[PDF] Add a ToUnicode mapping for fonts.
This makes text in PDFs searchable and copy&paste-able.
Code from arthurhsu@chromium.org. Original review: http://codereview.appspot.com/4428082/
Review URL: http://codereview.appspot.com/4525042
git-svn-id: http://skia.googlecode.com/svn/trunk@1280 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/pdf/SkPDFFont.cpp b/src/pdf/SkPDFFont.cpp
old mode 100644
new mode 100755
index acfe41e..cc249ca
--- a/src/pdf/SkPDFFont.cpp
+++ b/src/pdf/SkPDFFont.cpp
@@ -319,6 +319,92 @@
} // namespace
+static void append_tounicode_header(SkDynamicMemoryWStream* cmap) {
+ // 12 dict begin: 12 is an Adobe-suggested value. Shall not change.
+ // It's there to prevent old version Adobe Readers from malfunctioning.
+ const char* kHeader =
+ "/CIDInit /ProcSet findresource begin\n"
+ "12 dict begin\n"
+ "begincmap\n";
+ cmap->writeText(kHeader);
+
+ // The /CIDSystemInfo must be consistent to the one in
+ // SkPDFFont::populateCIDFont().
+ // We can not pass over the system info object here because the format is
+ // different. This is not a reference object.
+ const char* kSysInfo =
+ "/CIDSystemInfo\n"
+ "<< /Registry (Adobe)\n"
+ "/Ordering (UCS)\n"
+ "/Supplement 0\n"
+ ">> def\n";
+ cmap->writeText(kSysInfo);
+
+ // The CMapName must be consistent to /CIDSystemInfo above.
+ // /CMapType 2 means ToUnicode.
+ // We specify codespacerange from 0x0000 to 0xFFFF because we convert our
+ // code table from unsigned short (16-bits). Codespace range just tells the
+ // PDF processor the valid range. It does not matter whether a complete
+ // mapping is provided or not.
+ const char* kTypeInfo =
+ "/CMapName /Adobe-Identity-UCS def\n"
+ "/CMapType 2 def\n"
+ "1 begincodespacerange\n"
+ "<0000> <FFFF>\n"
+ "endcodespacerange\n";
+ cmap->writeText(kTypeInfo);
+}
+
+static void append_cmap_bfchar_table(uint16_t* glyph_id, SkUnichar* unicode,
+ size_t count,
+ SkDynamicMemoryWStream* cmap) {
+ cmap->writeDecAsText(count);
+ cmap->writeText(" beginbfchar\n");
+ for (size_t i = 0; i < count; ++i) {
+ cmap->writeText("<");
+ cmap->writeHexAsText(glyph_id[i], 4);
+ cmap->writeText("> <");
+ cmap->writeHexAsText(unicode[i], 4);
+ cmap->writeText(">\n");
+ }
+ cmap->writeText("endbfchar\n");
+}
+
+static void append_cmap_footer(SkDynamicMemoryWStream* cmap) {
+ const char* kFooter =
+ "endcmap\n"
+ "CMapName currentdict /CMap defineresource pop\n"
+ "end\n"
+ "end";
+ cmap->writeText(kFooter);
+}
+
+// Generate <bfchar> table according to PDF spec 1.4 and Adobe Technote 5014.
+static void append_cmap_bfchar_sections(
+ const SkTDArray<SkUnichar>& glyphUnicode,
+ SkDynamicMemoryWStream* cmap) {
+ // PDF spec defines that every bf* list can have at most 100 entries.
+ const size_t kMaxEntries = 100;
+ uint16_t glyphId[kMaxEntries];
+ SkUnichar unicode[kMaxEntries];
+ size_t index = 0;
+ for (int i = 0; i < glyphUnicode.count(); i++) {
+ if (glyphUnicode[i]) {
+ glyphId[index] = i;
+ unicode[index] = glyphUnicode[i];
+ ++index;
+ }
+ if (index == kMaxEntries) {
+ append_cmap_bfchar_table(glyphId, unicode, index, cmap);
+ index = 0;
+ }
+ }
+
+ if (index) {
+ append_cmap_bfchar_table(glyphId, unicode, index, cmap);
+ }
+}
+
/* Font subset design: It would be nice to be able to subset fonts
* (particularly type 3 fonts), but it's a lot of work and not a priority.
*
@@ -404,9 +490,13 @@
fontInfo = relatedFont->fFontInfo;
fontDescriptor = relatedFont->fDescriptor.get();
} else {
- fontInfo = SkFontHost::GetAdvancedTypefaceMetrics(fontID, SkTBitOr(
- SkAdvancedTypefaceMetrics::kHAdvance_PerGlyphInfo,
- SkAdvancedTypefaceMetrics::kGlyphNames_PerGlyphInfo));
+ SkAdvancedTypefaceMetrics::PerGlyphInfo info;
+ info = SkAdvancedTypefaceMetrics::kHAdvance_PerGlyphInfo;
+ info = SkTBitOr<SkAdvancedTypefaceMetrics::PerGlyphInfo>(
+ info, SkAdvancedTypefaceMetrics::kGlyphNames_PerGlyphInfo);
+ info = SkTBitOr<SkAdvancedTypefaceMetrics::PerGlyphInfo>(
+ info, SkAdvancedTypefaceMetrics::kToUnicode_PerGlyphInfo);
+ fontInfo = SkFontHost::GetAdvancedTypefaceMetrics(fontID, info);
SkSafeUnref(fontInfo.get()); // SkRefPtr and Get both took a reference.
}
@@ -497,7 +587,6 @@
}
void SkPDFFont::populateType0Font() {
- // TODO(vandebo) add a ToUnicode mapping.
fMultiByteGlyphs = true;
insert("Subtype", new SkPDFName("Type0"))->unref();
@@ -512,6 +601,26 @@
new SkPDFFont(fFontInfo.get(), fTypeface.get(), 1, true, NULL));
descendantFonts->append(new SkPDFObjRef(fResources.top()))->unref();
insert("DescendantFonts", descendantFonts.get());
+
+ populateToUnicodeTable();
+}
+
+void SkPDFFont::populateToUnicodeTable() {
+ if (fFontInfo.get() == NULL ||
+ fFontInfo->fGlyphToUnicode.begin() == NULL) {
+ return;
+ }
+
+ SkDynamicMemoryWStream cmap;
+ append_tounicode_header(&cmap);
+ append_cmap_bfchar_sections(fFontInfo->fGlyphToUnicode, &cmap);
+ append_cmap_footer(&cmap);
+ SkRefPtr<SkMemoryStream> cmapStream = new SkMemoryStream();
+ cmapStream->unref(); // SkRefPtr and new took a reference.
+ cmapStream->setMemoryOwned(cmap.detach(), cmap.getOffset());
+ SkRefPtr<SkPDFStream> pdfCmap = new SkPDFStream(cmapStream.get());
+ fResources.push(pdfCmap.get()); // Pass reference from new.
+ insert("ToUnicode", new SkPDFObjRef(pdfCmap.get()))->unref();
}
void SkPDFFont::populateCIDFont() {
@@ -522,6 +631,7 @@
insert("Subtype", new SkPDFName("CIDFontType0"))->unref();
} else if (fFontInfo->fType == SkAdvancedTypefaceMetrics::kTrueType_Font) {
insert("Subtype", new SkPDFName("CIDFontType2"))->unref();
+ insert("CIDToGIDMap", new SkPDFName("Identity"))->unref();
} else {
SkASSERT(false);
}
@@ -697,9 +807,12 @@
insert("FirstChar", new SkPDFInt(fFirstGlyphID))->unref();
insert("LastChar", new SkPDFInt(fLastGlyphID))->unref();
insert("Widths", widthArray.get());
+ insert("CIDToGIDMap", new SkPDFName("Identity"))->unref();
if (fFontInfo && fFontInfo->fLastGlyphID <= 255)
fFontInfo = NULL;
+
+ populateToUnicodeTable();
}
bool SkPDFFont::addFontDescriptor(int16_t defaultWidth) {
diff --git a/src/ports/SkFontHost_FreeType.cpp b/src/ports/SkFontHost_FreeType.cpp
index 5ed66c8..b3cc783 100644
--- a/src/ports/SkFontHost_FreeType.cpp
+++ b/src/ports/SkFontHost_FreeType.cpp
@@ -339,6 +339,56 @@
return true;
}
+static void populate_glyph_to_unicode(FT_Face& face,
+ SkTDArray<SkUnichar>* glyphToUnicode) {
+ // Check and see if we have Unicode cmaps.
+ for (int i = 0; i < face->num_charmaps; ++i) {
+ // CMaps known to support Unicode:
+ // Platform ID Encoding ID Name
+ // ----------- ----------- -----------------------------------
+ // 0 0,1 Apple Unicode
+ // 0 3 Apple Unicode 2.0 (preferred)
+ // 3 1 Microsoft Unicode UCS-2
+ // 3 10 Microsoft Unicode UCS-4 (preferred)
+ //
+ // See Apple TrueType Reference Manual
+ // http://developer.apple.com/fonts/TTRefMan/RM06/Chap6cmap.html
+ // http://developer.apple.com/fonts/TTRefMan/RM06/Chap6name.html#ID
+ // Microsoft OpenType Specification
+ // http://www.microsoft.com/typography/otspec/cmap.htm
+
+ FT_UShort platformId = face->charmaps[i]->platform_id;
+ FT_UShort encodingId = face->charmaps[i]->encoding_id;
+
+ if (platformId != 0 && platformId != 3) {
+ continue;
+ }
+ if (platformId == 3 && encodingId != 1 && encodingId != 10) {
+ continue;
+ }
+ bool preferredMap = ((platformId == 3 && encodingId == 10) ||
+ (platformId == 0 && encodingId == 3));
+
+ FT_Set_Charmap(face, face->charmaps[i]);
+ if (glyphToUnicode->isEmpty()) {
+ glyphToUnicode->setCount(face->num_glyphs);
+ memset(glyphToUnicode->begin(), 0,
+ sizeof(SkUnichar) * face->num_glyphs);
+ }
+
+ // Iterate through each cmap entry.
+ FT_UInt glyphIndex;
+ for (SkUnichar charCode = FT_Get_First_Char(face, &glyphIndex);
+ glyphIndex != 0;
+ charCode = FT_Get_Next_Char(face, charCode, &glyphIndex)) {
+ if (charCode &&
+ ((*glyphToUnicode)[glyphIndex] == 0 || preferredMap)) {
+ (*glyphToUnicode)[glyphIndex] = charCode;
+ }
+ }
+ }
+}
+
// static
SkAdvancedTypefaceMetrics* SkFontHost::GetAdvancedTypefaceMetrics(
uint32_t fontID,
@@ -509,6 +559,12 @@
}
}
+ if (perGlyphInfo & SkAdvancedTypefaceMetrics::kToUnicode_PerGlyphInfo &&
+ info->fType != SkAdvancedTypefaceMetrics::kType1_Font &&
+ face->num_charmaps) {
+ populate_glyph_to_unicode(face, &(info->fGlyphToUnicode));
+ }
+
if (!canEmbed(face))
info->fType = SkAdvancedTypefaceMetrics::kNotEmbeddable_Font;
diff --git a/src/ports/SkFontHost_win.cpp b/src/ports/SkFontHost_win.cpp
old mode 100644
new mode 100755
index bc66010..fd5b929
--- a/src/ports/SkFontHost_win.cpp
+++ b/src/ports/SkFontHost_win.cpp
@@ -194,6 +194,58 @@
}
}
+// Construct Glyph to Unicode table.
+// Unicode code points that require conjugate pairs in utf16 are not
+// supported.
+// TODO(arthurhsu): Add support for conjugate pairs. It looks like that may
+// require parsing the TTF cmap table (platform 4, encoding 12) directly instead
+// of calling GetFontUnicodeRange().
+static void populate_glyph_to_unicode(HDC fontHdc, const unsigned glyphCount,
+ SkTDArray<SkUnichar>* glyphToUnicode) {
+ DWORD glyphSetBufferSize = GetFontUnicodeRanges(fontHdc, NULL);
+ if (!glyphSetBufferSize) {
+ return;
+ }
+
+ SkAutoTDeleteArray<BYTE> glyphSetBuffer(new BYTE[glyphSetBufferSize]);
+ GLYPHSET* glyphSet =
+ reinterpret_cast<LPGLYPHSET>(glyphSetBuffer.get());
+ if (GetFontUnicodeRanges(fontHdc, glyphSet) != glyphSetBufferSize) {
+ return;
+ }
+
+ glyphToUnicode->setCount(glyphCount);
+ memset(glyphToUnicode->begin(), 0, glyphCount * sizeof(SkUnichar));
+ for (DWORD i = 0; i < glyphSet->cRanges; ++i) {
+ // There is no guarantee that within a Unicode range, the corresponding
+ // glyph id in a font file are continuous. So, even if we have ranges,
+ // we can't just use the first and last entry of the range to compute
+ // result. We need to enumerate them one by one.
+ int count = glyphSet->ranges[i].cGlyphs;
+ SkAutoTArray<WCHAR> chars(count + 1);
+ chars[count] = 0; // termintate string
+ SkAutoTArray<WORD> glyph(count);
+ for (USHORT j = 0; j < count; ++j) {
+ chars[j] = glyphSet->ranges[i].wcLow + j;
+ }
+ GetGlyphIndicesW(fontHdc, chars.get(), count, glyph.get(),
+ GGI_MARK_NONEXISTING_GLYPHS);
+ // If the glyph ID is valid, and the glyph is not mapped, then we will
+ // fill in the char id into the vector. If the glyph is mapped already,
+ // skip it.
+ // TODO(arthurhsu): better improve this. e.g. Get all used char ids from
+ // font cache, then generate this mapping table from there. It's
+ // unlikely to have collisions since glyph reuse happens mostly for
+ // different Unicode pages.
+ for (USHORT j = 0; j < count; ++j) {
+ if (glyph[j] != 0xffff && glyph[j] < glyphCount &&
+ (*glyphToUnicode)[glyph[j]] == 0) {
+ (*glyphToUnicode)[glyph[j]] = chars[j];
+ }
+ }
+ }
+}
+
//////////////////////////////////////////////////////////////////////////////////////////////
class SkScalerContext_Windows : public SkScalerContext {
@@ -649,6 +701,10 @@
info->fFontName.set(lf.lfFaceName);
#endif
+ if (perGlyphInfo & SkAdvancedTypefaceMetrics::kToUnicode_PerGlyphInfo) {
+ populate_glyph_to_unicode(hdc, glyphCount, &(info->fGlyphToUnicode));
+ }
+
if (otm.otmTextMetrics.tmPitchAndFamily & TMPF_TRUETYPE) {
info->fType = SkAdvancedTypefaceMetrics::kTrueType_Font;
} else {