git.sesse.net Git - fjl/blob - driver.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3
   4 #include "bytesource.h"
   5 #include "choice.h"
   6 #include "dehuff.h"
   7 #include "input.h"
   8
   9 struct jpeg_image {
  10         unsigned precision;
  11         unsigned width, height;
  12         unsigned num_components;
  13         unsigned hsample[256], vsample[256], qtable[256];
  14 };
  15
  16 ssize_t stdio_read(void* userdata, uint8_t* buf, size_t count)
  17 {
  18         return fread(buf, 1, count, (FILE*)userdata);
  19 }
  20
  21 void read_sof(struct byte_source* source, struct jpeg_image* image)
  22 {
  23         unsigned len = read_uint16(byte_source_input_func, source);
  24         assert(len >= 8);
  25         image->precision = read_uint8(byte_source_input_func, source);
  26         assert(image->precision == 8);
  27         image->width = read_uint16(byte_source_input_func, source);
  28         image->height = read_uint16(byte_source_input_func, source);
  29         image->num_components = read_uint8(byte_source_input_func, source);
  30         len -= 8;
  31
  32         fprintf(stderr, "%u-bit %ux%u JPEG with %u components\n",
  33                 image->precision, image->width, image->height, image->num_components);
  34
  35         for (unsigned i = 0; i < image->num_components; ++i) {
  36                 assert(len >= 3);
  37                 unsigned c = read_uint8(byte_source_input_func, source);
  38                 unsigned sampling_factors = read_uint8(byte_source_input_func, source);
  39                 image->hsample[c] = sampling_factors >> 4;
  40                 image->vsample[c] = sampling_factors & 0x0f;
  41                 image->qtable[c] = read_uint8(byte_source_input_func, source);
  42                 len -= 3;
  43
  44                 fprintf(stderr, "Component %u: sampling factors %u x %x, quantization table %u\n",
  45                         c, image->hsample[c], image->vsample[c], image->qtable[c]);
  46         }
  47 }
  48
  49 void read_scan(struct byte_source* source, struct jpeg_image* image, huffman_tables_t* tables)
  50 {
  51         unsigned len = read_uint16(byte_source_input_func, source);
  52         assert(len >= 2);
  53         len -= 2;
  54
  55         assert(len >= 1);
  56         unsigned num_components = read_uint8(byte_source_input_func, source);
  57         --len;
  58
  59         unsigned component_num[256];
  60         unsigned dc_huffman_table[256], ac_huffman_table[256];
  61         unsigned ss, se, ah_al;
  62         int last_dc[256];
  63
  64         for (unsigned i = 0; i < num_components; ++i) {
  65                 unsigned char td_ta;
  66                 assert(len >= 2);
  67                 component_num[i] = read_uint8(byte_source_input_func, source);
  68                 td_ta = read_uint8(byte_source_input_func, source);
  69                 len -= 2;
  70                 dc_huffman_table[i] = td_ta >> 4;
  71                 ac_huffman_table[i] = td_ta & 0x0f;
  72                 last_dc[i] = 0;
  73         }
  74
  75         assert(len >= 3);
  76         ss = read_uint8(byte_source_input_func, source);
  77         se = read_uint8(byte_source_input_func, source);
  78         ah_al = read_uint8(byte_source_input_func, source);
  79         len -= 3;
  80
  81         if (len != 0) {
  82                 fprintf(stderr, "Error: %u unused bytes at end of SOS segment\n", len);
  83         }
  84
  85         struct bit_source bits;
  86         init_bit_source(&bits, byte_source_input_func, source);
  87
  88         for ( ;; ) {
  89                 for (unsigned c = 0; c < num_components; ++c) {
  90                         unsigned cn = component_num[c];
  91                         unsigned nc = image->vsample[cn] * image->hsample[cn];
  92                         for (unsigned n = 0; n < nc; ++n) {
  93                                 const struct huffman_table* dc_table = &((*tables)[DC_CLASS][dc_huffman_table[c]]);
  94                                 const struct huffman_table* ac_table = &((*tables)[AC_CLASS][ac_huffman_table[c]]);
  95
  96                                 // decode DC component
  97                                 unsigned dc_category = read_huffman_symbol(dc_table, &bits);
  98                                 possibly_refill(&bits, dc_category);
  99                                 last_dc[c] += extend(read_bits(&bits, dc_category), dc_category);
 100
 101                 //              printf("dc=%d ac=", last_dc[c]);
 102                                 putchar(last_dc[c]);
 103
 104                                 // decode AC components
 105                                 int zz[63] = { 0 };
 106                                 for (unsigned i = 0; i < 63; ++i) {
 107                                         unsigned rs = read_huffman_symbol(ac_table, &bits);
 108                                         unsigned r = rs >> 4;
 109                                         unsigned s = rs & 0xf;
 110
 111                                         if (rs == 0x00) {
 112                                                 /* end of block */
 113                                                 break;
 114                                         }
 115                                         if (rs == 0xf0) {
 116                                                 /* 16 zero coefficients */
 117                                                 i += 15;
 118                                                 continue;
 119                                         }
 120
 121                                         possibly_refill(&bits, s);
 122
 123                                         i += r;
 124                                         zz[i] = extend(read_bits(&bits, s), s);
 125                                 }
 126
 127                                 for (unsigned i = 0; i < 63; ++i) {
 128                                         putchar(zz[i]);
 129                                         //printf("%d ", zz[i]);
 130                                 }
 131                                 //printf("\n");
 132                         }
 133                 }
 134         }
 135         if (len != 0) {
 136                 fprintf(stderr, "Error: %u unused bytes at end of SOS segment\n", len);
 137         }
 138 }
 139
 140 void skip_segment(struct byte_source* source)
 141 {
 142         uint8_t buf[4096];
 143         for ( ;; ) {
 144                 ssize_t ret = byte_source_input_func(source, buf, 4096);
 145                 if (ret == -1) {
 146                         fprintf(stderr, "Input error!\n");
 147                         exit(1);
 148                 }
 149                 if (ret == 0) {
 150                         return;
 151                 }
 152         }
 153 }
 154
 155 int main(void)
 156 {
 157         struct jpeg_image jpeg;
 158         init_choices();
 159
 160         struct byte_source source;
 161         init_byte_source(&source, stdio_read, stdin);
 162
 163         huffman_tables_t tables;
 164
 165         for ( ;; ) {
 166                 uint8_t m2 = byte_source_read_marker(&source);
 167                 assert(m2 != 0x00);
 168
 169                 fprintf(stderr, "Marker 0x%02x, at position %ld\n", m2, ftell(stdin) - source.bytes_available);
 170
 171                 switch (m2) {
 172                 case 0xe0:
 173                 case 0xe1:
 174                 case 0xe2:
 175                 case 0xe3:
 176                 case 0xe4:
 177                 case 0xe5:
 178                 case 0xe6:
 179                 case 0xe7:
 180                 case 0xe8:
 181                 case 0xe9:
 182                 case 0xea:
 183                 case 0xeb:
 184                 case 0xec:
 185                 case 0xed:
 186                 case 0xee:
 187                 case 0xef:
 188                         /* APP0 through APPF */
 189                 case 0xfc:
 190                         /* some EXIF stuff */
 191                 case 0xfe:
 192                         /* comment */
 193                 case 0xff:
 194                         /* ignore */
 195                 case 0xdb:
 196                         /* DQT */
 197                         skip_segment(&source);
 198                         break;
 199                 case 0xc0:
 200                         /* SOF0 (baseline DCT, Huffman encoded) */
 201                         read_sof(&source, &jpeg);
 202                         break;
 203                 case 0xd8:
 204                         /* SOI */
 205                         break;
 206                 case 0xc4:
 207                         /* DHT (define Huffman tables) */
 208                         read_huffman_tables(&tables, byte_source_input_func, &source);
 209                         break;
 210                 case 0xda:
 211                         /* SOS (start of scan) */
 212                         read_scan(&source, &jpeg, &tables);
 213                         break;
 214                 default:
 215                         fprintf(stderr, "Error: Unknown marker 0x%02x\n", m2);
 216                         exit(1);
 217                 }
 218         }
 219 }