# dlib C++ Library - jctrans.c

    /*
     * jctrans.c
     *
     * Copyright (C) 1995-1998, Thomas G. Lane.
     * Modified 2000-2011 by Guido Vollbeding.
     * This file is part of the Independent JPEG Group's software.
     * For conditions of distribution and use, see the accompanying README file.
     *
     * This file contains library routines for transcoding compression,
     * that is, writing raw DCT coefficient arrays to an output JPEG file.
     * The routines in jcapimin.c will also be needed by a transcoder.
     */

    #define JPEG_INTERNALS
    #include "jinclude.h"
    #include "jpeglib.h"

    /* Forward declarations */
    LOCAL(void) transencode_master_selection
    	JPP((j_compress_ptr cinfo, jvirt_barray_ptr * coef_arrays));
    LOCAL(void) transencode_coef_controller
    	JPP((j_compress_ptr cinfo, jvirt_barray_ptr * coef_arrays));

    /*
     * Compression initialization for writing raw-coefficient data.
     * Before calling this, all parameters and a data destination must be set up.
     * Call jpeg_finish_compress() to actually write the data.
     *
     * The number of passed virtual arrays must match cinfo->num_components.
     * Note that the virtual arrays need not be filled or even realized at
     * the time write_coefficients is called; indeed, if the virtual arrays
     * were requested from this compression object's memory manager, they
     * typically will be realized during this routine and filled afterwards.
     */

    GLOBAL(void)
    jpeg_write_coefficients (j_compress_ptr cinfo, jvirt_barray_ptr * coef_arrays)
    {
      if (cinfo->global_state != CSTATE_START)
        ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
      /* Mark all tables to be written */
      jpeg_suppress_tables(cinfo, FALSE);
      /* (Re)initialize error mgr and destination modules */
      (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
      (*cinfo->dest->init_destination) (cinfo);
      /* Perform master selection of active modules */
      transencode_master_selection(cinfo, coef_arrays);
      /* Wait for jpeg_finish_compress() call */
      cinfo->next_scanline = 0;	/* so jpeg_write_marker works */
      cinfo->global_state = CSTATE_WRCOEFS;
    }

    /*
     * Initialize the compression object with default parameters,
     * then copy from the source object all parameters needed for lossless
     * transcoding.  Parameters that can be varied without loss (such as
     * scan script and Huffman optimization) are left in their default states.
     */

    GLOBAL(void)
    jpeg_copy_critical_parameters (j_decompress_ptr srcinfo,
    			       j_compress_ptr dstinfo)
    {
      JQUANT_TBL ** qtblptr;
      jpeg_component_info *incomp, *outcomp;
      JQUANT_TBL *c_quant, *slot_quant;
      int tblno, ci, coefi;

      /* Safety check to ensure start_compress not called yet. */
      if (dstinfo->global_state != CSTATE_START)
        ERREXIT1(dstinfo, JERR_BAD_STATE, dstinfo->global_state);
      /* Copy fundamental image dimensions */
      dstinfo->image_width = srcinfo->image_width;
      dstinfo->image_height = srcinfo->image_height;
      dstinfo->input_components = srcinfo->num_components;
      dstinfo->in_color_space = srcinfo->jpeg_color_space;
      dstinfo->jpeg_width = srcinfo->output_width;
      dstinfo->jpeg_height = srcinfo->output_height;
      dstinfo->min_DCT_h_scaled_size = srcinfo->min_DCT_h_scaled_size;
      dstinfo->min_DCT_v_scaled_size = srcinfo->min_DCT_v_scaled_size;
      /* Initialize all parameters to default values */
      jpeg_set_defaults(dstinfo);
      /* jpeg_set_defaults may choose wrong colorspace, eg YCbCr if input is RGB.
       * Fix it to get the right header markers for the image colorspace.
       */
      jpeg_set_colorspace(dstinfo, srcinfo->jpeg_color_space);
      dstinfo->data_precision = srcinfo->data_precision;
      dstinfo->CCIR601_sampling = srcinfo->CCIR601_sampling;
      /* Copy the source's quantization tables. */
      for (tblno = 0; tblno < NUM_QUANT_TBLS; tblno++) {
        if (srcinfo->quant_tbl_ptrs[tblno] != NULL) {
          qtblptr = & dstinfo->quant_tbl_ptrs[tblno];
          if (*qtblptr == NULL)
    	*qtblptr = jpeg_alloc_quant_table((j_common_ptr) dstinfo);
          MEMCOPY((*qtblptr)->quantval,
    	      srcinfo->quant_tbl_ptrs[tblno]->quantval,
    	      SIZEOF((*qtblptr)->quantval));
          (*qtblptr)->sent_table = FALSE;
        }
      }
      /* Copy the source's per-component info.
       * Note we assume jpeg_set_defaults has allocated the dest comp_info array.
       */
      dstinfo->num_components = srcinfo->num_components;
      if (dstinfo->num_components < 1 || dstinfo->num_components > MAX_COMPONENTS)
        ERREXIT2(dstinfo, JERR_COMPONENT_COUNT, dstinfo->num_components,
    	     MAX_COMPONENTS);
      for (ci = 0, incomp = srcinfo->comp_info, outcomp = dstinfo->comp_info;
           ci < dstinfo->num_components; ci++, incomp++, outcomp++) {
        outcomp->component_id = incomp->component_id;
        outcomp->h_samp_factor = incomp->h_samp_factor;
        outcomp->v_samp_factor = incomp->v_samp_factor;
        outcomp->quant_tbl_no = incomp->quant_tbl_no;
        /* Make sure saved quantization table for component matches the qtable
         * slot.  If not, the input file re-used this qtable slot.
         * IJG encoder currently cannot duplicate this.
         */
        tblno = outcomp->quant_tbl_no;
        if (tblno < 0 || tblno >= NUM_QUANT_TBLS ||
    	srcinfo->quant_tbl_ptrs[tblno] == NULL)
          ERREXIT1(dstinfo, JERR_NO_QUANT_TABLE, tblno);
        slot_quant = srcinfo->quant_tbl_ptrs[tblno];
        c_quant = incomp->quant_table;
        if (c_quant != NULL) {
          for (coefi = 0; coefi < DCTSIZE2; coefi++) {
    	if (c_quant->quantval[coefi] != slot_quant->quantval[coefi])
    	  ERREXIT1(dstinfo, JERR_MISMATCHED_QUANT_TABLE, tblno);
          }
        }
        /* Note: we do not copy the source's Huffman table assignments;
         * instead we rely on jpeg_set_colorspace to have made a suitable choice.
         */
      }
      /* Also copy JFIF version and resolution information, if available.
       * Strictly speaking this isn't "critical" info, but it's nearly
       * always appropriate to copy it if available.  In particular,
       * if the application chooses to copy JFIF 1.02 extension markers from
       * the source file, we need to copy the version to make sure we don't
       * emit a file that has 1.02 extensions but a claimed version of 1.01.
       * We will *not*, however, copy version info from mislabeled "2.01" files.
       */
      if (srcinfo->saw_JFIF_marker) {
        if (srcinfo->JFIF_major_version == 1) {
          dstinfo->JFIF_major_version = srcinfo->JFIF_major_version;
          dstinfo->JFIF_minor_version = srcinfo->JFIF_minor_version;
        }
        dstinfo->density_unit = srcinfo->density_unit;
        dstinfo->X_density = srcinfo->X_density;
        dstinfo->Y_density = srcinfo->Y_density;
      }
    }

    /*
     * Master selection of compression modules for transcoding.
     * This substitutes for jcinit.c's initialization of the full compressor.
     */

    LOCAL(void)
    transencode_master_selection (j_compress_ptr cinfo,
    			      jvirt_barray_ptr * coef_arrays)
    {
      /* Initialize master control (includes parameter checking/processing) */
      jinit_c_master_control(cinfo, TRUE /* transcode only */);

      /* Entropy encoding: either Huffman or arithmetic coding. */
      if (cinfo->arith_code)
        jinit_arith_encoder(cinfo);
      else {
        jinit_huff_encoder(cinfo);
      }

      /* We need a special coefficient buffer controller. */
      transencode_coef_controller(cinfo, coef_arrays);

      jinit_marker_writer(cinfo);

      /* We can now tell the memory manager to allocate virtual arrays. */
      (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);

      /* Write the datastream header (SOI, JFIF) immediately.
       * Frame and scan headers are postponed till later.
       * This lets application insert special markers after the SOI.
       */
      (*cinfo->marker->write_file_header) (cinfo);
    }

    /*
     * The rest of this file is a special implementation of the coefficient
     * buffer controller.  This is similar to jccoefct.c, but it handles only
     * output from presupplied virtual arrays.  Furthermore, we generate any
     * dummy padding blocks on-the-fly rather than expecting them to be present
     * in the arrays.
     */

    /* Private buffer controller object */

    typedef struct {
      struct jpeg_c_coef_controller pub; /* public fields */

      JDIMENSION iMCU_row_num;	/* iMCU row # within image */
      JDIMENSION mcu_ctr;		/* counts MCUs processed in current row */
      int MCU_vert_offset;		/* counts MCU rows within iMCU row */
      int MCU_rows_per_iMCU_row;	/* number of such rows needed */

      /* Virtual block array for each component. */
      jvirt_barray_ptr * whole_image;

      /* Workspace for constructing dummy blocks at right/bottom edges. */
      JBLOCKROW dummy_buffer[C_MAX_BLOCKS_IN_MCU];
    } my_coef_controller;

    typedef my_coef_controller * my_coef_ptr;

    LOCAL(void)
    start_iMCU_row (j_compress_ptr cinfo)
    /* Reset within-iMCU-row counters for a new row */
    {
      my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

      /* In an interleaved scan, an MCU row is the same as an iMCU row.
       * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
       * But at the bottom of the image, process only what's left.
       */
      if (cinfo->comps_in_scan > 1) {
        coef->MCU_rows_per_iMCU_row = 1;
      } else {
        if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
          coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
        else
          coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
      }

      coef->mcu_ctr = 0;
      coef->MCU_vert_offset = 0;
    }

    /*
     * Initialize for a processing pass.
     */

    METHODDEF(void)
    start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
    {
      my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

      if (pass_mode != JBUF_CRANK_DEST)
        ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

      coef->iMCU_row_num = 0;
      start_iMCU_row(cinfo);
    }

    /*
     * Process some data.
     * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
     * per call, ie, v_samp_factor block rows for each component in the scan.
     * The data is obtained from the virtual arrays and fed to the entropy coder.
     * Returns TRUE if the iMCU row is completed, FALSE if suspended.
     *
     * NB: input_buf is ignored; it is likely to be a NULL pointer.
     */

    METHODDEF(boolean)
    compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
    {
      my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
      JDIMENSION MCU_col_num;	/* index of current MCU within row */
      JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
      JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
      int blkn, ci, xindex, yindex, yoffset, blockcnt;
      JDIMENSION start_col;
      JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
      JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
      JBLOCKROW buffer_ptr;
      jpeg_component_info *compptr;

      /* Align the virtual buffers for the components used in this scan. */
      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
        compptr = cinfo->cur_comp_info[ci];
        buffer[ci] = (*cinfo->mem->access_virt_barray)
          ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
           coef->iMCU_row_num * compptr->v_samp_factor,
           (JDIMENSION) compptr->v_samp_factor, FALSE);
      }

      /* Loop to process one whole iMCU row */
      for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
           yoffset++) {
        for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
    	 MCU_col_num++) {
          /* Construct list of pointers to DCT blocks belonging to this MCU */
          blkn = 0;			/* index of current DCT block within MCU */
          for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    	compptr = cinfo->cur_comp_info[ci];
    	start_col = MCU_col_num * compptr->MCU_width;
    	blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
    						: compptr->last_col_width;
    	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
    	  if (coef->iMCU_row_num < last_iMCU_row ||
    	      yindex+yoffset < compptr->last_row_height) {
    	    /* Fill in pointers to real blocks in this row */
    	    buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
    	    for (xindex = 0; xindex < blockcnt; xindex++)
    	      MCU_buffer[blkn++] = buffer_ptr++;
    	  } else {
    	    /* At bottom of image, need a whole row of dummy blocks */
    	    xindex = 0;
    	  }
    	  /* Fill in any dummy blocks needed in this row.
    	   * Dummy blocks are filled in the same way as in jccoefct.c:
    	   * all zeroes in the AC entries, DC entries equal to previous
    	   * block's DC value.  The init routine has already zeroed the
    	   * AC entries, so we need only set the DC entries correctly.
    	   */
    	  for (; xindex < compptr->MCU_width; xindex++) {
    	    MCU_buffer[blkn] = coef->dummy_buffer[blkn];
    	    MCU_buffer[blkn][0][0] = MCU_buffer[blkn-1][0][0];
    	    blkn++;
    	  }
    	}
          }
          /* Try to write the MCU. */
          if (! (*cinfo->entropy->encode_mcu) (cinfo, MCU_buffer)) {
    	/* Suspension forced; update state counters and exit */
    	coef->MCU_vert_offset = yoffset;
    	coef->mcu_ctr = MCU_col_num;
    	return FALSE;
          }
        }
        /* Completed an MCU row, but perhaps not an iMCU row */
        coef->mcu_ctr = 0;
      }
      /* Completed the iMCU row, advance counters for next one */
      coef->iMCU_row_num++;
      start_iMCU_row(cinfo);
      return TRUE;
    }

    /*
     * Initialize coefficient buffer controller.
     *
     * Each passed coefficient array must be the right size for that
     * coefficient: width_in_blocks wide and height_in_blocks high,
     * with unitheight at least v_samp_factor.
     */

    LOCAL(void)
    transencode_coef_controller (j_compress_ptr cinfo,
    			     jvirt_barray_ptr * coef_arrays)
    {
      my_coef_ptr coef;
      JBLOCKROW buffer;
      int i;

      coef = (my_coef_ptr)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				SIZEOF(my_coef_controller));
      cinfo->coef = (struct jpeg_c_coef_controller *) coef;
      coef->pub.start_pass = start_pass_coef;
      coef->pub.compress_data = compress_output;

      /* Save pointer to virtual arrays */
      coef->whole_image = coef_arrays;

      /* Allocate and pre-zero space for dummy DCT blocks. */
      buffer = (JBLOCKROW)
        (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
      FMEMZERO((void FAR *) buffer, C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
      for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
        coef->dummy_buffer[i] = buffer + i;
      }
    }