jpeglib.h

一个室内场景漫游程序

  /* for decompression, they are read from the SOS marker. */
  /* The decompressor output side may not use these variables. */
  int dc_tbl_no;		/* DC entropy table selector (0..3) */
  int ac_tbl_no;		/* AC entropy table selector (0..3) */
  
  /* Remaining fields should be treated as private by applications. */
  
  /* These values are computed during compression or decompression startup: */
  /* Component's size in DCT blocks.
   * Any dummy blocks added to complete an MCU are not counted; therefore
   * these values do not depend on whether a scan is interleaved or not.
   */
  JDIMENSION width_in_blocks;
  JDIMENSION height_in_blocks;
  /* Size of a DCT block in samples.  Always DCTSIZE for compression.
   * For decompression this is the size of the output from one DCT block,
   * reflecting any scaling we choose to apply during the IDCT step.
   * Values of 1,2,4,8 are likely to be supported.  Note that different
   * components may receive different IDCT scalings.
   */
  int DCT_scaled_size;
  /* The downsampled dimensions are the component's actual, unpadded number
   * of samples at the main buffer (preprocessing/compression interface), thus
   * downsampled_width = ceil(image_width * Hi/Hmax)
   * and similarly for height.  For decompression, IDCT scaling is included, so
   * downsampled_width = ceil(image_width * Hi/Hmax * DCT_scaled_size/DCTSIZE)
   */
  JDIMENSION downsampled_width;	 /* actual width in samples */
  JDIMENSION downsampled_height; /* actual height in samples */
  /* This flag is used only for decompression.  In cases where some of the
   * components will be ignored (eg grayscale output from YCbCr image),
   * we can skip most computations for the unused components.
   */
  boolean component_needed;	/* do we need the value of this component? */

  /* These values are computed before starting a scan of the component. */
  /* The decompressor output side may not use these variables. */
  int MCU_width;		/* number of blocks per MCU, horizontally */
  int MCU_height;		/* number of blocks per MCU, vertically */
  int MCU_blocks;		/* MCU_width * MCU_height */
  int MCU_sample_width;		/* MCU width in samples, MCU_width*DCT_scaled_size */
  int last_col_width;		/* # of non-dummy blocks across in last MCU */
  int last_row_height;		/* # of non-dummy blocks down in last MCU */

  /* Saved quantization table for component; NULL if none yet saved.
   * See jdinput.c comments about the need for this information.
   * This field is currently used only for decompression.
   */
  JQUANT_TBL * quant_table;

  /* Private per-component storage for DCT or IDCT subsystem. */
  void * dct_table;
} jpeg_component_info;


/* The script for encoding a multiple-scan file is an array of these: */

typedef struct {
  int comps_in_scan;		/* number of components encoded in this scan */
  int component_index[MAX_COMPS_IN_SCAN]; /* their SOF/comp_info[] indexes */
  int Ss, Se;			/* progressive JPEG spectral selection parms */
  int Ah, Al;			/* progressive JPEG successive approx. parms */
} jpeg_scan_info;

/* The decompressor can save APPn and COM markers in a list of these: */

typedef struct jpeg_marker_struct FAR * jpeg_saved_marker_ptr;

struct jpeg_marker_struct {
  jpeg_saved_marker_ptr next;	/* next in list, or NULL */
  UINT8 marker;			/* marker code: JPEG_COM, or JPEG_APP0+n */
  unsigned int original_length;	/* # bytes of data in the file */
  unsigned int data_length;	/* # bytes of data saved at data[] */
  JOCTET FAR * data;		/* the data contained in the marker */
  /* the marker length word is not counted in data_length or original_length */
};

/* Known color spaces. */

typedef enum {
	JCS_UNKNOWN,		/* error/unspecified */
	JCS_GRAYSCALE,		/* monochrome */
	JCS_RGB,		/* red/green/blue */
	JCS_YCbCr,		/* Y/Cb/Cr (also known as YUV) */
	JCS_CMYK,		/* C/M/Y/K */
	JCS_YCCK		/* Y/Cb/Cr/K */
} J_COLOR_SPACE;

/* DCT/IDCT algorithm options. */

typedef enum {
	JDCT_ISLOW,		/* slow but accurate integer algorithm */
	JDCT_IFAST,		/* faster, less accurate integer method */
	JDCT_FLOAT		/* floating-point: accurate, fast on fast HW */
} J_DCT_METHOD;

#ifndef JDCT_DEFAULT		/* may be overridden in jconfig.h */
#define JDCT_DEFAULT  JDCT_ISLOW
#endif
#ifndef JDCT_FASTEST		/* may be overridden in jconfig.h */
#define JDCT_FASTEST  JDCT_IFAST
#endif

/* Dithering options for decompression. */

typedef enum {
	JDITHER_NONE,		/* no dithering */
	JDITHER_ORDERED,	/* simple ordered dither */
	JDITHER_FS		/* Floyd-Steinberg error diffusion dither */
} J_DITHER_MODE;


/* Common fields between JPEG compression and decompression master structs. */

#define jpeg_common_fields \
  struct jpeg_error_mgr * err;	/* Error handler module */\
  struct jpeg_memory_mgr * mem;	/* Memory manager module */\
  struct jpeg_progress_mgr * progress; /* Progress monitor, or NULL if none */\
  void * client_data;		/* Available for use by application */\
  boolean is_decompressor;	/* So common code can tell which is which */\
  int global_state		/* For checking call sequence validity */

/* Routines that are to be used by both halves of the library are declared
 * to receive a pointer to this structure.  There are no actual instances of
 * jpeg_common_struct, only of jpeg_compress_struct and jpeg_decompress_struct.
 */
struct jpeg_common_struct {
  jpeg_common_fields;		/* Fields common to both master struct types */
  /* Additional fields follow in an actual jpeg_compress_struct or
   * jpeg_decompress_struct.  All three structs must agree on these
   * initial fields!  (This would be a lot cleaner in C++.)
   */
};

typedef struct jpeg_common_struct * j_common_ptr;
typedef struct jpeg_compress_struct * j_compress_ptr;
typedef struct jpeg_decompress_struct * j_decompress_ptr;


/* Master record for a compression instance */

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

  /* Destination for compressed data */
  struct jpeg_destination_mgr * dest;

  /* Description of source image --- these fields must be filled in by
   * outer application before starting compression.  in_color_space must
   * be correct before you can even call jpeg_set_defaults().
   */

  JDIMENSION image_width;	/* input image width */
  JDIMENSION image_height;	/* input image height */
  int input_components;		/* # of color components in input image */
  J_COLOR_SPACE in_color_space;	/* colorspace of input image */

  double input_gamma;		/* image gamma of input image */

  /* Compression parameters --- these fields must be set before calling
   * jpeg_start_compress().  We recommend calling jpeg_set_defaults() to
   * initialize everything to reasonable defaults, then changing anything
   * the application specifically wants to change.  That way you won't get
   * burnt when new parameters are added.  Also note that there are several
   * helper routines to simplify changing parameters.
   */

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

  int num_components;		/* # of color components in JPEG image */
  J_COLOR_SPACE jpeg_color_space; /* colorspace of JPEG image */

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

  int num_scans;		/* # of entries in scan_info array */
  const jpeg_scan_info * scan_info; /* script for multi-scan file, or NULL */
  /* The default value of scan_info is NULL, which causes a single-scan
   * sequential JPEG file to be emitted.  To create a multi-scan file,
   * set num_scans and scan_info to point to an array of scan definitions.
   */

  boolean raw_data_in;		/* TRUE=caller supplies downsampled data */
  boolean arith_code;		/* TRUE=arithmetic coding, FALSE=Huffman */
  boolean optimize_coding;	/* TRUE=optimize entropy encoding parms */
  boolean CCIR601_sampling;	/* TRUE=first samples are cosited */
  int smoothing_factor;		/* 1..100, or 0 for no input smoothing */
  J_DCT_METHOD dct_method;	/* DCT algorithm selector */

  /* The restart interval can be specified in absolute MCUs by setting
   * restart_interval, or in MCU rows by setting restart_in_rows
   * (in which case the correct restart_interval will be figured
   * for each scan).
   */
  unsigned int restart_interval; /* MCUs per restart, or 0 for no restart */
  int restart_in_rows;		/* if > 0, MCU rows per restart interval */

  /* Parameters controlling emission of special markers. */

  boolean write_JFIF_header;	/* should a JFIF marker be written? */
  UINT8 JFIF_major_version;	/* What to write for the JFIF version number */
  UINT8 JFIF_minor_version;
  /* These three values are not used by the JPEG code, merely copied */
  /* into the JFIF APP0 marker.  density_unit can be 0 for unknown, */
  /* 1 for dots/inch, or 2 for dots/cm.  Note that the pixel aspect */
  /* ratio is defined by X_density/Y_density even when density_unit=0. */
  UINT8 density_unit;		/* JFIF code for pixel size units */
  UINT16 X_density;		/* Horizontal pixel density */
  UINT16 Y_density;		/* Vertical pixel density */
  boolean write_Adobe_marker;	/* should an Adobe marker be written? */
  
  /* State variable: index of next scanline to be written to
   * jpeg_write_scanlines().  Application may use this to control its
   * processing loop, e.g., "while (next_scanline < image_height)".
   */

  JDIMENSION next_scanline;	/* 0 .. image_height-1  */

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

  /*
   * These fields are computed during compression startup
   */
  boolean progressive_mode;	/* TRUE if scan script uses progressive mode */
  int max_h_samp_factor;	/* largest h_samp_factor */
  int max_v_samp_factor;	/* largest v_samp_factor */

  JDIMENSION total_iMCU_rows;	/* # of iMCU rows to be input to coef ctlr */
  /* 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;
  jpeg_scan_info * script_space; /* workspace for jpeg_simple_progression */
  int script_space_size;
};


/* 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 */