third_party/ots/src/ltsh.cc

   1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ltsh.h"
   6
   7 #include "maxp.h"
   8
   9 // LTSH - Linear Threshold
  10 // http://www.microsoft.com/typography/otspec/ltsh.htm
  11
  12 #define TABLE_NAME "LTSH"
  13
  14 #define DROP_THIS_TABLE(...) \
  15   do { \
  16     OTS_FAILURE_MSG_(file, TABLE_NAME ": " __VA_ARGS__); \
  17     OTS_FAILURE_MSG("Table discarded"); \
  18     delete file->ltsh; \
  19     file->ltsh = 0; \
  20   } while (0)
  21
  22 namespace ots {
  23
  24 bool ots_ltsh_parse(OpenTypeFile *file, const uint8_t *data, size_t length) {
  25   Buffer table(data, length);
  26
  27   if (!file->maxp) {
  28     return OTS_FAILURE_MSG("Missing maxp table from font needed by ltsh");
  29   }
  30
  31   OpenTypeLTSH *ltsh = new OpenTypeLTSH;
  32   file->ltsh = ltsh;
  33
  34   uint16_t num_glyphs = 0;
  35   if (!table.ReadU16(&ltsh->version) ||
  36       !table.ReadU16(&num_glyphs)) {
  37     return OTS_FAILURE_MSG("Failed to read ltsh header");
  38   }
  39
  40   if (ltsh->version != 0) {
  41     DROP_THIS_TABLE("bad version: %u", ltsh->version);
  42     return true;
  43   }
  44
  45   if (num_glyphs != file->maxp->num_glyphs) {
  46     DROP_THIS_TABLE("bad num_glyphs: %u", num_glyphs);
  47     return true;
  48   }
  49
  50   ltsh->ypels.reserve(num_glyphs);
  51   for (unsigned i = 0; i < num_glyphs; ++i) {
  52     uint8_t pel = 0;
  53     if (!table.ReadU8(&pel)) {
  54       return OTS_FAILURE_MSG("Failed to read pixels for glyph %d", i);
  55     }
  56     ltsh->ypels.push_back(pel);
  57   }
  58
  59   return true;
  60 }
  61
  62 bool ots_ltsh_should_serialise(OpenTypeFile *file) {
  63   if (!file->glyf) return false;  // this table is not for CFF fonts.
  64   return file->ltsh != NULL;
  65 }
  66
  67 bool ots_ltsh_serialise(OTSStream *out, OpenTypeFile *file) {
  68   const OpenTypeLTSH *ltsh = file->ltsh;
  69
  70   const uint16_t num_ypels = static_cast<uint16_t>(ltsh->ypels.size());
  71   if (num_ypels != ltsh->ypels.size() ||
  72       !out->WriteU16(ltsh->version) ||
  73       !out->WriteU16(num_ypels)) {
  74     return OTS_FAILURE_MSG("Failed to write pels size");
  75   }
  76   for (uint16_t i = 0; i < num_ypels; ++i) {
  77     if (!out->Write(&(ltsh->ypels[i]), 1)) {
  78       return OTS_FAILURE_MSG("Failed to write pixel size for glyph %d", i);
  79     }
  80   }
  81
  82   return true;
  83 }
  84
  85 void ots_ltsh_free(OpenTypeFile *file) {
  86   delete file->ltsh;
  87 }
  88
  89 }  // namespace ots
  90
  91 #undef TABLE_NAME
  92 #undef DROP_THIS_TABLE