textencoding

package
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 Go to latest Published: Nov 21, 2024 License: MIT Imports: 17 Imported by: 0

Documentation

Overview

Package textencoding is used for handling text encoding (char code <-> glyph mapping) in unidoc both for reading and outputing PDF contents.

Index

Constants

View Source 
const (
	// MissingCodeRune replaces runes that can't be decoded. .
	MissingCodeRune = '\ufffd' // �

	// MissingCodeString replaces strings that can't be decoded.
	MissingCodeString = string(MissingCodeRune)
)

MissingCodeRune is the rune returned when there is no matching glyph. It was previously '?'.

Variables

This section is empty.

Functions

func ExpandLigatures 

func ExpandLigatures(runes []rune) string

ExpandLigatures returns `runes` as a string with ligatures expanded

func FromFontDifferences 

func FromFontDifferences(diffList *core.PdfObjectArray) (map[CharCode]GlyphName, error)

FromFontDifferences converts `diffList` (a /Differences array from an /Encoding object) to a map representing character code to glyph mappings.

func GlyphToRune 

func GlyphToRune(glyph GlyphName) (rune, bool)

GlyphToRune returns the rune corresponding to glyph `glyph` if there is one. TODO: Can we return a string here? e.g. When we are extracting text, we want to get "ffi" 

rather than 'ffi'. We only need a glyph ➞ rune map when we need to convert back to
glyphs.
We are currently applying RuneToString to the output of functions that call
GlyphToRune. While this gives the same result, it makes the calling code complex and
fragile.

TODO: Can we combine all the tables glyphAliases, glyphlistGlyphToRuneMap, 

texGlyphlistGlyphToStringMap, additionalGlyphlistGlyphToRuneMap and ".notdef"?

func RegisterSimpleEncoding 

func RegisterSimpleEncoding(name string, fnc func() SimpleEncoder)

RegisterSimpleEncoding registers a SimpleEncoder constructer by PDF encoding name.

func RuneToString 

func RuneToString(r rune) string

RuneToString converts rune `r` to a string. It unpacks `ligatures`.

Types

type CMapEncoder 

type CMapEncoder struct {
	// contains filtered or unexported fields
}

CMapEncoder encodes/decodes strings based on CMap mappings.

func NewCMapEncoder 

func NewCMapEncoder(baseName string, codeToCID, cidToUnicode *cmap.CMap) CMapEncoder

NewCMapEncoder returns a new CMapEncoder based on the predefined encoding `baseName`. If `codeToCID` is nil, Identity encoding is assumed. `cidToUnicode` must not be nil.

func (CMapEncoder) CharcodeToRune 

func (enc CMapEncoder) CharcodeToRune(code CharCode) (rune, bool)

CharcodeToRune converts PDF character code `code` to a rune. The bool return flag is true if there was a match, and false otherwise.

func (CMapEncoder) Decode 

func (enc CMapEncoder) Decode(raw []byte) string

Decode converts PDF encoded string to a Go unicode string.

func (CMapEncoder) Encode 

func (enc CMapEncoder) Encode(str string) []byte

Encode converts the Go unicode string to a PDF encoded string.

func (CMapEncoder) RuneToCharcode 

func (enc CMapEncoder) RuneToCharcode(r rune) (CharCode, bool)

RuneToCharcode converts rune `r` to a PDF character code. The bool return flag is true if there was a match, and false otherwise.

func (CMapEncoder) String 

func (enc CMapEncoder) String() string

String returns a string that describes `enc`.

func (CMapEncoder) ToPdfObject 

func (enc CMapEncoder) ToPdfObject() core.PdfObject

ToPdfObject returns a PDF Object that represents the encoding.

type CharCode 

type CharCode uint16

CharCode is a character code used in the specific encoding.

type GID 

type GID uint16

GID is a glyph index.

type GlyphName 

type GlyphName string

GlyphName is a name of a glyph.

func RuneToGlyph 

func RuneToGlyph(r rune) (GlyphName, bool)

RuneToGlyph is the reverse of the table lookups in GlyphToRune.

type IdentityEncoder 

type IdentityEncoder struct {
	// contains filtered or unexported fields
}

IdentityEncoder represents an 2-byte identity encoding. NOTE: In many cases this is just used to encode/decode to glyph index and does not have a unicode 

meaning, except via the ToUnicode maps.

TODO: The use of runes as indicators for glyph indices and not-utf8 runes is not good and confusing. 

Might be better to combine the Identity encoder with a ToUnicode map and keep track of the actual
runes and character codes, CMaps together.

func NewIdentityTextEncoder 

func NewIdentityTextEncoder(baseName string) *IdentityEncoder

NewIdentityTextEncoder returns a new IdentityEncoder based on predefined encoding `baseName` and difference map `differences`.

func (*IdentityEncoder) CharcodeToRune 

func (enc *IdentityEncoder) CharcodeToRune(code CharCode) (rune, bool)

CharcodeToRune converts PDF character code `code` to a rune. The bool return flag is true if there was a match, and false otherwise. TODO: Here the `r` is not necessarily an actual rune but a glyph index (unless both).

func (*IdentityEncoder) Decode 

func (enc *IdentityEncoder) Decode(raw []byte) string

Decode converts PDF encoded string to a Go unicode string.

func (*IdentityEncoder) Encode 

func (enc *IdentityEncoder) Encode(str string) []byte

Encode converts the Go unicode string to a PDF encoded string.

func (*IdentityEncoder) GlyphToRune 

func (enc *IdentityEncoder) GlyphToRune(glyph GlyphName) (rune, bool)

GlyphToRune returns the rune corresponding to glyph name `glyph`. The bool return flag is true if there was a match, and false otherwise.

func (*IdentityEncoder) RegisteredRunes 

func (enc *IdentityEncoder) RegisteredRunes() []rune

RegisteredRunes returns the slice of runes that have been registered as used by the encoder.

func (*IdentityEncoder) RuneToCharcode 

func (enc *IdentityEncoder) RuneToCharcode(r rune) (CharCode, bool)

RuneToCharcode converts rune `r` to a PDF character code. The bool return flag is true if there was a match, and false otherwise. TODO: Here the `r` is an actual rune.

func (*IdentityEncoder) RuneToGlyph 

func (enc *IdentityEncoder) RuneToGlyph(r rune) (GlyphName, bool)

RuneToGlyph returns the glyph name for rune `r`. The bool return flag is true if there was a match, and false otherwise.

func (*IdentityEncoder) String 

func (enc *IdentityEncoder) String() string

String returns a string that describes `enc`.

func (*IdentityEncoder) ToPdfObject 

func (enc *IdentityEncoder) ToPdfObject() core.PdfObject

ToPdfObject returns a nil as it is not truly a PDF object and should not be attempted to store in file.

type SimpleEncoder 

type SimpleEncoder interface {
	TextEncoder
	BaseName() string
	Charcodes() []CharCode
}

SimpleEncoder represents a 1 byte encoding.

func ApplyDifferences 

func ApplyDifferences(base SimpleEncoder, differences map[CharCode]GlyphName) SimpleEncoder

ApplyDifferences modifies or wraps the base encoding and overlays differences over it.

func NewCustomSimpleTextEncoder 

func NewCustomSimpleTextEncoder(encoding, differences map[CharCode]GlyphName) (SimpleEncoder, error)

NewCustomSimpleTextEncoder returns a simpleEncoder based on map `encoding` and difference map `differences`.

func NewMacExpertEncoder 

func NewMacExpertEncoder() SimpleEncoder

NewMacExpertEncoder returns a SimpleEncoder that implements MacExpertEncoding.

func NewMacRomanEncoder 

func NewMacRomanEncoder() SimpleEncoder

NewMacRomanEncoder returns a SimpleEncoder that implements MacRomanEncoding.

func NewPdfDocEncoder 

func NewPdfDocEncoder() SimpleEncoder

NewPdfDocEncoder returns a SimpleEncoder that implements PdfDocEncoding.

func NewSimpleTextEncoder 

func NewSimpleTextEncoder(baseName string, differences map[CharCode]GlyphName) (SimpleEncoder, error)

NewSimpleTextEncoder returns a simpleEncoder based on predefined encoding `baseName` and difference map `differences`.

func NewStandardEncoder 

func NewStandardEncoder() SimpleEncoder

NewStandardEncoder returns a SimpleEncoder that implements StandardEncoding.

func NewSymbolEncoder 

func NewSymbolEncoder() SimpleEncoder

NewSymbolEncoder returns a SimpleEncoder that implements SymbolEncoding.

func NewWinAnsiEncoder 

func NewWinAnsiEncoder() SimpleEncoder

NewWinAnsiEncoder returns a simpleEncoder that implements WinAnsiEncoding.

func NewZapfDingbatsEncoder 

func NewZapfDingbatsEncoder() SimpleEncoder

NewZapfDingbatsEncoder returns a SimpleEncoder that implements ZapfDingbatsEncoding.

type TextEncoder 

type TextEncoder interface {
	// String returns a string that describes the TextEncoder instance.
	String() string

	// Encode converts the Go unicode string to a PDF encoded string.
	Encode(str string) []byte

	// Decode converts PDF encoded string to a Go unicode string.
	Decode(raw []byte) string

	// RuneToCharcode returns the PDF character code corresponding to rune `r`.
	// The bool return flag is true if there was a match, and false otherwise.
	// This is usually implemented as RuneToGlyph->GlyphToCharcode
	RuneToCharcode(r rune) (CharCode, bool)

	// CharcodeToRune returns the rune corresponding to character code `code`.
	// The bool return flag is true if there was a match, and false otherwise.
	// This is usually implemented as CharcodeToGlyph->GlyphToRune
	CharcodeToRune(code CharCode) (rune, bool)

	// ToPdfObject returns a PDF Object that represents the encoding.
	ToPdfObject() core.PdfObject
}

TextEncoder defines the common methods that a text encoder implementation must have in UniDoc.

type TrueTypeFontEncoder 

type TrueTypeFontEncoder struct {
	// contains filtered or unexported fields
}

TrueTypeFontEncoder handles text encoding for composite TrueType fonts. It performs mapping between character ids and glyph ids. It has a preloaded rune (unicode code point) to glyph index map that has been loaded from a font. Corresponds to Identity-H CMap and Identity encoding.

func NewTrueTypeFontEncoder 

func NewTrueTypeFontEncoder(runeToGIDMap map[rune]GID) *TrueTypeFontEncoder

NewTrueTypeFontEncoder creates a new text encoder for TTF fonts with a runeToGlyphIndexMap that has been preloaded from the font file. The new instance is preloaded with a CMapIdentityH (Identity-H) CMap which maps 2-byte charcodes to CIDs (glyph index).

func (*TrueTypeFontEncoder) CharcodeToRune 

func (enc *TrueTypeFontEncoder) CharcodeToRune(code CharCode) (rune, bool)

CharcodeToRune converts PDF character code `code` to a rune. The bool return flag is true if there was a match, and false otherwise.

func (*TrueTypeFontEncoder) Decode 

func (enc *TrueTypeFontEncoder) Decode(raw []byte) string

Decode converts PDF encoded string to a Go unicode string.

func (*TrueTypeFontEncoder) Encode 

func (enc *TrueTypeFontEncoder) Encode(str string) []byte

Encode converts the Go unicode string to a PDF encoded string.

func (*TrueTypeFontEncoder) GlyphToCharcode 

func (enc *TrueTypeFontEncoder) GlyphToCharcode(glyph GlyphName) (CharCode, bool)

GlyphToCharcode returns character code matching the glyph name `glyph`. The bool return flag is true if there was a match, and false otherwise.

func (*TrueTypeFontEncoder) RegisteredRunes 

func (enc *TrueTypeFontEncoder) RegisteredRunes() []rune

RegisteredRunes returns the slice of runes that have been registered as used by the encoder.

func (*TrueTypeFontEncoder) RuneToCharcode 

func (enc *TrueTypeFontEncoder) RuneToCharcode(r rune) (CharCode, bool)

RuneToCharcode converts rune `r` to a PDF character code. The bool return flag is true if there was a match, and false otherwise.

func (*TrueTypeFontEncoder) String 

func (enc *TrueTypeFontEncoder) String() string

String returns a string that describes `enc`.

func (*TrueTypeFontEncoder) SubsetRegistered 

func (enc *TrueTypeFontEncoder) SubsetRegistered()

SubsetRegistered subsets `enc` to only registered runes (that have been registered via encoding). NOTE: Make sure to call this soon before writing (once all needed runes have been registered).

func (*TrueTypeFontEncoder) ToPdfObject 

func (enc *TrueTypeFontEncoder) ToPdfObject() core.PdfObject

ToPdfObject returns a nil as it is not truly a PDF object and should not be attempted to store in file.

type UTF16Encoder 

type UTF16Encoder struct {
	// contains filtered or unexported fields
}

UTF16Encoder represents UTF-16 encoding.

func NewUTF16TextEncoder 

func NewUTF16TextEncoder(baseName string) UTF16Encoder

NewUTF16TextEncoder returns a new UTF16Encoder based on the predefined encoding `baseName`.

func (UTF16Encoder) CharcodeToRune 

func (enc UTF16Encoder) CharcodeToRune(code CharCode) (rune, bool)

CharcodeToRune converts PDF character code `code` to a rune. The bool return flag is true if there was a match, and false otherwise.

func (UTF16Encoder) Decode 

func (enc UTF16Encoder) Decode(raw []byte) string

Decode converts PDF encoded string to a Go unicode string.

func (UTF16Encoder) Encode 

func (enc UTF16Encoder) Encode(str string) []byte

Encode converts the Go unicode string to a PDF encoded string.

func (UTF16Encoder) RuneToCharcode 

func (enc UTF16Encoder) RuneToCharcode(r rune) (CharCode, bool)

RuneToCharcode converts rune `r` to a PDF character code. The bool return flag is true if there was a match, and false otherwise.

func (UTF16Encoder) String 

func (enc UTF16Encoder) String() string

String returns a string that describes `enc`.

func (UTF16Encoder) ToPdfObject 

func (enc UTF16Encoder) ToPdfObject() core.PdfObject

ToPdfObject returns a PDF Object that represents the encoding.

Source Files

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