Quelle transform.cc Sprache: C

/* Copyright 2013 Google Inc. All Rights Reserved.

   Distributed under MIT license.
   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/

/* Library for preprocessing fonts as part of the WOFF 2.0 conversion. */

#include "./transform.h"

#include <complex>  // for std::abs

#include "./buffer.h"
#include "./font.h"
#include "./glyph.h"
#include "./table_tags.h"
#include "./variable_length.h"

namespace woff2 {

namespace {

const int FLAG_ARG_1_AND_2_ARE_WORDS = 1 << 0;
const int FLAG_WE_HAVE_INSTRUCTIONS = 1 << 8;
const int FLAG_OVERLAP_SIMPLE_BITMAP = 1 << 0;

void WriteBytes(std::vector<uint8_t>* out, const uint8_t* data, size_t len) {
  if (len == 0) return;
  size_t offset = out->size();
  out->resize(offset + len);
  memcpy(&(*out)[offset], data, len);
}

void WriteBytes(std::vector<uint8_t>* out, const std::vector<uint8_t>& in) {
  for (size_t i = 0; i < in.size(); ++i) {
    out->push_back(in[i]);
  }
}

void WriteUShort(std::vector<uint8_t>* out, int value) {
  out->push_back(value >> 8);
  out->push_back(value & 255);
}

void WriteLong(std::vector<uint8_t>* out, int value) {
  out->push_back((value >> 24) & 255);
  out->push_back((value >> 16) & 255);
  out->push_back((value >> 8) & 255);
  out->push_back(value & 255);
}

// Glyf table preprocessing, based on
// GlyfEncoder.java
class GlyfEncoder {
public:
  explicit GlyfEncoder(int num_glyphs)
      : n_glyphs_(num_glyphs) {
    bbox_bitmap_.resize(((num_glyphs + 31) >> 5) << 2);
  }

  bool Encode(int glyph_id, const Glyph& glyph) {
    if (glyph.composite_data_size > 0) {
      WriteCompositeGlyph(glyph_id, glyph);
    } else if (glyph.contours.size() > 0) {
      WriteSimpleGlyph(glyph_id, glyph);
    } else {
      WriteUShort(&n_contour_stream_, 0);
    }
    return true;
  }

  void GetTransformedGlyfBytes(std::vector<uint8_t>* result) {
    WriteUShort(result, 0);  // Version
    WriteUShort(result, overlap_bitmap_.empty()
                            ? 0x00
                            : FLAG_OVERLAP_SIMPLE_BITMAP);  // Flags
    WriteUShort(result, n_glyphs_);
    WriteUShort(result, 0);  // index_format, will be set later
    WriteLong(result, n_contour_stream_.size());
    WriteLong(result, n_points_stream_.size());
    WriteLong(result, flag_byte_stream_.size());
    WriteLong(result, glyph_stream_.size());
    WriteLong(result, composite_stream_.size());
    WriteLong(result, bbox_bitmap_.size() + bbox_stream_.size());
    WriteLong(result, instruction_stream_.size());
    WriteBytes(result, n_contour_stream_);
    WriteBytes(result, n_points_stream_);
    WriteBytes(result, flag_byte_stream_);
    WriteBytes(result, glyph_stream_);
    WriteBytes(result, composite_stream_);
    WriteBytes(result, bbox_bitmap_);
    WriteBytes(result, bbox_stream_);
    WriteBytes(result, instruction_stream_);
    if (!overlap_bitmap_.empty()) {
      WriteBytes(result, overlap_bitmap_);
    }
  }

private:
  void WriteInstructions(const Glyph& glyph) {
    Write255UShort(&glyph_stream_, glyph.instructions_size);
    WriteBytes(&instruction_stream_,
               glyph.instructions_data, glyph.instructions_size);
  }

  bool ShouldWriteSimpleGlyphBbox(const Glyph& glyph) {
    if (glyph.contours.empty() || glyph.contours[0].empty()) {
      return glyph.x_min || glyph.y_min || glyph.x_max || glyph.y_max;
    }

    int16_t x_min = glyph.contours[0][0].x;
    int16_t y_min = glyph.contours[0][0].y;
    int16_t x_max = x_min;
    int16_t y_max = y_min;
    for (const auto& contour : glyph.contours) {
      for (const auto& point : contour) {
        if (point.x < x_min) x_min = point.x;
        if (point.x > x_max) x_max = point.x;
        if (point.y < y_min) y_min = point.y;
        if (point.y > y_max) y_max = point.y;
      }
    }

    if (glyph.x_min != x_min)
      return true;
    if (glyph.y_min != y_min)
      return true;
    if (glyph.x_max != x_max)
      return true;
    if (glyph.y_max != y_max)
      return true;

    return false;
  }

  void WriteSimpleGlyph(int glyph_id, const Glyph& glyph) {
    if (glyph.overlap_simple_flag_set) {
      EnsureOverlapBitmap();
      overlap_bitmap_[glyph_id >> 3] |= 0x80 >> (glyph_id & 7);
    }
    int num_contours = glyph.contours.size();
    WriteUShort(&n_contour_stream_, num_contours);
    if (ShouldWriteSimpleGlyphBbox(glyph)) {
      WriteBbox(glyph_id, glyph);
    }
    for (int i = 0; i < num_contours; i++) {
      Write255UShort(&n_points_stream_, glyph.contours[i].size());
    }
    int lastX = 0;
    int lastY = 0;
    for (int i = 0; i < num_contours; i++) {
      int num_points = glyph.contours[i].size();
      for (int j = 0; j < num_points; j++) {
        int x = glyph.contours[i][j].x;
        int y = glyph.contours[i][j].y;
        int dx = x - lastX;
        int dy = y - lastY;
        WriteTriplet(glyph.contours[i][j].on_curve, dx, dy);
        lastX = x;
        lastY = y;
      }
    }
    if (num_contours > 0) {
      WriteInstructions(glyph);
    }
  }

  void WriteCompositeGlyph(int glyph_id, const Glyph& glyph) {
    WriteUShort(&n_contour_stream_, -1);
    WriteBbox(glyph_id, glyph);
    WriteBytes(&composite_stream_,
               glyph.composite_data,
               glyph.composite_data_size);
    if (glyph.have_instructions) {
      WriteInstructions(glyph);
    }
  }

  void WriteBbox(int glyph_id, const Glyph& glyph) {
    bbox_bitmap_[glyph_id >> 3] |= 0x80 >> (glyph_id & 7);
    WriteUShort(&bbox_stream_, glyph.x_min);
    WriteUShort(&bbox_stream_, glyph.y_min);
    WriteUShort(&bbox_stream_, glyph.x_max);
    WriteUShort(&bbox_stream_, glyph.y_max);
  }

  void WriteTriplet(bool on_curve, int x, int y) {
    int abs_x = std::abs(x);
    int abs_y = std::abs(y);
    int on_curve_bit = on_curve ? 0 : 128;
    int x_sign_bit = (x < 0) ? 0 : 1;
    int y_sign_bit = (y < 0) ? 0 : 1;
    int xy_sign_bits = x_sign_bit + 2 * y_sign_bit;
    if (x == 0 && abs_y < 1280) {
      flag_byte_stream_.push_back(on_curve_bit +
                                  ((abs_y & 0xf00) >> 7) + y_sign_bit);
      glyph_stream_.push_back(abs_y & 0xff);
    } else if (y == 0 && abs_x < 1280) {
      flag_byte_stream_.push_back(on_curve_bit + 10 +
                                  ((abs_x & 0xf00) >> 7) + x_sign_bit);
      glyph_stream_.push_back(abs_x & 0xff);
    } else if (abs_x < 65 && abs_y < 65) {
      flag_byte_stream_.push_back(on_curve_bit + 20 +
                                  ((abs_x - 1) & 0x30) +
                                  (((abs_y - 1) & 0x30) >> 2) +
                                  xy_sign_bits);
      glyph_stream_.push_back((((abs_x - 1) & 0xf) << 4) | ((abs_y - 1) & 0xf));
    } else if (abs_x < 769 && abs_y < 769) {
      flag_byte_stream_.push_back(on_curve_bit + 84 +
                                  12 * (((abs_x - 1) & 0x300) >> 8) +
                                  (((abs_y - 1) & 0x300) >> 6) + xy_sign_bits);
      glyph_stream_.push_back((abs_x - 1) & 0xff);
      glyph_stream_.push_back((abs_y - 1) & 0xff);
    } else if (abs_x < 4096 && abs_y < 4096) {
      flag_byte_stream_.push_back(on_curve_bit + 120 + xy_sign_bits);
      glyph_stream_.push_back(abs_x >> 4);
      glyph_stream_.push_back(((abs_x & 0xf) << 4) | (abs_y >> 8));
      glyph_stream_.push_back(abs_y & 0xff);
    } else {
      flag_byte_stream_.push_back(on_curve_bit + 124 + xy_sign_bits);
      glyph_stream_.push_back(abs_x >> 8);
      glyph_stream_.push_back(abs_x & 0xff);
      glyph_stream_.push_back(abs_y >> 8);
      glyph_stream_.push_back(abs_y & 0xff);
    }
  }

  void EnsureOverlapBitmap() {
    if (overlap_bitmap_.empty()) {
      overlap_bitmap_.resize((n_glyphs_ + 7) >> 3);
    }
  }

  std::vector<uint8_t> n_contour_stream_;
  std::vector<uint8_t> n_points_stream_;
  std::vector<uint8_t> flag_byte_stream_;
  std::vector<uint8_t> composite_stream_;
  std::vector<uint8_t> bbox_bitmap_;
  std::vector<uint8_t> bbox_stream_;
  std::vector<uint8_t> glyph_stream_;
  std::vector<uint8_t> instruction_stream_;
  std::vector<uint8_t> overlap_bitmap_;
  int n_glyphs_;
};

}  // namespace

bool TransformGlyfAndLocaTables(Font* font) {
  // no transform for CFF
  const Font::Table* glyf_table = font->FindTable(kGlyfTableTag);
  const Font::Table* loca_table = font->FindTable(kLocaTableTag);

  // If you don't have glyf/loca this transform isn't very interesting
  if (loca_table == NULL && glyf_table == NULL) {
    return true;
  }
  // It would be best if you didn't have just one of glyf/loca
  if ((glyf_table == NULL) != (loca_table == NULL)) {
    return FONT_COMPRESSION_FAILURE();
  }
  // Must share neither or both loca & glyf
  if (loca_table->IsReused() != glyf_table->IsReused()) {
    return FONT_COMPRESSION_FAILURE();
  }
  if (loca_table->IsReused()) {
    return true;
  }

  Font::Table* transformed_glyf = &font->tables[kGlyfTableTag ^ 0x80808080];
  Font::Table* transformed_loca = &font->tables[kLocaTableTag ^ 0x80808080];

  int num_glyphs = NumGlyphs(*font);
  GlyfEncoder encoder(num_glyphs);
  for (int i = 0; i < num_glyphs; ++i) {
    Glyph glyph;
    const uint8_t* glyph_data;
    size_t glyph_size;
    if (!GetGlyphData(*font, i, &glyph_data, &glyph_size) ||
        (glyph_size > 0 && !ReadGlyph(glyph_data, glyph_size, &glyph))) {
      return FONT_COMPRESSION_FAILURE();
    }
    encoder.Encode(i, glyph);
  }
  encoder.GetTransformedGlyfBytes(&transformed_glyf->buffer);

  const Font::Table* head_table = font->FindTable(kHeadTableTag);
  if (head_table == NULL || head_table->length < 52) {
    return FONT_COMPRESSION_FAILURE();
  }
  transformed_glyf->buffer[7] = head_table->data[51];  // index_format

  transformed_glyf->tag = kGlyfTableTag ^ 0x80808080;
  transformed_glyf->length = transformed_glyf->buffer.size();
  transformed_glyf->data = transformed_glyf->buffer.data();

  transformed_loca->tag = kLocaTableTag ^ 0x80808080;
  transformed_loca->length = 0;
  transformed_loca->data = NULL;

  return true;
}

// See https://www.microsoft.com/typography/otspec/hmtx.htm
// See WOFF2 spec, 5.4. Transformed hmtx table format
bool TransformHmtxTable(Font* font) {
  const Font::Table* glyf_table = font->FindTable(kGlyfTableTag);
  const Font::Table* hmtx_table = font->FindTable(kHmtxTableTag);
  const Font::Table* hhea_table = font->FindTable(kHheaTableTag);

  // If you don't have hmtx or a glyf not much is going to happen here
  if (hmtx_table == NULL || glyf_table == NULL) {
    return true;
  }

  // hmtx without hhea doesn't make sense
  if (hhea_table == NULL) {
    return FONT_COMPRESSION_FAILURE();
  }

  // Skip 34 to reach 'hhea' numberOfHMetrics
  Buffer hhea_buf(hhea_table->data, hhea_table->length);
  uint16_t num_hmetrics;
  if (!hhea_buf.Skip(34) || !hhea_buf.ReadU16(&num_hmetrics)) {
    return FONT_COMPRESSION_FAILURE();
  }

  // Must have at least one hMetric
  if (num_hmetrics < 1) {
    return FONT_COMPRESSION_FAILURE();
  }

  int num_glyphs = NumGlyphs(*font);

  // Most fonts can be transformed; assume it's a go until proven otherwise
  std::vector<uint16_t> advance_widths;
  std::vector<int16_t> proportional_lsbs;
  std::vector<int16_t> monospace_lsbs;

  bool remove_proportional_lsb = true;
  bool remove_monospace_lsb = (num_glyphs - num_hmetrics) > 0;

  Buffer hmtx_buf(hmtx_table->data, hmtx_table->length);
  for (int i = 0; i < num_glyphs; i++) {
    Glyph glyph;
    const uint8_t* glyph_data;
    size_t glyph_size;
    if (!GetGlyphData(*font, i, &glyph_data, &glyph_size) ||
        (glyph_size > 0 && !ReadGlyph(glyph_data, glyph_size, &glyph))) {
      return FONT_COMPRESSION_FAILURE();
    }

    uint16_t advance_width = 0;
    int16_t lsb = 0;

    if (i < num_hmetrics) {
      // [0, num_hmetrics) are proportional hMetrics
      if (!hmtx_buf.ReadU16(&advance_width)) {
        return FONT_COMPRESSION_FAILURE();
      }

      if (!hmtx_buf.ReadS16(&lsb)) {
        return FONT_COMPRESSION_FAILURE();
      }

      if (glyph_size > 0 && glyph.x_min != lsb) {
        remove_proportional_lsb = false;
      }

      advance_widths.push_back(advance_width);
      proportional_lsbs.push_back(lsb);
    } else {
      // [num_hmetrics, num_glyphs) are monospace leftSideBearing's
      if (!hmtx_buf.ReadS16(&lsb)) {
        return FONT_COMPRESSION_FAILURE();
      }
      if (glyph_size > 0 && glyph.x_min != lsb) {
        remove_monospace_lsb = false;
      }
      monospace_lsbs.push_back(lsb);
    }

    // If we know we can't optimize, bail out completely
    if (!remove_proportional_lsb && !remove_monospace_lsb) {
      return true;
    }
  }

  Font::Table* transformed_hmtx = &font->tables[kHmtxTableTag ^ 0x80808080];

  uint8_t flags = 0;
  size_t transformed_size = 1 + 2 * advance_widths.size();
  if (remove_proportional_lsb) {
    flags |= 1;
  } else {
    transformed_size += 2 * proportional_lsbs.size();
  }
  if (remove_monospace_lsb) {
    flags |= 1 << 1;
  } else {
    transformed_size += 2 * monospace_lsbs.size();
  }

  transformed_hmtx->buffer.reserve(transformed_size);
  std::vector<uint8_t>* out = &transformed_hmtx->buffer;
  WriteBytes(out, &flags, 1);
  for (uint16_t advance_width : advance_widths) {
    WriteUShort(out, advance_width);
  }

  if (!remove_proportional_lsb) {
    for (int16_t lsb : proportional_lsbs) {
      WriteUShort(out, lsb);
    }
  }
  if (!remove_monospace_lsb) {
    for (int16_t lsb : monospace_lsbs) {
      WriteUShort(out, lsb);
    }
  }

  transformed_hmtx->tag = kHmtxTableTag ^ 0x80808080;
  transformed_hmtx->flag_byte = 1 << 6;
  transformed_hmtx->length = transformed_hmtx->buffer.size();
  transformed_hmtx->data = transformed_hmtx->buffer.data();

  return true;
}

} // namespace woff2

quality96%

¤ Dauer der Verarbeitung: 0.12 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.