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jpegSize.cpp File Reference

#include "jpegSize.h"
#include <stdio.h>

Include dependency graph for jpegSize.cpp:

Go to the source code of this file.

Defines

#define NEXTBYTE()   getc(infile)
#define M_SOF0   0xC0 /* Start Of Frame N */
#define M_SOF1   0xC1 /* N indicates which compression process */
#define M_SOF2   0xC2 /* Only SOF0-SOF2 are now in common use */
#define M_SOF3   0xC3
#define M_SOF5   0xC5 /* NB: codes C4 and CC are NOT SOF markers */
#define M_SOF6   0xC6
#define M_SOF7   0xC7
#define M_SOF9   0xC9
#define M_SOF10   0xCA
#define M_SOF11   0xCB
#define M_SOF13   0xCD
#define M_SOF14   0xCE
#define M_SOF15   0xCF
#define M_SOI   0xD8 /* Start Of Image (beginning of datastream) */
#define M_EOI   0xD9 /* End Of Image (end of datastream) */
#define M_SOS   0xDA /* Start Of Scan (begins compressed data) */
#define M_APP0   0xE0 /* Application-specific marker, type N */
#define M_APP12   0xEC /* (we don't bother to list all 16 APPn's) */
#define M_COM   0xFE /* COMment */
#define READ_BINARY   "rb"

Functions

bool process_SOFn (int &width, int &height)
bool skip_variable ()
bool read_1_byte (int *res)
bool read_2_bytes (unsigned int *res)
bool first_marker (int *res)
bool next_marker (int *res)
bool getJPEGSize (const char *filename, int &width, int &height)

Variables

FILE * infile


Define Documentation

#define M_APP0   0xE0 /* Application-specific marker, type N */
 

Definition at line 42 of file jpegSize.cpp.

#define M_APP12   0xEC /* (we don't bother to list all 16 APPn's) */
 

Definition at line 43 of file jpegSize.cpp.

#define M_COM   0xFE /* COMment */
 

Definition at line 44 of file jpegSize.cpp.

#define M_EOI   0xD9 /* End Of Image (end of datastream) */
 

Definition at line 40 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF0   0xC0 /* Start Of Frame N */
 

Definition at line 26 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF1   0xC1 /* N indicates which compression process */
 

Definition at line 27 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF10   0xCA
 

Definition at line 34 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF11   0xCB
 

Definition at line 35 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF13   0xCD
 

Definition at line 36 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF14   0xCE
 

Definition at line 37 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF15   0xCF
 

Definition at line 38 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF2   0xC2 /* Only SOF0-SOF2 are now in common use */
 

Definition at line 28 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF3   0xC3
 

Definition at line 29 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF5   0xC5 /* NB: codes C4 and CC are NOT SOF markers */
 

Definition at line 30 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF6   0xC6
 

Definition at line 31 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF7   0xC7
 

Definition at line 32 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOF9   0xC9
 

Definition at line 33 of file jpegSize.cpp.

Referenced by getJPEGSize().

#define M_SOI   0xD8 /* Start Of Image (beginning of datastream) */
 

Definition at line 39 of file jpegSize.cpp.

Referenced by first_marker().

#define M_SOS   0xDA /* Start Of Scan (begins compressed data) */
 

Definition at line 41 of file jpegSize.cpp.

Referenced by getJPEGSize().

 
#define NEXTBYTE  )     getc(infile)
 

Definition at line 18 of file jpegSize.cpp.

Referenced by first_marker(), read_1_byte(), and read_2_bytes().

#define READ_BINARY   "rb"
 

Definition at line 52 of file jpegSize.cpp.

Referenced by getJPEGSize().


Function Documentation

bool first_marker int *  res  ) 
 

Definition at line 149 of file jpegSize.cpp.

References M_SOI, and NEXTBYTE.

Referenced by getJPEGSize().

00150 { 00151 int c1, c2; 00152 c1 = NEXTBYTE(); 00153 c2 = NEXTBYTE(); 00154 if (c1 != 0xFF || c2 != M_SOI) 00155 return false; 00156 else 00157 { 00158 *res = c2; 00159 return true; 00160 } 00161 }

bool getJPEGSize const char *  filename,
int &  width,
int &  height
 

Definition at line 65 of file jpegSize.cpp.

References first_marker(), height, infile, M_EOI, M_SOF0, M_SOF1, M_SOF10, M_SOF11, M_SOF13, M_SOF14, M_SOF15, M_SOF2, M_SOF3, M_SOF5, M_SOF6, M_SOF7, M_SOF9, M_SOS, next_marker(), process_SOFn(), READ_BINARY, skip_variable(), and width.

Referenced by getImageSize(), and isJpeg().

00066 { 00067 //open file 00068 if ((infile = fopen(filename, READ_BINARY)) == NULL) 00069 return false; 00070 00071 //this is scan_JPEG_header (int verbose) 00072 //Parse the marker stream until SOFn is seen; 00073 int marker; 00074 00075 //Expect SOI at start of file 00076 if (!first_marker(&marker)) 00077 { 00078 fclose(infile); 00079 return false; 00080 } 00081 00082 /* Scan miscellaneous markers until we reach SOFn. */ 00083 for (;;) 00084 { 00085 if(!next_marker(&marker)) 00086 { 00087 fclose(infile); 00088 return false; 00089 } 00090 00091 switch (marker) 00092 { 00093 /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be, 00094 * treated as SOFn. C4 in particular is actually DHT. 00095 */ 00096 case M_SOF0: /* Baseline */ 00097 case M_SOF1: /* Extended sequential, Huffman */ 00098 case M_SOF2: /* Progressive, Huffman */ 00099 case M_SOF3: /* Lossless, Huffman */ 00100 case M_SOF5: /* Differential sequential, Huffman */ 00101 case M_SOF6: /* Differential progressive, Huffman */ 00102 case M_SOF7: /* Differential lossless, Huffman */ 00103 case M_SOF9: /* Extended sequential, arithmetic */ 00104 case M_SOF10: /* Progressive, arithmetic */ 00105 case M_SOF11: /* Lossless, arithmetic */ 00106 case M_SOF13: /* Differential sequential, arithmetic */ 00107 case M_SOF14: /* Differential progressive, arithmetic */ 00108 case M_SOF15: /* Differential lossless, arithmetic */ 00109 if(!process_SOFn(width, height)) 00110 { 00111 fclose(infile); 00112 return false; 00113 } 00114 else 00115 { 00116 fclose(infile); 00117 return true; 00118 } 00119 case M_SOS: /* stop before hitting compressed data */ 00120 { 00121 fclose(infile); 00122 return false; 00123 } 00124 case M_EOI: /* in case it's a tables-only JPEG stream */ 00125 { 00126 fclose(infile); 00127 return false; 00128 } 00129 default: /* Anything else just gets skipped */ 00130 skip_variable(); /* we assume it has a parameter count... */ 00131 break; 00132 } 00133 } /* end loop */ 00134 00135 00136 //cout << "ERROR!\n"; 00137 return false; 00138 00139 }

bool next_marker int *  res  ) 
 

Definition at line 172 of file jpegSize.cpp.

References read_1_byte().

Referenced by getJPEGSize().

00173 { 00174 int c; 00175 int discarded_bytes = 0; 00176 00177 /* Find 0xFF byte; count and skip any non-FFs. */ 00178 if(!read_1_byte(&c)) 00179 return false; 00180 while (c != 0xFF) 00181 { 00182 discarded_bytes++; 00183 if(!read_1_byte(&c)) 00184 return false; 00185 } 00186 /* Get marker code byte, swallowing any duplicate FF bytes. Extra FFs 00187 * are legal as pad bytes, so don't count them in discarded_bytes. 00188 */ 00189 do 00190 { 00191 if(!read_1_byte(&c)) 00192 return false; 00193 } while (c == 0xFF); 00194 00195 // if (discarded_bytes != 0) { cout << "Warning: garbage data found in JPEG file\n"; } 00196 00197 *res = c; 00198 return true; 00199 }

bool process_SOFn int &  width,
int &  height
 

Definition at line 261 of file jpegSize.cpp.

References height, read_1_byte(), read_2_bytes(), and width.

Referenced by getJPEGSize().

00262 { 00263 unsigned int length; 00264 unsigned int image_height, image_width; 00265 int data_precision; 00266 00267 if(!read_2_bytes(&length) || 00268 !read_1_byte(&data_precision) || 00269 !read_2_bytes(&image_height) || 00270 !read_2_bytes(&image_width) ) 00271 return false; 00272 00273 width = (int) image_width; 00274 height = (int) image_height; 00275 return true; 00276 }

bool read_1_byte int *  res  ) 
 

Definition at line 202 of file jpegSize.cpp.

References NEXTBYTE.

Referenced by next_marker(), process_SOFn(), and skip_variable().

00203 { 00204 int c = NEXTBYTE(); 00205 if (c == EOF) 00206 return false; 00207 else 00208 { 00209 *res = c; 00210 return true; 00211 } 00212 }

bool read_2_bytes unsigned int *  res  ) 
 

Definition at line 216 of file jpegSize.cpp.

References NEXTBYTE.

Referenced by process_SOFn(), and skip_variable().

00217 { 00218 int c1, c2; 00219 c1 = NEXTBYTE(); 00220 if (c1 == EOF) 00221 return false; 00222 c2 = NEXTBYTE(); 00223 if (c2 == EOF) 00224 return false; 00225 *res = (((unsigned int) c1) << 8) + ((unsigned int) c2); 00226 return true; 00227 }

bool skip_variable  ) 
 

Definition at line 237 of file jpegSize.cpp.

References read_1_byte(), and read_2_bytes().

Referenced by getJPEGSize().

00239 { 00240 unsigned int length; 00241 00242 /* Get the marker parameter length count */ 00243 if(!read_2_bytes(&length)) 00244 return false; 00245 /* Length includes itself, so must be at least 2 */ 00246 if (length < 2) 00247 return false; 00248 length -= 2; 00249 /* Skip over the remaining bytes */ 00250 while (length > 0) 00251 { 00252 int tmp; 00253 if(!read_1_byte(&tmp)) 00254 return false; 00255 length--; 00256 } 00257 return false; 00258 }


Variable Documentation

FILE* infile
 

Definition at line 56 of file jpegSize.cpp.

Referenced by getJPEGSize().


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