libjpeg.pas

很好的源代码

     * calling jpeg_start_decompress().  Note that jpeg_read_header() initializes
     * them to default values.
     *)

    out_color_space: J_COLOR_SPACE; (* colorspace for output *)

    scale_num, scale_denom: uint; (* fraction by which to scale image *)

    output_gamma: double;		(* image gamma wanted in output *)

    buffered_image: boolean;	(* TRUE=multiple output passes *)
    raw_data_out: boolean ;		(* TRUE=downsampled data wanted *)

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

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

    output_width: JDIMENSION ;	(* scaled image width *)
    output_height: JDIMENSION ;	(* scaled image height *)
    out_color_components: int ;	(* # of color components in out_color_space *)
    output_components: int ;	(* # of color components returned *)
    (* output_components is 1 (a colormap index) when quantizing colors;
     * otherwise it equals out_color_components.
     *)
    rec_outbuf_height: int ;	(* 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.
     *)
    actual_number_of_colors: int ;	(* number of entries in use *)
    colormap: JSAMPARRAY ;		(* 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)".
     *)
    output_scanline: JDIMENSION ;	(* 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.
     *)
    input_scan_number: int ;	(* Number of SOS markers seen so far *)
    input_iMCU_row: JDIMENSION ;	(* 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.
     *)
    output_scan_number: int ;	(* Nominal scan number being displayed *)
    output_iMCU_row: JDIMENSION ;	(* 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.
     *)
    coef_bits: pcoef_bits; (* -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.
     *)

    quant_tbl_ptrs: array [0..NUM_QUANT_TBLS-1] of PJQUANT_TBL;
    (* ptrs to coefficient quantization tables, or NULL if not defined *)

    dc_huff_tbl_ptrs: array [0..NUM_HUFF_TBLS-1] of PJHUFF_TBL;
    ac_huff_tbl_ptrs: array [0..NUM_HUFF_TBLS-1] of PJHUFF_TBL;
    (* 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.
     *)

    data_precision: int ;		(* bits of precision in image data *)

    comp_info: pjpeg_component_info;
    (* comp_info[i] describes component that appears i'th in SOF *)

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

    arith_dc_L: array [0..NUM_ARITH_TBLS-1] of UINT8; (* L values for DC arith-coding tables *)
    arith_dc_U: array [0..NUM_ARITH_TBLS-1] of UINT8; (* U values for DC arith-coding tables *)
    arith_ac_K: array [0..NUM_ARITH_TBLS-1] of UINT8; (* Kx values for AC arith-coding tables *)

    restart_interval: uint ; (* MCUs per restart interval, or 0 for no restart *)

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

    CCIR601_sampling: boolean ;	(* TRUE=first samples are cosited *)

    (* Aside from the specific data retained from APPn markers known to the
     * library, the uninterpreted contents of any or all APPn and COM markers
     * can be saved in a list for examination by the application.
     *)
    marker_list: jpeg_saved_marker_ptr ; (* Head of list of saved markers *)

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

    (*
     * These fields are computed during decompression startup
     *)
    max_h_samp_factor: int ;	(* largest h_samp_factor *)
    max_v_samp_factor: int ;	(* largest v_samp_factor *)

    min_DCT_scaled_size: int ;	(* smallest DCT_scaled_size of any component *)

    total_iMCU_rows: JDIMENSION ;	(* # 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.
     *)

    sample_range_limit: PJSAMPLE; (* 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.
     *)
    comps_in_scan: int ;		(* # of JPEG components in this scan *)
    cur_comp_info: array [0..MAX_COMPS_IN_SCAN-1] of pjpeg_component_info;
    (* *cur_comp_info[i] describes component that appears i'th in SOS *)

    MCUs_per_row: JDIMENSION ;	(* # of MCUs across the image *)
    MCU_rows_in_scan: JDIMENSION ;	(* # of MCU rows in the image *)

    blocks_in_MCU: int ;		(* # of DCT blocks per MCU *)
    MCU_membership: array [0..D_MAX_BLOCKS_IN_MCU-1] of int;
    (* MCU_membership[i] is index in cur_comp_info of component owning *)
    (* i'th block in an MCU *)

    Ss, Se, Ah, Al: int;		(* 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.
     *)
    unread_marker: int ;

    (*
     * Links to decompression subobjects (methods, private variables of modules)
     *)
    master: pjpeg_decomp_master;
    main: pjpeg_d_main_controller;
    coef: pjpeg_d_coef_controller;
    post: pjpeg_d_post_controller;
    inputctl: pjpeg_input_controller;
    marker: pjpeg_marker_reader;
    entropy: pjpeg_entropy_decoder;
    idct: pjpeg_inverse_dct;
    upsample: pjpeg_upsampler;
    cconvert: pjpeg_color_deconverter;
    cquantize: pjpeg_color_quantizer;
  end;

  pjpeg_compress_struct = ^jpeg_compress_struct;
  jpeg_compress_struct = record
    err: pjpeg_error_mgr;	(* Error handler module *)
    mem: pjpeg_memory_mgr;	(* Memory manager module *)
    progress: pjpeg_progress_mgr; (* Progress monitor, or NULL if none *)
    client_data: Pointer;		(* Available for use by application *)
    is_decompressor: Boolean;	(* So common code can tell which is which *)
    global_state: int;		(* For checking call sequence validity *)

    (* Destination for compressed data *)
    dest: pjpeg_destination_mgr;

    (* 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().
     *)

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

    input_gamma: double;		(* 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.
     *)

    data_precision: int;		(* bits of precision in image data *)

    num_components: int;		(* # of color components in JPEG image *)
    jpeg_color_space: J_COLOR_SPACE; (* colorspace of JPEG image *)

    comp_info: pjpeg_component_info;
    (* comp_info[i] describes component that appears i'th in SOF *)

    quant_tbl_ptrs: array [0..NUM_QUANT_TBLS-1] of PJQUANT_TBL;
    (* ptrs to coefficient quantization tables, or NULL if not defined *)

    dc_huff_tbl_ptrs: array [0..NUM_HUFF_TBLS-1] of PJHUFF_TBL;
    ac_huff_tbl_ptrs: array [0..NUM_HUFF_TBLS-1] of PJHUFF_TBL;
    (* ptrs to Huffman coding tables, or NULL if not defined *)

    arith_dc_L: array [0..NUM_ARITH_TBLS-1] of UINT8; (* L values for DC arith-coding tables *)
    arith_dc_U: array [0..NUM_ARITH_TBLS-1] of UINT8; (* U values for DC arith-coding tables *)
    arith_ac_K: array [0..NUM_ARITH_TBLS-1] of UINT8; (* Kx values for AC arith-coding tables *)

    num_scans: int;		(* # of entries in scan_info array *)
    scan_info: pjpeg_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.
     *)

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

    (* The restart interval can be specified in absolute MCUs by setting