jpeglib.h

1. 实现BMP文件到JPEG文件的压缩转换。 2. 自选：实现从JPEG文件到BMP文件转换。 3. 采用C/C++编写程序

  /* The coefficient controller receives data in units of MCU rows as defined
   * for fully interleaved scans (whether the JPEG file is interleaved or not).
   * There are v_samp_factor * DCTSIZE sample rows of each component in an
   * "iMCU" (interleaved MCU) row.
   */
  
  /*
   * These fields are valid during any one scan.
   * They describe the components and MCUs actually appearing in the scan.
   */
  int comps_in_scan;		/* # of JPEG components in this scan */
  jpeg_component_info * cur_comp_info[MAX_COMPS_IN_SCAN];
  /* *cur_comp_info[i] describes component that appears i'th in SOS */
  
  JDIMENSION MCUs_per_row;	/* # of MCUs across the image */
  JDIMENSION MCU_rows_in_scan;	/* # of MCU rows in the image */
  
  int blocks_in_MCU;		/* # of DCT blocks per MCU */
  int MCU_membership[C_MAX_BLOCKS_IN_MCU];
  /* MCU_membership[i] is index in cur_comp_info of component owning */
  /* i'th block in an MCU */

  int Ss, Se, Ah, Al;		/* progressive JPEG parameters for scan */

  /*
   * Links to compression subobjects (methods and private variables of modules)
   */
  struct jpeg_comp_master * master;
  struct jpeg_c_main_controller * main;
  struct jpeg_c_prep_controller * prep;
  struct jpeg_c_coef_controller * coef;
  struct jpeg_marker_writer * marker;
  struct jpeg_color_converter * cconvert;
  struct jpeg_downsampler * downsample;
  struct jpeg_forward_dct * fdct;
  struct jpeg_entropy_encoder * entropy;
};


/* Master record for a decompression instance */

struct jpeg_decompress_struct {
  jpeg_common_fields;		/* Fields shared with jpeg_compress_struct */

  /* Source of compressed data */
  struct jpeg_source_mgr * src;

  /* Basic description of image --- filled in by jpeg_read_header(). */
  /* Application may inspect these values to decide how to process image. */

  JDIMENSION image_width;	/* nominal image width (from SOF marker) */
  JDIMENSION image_height;	/* nominal image height */
  int num_components;		/* # of color components in JPEG image */
  J_COLOR_SPACE jpeg_color_space; /* colorspace of JPEG image */

  /* Decompression processing parameters --- these fields must be set before
   * calling jpeg_start_decompress().  Note that jpeg_read_header() initializes
   * them to default values.
   */

  J_COLOR_SPACE out_color_space; /* colorspace for output */

  unsigned int scale_num, scale_denom; /* fraction by which to scale image */

  double output_gamma;		/* image gamma wanted in output */

  boolean buffered_image;	/* TRUE=multiple output passes */
  boolean raw_data_out;		/* TRUE=downsampled data wanted */

  J_DCT_METHOD dct_method;	/* IDCT algorithm selector */
  boolean do_fancy_upsampling;	/* TRUE=apply fancy upsampling */
  boolean do_block_smoothing;	/* TRUE=apply interblock smoothing */

  boolean quantize_colors;	/* TRUE=colormapped output wanted */
  /* the following are ignored if not quantize_colors: */
  J_DITHER_MODE dither_mode;	/* type of color dithering to use */
  boolean two_pass_quantize;	/* TRUE=use two-pass color quantization */
  int desired_number_of_colors;	/* max # colors to use in created colormap */
  /* these are significant only in buffered-image mode: */
  boolean enable_1pass_quant;	/* enable future use of 1-pass quantizer */
  boolean enable_external_quant;/* enable future use of external colormap */
  boolean enable_2pass_quant;	/* enable future use of 2-pass quantizer */

  /* Description of actual output image that will be returned to application.
   * These fields are computed by jpeg_start_decompress().
   * You can also use jpeg_calc_output_dimensions() to determine these values
   * in advance of calling jpeg_start_decompress().
   */

  JDIMENSION output_width;	/* scaled image width */
  JDIMENSION output_height;	/* scaled image height */
  int out_color_components;	/* # of color components in out_color_space */
  int output_components;	/* # of color components returned */
  /* output_components is 1 (a colormap index) when quantizing colors;
   * otherwise it equals out_color_components.
   */
  int rec_outbuf_height;	/* min recommended height of scanline buffer */
  /* If the buffer passed to jpeg_read_scanlines() is less than this many rows
   * high, space and time will be wasted due to unnecessary data copying.
   * Usually rec_outbuf_height will be 1 or 2, at most 4.
   */

  /* When quantizing colors, the output colormap is described by these fields.
   * The application can supply a colormap by setting colormap non-NULL before
   * calling jpeg_start_decompress; otherwise a colormap is created during
   * jpeg_start_decompress or jpeg_start_output.
   * The map has out_color_components rows and actual_number_of_colors columns.
   */
  int actual_number_of_colors;	/* number of entries in use */
  JSAMPARRAY colormap;		/* The color map as a 2-D pixel array */

  /* State variables: these variables indicate the progress of decompression.
   * The application may examine these but must not modify them.
   */

  /* Row index of next scanline to be read from jpeg_read_scanlines().
   * Application may use this to control its processing loop, e.g.,
   * "while (output_scanline < output_height)".
   */
  JDIMENSION output_scanline;	/* 0 .. output_height-1  */

  /* Current input scan number and number of iMCU rows completed in scan.
   * These indicate the progress of the decompressor input side.
   */
  int input_scan_number;	/* Number of SOS markers seen so far */
  JDIMENSION input_iMCU_row;	/* Number of iMCU rows completed */

  /* The "output scan number" is the notional scan being displayed by the
   * output side.  The decompressor will not allow output scan/row number
   * to get ahead of input scan/row, but it can fall arbitrarily far behind.
   */
  int output_scan_number;	/* Nominal scan number being displayed */
  JDIMENSION output_iMCU_row;	/* Number of iMCU rows read */

  /* Current progression status.  coef_bits[c][i] indicates the precision
   * with which component c's DCT coefficient i (in zigzag order) is known.
   * It is -1 when no data has yet been received, otherwise it is the point
   * transform (shift) value for the most recent scan of the coefficient
   * (thus, 0 at completion of the progression).
   * This pointer is NULL when reading a non-progressive file.
   */
  int (*coef_bits)[DCTSIZE2];	/* -1 or current Al value for each coef */

  /* Internal JPEG parameters --- the application usually need not look at
   * these fields.  Note that the decompressor output side may not use
   * any parameters that can change between scans.
   */

  /* Quantization and Huffman tables are carried forward across input
   * datastreams when processing abbreviated JPEG datastreams.
   */

  JQUANT_TBL * quant_tbl_ptrs[NUM_QUANT_TBLS];
  /* ptrs to coefficient quantization tables, or NULL if not defined */

  JHUFF_TBL * dc_huff_tbl_ptrs[NUM_HUFF_TBLS];
  JHUFF_TBL * ac_huff_tbl_ptrs[NUM_HUFF_TBLS];
  /* ptrs to Huffman coding tables, or NULL if not defined */

  /* These parameters are never carried across datastreams, since they
   * are given in SOF/SOS markers or defined to be reset by SOI.
   */

  int data_precision;		/* bits of precision in image data */

  jpeg_component_info * comp_info;
  /* comp_info[i] describes component that appears i'th in SOF */

  boolean progressive_mode;	/* TRUE if SOFn specifies progressive mode */
  boolean arith_code;		/* TRUE=arithmetic coding, FALSE=Huffman */

  UINT8 arith_dc_L[NUM_ARITH_TBLS]; /* L values for DC arith-coding tables */
  UINT8 arith_dc_U[NUM_ARITH_TBLS]; /* U values for DC arith-coding tables */
  UINT8 arith_ac_K[NUM_ARITH_TBLS]; /* Kx values for AC arith-coding tables */

  unsigned int restart_interval; /* MCUs per restart interval, or 0 for no restart */

  /* These fields record data obtained from optional markers recognized by
   * the JPEG library.
   */
  boolean saw_JFIF_marker;	/* TRUE iff a JFIF APP0 marker was found */
  /* Data copied from JFIF marker: */
  UINT8 density_unit;		/* JFIF code for pixel size units */
  UINT16 X_density;		/* Horizontal pixel density */
  UINT16 Y_density;		/* Vertical pixel density */
  boolean saw_Adobe_marker;	/* TRUE iff an Adobe APP14 marker was found */
  UINT8 Adobe_transform;	/* Color transform code from Adobe marker */

  boolean CCIR601_sampling;	/* TRUE=first samples are cosited */

  /* Remaining fields are known throughout decompressor, but generally
   * should not be touched by a surrounding application.
   */

  /*
   * These fields are computed during decompression startup
   */
  int max_h_samp_factor;	/* largest h_samp_factor */
  int max_v_samp_factor;	/* largest v_samp_factor */

  int min_DCT_scaled_size;	/* smallest DCT_scaled_size of any component */

  JDIMENSION total_iMCU_rows;	/* # of iMCU rows in image */
  /* The coefficient controller's input and output progress is measured in
   * units of "iMCU" (interleaved MCU) rows.  These are the same as MCU rows
   * in fully interleaved JPEG scans, but are used whether the scan is
   * interleaved or not.  We define an iMCU row as v_samp_factor DCT block
   * rows of each component.  Therefore, the IDCT output contains
   * v_samp_factor*DCT_scaled_size sample rows of a component per iMCU row.
   */

  JSAMPLE * sample_range_limit; /* table for fast range-limiting */

  /*
   * These fields are valid during any one scan.
   * They describe the components and MCUs actually appearing in the scan.
   * Note that the decompressor output side must not use these fields.
   */
  int comps_in_scan;		/* # of JPEG components in this scan */
  jpeg_component_info * cur_comp_info[MAX_COMPS_IN_SCAN];
  /* *cur_comp_info[i] describes component that appears i'th in SOS */

  JDIMENSION MCUs_per_row;	/* # of MCUs across the image */
  JDIMENSION MCU_rows_in_scan;	/* # of MCU rows in the image */

  int blocks_in_MCU;		/* # of DCT blocks per MCU */
  int MCU_membership[D_MAX_BLOCKS_IN_MCU];
  /* MCU_membership[i] is index in cur_comp_info of component owning */
  /* i'th block in an MCU */

  int Ss, Se, Ah, Al;		/* progressive JPEG parameters for scan */

  /* This field is shared between entropy decoder and marker parser.
   * It is either zero or the code of a JPEG marker that has been
   * read from the data source, but has not yet been processed.
   */
  int unread_marker;

  /*
   * Links to decompression subobjects (methods, private variables of modules)
   */
  struct jpeg_decomp_master * master;
  struct jpeg_d_main_controller * main;
  struct jpeg_d_coef_controller * coef;
  struct jpeg_d_post_controller * post;
  struct jpeg_input_controller * inputctl;
  struct jpeg_marker_reader * marker;
  struct jpeg_entropy_decoder * entropy;
  struct jpeg_inverse_dct * idct;
  struct jpeg_upsampler * upsample;
  struct jpeg_color_deconverter * cconvert;
  struct jpeg_color_quantizer * cquantize;
};


/* "Object" declarations for JPEG modules that may be supplied or called
 * directly by the surrounding application.
 * As with all objects in the JPEG library, these structs only define the
 * publicly visible methods and state variables of a module.  Additional
 * private fields may exist after the public ones.
 */


/* Error handler object */

struct jpeg_error_mgr {
  /* Error exit handler: does not return to caller */
  JMETHOD(void, error_exit, (j_common_ptr cinfo));
  /* Conditionally emit a trace or warning message */
  JMETHOD(void, emit_message, (j_common_ptr cinfo, int msg_level));
  /* Routine that actually outputs a trace or error message */
  JMETHOD(void, output_message, (j_common_ptr cinfo));
  /* Format a message string for the most recent JPEG error or message */
  JMETHOD(void, format_message, (j_common_ptr cinfo, char * buffer));
#define JMSG_LENGTH_MAX  200	/* recommended size of format_message buffer */
  /* Reset error state variables at start of a new image */
  JMETHOD(void, reset_error_mgr, (j_common_ptr cinfo));
  
  /* The message ID code and any parameters are saved here.
   * A message can have one string parameter or up to 8 int parameters.
   */
  int msg_code;
#define JMSG_STR_PARM_MAX  80
  union {
    int i[8];
    char s[JMSG_STR_PARM_MAX];
  } msg_parm;
  
  /* Standard state variables for error facility */
  
  int trace_level;		/* max msg_level that will be displayed */
  
  /* For recoverable corrupt-data errors, we emit a warning message,
   * but keep going unless emit_message chooses to abort.  emit_message
   * should count warnings in num_warnings.  The surrounding application
   * can check for bad data by seeing if num_warnings is nonzero at the
   * end of processing.
   */
  long num_warnings;		/* number of corrupt-data warnings */

  /* These fields point to the table(s) of error message strings.
   * An application can change the table pointer to switch to a different
   * message list (typically, to change the language in which errors are
   * reported).  Some applications may wish to add additional error codes
   * that will be handled by the JPEG library error mechanism; the second
   * table pointer is used for this purpose.
   *
   * First table includes all errors generated by JPEG library itself.
   * Error code 0 is reserved for a "no such error string" message.
   */
  const char * const * jpeg_message_table; /* Library errors */
  int last_jpeg_message;    /* Table contains strings 0..last_jpeg_message */
  /* Second table can be added by application (see cjpeg/djpeg for example).
   * It contains strings numbered first_addon_message..last_addon_message.
   */
  const char * const * addon_message_table; /* Non-library errors */
  int first_addon_message;	/* code for first string in addon table */
  int last_addon_message;	/* code for last string in addon table */
};


/* Progress monitor object */

struct jpeg_progress_mgr {
  JMETHOD(void, progress_monitor, (j_common_ptr cinfo));

  long pass_counter;		/* work units completed in this pass */
  long pass_limit;		/* total number of work units in this pass */
  int completed_passes;		/* passes completed so far */
  int total_passes;		/* total number of passes expected */
};


/* Data destination object for compression */

struct jpeg_destination_mgr {
  JOCTET * next_output_byte;	/* => next byte to write in buffer */
  size_t free_in_buffer;	/* # of byte spaces remaining in buffer */

  JMETHOD(void, init_destination, (j_compress_ptr cinfo));
  JMETHOD(boolean, empty_output_buffer, (j_compress_ptr cinfo));
  JMETHOD(void, term_destination, (j_compress_ptr cinfo));
};


/* Data source object for decompression */

struct jpeg_source_mgr {
  const JOCTET * next_input_byte; /* => next byte to read from buffer */
  size_t bytes_in_buffer;	/* # of bytes remaining in buffer */

  JMETHOD(void, init_source, (j_decompress_ptr cinfo));