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-rw-r--r--modules/woff2/src/transform.cc430
1 files changed, 430 insertions, 0 deletions
diff --git a/modules/woff2/src/transform.cc b/modules/woff2/src/transform.cc
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+/* 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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