SkPDFFont.cpp File Reference

#include "src/pdf/SkPDFFont.h"
#include "include/core/SkBitmap.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkData.h"
#include "include/core/SkDrawable.h"
#include "include/core/SkFont.h"
#include "include/core/SkFontMetrics.h"
#include "include/core/SkFontStyle.h"
#include "include/core/SkFontTypes.h"
#include "include/core/SkImage.h"
#include "include/core/SkImageInfo.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPath.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "include/core/SkStream.h"
#include "include/core/SkString.h"
#include "include/core/SkSurfaceProps.h"
#include "include/private/base/SkDebug.h"
#include "include/private/base/SkTPin.h"
#include "include/private/base/SkTo.h"
#include "src/base/SkBitmaskEnum.h"
#include "src/base/SkUTF.h"
#include "src/core/SkDevice.h"
#include "src/core/SkGlyph.h"
#include "src/core/SkMask.h"
#include "src/core/SkScalerContext.h"
#include "src/core/SkStrike.h"
#include "src/core/SkStrikeSpec.h"
#include "src/core/SkTHash.h"
#include "src/pdf/SkPDFBitmap.h"
#include "src/pdf/SkPDFDevice.h"
#include "src/pdf/SkPDFDocumentPriv.h"
#include "src/pdf/SkPDFFormXObject.h"
#include "src/pdf/SkPDFMakeCIDGlyphWidthsArray.h"
#include "src/pdf/SkPDFMakeToUnicodeCmap.h"
#include "src/pdf/SkPDFSubsetFont.h"
#include "src/pdf/SkPDFType1Font.h"
#include "src/pdf/SkPDFUtils.h"
#include <limits.h>
#include <algorithm>
#include <cstddef>
#include <initializer_list>
#include <memory>
#include <utility>

Go to the source code of this file.

Classes
struct	ImageAndOffset

Functions
static bool	can_embed (const SkAdvancedTypefaceMetrics &metrics)
static bool	can_subset (const SkAdvancedTypefaceMetrics &metrics)
static SkGlyphID	first_nonzero_glyph_for_single_byte_encoding (SkGlyphID gid)
static void	emit_subset_type0 (const SkPDFFont &font, SkPDFDocument *doc)
static ImageAndOffset	to_image (SkGlyphID gid, SkBulkGlyphMetricsAndImages *smallGlyphs)
static SkPDFIndirectReference	type3_descriptor (SkPDFDocument *doc, const SkTypeface *typeface, SkScalar xHeight)
SkStrikeSpec	make_small_strike (const SkTypeface &typeface)
static void	emit_subset_type3 (const SkPDFFont &pdfFont, SkPDFDocument *doc)

Variables
static constexpr float	kBitmapFontSize = 64

Function Documentation

can_embed()

static bool can_embed ( const SkAdvancedTypefaceMetrics &  metrics )

static

Definition at line 110 of file SkPDFFont.cpp.

                                                                {
    return !SkToBool(metrics.fFlags & SkAdvancedTypefaceMetrics::kNotEmbeddable_FontFlag);
}

can_subset()

static bool can_subset ( const SkAdvancedTypefaceMetrics &  metrics )

static

Definition at line 114 of file SkPDFFont.cpp.

                                                                 {
    return !SkToBool(metrics.fFlags & SkAdvancedTypefaceMetrics::kNotSubsettable_FontFlag);
}

emit_subset_type0()

static void emit_subset_type0 ( const SkPDFFont &  font, SkPDFDocument *  doc  )

static

Definition at line 295 of file SkPDFFont.cpp.

                                                                         {
    const SkAdvancedTypefaceMetrics* metricsPtr = SkPDFFont::GetMetrics(font.typeface(), doc);
    SkASSERT(metricsPtr);
    if (!metricsPtr) {
        return;
    }
    const SkAdvancedTypefaceMetrics& metrics = *metricsPtr;
    SkASSERT(can_embed(metrics));
    SkAdvancedTypefaceMetrics::FontType type = font.getType();
    SkTypeface* face = font.typeface();
    SkASSERT(face);
 
    auto descriptor = SkPDFMakeDict("FontDescriptor");
    uint16_t emSize = SkToU16(font.typeface()->getUnitsPerEm());
    SkPDFFont::PopulateCommonFontDescriptor(descriptor.get(), metrics, emSize, 0);
 
    int ttcIndex;
    std::unique_ptr<SkStreamAsset> fontAsset = face->openStream(&ttcIndex);
    size_t fontSize = fontAsset ? fontAsset->getLength() : 0;
    if (0 == fontSize) {
        SkDebugf("Error: (SkTypeface)(%p)::openStream() returned "
                 "empty stream (%p) when identified as kType1CID_Font "
                 "or kTrueType_Font.\n", face, fontAsset.get());
    } else if (type == SkAdvancedTypefaceMetrics::kTrueType_Font ||
               type == SkAdvancedTypefaceMetrics::kCFF_Font)
    {
        sk_sp<SkData> subsetFontData;
        if (can_subset(metrics)) {
            SkASSERT(font.firstGlyphID() == 1);
            subsetFontData = SkPDFSubsetFont(*face, font.glyphUsage());
        }
        std::unique_ptr<SkStreamAsset> subsetFontAsset;
        if (subsetFontData) {
            subsetFontAsset = SkMemoryStream::Make(std::move(subsetFontData));
        } else {
            // If subsetting fails, fall back to original font data.
            subsetFontAsset = std::move(fontAsset);
        }
        std::unique_ptr<SkPDFDict> streamDict = SkPDFMakeDict();
        streamDict->insertInt("Length1", subsetFontAsset->getLength());
        const char* fontFileKey;
        if (type == SkAdvancedTypefaceMetrics::kTrueType_Font) {
            fontFileKey = "FontFile2";
        } else {
            streamDict->insertName("Subtype", "OpenType");
            fontFileKey = "FontFile3";
        }
        descriptor->insertRef(fontFileKey,
                              SkPDFStreamOut(std::move(streamDict), std::move(subsetFontAsset),
                                             doc, SkPDFSteamCompressionEnabled::Yes));
    } else if (type == SkAdvancedTypefaceMetrics::kType1CID_Font) {
        std::unique_ptr<SkPDFDict> streamDict = SkPDFMakeDict();
        streamDict->insertName("Subtype", "CIDFontType0C");
        descriptor->insertRef("FontFile3",
                              SkPDFStreamOut(std::move(streamDict), std::move(fontAsset),
                                             doc, SkPDFSteamCompressionEnabled::Yes));
    } else {
        SkASSERT(false);
    }
 
    auto newCIDFont = SkPDFMakeDict("Font");
    newCIDFont->insertRef("FontDescriptor", doc->emit(*descriptor));
    newCIDFont->insertName("BaseFont", metrics.fPostScriptName);
 
    switch (type) {
        case SkAdvancedTypefaceMetrics::kType1CID_Font:
            newCIDFont->insertName("Subtype", "CIDFontType0");
            break;
        case SkAdvancedTypefaceMetrics::kCFF_Font:
            newCIDFont->insertName("Subtype", "CIDFontType0");
            newCIDFont->insertName("CIDToGIDMap", "Identity");
            break;
        case SkAdvancedTypefaceMetrics::kTrueType_Font:
            newCIDFont->insertName("Subtype", "CIDFontType2");
            newCIDFont->insertName("CIDToGIDMap", "Identity");
            break;
        default:
            SkASSERT(false);
    }
    auto sysInfo = SkPDFMakeDict();
    // These are actually ASCII strings.
    sysInfo->insertByteString("Registry", "Adobe");
    sysInfo->insertByteString("Ordering", "Identity");
    sysInfo->insertInt("Supplement", 0);
    newCIDFont->insertObject("CIDSystemInfo", std::move(sysInfo));
 
    // Unfortunately, poppler enforces DW (default width) must be an integer.
    int32_t defaultWidth = 0;
    {
        std::unique_ptr<SkPDFArray> widths = SkPDFMakeCIDGlyphWidthsArray(
                *face, font.glyphUsage(), &defaultWidth);
        if (widths && widths->size() > 0) {
            newCIDFont->insertObject("W", std::move(widths));
        }
        newCIDFont->insertInt("DW", defaultWidth);
    }
 
    ////////////////////////////////////////////////////////////////////////////
 
    SkPDFDict fontDict("Font");
    fontDict.insertName("Subtype", "Type0");
    fontDict.insertName("BaseFont", metrics.fPostScriptName);
    fontDict.insertName("Encoding", "Identity-H");
    auto descendantFonts = SkPDFMakeArray();
    descendantFonts->appendRef(doc->emit(*newCIDFont));
    fontDict.insertObject("DescendantFonts", std::move(descendantFonts));
 
    const std::vector<SkUnichar>& glyphToUnicode =
        SkPDFFont::GetUnicodeMap(font.typeface(), doc);
    SkASSERT(SkToSizeT(font.typeface()->countGlyphs()) == glyphToUnicode.size());
    std::unique_ptr<SkStreamAsset> toUnicode =
            SkPDFMakeToUnicodeCmap(glyphToUnicode.data(),
                                   &font.glyphUsage(),
                                   font.multiByteGlyphs(),
                                   font.firstGlyphID(),
                                   font.lastGlyphID());
    fontDict.insertRef("ToUnicode", SkPDFStreamOut(nullptr, std::move(toUnicode), doc));
 
    doc->emit(fontDict, font.indirectReference());
}

emit_subset_type3()

static void emit_subset_type3 ( const SkPDFFont &  pdfFont, SkPDFDocument *  doc  )

static

Definition at line 568 of file SkPDFFont.cpp.

                                                                            {
    SkTypeface* typeface = pdfFont.typeface();
    SkGlyphID firstGlyphID = pdfFont.firstGlyphID();
    SkGlyphID lastGlyphID = pdfFont.lastGlyphID();
    const SkPDFGlyphUse& subset = pdfFont.glyphUsage();
    SkASSERT(lastGlyphID >= firstGlyphID);
    // Remove unused glyphs at the end of the range.
    // Keep the lastGlyphID >= firstGlyphID invariant true.
    while (lastGlyphID > firstGlyphID && !subset.has(lastGlyphID)) {
        --lastGlyphID;
    }
    int unitsPerEm;
    SkStrikeSpec strikeSpec = SkStrikeSpec::MakePDFVector(*typeface, &unitsPerEm);
    auto strike = strikeSpec.findOrCreateStrike();
    SkASSERT(strike);
    SkScalar emSize = (SkScalar)unitsPerEm;
    SkScalar xHeight = strike->getFontMetrics().fXHeight;
    SkBulkGlyphMetricsAndPaths metricsAndPaths((sk_sp<SkStrike>(strike)));
    SkBulkGlyphMetricsAndDrawables metricsAndDrawables(std::move(strike));
 
    SkStrikeSpec strikeSpecSmall = kBitmapFontSize > 0 ? make_small_strike(*typeface)
                                                       : strikeSpec;
 
    SkBulkGlyphMetricsAndImages smallGlyphs(strikeSpecSmall);
    float bitmapScale = kBitmapFontSize > 0 ? emSize / kBitmapFontSize : 1.0f;
 
    SkPDFDict font("Font");
    font.insertName("Subtype", "Type3");
    // Flip about the x-axis and scale by 1/emSize.
    SkMatrix fontMatrix;
    fontMatrix.setScale(SkScalarInvert(emSize), -SkScalarInvert(emSize));
    font.insertObject("FontMatrix", SkPDFUtils::MatrixToArray(fontMatrix));
 
    auto charProcs = SkPDFMakeDict();
    auto encoding = SkPDFMakeDict("Encoding");
 
    auto encDiffs = SkPDFMakeArray();
    // length(firstGlyphID .. lastGlyphID) ==  lastGlyphID - firstGlyphID + 1
    // plus 1 for glyph 0;
    SkASSERT(firstGlyphID > 0);
    SkASSERT(lastGlyphID >= firstGlyphID);
    int glyphCount = lastGlyphID - firstGlyphID + 2;
    // one other entry for the index of first glyph.
    encDiffs->reserve(glyphCount + 1);
    encDiffs->appendInt(0);  // index of first glyph
 
    auto widthArray = SkPDFMakeArray();
    widthArray->reserve(glyphCount);
 
    SkIRect bbox = SkIRect::MakeEmpty();
 
    std::vector<std::pair<SkGlyphID, SkPDFIndirectReference>> imageGlyphs;
    for (SkGlyphID gID : SingleByteGlyphIdIterator(firstGlyphID, lastGlyphID)) {
        bool skipGlyph = gID != 0 && !subset.has(gID);
        SkString characterName;
        SkScalar advance = 0.0f;
        SkIRect glyphBBox;
        if (skipGlyph) {
            characterName.set("g0");
        } else {
            characterName.printf("g%X", gID);
            const SkGlyph* pathGlyph = metricsAndPaths.glyph(gID);
            const SkGlyph* drawableGlyph = metricsAndDrawables.glyph(gID);
            advance = pathGlyph->advanceX();
            glyphBBox = pathGlyph->iRect();
            bbox.join(glyphBBox);
            const SkPath* path = pathGlyph->path();
            SkDrawable* drawable = drawableGlyph->drawable();
            SkDynamicMemoryWStream content;
            if (drawable && !drawable->getBounds().isEmpty()) {
                sk_sp<SkPDFDevice> glyphDevice = sk_make_sp<SkPDFDevice>(glyphBBox.size(), doc);
                SkCanvas canvas(glyphDevice);
                canvas.translate(-glyphBBox.fLeft, -glyphBBox.fTop);
                canvas.drawDrawable(drawable);
                SkPDFIndirectReference xobject = SkPDFMakeFormXObject(
                        doc, glyphDevice->content(),
                        SkPDFMakeArray(0, 0, glyphBBox.width(), glyphBBox.height()),
                        glyphDevice->makeResourceDict(),
                        SkMatrix::Translate(glyphBBox.fLeft, glyphBBox.fTop), nullptr);
                imageGlyphs.emplace_back(gID, xobject);
                SkPDFUtils::AppendScalar(drawableGlyph->advanceX(), &content);
                content.writeText(" 0 d0\n1 0 0 1 0 0 cm\n/X");
                content.write(characterName.c_str(), characterName.size());
                content.writeText(" Do\n");
            } else if (path && !path->isEmpty()) {
                setGlyphWidthAndBoundingBox(pathGlyph->advanceX(), glyphBBox, &content);
                SkPDFUtils::EmitPath(*path, SkPaint::kFill_Style, &content);
                SkPDFUtils::PaintPath(SkPaint::kFill_Style, path->getFillType(), &content);
            } else {
                auto pimg = to_image(gID, &smallGlyphs);
                if (!pimg.fImage) {
                    setGlyphWidthAndBoundingBox(pathGlyph->advanceX(), glyphBBox, &content);
                } else {
                    using SkPDFUtils::AppendScalar;
                    imageGlyphs.emplace_back(gID, SkPDFSerializeImage(pimg.fImage.get(), doc));
                    AppendScalar(pathGlyph->advanceX(), &content);
                    content.writeText(" 0 d0\n");
                    AppendScalar(pimg.fImage->width() * bitmapScale, &content);
                    content.writeText(" 0 0 ");
                    AppendScalar(-pimg.fImage->height() * bitmapScale, &content);
                    content.writeText(" ");
                    AppendScalar(pimg.fOffset.x() * bitmapScale, &content);
                    content.writeText(" ");
                    AppendScalar((pimg.fImage->height() + pimg.fOffset.y()) * bitmapScale,
                                 &content);
                    content.writeText(" cm\n/X");
                    content.write(characterName.c_str(), characterName.size());
                    content.writeText(" Do\n");
                }
            }
            charProcs->insertRef(characterName, SkPDFStreamOut(nullptr,
                                                               content.detachAsStream(), doc));
        }
        encDiffs->appendName(std::move(characterName));
        widthArray->appendScalar(advance);
    }
 
    if (!imageGlyphs.empty()) {
        auto d0 = SkPDFMakeDict();
        for (const auto& pair : imageGlyphs) {
            d0->insertRef(SkStringPrintf("Xg%X", pair.first), pair.second);
        }
        auto d1 = SkPDFMakeDict();
        d1->insertObject("XObject", std::move(d0));
        font.insertObject("Resources", std::move(d1));
    }
 
    encoding->insertObject("Differences", std::move(encDiffs));
    font.insertInt("FirstChar", 0);
    font.insertInt("LastChar", lastGlyphID - firstGlyphID + 1);
    /* FontBBox: "A rectangle expressed in the glyph coordinate
      system, specifying the font bounding box. This is the smallest
      rectangle enclosing the shape that would result if all of the
      glyphs of the font were placed with their origins coincident and
      then filled." */
    font.insertObject("FontBBox", SkPDFMakeArray(bbox.left(),
                                                  bbox.bottom(),
                                                  bbox.right(),
                                                  bbox.top()));
 
    font.insertName("CIDToGIDMap", "Identity");
 
    const std::vector<SkUnichar>& glyphToUnicode = SkPDFFont::GetUnicodeMap(typeface, doc);
    SkASSERT(glyphToUnicode.size() == SkToSizeT(typeface->countGlyphs()));
    auto toUnicodeCmap = SkPDFMakeToUnicodeCmap(glyphToUnicode.data(),
                                                &subset,
                                                false,
                                                firstGlyphID,
                                                lastGlyphID);
    font.insertRef("ToUnicode", SkPDFStreamOut(nullptr, std::move(toUnicodeCmap), doc));
    font.insertRef("FontDescriptor", type3_descriptor(doc, typeface, xHeight));
    font.insertObject("Widths", std::move(widthArray));
    font.insertObject("Encoding", std::move(encoding));
    font.insertObject("CharProcs", std::move(charProcs));
 
    doc->emit(font, pdfFont.indirectReference());
}

first_nonzero_glyph_for_single_byte_encoding()

static SkGlyphID first_nonzero_glyph_for_single_byte_encoding ( SkGlyphID  gid )

static

Definition at line 204 of file SkPDFFont.cpp.

                                                                             {
    return gid != 0 ? gid - (gid - 1) % 255 : 1;
}

make_small_strike()

SkStrikeSpec make_small_strike

(

const SkTypeface &

typeface

)

Definition at line 557 of file SkPDFFont.cpp.

                                                           {
    SkFont font(sk_ref_sp(&typeface), kBitmapFontSize);
    font.setHinting(SkFontHinting::kNone);
    font.setEdging(SkFont::Edging::kAlias);
    return SkStrikeSpec::MakeMask(font,
                                  SkPaint(),
                                  SkSurfaceProps(),
                                  SkScalerContextFlags::kFakeGammaAndBoostContrast,
                                  SkMatrix::I());
}

to_image()

static ImageAndOffset to_image ( SkGlyphID  gid, SkBulkGlyphMetricsAndImages *  smallGlyphs  )

static

Definition at line 454 of file SkPDFFont.cpp.

                                                                                        {
    const SkGlyph* glyph = smallGlyphs->glyph(SkPackedGlyphID{gid});
    SkMask mask = glyph->mask();
    if (!mask.fImage) {
        return {nullptr, {0, 0}};
    }
    SkIRect bounds = mask.fBounds;
    SkBitmap bm;
    switch (mask.fFormat) {
        case SkMask::kBW_Format:
            bm.allocPixels(SkImageInfo::MakeA8(bounds.width(), bounds.height()));
            for (int y = 0; y < bm.height(); ++y) {
                for (int x8 = 0; x8 < bm.width(); x8 += 8) {
                    uint8_t v = *mask.getAddr1(x8 + bounds.x(), y + bounds.y());
                    int e = std::min(x8 + 8, bm.width());
                    for (int x = x8; x < e; ++x) {
                        *bm.getAddr8(x, y) = (v >> (x & 0x7)) & 0x1 ? 0xFF : 0x00;
                    }
                }
            }
            bm.setImmutable();
            return {bm.asImage(), {bounds.x(), bounds.y()}};
        case SkMask::kA8_Format:
            return {SkImages::RasterFromData(
                        SkImageInfo::MakeA8(bounds.width(), bounds.height()),
                        SkData::MakeWithCopy(mask.fImage, mask.computeTotalImageSize()),
                        mask.fRowBytes),
                    {bounds.x(), bounds.y()}};
        case SkMask::kARGB32_Format:
            return {SkImages::RasterFromData(
                        SkImageInfo::MakeN32Premul(bounds.width(), bounds.height()),
                        SkData::MakeWithCopy(mask.fImage, mask.computeTotalImageSize()),
                        mask.fRowBytes),
                    {bounds.x(), bounds.y()}};
        case SkMask::k3D_Format:
        case SkMask::kLCD16_Format:
        default:
            SkASSERT(false);
            return {nullptr, {0, 0}};
    }
}

type3_descriptor()

static SkPDFIndirectReference type3_descriptor ( SkPDFDocument *  doc, const SkTypeface *  typeface, SkScalar  xHeight  )

static

PDF32000_2008: FontFamily should be used for Type3 fonts in Tagged PDF documents.

PDF32000_2008: FontStretch should be used for Type3 fonts in Tagged PDF documents.

PDF32000_2008: FontWeight should be used for Type3 fonts in Tagged PDF documents.

Definition at line 496 of file SkPDFFont.cpp.

                                                                 {
    if (SkPDFIndirectReference* ptr = doc->fType3FontDescriptors.find(typeface->uniqueID())) {
        return *ptr;
    }
 
    SkPDFDict descriptor("FontDescriptor");
    int32_t fontDescriptorFlags = kPdfSymbolic;
 
    /** PDF32000_2008: FontFamily should be used for Type3 fonts in Tagged PDF documents. */
    SkString familyName;
    typeface->getFamilyName(&familyName);
    if (!familyName.isEmpty()) {
        descriptor.insertByteString("FontFamily", familyName);
    }
 
    /** PDF32000_2008: FontStretch should be used for Type3 fonts in Tagged PDF documents. */
    static constexpr const char* stretchNames[9] = {
        "UltraCondensed",
        "ExtraCondensed",
        "Condensed",
        "SemiCondensed",
        "Normal",
        "SemiExpanded",
        "Expanded",
        "ExtraExpanded",
        "UltraExpanded",
    };
    const char* stretchName = stretchNames[typeface->fontStyle().width() - 1];
    descriptor.insertName("FontStretch", stretchName);
 
    /** PDF32000_2008: FontWeight should be used for Type3 fonts in Tagged PDF documents. */
    int weight = (typeface->fontStyle().weight() + 50) / 100;
    descriptor.insertInt("FontWeight", SkTPin(weight, 1, 9) * 100);
 
    if (const SkAdvancedTypefaceMetrics* metrics = SkPDFFont::GetMetrics(typeface, doc)) {
        // Type3 FontDescriptor does not require all the same fields.
        descriptor.insertName("FontName", metrics->fPostScriptName);
        descriptor.insertInt("ItalicAngle", metrics->fItalicAngle);
        fontDescriptorFlags |= (int32_t)metrics->fStyle;
        // Adobe requests CapHeight, XHeight, and StemV be added
        // to "greatly help our workflow downstream".
        if (metrics->fCapHeight != 0) { descriptor.insertInt("CapHeight", metrics->fCapHeight); }
        if (metrics->fStemV     != 0) { descriptor.insertInt("StemV",     metrics->fStemV);     }
        if (xHeight != 0) {
            descriptor.insertScalar("XHeight", xHeight);
        }
    }
    descriptor.insertInt("Flags", fontDescriptorFlags);
    SkPDFIndirectReference ref = doc->emit(descriptor);
    doc->fType3FontDescriptors.set(typeface->uniqueID(), ref);
    return ref;
}

Variable Documentation

kBitmapFontSize

constexpr float kBitmapFontSize = 64

staticconstexpr

Definition at line 554 of file SkPDFFont.cpp.