font/sfnt: implement Font.Kern.
Change-Id: I9ffb93dd3ee08b8871dadf5bc36578710b800199 Reviewed-on: https://go-review.googlesource.com/37410 Reviewed-by: David Crawshaw <crawshaw@golang.org>
This commit is contained in:
Nigel Tao
parent
b952c941a6
commit
c8ae36c95e
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@ -31,11 +31,13 @@ go test golang.org/x/image/font/sfnt -test.run=ProprietaryMicrosoft -args -propr
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// TODO: enable Apple/Microsoft tests by default on Darwin/Windows?
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import (
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"errors"
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"flag"
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"io/ioutil"
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"path/filepath"
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"testing"
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"golang.org/x/image/font"
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"golang.org/x/image/math/fixed"
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)
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@ -134,7 +136,7 @@ func testProprietary(t *testing.T, proprietor, filename string, minNumGlyphs, fi
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if err != nil {
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t.Fatalf("Parse: %v", err)
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}
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ppem := fixed.Int26_6(f.UnitsPerEm()) << 6
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ppem := fixed.Int26_6(f.UnitsPerEm())
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qualifiedFilename := proprietor + "/" + filename
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var buf Buffer
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@ -183,6 +185,33 @@ func testProprietary(t *testing.T, proprietor, filename string, minNumGlyphs, fi
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continue
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}
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}
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kernLoop:
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for _, tc := range proprietaryKernTestCases[qualifiedFilename] {
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var indexes [2]GlyphIndex
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for i := range indexes {
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x, err := f.GlyphIndex(&buf, tc.runes[i])
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if x == 0 && err == nil {
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err = errors.New("no glyph index found")
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}
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if err != nil {
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t.Errorf("GlyphIndex(%q): %v", tc.runes[0], err)
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continue kernLoop
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}
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indexes[i] = x
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}
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kern, err := f.Kern(&buf, indexes[0], indexes[1], tc.ppem, tc.hinting)
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if err != nil {
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t.Errorf("Kern(%q, %q, ppem=%d, hinting=%v): %v",
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tc.runes[0], tc.runes[1], tc.ppem, tc.hinting, err)
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continue
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}
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if got := Units(kern); got != tc.want {
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t.Errorf("Kern(%q, %q, ppem=%d, hinting=%v): got %d, want %d",
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tc.runes[0], tc.runes[1], tc.ppem, tc.hinting, got, tc.want)
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continue
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}
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}
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}
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// proprietaryVersions holds the expected version string of each proprietary
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@ -282,3 +311,45 @@ var proprietaryGlyphIndexTestCases = map[string]map[rune]GlyphIndex{
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'\uf042': 37, // PRIVATE USE AREA
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},
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}
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type kernTestCase struct {
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ppem fixed.Int26_6
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hinting font.Hinting
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runes [2]rune
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want Units
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}
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// proprietaryKernTestCases hold a sample of each font's kerning pairs. The
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// numerical values can be verified by running the ttx tool.
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var proprietaryKernTestCases = map[string][]kernTestCase{
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"microsoft/Arial.ttf": {
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{2048, font.HintingNone, [2]rune{'A', 'V'}, -152},
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// U+03B8 GREEK SMALL LETTER THETA
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// U+03BB GREEK SMALL LETTER LAMDA
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{2048, font.HintingNone, [2]rune{'\u03b8', '\u03bb'}, -39},
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{2048, font.HintingNone, [2]rune{'\u03bb', '\u03b8'}, -0},
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},
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"microsoft/Comic_Sans_MS.ttf": {
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{2048, font.HintingNone, [2]rune{'A', 'V'}, 0},
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},
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"microsoft/Times_New_Roman.ttf": {
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{768, font.HintingNone, [2]rune{'A', 'V'}, -99},
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{768, font.HintingFull, [2]rune{'A', 'V'}, -128},
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{2048, font.HintingNone, [2]rune{'A', 'A'}, 0},
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{2048, font.HintingNone, [2]rune{'A', 'T'}, -227},
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{2048, font.HintingNone, [2]rune{'A', 'V'}, -264},
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{2048, font.HintingNone, [2]rune{'T', 'A'}, -164},
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{2048, font.HintingNone, [2]rune{'T', 'T'}, 0},
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{2048, font.HintingNone, [2]rune{'T', 'V'}, 0},
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{2048, font.HintingNone, [2]rune{'V', 'A'}, -264},
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{2048, font.HintingNone, [2]rune{'V', 'T'}, 0},
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{2048, font.HintingNone, [2]rune{'V', 'V'}, 0},
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// U+0390 GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS
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// U+0393 GREEK CAPITAL LETTER GAMMA
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{2048, font.HintingNone, [2]rune{'\u0390', '\u0393'}, 0},
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{2048, font.HintingNone, [2]rune{'\u0393', '\u0390'}, 76},
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},
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"microsoft/Webdings.ttf": {
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{2048, font.HintingNone, [2]rune{'\uf041', '\uf042'}, 0},
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},
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}
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@ -23,6 +23,7 @@ import (
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"errors"
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"io"
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"golang.org/x/image/font"
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"golang.org/x/image/math/fixed"
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"golang.org/x/text/encoding/charmap"
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)
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@ -63,6 +64,7 @@ var (
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errInvalidCmapTable = errors.New("sfnt: invalid cmap table")
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errInvalidGlyphData = errors.New("sfnt: invalid glyph data")
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errInvalidHeadTable = errors.New("sfnt: invalid head table")
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errInvalidKernTable = errors.New("sfnt: invalid kern table")
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errInvalidLocaTable = errors.New("sfnt: invalid loca table")
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errInvalidLocationData = errors.New("sfnt: invalid location data")
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errInvalidMaxpTable = errors.New("sfnt: invalid maxp table")
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@ -78,6 +80,7 @@ var (
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errUnsupportedCmapEncodings = errors.New("sfnt: unsupported cmap encodings")
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errUnsupportedCompoundGlyph = errors.New("sfnt: unsupported compound glyph")
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errUnsupportedGlyphDataLength = errors.New("sfnt: unsupported glyph data length")
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errUnsupportedKernTable = errors.New("sfnt: unsupported kern table")
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errUnsupportedRealNumberEncoding = errors.New("sfnt: unsupported real number encoding")
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errUnsupportedNumberOfCmapSegments = errors.New("sfnt: unsupported number of cmap segments")
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errUnsupportedNumberOfHints = errors.New("sfnt: unsupported number of hints")
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@ -286,11 +289,17 @@ func ParseReaderAt(src io.ReaderAt) (*Font, error) {
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// The Font methods that don't take a *Buffer argument are always safe to call
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// concurrently.
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//
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// Some methods provide lengths or co-ordinates, e.g. bounds, font metrics and
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// Some methods provide lengths or coordinates, e.g. bounds, font metrics and
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// control points. All of these methods take a ppem parameter, which is the
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// number of pixels in 1 em, expressed as a 26.6 fixed point value. For
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// example, if 1 em is 10 pixels then ppem is fixed.I(10), which equals
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// fixed.Int26_6(10 << 6).
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//
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// To get those lengths or coordinates in terms of font units instead of
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// pixels, use ppem = fixed.Int26_6(f.UnitsPerEm()) and if those methods take a
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// font.Hinting parameter, use font.HintingNone. The return values will have
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// type fixed.Int26_6, but those numbers can be converted back to Units with no
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// further scaling necessary.
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type Font struct {
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src source
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@ -327,12 +336,15 @@ type Font struct {
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// https://www.microsoft.com/typography/otspec/otff.htm#otttables
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// "Other OpenType Tables".
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//
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// TODO: hdmx, kern, vmtx? Others?
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// TODO: hdmx, vmtx? Others?
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kern table
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cached struct {
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glyphIndex func(f *Font, b *Buffer, r rune) (GlyphIndex, error)
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indexToLocFormat bool // false means short, true means long.
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isPostScript bool
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kernNumPairs int32
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kernOffset int32
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postTableVersion uint32
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unitsPerEm Units
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@ -375,6 +387,10 @@ func (f *Font) initialize() error {
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if err != nil {
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return err
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}
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buf, err = f.parseKern(buf)
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if err != nil {
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return err
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}
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buf, err = f.parsePost(buf)
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if err != nil {
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return err
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@ -444,6 +460,8 @@ func (f *Font) initializeTables(buf []byte) ([]byte, error) {
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f.hhea = table{o, n}
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case 0x686d7478:
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f.hmtx = table{o, n}
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case 0x6b65726e:
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f.kern = table{o, n}
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case 0x6c6f6361:
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f.loca = table{o, n}
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case 0x6d617870:
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@ -542,6 +560,90 @@ func (f *Font) parseHead(buf []byte) ([]byte, error) {
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return buf, nil
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}
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func (f *Font) parseKern(buf []byte) ([]byte, error) {
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// https://www.microsoft.com/typography/otspec/kern.htm
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if f.kern.length == 0 {
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return buf, nil
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}
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const headerSize = 4
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if f.kern.length < headerSize {
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return nil, errInvalidKernTable
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}
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buf, err := f.src.view(buf, int(f.kern.offset), headerSize)
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if err != nil {
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return nil, err
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}
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offset := int(f.kern.offset) + headerSize
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length := int(f.kern.length) - headerSize
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switch version := u16(buf); version {
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case 0:
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// TODO: support numTables != 1. Testing that requires finding such a font.
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if numTables := int(u16(buf[2:])); numTables != 1 {
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return nil, errUnsupportedKernTable
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}
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return f.parseKernVersion0(buf, offset, length)
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case 1:
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// TODO: find such a (proprietary?) font, and support it. Both of
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// https://www.microsoft.com/typography/otspec/kern.htm
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// https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6kern.html
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// say that such fonts work on Mac OS but not on Windows.
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}
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return nil, errUnsupportedKernTable
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}
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func (f *Font) parseKernVersion0(buf []byte, offset, length int) ([]byte, error) {
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const headerSize = 6
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if length < headerSize {
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return nil, errInvalidKernTable
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}
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buf, err := f.src.view(buf, offset, headerSize)
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if err != nil {
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return nil, err
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}
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if version := u16(buf); version != 0 {
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return nil, errUnsupportedKernTable
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}
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subtableLength := int(u16(buf[2:]))
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if subtableLength < headerSize || length < subtableLength {
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return nil, errInvalidKernTable
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}
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if coverageBits := buf[5]; coverageBits != 0x01 {
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// We only support horizontal kerning.
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return nil, errUnsupportedKernTable
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}
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offset += headerSize
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length -= headerSize
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subtableLength -= headerSize
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switch format := buf[4]; format {
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case 0:
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return f.parseKernFormat0(buf, offset, subtableLength)
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case 2:
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// TODO: find such a (proprietary?) font, and support it.
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}
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return nil, errUnsupportedKernTable
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}
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func (f *Font) parseKernFormat0(buf []byte, offset, length int) ([]byte, error) {
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const headerSize, entrySize = 8, 6
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if length < headerSize {
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return nil, errInvalidKernTable
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}
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buf, err := f.src.view(buf, offset, headerSize)
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if err != nil {
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return nil, err
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}
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numPairs := u16(buf)
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if length != headerSize+entrySize*int(numPairs) {
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return nil, errInvalidKernTable
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}
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f.cached.kernNumPairs = int32(numPairs)
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f.cached.kernOffset = int32(offset) + headerSize
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return buf, nil
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}
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func (f *Font) parseMaxp(buf []byte) ([]byte, error) {
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// https://www.microsoft.com/typography/otspec/maxp.htm
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@ -763,6 +865,64 @@ func (f *Font) GlyphName(b *Buffer, x GlyphIndex) (string, error) {
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}
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}
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// Kern returns the horizontal adjustment for the kerning pair (x0, x1). A
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// positive kern means to move the glyphs further apart. ppem is the number of
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// pixels in 1 em.
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//
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// It returns ErrNotFound if either glyph index is out of range.
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func (f *Font) Kern(b *Buffer, x0, x1 GlyphIndex, ppem fixed.Int26_6, h font.Hinting) (fixed.Int26_6, error) {
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// TODO: how should this work with the GPOS table and CFF fonts?
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// https://www.microsoft.com/typography/otspec/kern.htm says that
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// "OpenType™ fonts containing CFF outlines are not supported by the 'kern'
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// table and must use the 'GPOS' OpenType Layout table."
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if n := f.NumGlyphs(); int(x0) >= n || int(x1) >= n {
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return 0, ErrNotFound
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}
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// Not every font has a kern table. If it doesn't, there's no need to
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// allocate a Buffer.
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if f.kern.length == 0 {
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return 0, nil
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}
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if b == nil {
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b = &Buffer{}
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}
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key := uint32(x0)<<16 | uint32(x1)
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lo, hi := int32(0), f.cached.kernNumPairs
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for lo < hi {
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i := (lo + hi) / 2
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// TODO: this view call inside the inner loop can lead to many small
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// reads instead of fewer larger reads, which can be expensive. We
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// should be able to do better, although we don't want to make (one)
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// arbitrarily large read. Perhaps we should round up reads to 4K or 8K
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// chunks. For reference, Arial.ttf's kern table is 5472 bytes.
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// Times_New_Roman.ttf's kern table is 5220 bytes.
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const entrySize = 6
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buf, err := b.view(&f.src, int(f.cached.kernOffset+i*entrySize), entrySize)
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if err != nil {
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return 0, err
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}
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k := u32(buf)
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if k < key {
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lo = i + 1
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} else if k > key {
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hi = i
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} else {
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kern := fixed.Int26_6(int16(u16(buf[4:])))
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kern = scale(kern*ppem, f.cached.unitsPerEm)
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if h == font.HintingFull {
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// Quantize the fixed.Int26_6 value to the nearest pixel.
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kern = (kern + 32) &^ 63
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}
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return kern, nil
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}
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}
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return 0, nil
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}
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// Name returns the name value keyed by the given NameID.
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//
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// It returns ErrNotFound if there is no value for that key.
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@ -15,69 +15,31 @@ import (
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"golang.org/x/image/math/fixed"
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)
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func moveTo(xa, ya int) Segment {
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func moveTo(xa, ya fixed.Int26_6) Segment {
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return Segment{
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Op: SegmentOpMoveTo,
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Args: [6]fixed.Int26_6{
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0: fixed.I(xa),
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1: fixed.I(ya),
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},
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Op: SegmentOpMoveTo,
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Args: [6]fixed.Int26_6{xa, ya},
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}
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}
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func moveTo26_6(xa, ya fixed.Int26_6) Segment {
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func lineTo(xa, ya fixed.Int26_6) Segment {
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return Segment{
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Op: SegmentOpMoveTo,
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Args: [6]fixed.Int26_6{
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0: xa,
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1: ya,
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},
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Op: SegmentOpLineTo,
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Args: [6]fixed.Int26_6{xa, ya},
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}
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}
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func lineTo(xa, ya int) Segment {
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func quadTo(xa, ya, xb, yb fixed.Int26_6) Segment {
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return Segment{
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Op: SegmentOpLineTo,
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Args: [6]fixed.Int26_6{
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0: fixed.I(xa),
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1: fixed.I(ya),
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},
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Op: SegmentOpQuadTo,
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Args: [6]fixed.Int26_6{xa, ya, xb, yb},
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}
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}
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func lineTo26_6(xa, ya fixed.Int26_6) Segment {
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func cubeTo(xa, ya, xb, yb, xc, yc fixed.Int26_6) Segment {
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return Segment{
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Op: SegmentOpLineTo,
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Args: [6]fixed.Int26_6{
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0: xa,
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1: ya,
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},
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}
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}
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func quadTo(xa, ya, xb, yb int) Segment {
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return Segment{
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Op: SegmentOpQuadTo,
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Args: [6]fixed.Int26_6{
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0: fixed.I(xa),
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1: fixed.I(ya),
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2: fixed.I(xb),
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3: fixed.I(yb),
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},
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}
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}
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func cubeTo(xa, ya, xb, yb, xc, yc int) Segment {
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return Segment{
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Op: SegmentOpCubeTo,
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Args: [6]fixed.Int26_6{
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0: fixed.I(xa),
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1: fixed.I(ya),
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2: fixed.I(xb),
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3: fixed.I(yb),
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4: fixed.I(xc),
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5: fixed.I(yc),
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},
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Op: SegmentOpCubeTo,
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Args: [6]fixed.Int26_6{xa, ya, xb, yb, xc, yc},
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}
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}
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@ -430,7 +392,7 @@ func testSegments(t *testing.T, filename string, wants [][]Segment) {
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if err != nil {
|
||||
t.Fatalf("Parse: %v", err)
|
||||
}
|
||||
ppem := fixed.Int26_6(f.UnitsPerEm()) << 6
|
||||
ppem := fixed.Int26_6(f.UnitsPerEm())
|
||||
|
||||
if ng := f.NumGlyphs(); ng != len(wants) {
|
||||
t.Fatalf("NumGlyphs: got %d, want %d", ng, len(wants))
|
||||
|
|
@ -481,16 +443,16 @@ func TestPPEM(t *testing.T) {
|
|||
ppem fixed.Int26_6
|
||||
want []Segment
|
||||
}{{
|
||||
ppem: fixed.I(12),
|
||||
ppem: fixed.Int26_6(12 << 6),
|
||||
want: []Segment{
|
||||
moveTo26_6(77, 0),
|
||||
lineTo26_6(77, 614),
|
||||
lineTo26_6(230, 614),
|
||||
lineTo26_6(230, 0),
|
||||
lineTo26_6(77, 0),
|
||||
moveTo(77, 0),
|
||||
lineTo(77, 614),
|
||||
lineTo(230, 614),
|
||||
lineTo(230, 0),
|
||||
lineTo(77, 0),
|
||||
},
|
||||
}, {
|
||||
ppem: fixed.I(2048),
|
||||
ppem: fixed.Int26_6(2048),
|
||||
want: []Segment{
|
||||
moveTo(205, 0),
|
||||
lineTo(205, 1638),
|
||||
|
|
|
|||
|
|
@ -131,12 +131,12 @@ func appendGlyfSegments(dst []Segment, data []byte) ([]Segment, error) {
|
|||
|
||||
// For simple (non-compound) glyphs, the remainder of the glyf data
|
||||
// consists of (flags, x, y) points: the Bézier curve segments. These are
|
||||
// stored in columns (all the flags first, then all the x co-ordinates,
|
||||
// then all the y co-ordinates), not rows, as it compresses better.
|
||||
// stored in columns (all the flags first, then all the x coordinates, then
|
||||
// all the y coordinates), not rows, as it compresses better.
|
||||
//
|
||||
// Decoding those points in row order involves two passes. The first pass
|
||||
// determines the indexes (relative to the data slice) of where the flags,
|
||||
// the x co-ordinates and the y co-ordinates each start.
|
||||
// the x coordinates and the y coordinates each start.
|
||||
flagIndex := int32(index)
|
||||
xIndex, yIndex, ok := findXYIndexes(data, index, numPoints)
|
||||
if !ok {
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user