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   uint8_t num_components;
  44   JpegComponent components[kJpegMaxComponents];
  45 };
  46
  47 // Parsing result of JPEG SOS marker.
  48 struct JpegScanHeader {
  49   uint8_t num_components;
  50   struct Component {
  51     uint8_t component_selector;
  52     uint8_t dc_selector;
  53     uint8_t ac_selector;
  54   } components[kJpegMaxComponents];
  55 };
  56
  57 struct JpegParseResult {
  58   JpegFrameHeader frame_header;
  59   JpegHuffmanTable dc_table[kJpegMaxHuffmanTableNumBaseline];
  60   JpegHuffmanTable ac_table[kJpegMaxHuffmanTableNumBaseline];
  61   JpegQuantizationTable q_table[kJpegMaxQuantizationTableNum];
  62   uint16_t restart_interval;
  63   JpegScanHeader scan;
  64   const char* data;
  65   size_t data_size;
  66 };
  67
  68 // Parses JPEG picture in |buffer| with |length|.  Returns true iff header is
  69 // valid and JPEG baseline sequential process is present. If parsed
  70 // successfully, |result| is the parsed result.
  71 // It's not a full featured JPEG parser implememtation. It only parses JPEG
  72 // baseline sequential process. For explanations of each struct and its
  73 // members, see JPEG specification at
  74 // http://www.w3.org/Graphics/JPEG/itu-t81.pdf.
  75 MEDIA_EXPORT bool ParseJpegPicture(const uint8_t* buffer,
  76                                    size_t length,
  77                                    JpegParseResult* result);
  78
  79 }  // namespace media
  80
  81 #endif  // MEDIA_FILTERS_JPEG_PARSER_H_