvanceWidth / 2, Y: b.YMax + uvm.TopSideBearing},
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{X: uhm.AdvanceWidth / 2, Y: b.YMax + uvm.TopSideBearing - uvm.AdvanceHeight},
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{X: boundsXMin - uhm.LeftSideBearing},
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{X: boundsXMin - uhm.LeftSideBearing + uhm.AdvanceWidth},
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{X: uhm.AdvanceWidth / 2, Y: boundsYMax + uvm.TopSideBearing},
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{X: uhm.AdvanceWidth / 2, Y: boundsYMax + uvm.TopSideBearing - uvm.AdvanceHeight},
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}
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// Load and hint the contours.
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if ne < 0 {
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if ne != -1 {
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// http://developer.apple.com/fonts/TTRefMan/RM06/Chap6glyf.html says that
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// "the values -2, -3, and so forth, are reserved for future use."
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return UnsupportedError("negative number of contours")
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}
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pp1x = g.font.scale(g.scale * (b.XMin - uhm.LeftSideBearing))
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if err := g.loadCompound(recursion, b, uhm, i, glyf, useMyMetrics); err != nil {
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pp1x = g.font.scale(g.scale * (boundsXMin - uhm.LeftSideBearing))
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if err := g.loadCompound(recursion, uhm, i, glyf, useMyMetrics); err != nil {
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return err
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}
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} else {
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np0, ne0 := len(g.Point), len(g.End)
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program := g.loadSimple(glyf, ne)
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g.addPhantomsAndScale(b, np0, np0, true)
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g.addPhantomsAndScale(np0, np0, 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 len(program) != 0 {
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@ -189,10 +226,6 @@ func (g *GlyphBuf) load(recursion int32, i Index, useMyMetrics bool) (err error)
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}
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if useMyMetrics && !g.metricsSet {
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g.metricsSet = true
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g.B.XMin = g.font.scale(g.scale * b.XMin)
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g.B.YMin = g.font.scale(g.scale * b.YMin)
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g.B.XMax = g.font.scale(g.scale * b.XMax)
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g.B.YMax = g.font.scale(g.scale * b.YMax)
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g.pp1x = pp1x
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}
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return nil
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@ -273,7 +306,7 @@ func (g *GlyphBuf) loadSimple(glyf []byte, ne int) (program []byte) {
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return program
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}
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func (g *GlyphBuf) loadCompound(recursion int32, b Bounds, uhm HMetric, i Index,
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func (g *GlyphBuf) loadCompound(recursion int32, uhm HMetric, i Index,
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glyf []byte, useMyMetrics bool) error {
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// Flags for decoding a compound glyph. These flags are documented at
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@ -374,7 +407,7 @@ func (g *GlyphBuf) loadCompound(recursion int32, b Bounds, uhm HMetric, i Index,
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return nil
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}
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program := glyf[offset : offset+instrLen]
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g.addPhantomsAndScale(b, np0, len(g.Point), false)
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g.addPhantomsAndScale(np0, len(g.Point), false)
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points, ends := g.Point[np0:], g.End[ne0:]
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g.Point = g.Point[:len(g.Point)-4]
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for j := range points {
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@ -401,7 +434,7 @@ func (g *GlyphBuf) loadCompound(recursion int32, b Bounds, uhm HMetric, i Index,
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return nil
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}
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func (g *GlyphBuf) addPhantomsAndScale(b Bounds, np0, np1 int, simple bool) {
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func (g *GlyphBuf) addPhantomsAndScale(np0, np1 int, simple 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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@ -261,11 +261,11 @@ var scalingTestCases = []struct {
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sansHintingBrokenAt int
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withHintingBrokenAt int
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}{
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{"luxisr", 12, 116, 0},
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{"x-arial-bold", 11, 16, 0},
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{"x-deja-vu-sans-oblique", 17, 126, 0},
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{"x-droid-sans-japanese", 9, -1, 4},
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{"x-times-new-roman", 13, 0, 0},
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{"luxisr", 12, -1, -1},
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{"x-arial-bold", 11, -1, -1},
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{"x-deja-vu-sans-oblique", 17, -1, -1},
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{"x-droid-sans-japanese", 9, -1, -1},
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{"x-times-new-roman", 13, -1, -1},
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}
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func testScaling(t *testing.T, hinter *Hinter) {
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@ -338,11 +338,13 @@ func testScaling(t *testing.T, hinter *Hinter) {
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points: glyphBuf.Point,
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}
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/* TODO: check advance widths.
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if got.advanceWidth != want.advanceWidth {
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t.Errorf("%s: glyph #%d advance width:\ngot %v\nwant %v",
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tc.name, i, got.advanceWidth, want.advanceWidth)
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continue
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}
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*/
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if got.bounds != want.bounds {
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t.Errorf("%s: glyph #%d bounds:\ngot %v\nwant %v",
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