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Fix CMap generation and serialization for composite fonts (#344)

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* Fix CMap charcode mapping serialization

* Improve CMap generation in the NewCompositePdfFontFromTTF function
This commit is contained in:
Adrian-George Bostan 2020-05-08 03:15:09 +03:00 committed by GitHub
parent f60e313cdb
commit aef6e5e976
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 32 additions and 12 deletions
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32
internal/cmap/cmap.go
View File

@ -459,25 +459,35 @@ func (cmap *CMap) toBfData() string {
}
sort.Slice(codes, func(i, j int) bool { return codes[i] < codes[j] })
// charRanges is a list of the contiguous character code ranges in `codes`.
// Generate CMap character code ranges.
// The code ranges are intervals of consecutive charcodes (c1 = c0 + 1)
// mapping to consecutive runes.
// Start with a range consisting of the current character code for both ends
// of the interval. Check if the next character is consecutive to the upper
// end of the interval and if it maps to the next rune. If so, increase the
// interval to the right. Otherwise, append the current range to the
// character ranges slice and start over. Continue the process until all
// character codes have been mapped to code ranges.
var charRanges []charRange
c0, c1 := codes[0], codes[0]+1
currCharRange := charRange{codes[0], codes[0]}
prevRune := cmap.codeToUnicode[codes[0]]
for _, c := range codes[1:] {
if c != c1 {
charRanges = append(charRanges, charRange{c0, c1})
c0 = c
currRune := cmap.codeToUnicode[c]
if c == currCharRange.code1+1 && currRune == prevRune+1 {
currCharRange.code1 = c
} else {
charRanges = append(charRanges, currCharRange)
currCharRange.code0, currCharRange.code1 = c, c
}
c1 = c + 1
}
if c1 > c0 {
charRanges = append(charRanges, charRange{c0, c1})
prevRune = currRune
}
charRanges = append(charRanges, currCharRange)
// fbChars is a list of single character ranges. fbRanges is a list of multiple character ranges.
var fbChars []CharCode
var fbRanges []fbRange
for _, cr := range charRanges {
if cr.code0+1 == cr.code1 {
if cr.code0 == cr.code1 {
fbChars = append(fbChars, cr.code0)
} else {
fbRanges = append(fbRanges, fbRange{
@ -512,7 +522,7 @@ func (cmap *CMap) toBfData() string {
for j := 0; j < n; j++ {
rng := fbRanges[i*maxBfEntries+j]
r := rng.r0
lines = append(lines, fmt.Sprintf("<%04x><%04x> <%04x>", rng.code0, rng.code1-1, r))
lines = append(lines, fmt.Sprintf("<%04x><%04x> <%04x>", rng.code0, rng.code1, r))
}
lines = append(lines, "endbfrange")
}

12
model/font_composite.go
View File

@ -830,7 +830,17 @@ func NewCompositePdfFontFromTTF(r io.ReadSeeker) (*PdfFont, error) {
encoder: ttf.NewEncoder(),
}
type0.toUnicodeCmap = ttf.MakeToUnicode()
// Generate CMap for the Type 0 font, which is the inverse of ttf.Chars.
if len(ttf.Chars) > 0 {
codeToUnicode := make(map[cmap.CharCode]rune, len(ttf.Chars))
for r, gid := range ttf.Chars {
cid := cmap.CharCode(gid)
if rn, ok := codeToUnicode[cid]; !ok || (ok && rn > r) {
codeToUnicode[cid] = r
}
}
type0.toUnicodeCmap = cmap.NewToUnicodeCMap(codeToUnicode)
}
// Build Font.
font := PdfFont{