media/filters/jpeg_parser.h

   1 // Copyright 2015 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 #ifndef MEDIA_FILTERS_JPEG_PARSER_H_
   6 #define MEDIA_FILTERS_JPEG_PARSER_H_
   7
   8 #include <stddef.h>
   9 #include <stdint.h>
  10 #include "media/base/media_export.h"
  11
  12 namespace media {
  13
  14 const size_t kJpegMaxHuffmanTableNumBaseline = 2;
  15 const size_t kJpegMaxComponents = 4;
  16 const size_t kJpegMaxQuantizationTableNum = 4;
  17
  18 // Parsing result of JPEG DHT marker.
  19 struct JpegHuffmanTable {
  20   bool valid;
  21   uint8_t code_length[16];
  22   uint8_t code_value[256];
  23 };
  24
  25 // Parsing result of JPEG DQT marker.
  26 struct JpegQuantizationTable {
  27   bool valid;
  28   uint8_t value[64];  // baseline only supports 8 bits quantization table
  29 };
  30
  31 // Parsing result of a JPEG component.
  32 struct JpegComponent {
  33   uint8_t id;
  34   uint8_t horizontal_sampling_factor;
  35   uint8_t vertical_sampling_factor;
  36   uint8_t quantization_table_selector;
  37 };
  38
  39 // Parsing result of a JPEG SOF marker.
  40 struct JpegFrameHeader {
  41   uint16_t visible_width;
  42   uint16_t visible_height;
  43   uint16_t coded_width;
  44   uint16_t coded_height;
  45   uint8_t num_components;
  46   JpegComponent components[kJpegMaxComponents];
  47 };
  48
  49 // Parsing result of JPEG SOS marker.
  50 struct JpegScanHeader {
  51   uint8_t num_components;
  52   struct Component {
  53     uint8_t component_selector;
  54     uint8_t dc_selector;
  55     uint8_t ac_selector;
  56   } components[kJpegMaxComponents];
  57 };
  58
  59 struct JpegParseResult {
  60   JpegFrameHeader frame_header;
  61   JpegHuffmanTable dc_table[kJpegMaxHuffmanTableNumBaseline];
  62   JpegHuffmanTable ac_table[kJpegMaxHuffmanTableNumBaseline];
  63   JpegQuantizationTable q_table[kJpegMaxQuantizationTableNum];
  64   uint16_t restart_interval;
  65   JpegScanHeader scan;
  66   const char* data;
  67   size_t data_size;
  68 };
  69
  70 // Parses JPEG picture in |buffer| with |length|.  Returns true iff header is
  71 // valid and JPEG baseline sequential process is present. If parsed
  72 // successfully, |result| is the parsed result.
  73 // It's not a full featured JPEG parser implememtation. It only parses JPEG
  74 // baseline sequential process. For explanations of each struct and its
  75 // members, see JPEG specification at
  76 // http://www.w3.org/Graphics/JPEG/itu-t81.pdf.
  77 MEDIA_EXPORT bool ParseJpegPicture(const uint8_t* buffer,
  78                                    size_t length,
  79                                    JpegParseResult* result);
  80
  81 }  // namespace media
  82
  83 #endif  // MEDIA_FILTERS_JPEG_PARSER_H_