/* 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
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