tif_ojpeg.c

一个国人自己实现图像库的程序（有参考价值）

              case 0xC1: /* SOF1  */
              case 0xC2: /* SOF2  */
              case 0xC3: /* SOF3  */
              case 0xC4: /* DHT   */
              case 0xC5: /* SOF5  */
              case 0xC6: /* SOF6  */
              case 0xC7: /* SOF7  */
              case 0xC9: /* SOF9  */
              case 0xCA: /* SOF10 */
              case 0xCB: /* SOF11 */
              case 0xCC: /* DAC   */
              case 0xCD: /* SOF13 */
              case 0xCE: /* SOF14 */
              case 0xCF: /* SOF15 */
              case 0xDB: /* DQT   */
              case 0xDD: /* DRI   */
              case 0xDF: /* EXP   */
              case 0xE0: /* APP0  */
              case 0xE1: /* APP1  */
              case 0xE2: /* APP2  */
              case 0xE3: /* APP3  */
              case 0xE4: /* APP4  */
              case 0xE5: /* APP5  */
              case 0xE6: /* APP6  */
              case 0xE7: /* APP7  */
              case 0xE8: /* APP8  */
              case 0xE9: /* APP9  */
              case 0xEA: /* APP10 */
              case 0xEB: /* APP11 */
              case 0xEC: /* APP12 */
              case 0xED: /* APP13 */
              case 0xEE: /* APP14 */
              case 0xEF: /* APP15 */
              case 0xFE: /* COM   */
                         p += (p[2] << 8 | p[3]) + 2;
            };
     L: if (p - (unsigned char *)sp->jpegtables > 2) /* fake "JPEGTables" */
          {

         /* In case our client application asks, pretend that this image file
            contains a modern "JPEGTables" TIFF record by copying to a buffer
            the initial part of the JFIF bit-stream that we just scanned, from
            the SOI marker through the "metadata" tables, then append an EOI
            marker and flag the "JPEGTables" TIFF record as "present".
         */
            sp->jpegtables_length = p - (unsigned char*)sp->jpegtables + 2;
            p = sp->jpegtables;
            if (!(sp->jpegtables = _TIFFmalloc(sp->jpegtables_length)))
              {
                TIFFError(module,no_jtable_space);
                return 0;
              };
            _TIFFmemcpy(sp->jpegtables,p,sp->jpegtables_length-2);
            p = (unsigned char *)sp->jpegtables + sp->jpegtables_length;
            p[-2] = 0xFF; p[-1] = JPEG_EOI; /* Append EOI marker */
            TIFFSetFieldBit(tif,FIELD_JPEGTABLES);
            tif->tif_flags |= TIFF_DIRTYDIRECT;
          }
        else sp->jpegtables = 0; /* Don't simulate "JPEGTables" */
        if (TIFFojpeg_read_header(sp,TRUE) != JPEG_HEADER_OK) return 0;
        if (   sp->cinfo.d.image_width  != segment_width
            || sp->cinfo.d.image_height != segment_height
           )
          {
            TIFFError(module,"Improper JPEG strip/tile size");
            return 0;
          };
        if ( ( td->td_planarconfig == PLANARCONFIG_CONTIG
             ? td->td_samplesperpixel
             : 1
             ) != sp->cinfo.d.num_components
           )
          {
            TIFFError(module,"Improper JPEG component count");
            return 0;
          };
        if (sp->cinfo.d.data_precision != td->td_bitspersample)
          {
            TIFFError(module,"Improper JPEG data precision");
            return 0;
          };
        if (td->td_planarconfig == PLANARCONFIG_CONTIG)
          { int ci;

         /* Component 0 should have expected sampling factors. */

            if (   sp->cinfo.d.comp_info[0].h_samp_factor != sp->h_sampling
                || sp->cinfo.d.comp_info[0].v_samp_factor != sp->v_sampling
               )
              {
                TIFFError(module,bad_factors);
                return 0;
              };
            ci = 1; /* The rest should have sampling factors 1,1 */
            do if (   sp->cinfo.d.comp_info[ci].h_samp_factor != 1
                   || sp->cinfo.d.comp_info[ci].v_samp_factor != 1
                  )
                 {
                   TIFFError(module,bad_factors);
                   return 0;
                 }
            while (++ci < sp->cinfo.d.num_components);
          }
        else

       /* PLANARCONFIG_SEPARATE's single component should have sampling factors
          1,1.
       */
          if (   sp->cinfo.d.comp_info[0].h_samp_factor != 1
              || sp->cinfo.d.comp_info[0].v_samp_factor != 1
             )
            {
              TIFFError(module,bad_factors);
              return 0;
            }
      }
    else /* not JFIF image */
      { int (*save)(j_decompress_ptr cinfo) = sp->cinfo.d.marker->read_markers;
        register int i;

     /* We're not assuming that this file's JPEG bit stream has any header
        "metadata", so fool the JPEG Library into thinking that we read a
        "Start of Input" (SOI) marker and a "Start of Frame" (SOFx) marker, then
        force it to read a simulated "Start of Scan" (SOS) marker when we call
        "TIFFojpeg_read_header()" below.  This should cause the JPEG Library to
        establish reasonable defaults.
     */
        sp->cinfo.d.marker->saw_SOI =       /* Pretend we saw SOI marker */
        sp->cinfo.d.marker->saw_SOF = TRUE; /* Pretend we saw SOF marker */
        sp->cinfo.d.marker->read_markers =
          sp->is_WANG ? suspend : fake_SOS_marker;
        sp->cinfo.d.global_state = DSTATE_INHEADER;
        sp->cinfo.d.Se = DCTSIZE2-1; /* Suppress JPEG Library warning */
        sp->cinfo.d.image_width  = segment_width;
        sp->cinfo.d.image_height = segment_height;
        sp->cinfo.d.data_precision = td->td_bitspersample;

     /* The following color-space initialization, including the complicated
        "switch"-statement below, essentially duplicates the logic used by the
        JPEG Library's "jpeg_init_colorspace()" subroutine during compression.
     */
        sp->cinfo.d.num_components = td->td_planarconfig == PLANARCONFIG_CONTIG
                                    ? td->td_samplesperpixel
                                    : 1;
        sp->cinfo.d.comp_info = (jpeg_component_info *)
          (*sp->cinfo.d.mem->alloc_small)
            ( &sp->cinfo.comm
            , JPOOL_IMAGE
            , sp->cinfo.d.num_components * sizeof *sp->cinfo.d.comp_info
            );
        i = 0;
        do
          {
            sp->cinfo.d.comp_info[i].component_index = i;
            sp->cinfo.d.comp_info[i].component_needed = TRUE;
            sp->cinfo.d.cur_comp_info[i] = &sp->cinfo.d.comp_info[i];
          }
        while (++i < sp->cinfo.d.num_components);
        switch (in_color_space)
          {
            case JCS_UNKNOWN  :
              i = 0;
              do
                {
                  sp->cinfo.d.comp_info[i].component_id = i;
                  sp->cinfo.d.comp_info[i].h_samp_factor =
                  sp->cinfo.d.comp_info[i].v_samp_factor = 1;
                }
              while (++i < sp->cinfo.d.num_components);
              break;
            case JCS_GRAYSCALE:
              sp->cinfo.d.comp_info[0].component_id =
              sp->cinfo.d.comp_info[0].h_samp_factor =
              sp->cinfo.d.comp_info[0].v_samp_factor = 1;
              break;
            case JCS_RGB      :
              sp->cinfo.d.comp_info[0].component_id = 'R';
              sp->cinfo.d.comp_info[1].component_id = 'G';
              sp->cinfo.d.comp_info[2].component_id = 'B';
              i = 0;
              do sp->cinfo.d.comp_info[i].h_samp_factor =
                 sp->cinfo.d.comp_info[i].v_samp_factor = 1;
              while (++i < sp->cinfo.d.num_components);
              break;
            case JCS_CMYK     :
              sp->cinfo.d.comp_info[0].component_id = 'C';
              sp->cinfo.d.comp_info[1].component_id = 'Y';
              sp->cinfo.d.comp_info[2].component_id = 'M';
              sp->cinfo.d.comp_info[3].component_id = 'K';
              i = 0;
              do sp->cinfo.d.comp_info[i].h_samp_factor =
                 sp->cinfo.d.comp_info[i].v_samp_factor = 1;
              while (++i < sp->cinfo.d.num_components);
              break;
            case JCS_YCbCr    :
              i = 0;
              do
                {
                  sp->cinfo.d.comp_info[i].component_id = i+1;
                  sp->cinfo.d.comp_info[i].h_samp_factor =
                  sp->cinfo.d.comp_info[i].v_samp_factor = 1;
                  sp->cinfo.d.comp_info[i].quant_tbl_no =
                  sp->cinfo.d.comp_info[i].dc_tbl_no =
                  sp->cinfo.d.comp_info[i].ac_tbl_no = i > 0;
                }
              while (++i < sp->cinfo.d.num_components);
              sp->cinfo.d.comp_info[0].h_samp_factor = sp->h_sampling;
              sp->cinfo.d.comp_info[0].v_samp_factor = sp->v_sampling;
          };
        sp->cinfo.d.comps_in_scan = sp->cinfo.d.num_components;
        i = TIFFojpeg_read_header(sp,(unsigned char)(!sp->is_WANG));
        sp->cinfo.d.marker->read_markers = save; /* Restore input method */
        if (sp->is_WANG) /* Microsoft Wang Imaging for Windows file */
          {
            if (i != JPEG_SUSPENDED) return 0;

         /* BOGOSITY ALERT!  Files generated by Microsoft's Wang Imaging
                             application are a special--and, technically
            illegal--case.  A JPEG SOS marker and rest of the data stream should
            be located at the end of the file, in a position identified by the
            0th Strip offset.
         */
            i = td->td_nstrips - 1;
            sp->src.next_input_byte = tif->tif_base + td->td_stripoffset[0];
            sp->src.bytes_in_buffer = td->td_stripoffset[i] -
              td->td_stripoffset[0] + td->td_stripbytecount[i];
            i = TIFFojpeg_read_header(sp,TRUE);
          };
        if (i != JPEG_HEADER_OK) return 0;
      };

 /* The JPEG Library doesn't seem to be as smart as we are about choosing
    suitable default input- and output color spaces for decompression, so fix
    things up here.
 */
    sp->cinfo.d.out_color_space =
      ((sp->cinfo.d.jpeg_color_space = in_color_space) == JCS_YCbCr)
      ? (sp->jpegcolormode == JPEGCOLORMODE_RGB ? JCS_RGB : JCS_YCbCr)
      : JCS_UNKNOWN; /* Suppress color-space handling */
    tif->tif_decoderow = tif->tif_decodestrip = tif->tif_decodetile =
      (sp->cinfo.d.raw_data_out = downsampled_output)
      ? OJPEGDecodeRaw : OJPEGDecode;
    if (!TIFFojpeg_start_decompress(sp)) return 0; /* Start JPEG decompressor */
    if (downsampled_output) /* allocate downsampled-data buffers */
      {
        if (!alloc_downsampled_buffers(tif,sp->cinfo.d.comp_info,
                                       sp->cinfo.d.num_components)
           ) return 0;
        sp->scancount = DCTSIZE; /* mark buffer empty */
      };
    return 1;
#   undef td
  }

static int
OJPEGVSetField(register TIFF *tif,ttag_t tag,va_list ap)
  { uint32 v32;
    register OJPEGState *sp = OJState(tif);
#   define td (&tif->tif_dir)

    switch (tag)
      {
#       ifdef COLORIMETRY_SUPPORT

     /* If a "ReferenceBlackWhite" TIFF tag appears in the file explicitly, undo
        any modified default definition that we might have installed below, then
        install the real one.
     */
        case TIFFTAG_REFERENCEBLACKWHITE   : if (td->td_refblackwhite)
                                               {
                                                 _TIFFfree(td->td_refblackwhite);
                                                 td->td_refblackwhite = 0;
                                               };
#       endif /* COLORIMETRY_SUPPORT */
        default                            : return
                                               (*sp->vsetparent)(tif,tag,ap);
#       ifdef COLORIMETRY_SUPPORT

     /* BEWARE OF KLUDGE:  Some old-format JPEG-in-TIFF files, including those
                           created by Microsoft's Wang Imaging application,
        illegally omit a "ReferenceBlackWhite" TIFF tag, even though the TIFF
        specification's default is intended for the RGB color space and is in-
        appropriate for the YCbCr color space ordinarily used for JPEG images.
        Since many TIFF client applications request the value of this tag
        immediately after a TIFF image directory is parsed, and before any other
        code in this module receives control, we are forced to fix this problem
        very early in image-file processing.  Fortunately, legal TIFF files are
        supposed to store their tags in numeric order, so a mandatory
        "PhotometricInterpretation" tag should always appear before an optional
        "ReferenceBlackWhite" tag.  So, we slyly peek ahead when we discover the
        desired photometry, by installing modified black and white reference
        levels.
     */
        case TIFFTAG_PHOTOMETRIC           :
          if (   (v32 = (*sp->vsetparent)(tif,tag,ap))
              && td->td_photometric == PHOTOMETRIC_YCBCR
             )
            if (td->td_refblackwhite = _TIFFmalloc(6*sizeof(float)))
              { register long top = 1 << td->td_bitspersample;

                td->td_refblackwhite[0] = 0;
                td->td_refblackwhite[1] = td->td_refblackwhite[3] =
                td->td_refblackwhite[5] = (float)(top - 1);
                td->td_refblackwhite[2] = td->td_refblackwhite[4] = (float)(top >> 1);
              }
            else
              {
                TIFFError(tif->tif_name,"Cannot define default reference black and white levels");
                v32 = 0;
              };
          return v32;
#       endif /* COLORIMETRY_SUPPORT */

     /* BEWARE OF KLUDGE:  According to Charles Auer <[e-mail]>, if our
                           input is a multi-image (multi-directory) JPEG-in-TIFF
        file created by Microsoft's Wang Imaging application, for some reason
        the first directory excludes the vendor-specific "WANG PageControl" tag
        (32934) that we check below, so the only other way to identify these
        directories is apparently to look for a software-identification tag with
        the substring, "Wang Labs".  Single-image files can apparently pass both
        tests, which causes no harm here, but what a mes