font/sfnt: add a Font.Name method.

Also make all of the Buffer fields non-exported. LoadGlyph now returns
the segments instead of setting Buffer.Segments for the caller to use.

Change-Id: I3f87070da5e8f014f88dbca70b62a4cd30e3fd66
Reviewed-on: https://go-review.googlesource.com/34532
Reviewed-by: Dave Day <djd@golang.org>
This commit is contained in:
Nigel Tao 2016-12-17 12:44:26 +11:00
parent ed90ab82a8
commit 2d771d3c32
2 changed files with 198 additions and 31 deletions

View File

@ -19,6 +19,7 @@ import (
"io" "io"
"golang.org/x/image/math/fixed" "golang.org/x/image/math/fixed"
"golang.org/x/text/encoding/charmap"
) )
// These constants are not part of the specifications, but are limitations used // These constants are not part of the specifications, but are limitations used
@ -34,22 +35,26 @@ const (
) )
var ( var (
errGlyphIndexOutOfRange = errors.New("sfnt: glyph index out of range") // ErrNotFound indicates that the requested value was not found.
ErrNotFound = errors.New("sfnt: not found")
errInvalidBounds = errors.New("sfnt: invalid bounds") errInvalidBounds = errors.New("sfnt: invalid bounds")
errInvalidCFFTable = errors.New("sfnt: invalid CFF table") errInvalidCFFTable = errors.New("sfnt: invalid CFF table")
errInvalidHeadTable = errors.New("sfnt: invalid head table") errInvalidHeadTable = errors.New("sfnt: invalid head table")
errInvalidLocationData = errors.New("sfnt: invalid location data") errInvalidLocationData = errors.New("sfnt: invalid location data")
errInvalidMaxpTable = errors.New("sfnt: invalid maxp table") errInvalidMaxpTable = errors.New("sfnt: invalid maxp table")
errInvalidNameTable = errors.New("sfnt: invalid name table")
errInvalidSourceData = errors.New("sfnt: invalid source data") errInvalidSourceData = errors.New("sfnt: invalid source data")
errInvalidTableOffset = errors.New("sfnt: invalid table offset") errInvalidTableOffset = errors.New("sfnt: invalid table offset")
errInvalidTableTagOrder = errors.New("sfnt: invalid table tag order") errInvalidTableTagOrder = errors.New("sfnt: invalid table tag order")
errInvalidUCS2String = errors.New("sfnt: invalid UCS-2 string")
errInvalidVersion = errors.New("sfnt: invalid version") errInvalidVersion = errors.New("sfnt: invalid version")
errUnsupportedCFFVersion = errors.New("sfnt: unsupported CFF version") errUnsupportedCFFVersion = errors.New("sfnt: unsupported CFF version")
errUnsupportedRealNumberEncoding = errors.New("sfnt: unsupported real number encoding") errUnsupportedRealNumberEncoding = errors.New("sfnt: unsupported real number encoding")
errUnsupportedNumberOfHints = errors.New("sfnt: unsupported number of hints") errUnsupportedNumberOfHints = errors.New("sfnt: unsupported number of hints")
errUnsupportedNumberOfTables = errors.New("sfnt: unsupported number of tables") errUnsupportedNumberOfTables = errors.New("sfnt: unsupported number of tables")
errUnsupportedPlatformEncoding = errors.New("sfnt: unsupported platform encoding")
errUnsupportedTableOffsetLength = errors.New("sfnt: unsupported table offset or length") errUnsupportedTableOffsetLength = errors.New("sfnt: unsupported table offset or length")
errUnsupportedType2Charstring = errors.New("sfnt: unsupported Type 2 Charstring") errUnsupportedType2Charstring = errors.New("sfnt: unsupported Type 2 Charstring")
) )
@ -57,12 +62,57 @@ var (
// GlyphIndex is a glyph index in a Font. // GlyphIndex is a glyph index in a Font.
type GlyphIndex uint16 type GlyphIndex uint16
// NameID identifies a name table entry.
//
// See the "Name IDs" section of
// https://www.microsoft.com/typography/otspec/name.htm
type NameID uint16
const (
NameIDCopyright NameID = 0
NameIDFamily = 1
NameIDSubfamily = 2
NameIDUniqueIdentifier = 3
NameIDFull = 4
NameIDVersion = 5
NameIDPostScript = 6
NameIDTrademark = 7
NameIDManufacturer = 8
NameIDDesigner = 9
NameIDDescription = 10
NameIDVendorURL = 11
NameIDDesignerURL = 12
NameIDLicense = 13
NameIDLicenseURL = 14
NameIDTypographicFamily = 16
NameIDTypographicSubfamily = 17
NameIDCompatibleFull = 18
NameIDSampleText = 19
NameIDPostScriptCID = 20
NameIDWWSFamily = 21
NameIDWWSSubfamily = 22
NameIDLightBackgroundPalette = 23
NameIDDarkBackgroundPalette = 24
NameIDVariationsPostScriptPrefix = 25
)
// Units are an integral number of abstract, scalable "font units". The em // Units are an integral number of abstract, scalable "font units". The em
// square is typically 1000 or 2048 "font units". This would map to a certain // square is typically 1000 or 2048 "font units". This would map to a certain
// number (e.g. 30 pixels) of physical pixels, depending on things like the // number (e.g. 30 pixels) of physical pixels, depending on things like the
// display resolution (DPI) and font size (e.g. a 12 point font). // display resolution (DPI) and font size (e.g. a 12 point font).
type Units int32 type Units int32
// Platform IDs and Platform Specific IDs as per
// https://www.microsoft.com/typography/otspec/name.htm
const (
pidMacintosh = 1
pidWindows = 3
psidMacintoshRoman = 0
psidWindowsUCS2 = 1
)
func u16(b []byte) uint16 { func u16(b []byte) uint16 {
_ = b[1] // Bounds check hint to compiler. _ = b[1] // Bounds check hint to compiler.
return uint16(b[0])<<8 | uint16(b[1])<<0 return uint16(b[0])<<8 | uint16(b[1])<<0
@ -178,10 +228,20 @@ func ParseReaderAt(src io.ReaderAt) (*Font, error) {
// Font is an SFNT font. // Font is an SFNT font.
// //
// All of its methods are safe to call concurrently, although the method // Many of its methods take a *Buffer argument, as re-using buffers can reduce
// arguments may have further restrictions. For example, it is valid to have // the total memory allocation of repeated Font method calls, such as measuring
// multiple concurrent Font.LoadGlyph calls to the same *Font receiver, as long // and rasterizing every unique glyph in a string of text. If efficiency is not
// as each call has a different Buffer. // a concern, passing a nil *Buffer is valid, and implies using a temporary
// buffer for a single call.
//
// It is valid to re-use a *Buffer with multiple Font method calls, even with
// different *Font receivers, as long as they are not concurrent calls.
//
// All of the Font methods are safe to call concurrently, as long as each call
// has a different *Buffer (or nil).
//
// The Font methods that don't take a *Buffer argument are always safe to call
// concurrently.
type Font struct { type Font struct {
src source src source
@ -369,14 +429,14 @@ func (f *Font) initialize() error {
// TODO: func (f *Font) GlyphIndex(r rune) (x GlyphIndex, ok bool) // TODO: func (f *Font) GlyphIndex(r rune) (x GlyphIndex, ok bool)
// This will require parsing the cmap table. // This will require parsing the cmap table.
func (f *Font) viewGlyphData(buf []byte, x GlyphIndex) ([]byte, error) { func (f *Font) viewGlyphData(b *Buffer, x GlyphIndex) ([]byte, error) {
xx := int(x) xx := int(x)
if f.NumGlyphs() <= xx { if f.NumGlyphs() <= xx {
return nil, errGlyphIndexOutOfRange return nil, ErrNotFound
} }
i := f.cached.locations[xx+0] i := f.cached.locations[xx+0]
j := f.cached.locations[xx+1] j := f.cached.locations[xx+1]
return f.src.view(buf, int(i), int(j-i)) return b.view(&f.src, int(i), int(j-i))
} }
// LoadGlyphOptions are the options to the Font.LoadGlyph method. // LoadGlyphOptions are the options to the Font.LoadGlyph method.
@ -384,48 +444,145 @@ type LoadGlyphOptions struct {
// TODO: scale / transform / hinting. // TODO: scale / transform / hinting.
} }
// LoadGlyph loads the glyphs vectors for the x'th glyph into b.Segments. // LoadGlyph returns the vector segments for the x'th glyph.
func (f *Font) LoadGlyph(b *Buffer, x GlyphIndex, opts *LoadGlyphOptions) error {
buf, err := f.viewGlyphData(b.buf, x)
if err != nil {
return err
}
// Only update b.buf if it is safe to re-use buf.
if f.src.viewBufferWritable() {
b.buf = buf
}
b.Segments = b.Segments[:0]
if f.cached.isPostScript {
b.psi.type2Charstrings.initialize(b.Segments)
if err := b.psi.run(psContextType2Charstring, buf); err != nil {
return err
}
b.Segments = b.psi.type2Charstrings.segments
} else {
return errors.New("sfnt: TODO: load glyf data")
}
// TODO: look at opts to scale / transform / hint the Buffer.Segments.
return nil
}
// Buffer holds the result of the Font.LoadGlyph method. It is valid to re-use
// a Buffer with multiple Font.LoadGlyph calls, even with different *Font
// receivers, as long as they are not concurrent calls.
// //
// It is also valid to have multiple concurrent Font.LoadGlyph calls to the // If b is non-nil, the segments become invalid to use once b is re-used.
// same *Font receiver, as long as each call has a different Buffer. //
// It returns ErrNotFound if the glyph index is out of range.
func (f *Font) LoadGlyph(b *Buffer, x GlyphIndex, opts *LoadGlyphOptions) ([]Segment, error) {
if b == nil {
b = &Buffer{}
}
buf, err := f.viewGlyphData(b, x)
if err != nil {
return nil, err
}
b.segments = b.segments[:0]
if f.cached.isPostScript {
b.psi.type2Charstrings.initialize(b.segments)
if err := b.psi.run(psContextType2Charstring, buf); err != nil {
return nil, err
}
b.segments = b.psi.type2Charstrings.segments
} else {
return nil, errors.New("sfnt: TODO: load glyf data")
}
// TODO: look at opts to scale / transform / hint the Buffer.segments.
return b.segments, nil
}
// Name returns the name value keyed by the given NameID.
//
// It returns ErrNotFound if there is no value for that key.
func (f *Font) Name(b *Buffer, id NameID) (string, error) {
if b == nil {
b = &Buffer{}
}
const headerSize, entrySize = 6, 12
if f.name.length < headerSize {
return "", errInvalidNameTable
}
buf, err := b.view(&f.src, int(f.name.offset), headerSize)
if err != nil {
return "", err
}
nSubtables := u16(buf[2:])
if f.name.length < headerSize+entrySize*uint32(nSubtables) {
return "", errInvalidNameTable
}
stringOffset := u16(buf[4:])
seen := false
for i, n := 0, int(nSubtables); i < n; i++ {
buf, err := b.view(&f.src, int(f.name.offset)+headerSize+entrySize*i, entrySize)
if err != nil {
return "", err
}
if u16(buf[6:]) != uint16(id) {
continue
}
seen = true
var stringify func([]byte) (string, error)
switch u32(buf) {
default:
continue
case pidMacintosh<<16 | psidMacintoshRoman:
stringify = stringifyMacintosh
case pidWindows<<16 | psidWindowsUCS2:
stringify = stringifyUCS2
}
nameLength := u16(buf[8:])
nameOffset := u16(buf[10:])
buf, err = b.view(&f.src, int(f.name.offset)+int(nameOffset)+int(stringOffset), int(nameLength))
if err != nil {
return "", err
}
return stringify(buf)
}
if seen {
return "", errUnsupportedPlatformEncoding
}
return "", ErrNotFound
}
func stringifyMacintosh(b []byte) (string, error) {
for _, c := range b {
if c >= 0x80 {
// b contains some non-ASCII bytes.
s, _ := charmap.Macintosh.NewDecoder().Bytes(b)
return string(s), nil
}
}
// b contains only ASCII bytes.
return string(b), nil
}
func stringifyUCS2(b []byte) (string, error) {
if len(b)&1 != 0 {
return "", errInvalidUCS2String
}
r := make([]rune, len(b)/2)
for i := range r {
r[i] = rune(u16(b))
b = b[2:]
}
return string(r), nil
}
// Buffer holds re-usable buffers that can reduce the total memory allocation
// of repeated Font method calls.
//
// See the Font type's documentation comment for more details.
type Buffer struct { type Buffer struct {
Segments []Segment
// buf is a byte buffer for when a Font's source is an io.ReaderAt. // buf is a byte buffer for when a Font's source is an io.ReaderAt.
buf []byte buf []byte
// segments holds glyph vector path segments.
segments []Segment
// psi is a PostScript interpreter for when the Font is an OpenType/CFF // psi is a PostScript interpreter for when the Font is an OpenType/CFF
// font. // font.
psi psInterpreter psi psInterpreter
} }
func (b *Buffer) view(src *source, offset, length int) ([]byte, error) {
buf, err := src.view(b.buf, offset, length)
if err != nil {
return nil, err
}
// Only update b.buf if it is safe to re-use buf.
if src.viewBufferWritable() {
b.buf = buf
}
return buf, nil
}
// Segment is a segment of a vector path. // Segment is a segment of a vector path.
type Segment struct { type Segment struct {
Op SegmentOp Op SegmentOp

View File

@ -166,11 +166,11 @@ func TestPostScript(t *testing.T) {
var b Buffer var b Buffer
loop: loop:
for i, want := range wants { for i, want := range wants {
if err := f.LoadGlyph(&b, GlyphIndex(i), nil); err != nil { got, err := f.LoadGlyph(&b, GlyphIndex(i), nil)
if err != nil {
t.Errorf("i=%d: LoadGlyph: %v", i, err) t.Errorf("i=%d: LoadGlyph: %v", i, err)
continue continue
} }
got := b.Segments
if len(got) != len(want) { if len(got) != len(want) {
t.Errorf("i=%d: got %d elements, want %d\noverall:\ngot %v\nwant %v", t.Errorf("i=%d: got %d elements, want %d\noverall:\ngot %v\nwant %v",
i, len(got), len(want), got, want) i, len(got), len(want), got, want)
@ -184,4 +184,14 @@ loop:
} }
} }
} }
if _, err := f.LoadGlyph(nil, 0xffff, nil); err != ErrNotFound {
t.Errorf("LoadGlyph(..., 0xffff, ...):\ngot %v\nwant %v", err, ErrNotFound)
}
name, err := f.Name(nil, NameIDFamily)
if err != nil {
t.Errorf("Name: %v", err)
} else if want := "CFFTest"; name != want {
t.Errorf("Name:\ngot %q\nwant %q", name, want)
}
} }