source: liacs/MIR2010/SourceCode/cximage/jpeg/jcprepct.c@ 422

/*

 * jcprepct.c

 *

 * Copyright (C) 1994-1996, Thomas G. Lane.

 * 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 the compression preprocessing controller.

 * This controller manages the color conversion, downsampling,

 * and edge expansion steps.

 *

 * Most of the complexity here is associated with buffering input rows

 * as required by the downsampler.  See the comments at the head of

 * jcsample.c for the downsampler's needs.

 */



#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"





/* At present, jcsample.c can request context rows only for smoothing.

 * In the future, we might also need context rows for CCIR601 sampling

 * or other more-complex downsampling procedures.  The code to support

 * context rows should be compiled only if needed.

 */

#ifdef INPUT_SMOOTHING_SUPPORTED

#define CONTEXT_ROWS_SUPPORTED

#endif





/*

 * For the simple (no-context-row) case, we just need to buffer one

 * row group's worth of pixels for the downsampling step.  At the bottom of

 * the image, we pad to a full row group by replicating the last pixel row.

 * The downsampler's last output row is then replicated if needed to pad

 * out to a full iMCU row.

 *

 * When providing context rows, we must buffer three row groups' worth of

 * pixels.  Three row groups are physically allocated, but the row pointer

 * arrays are made five row groups high, with the extra pointers above and

 * below "wrapping around" to point to the last and first real row groups.

 * This allows the downsampler to access the proper context rows.

 * At the top and bottom of the image, we create dummy context rows by

 * copying the first or last real pixel row.  This copying could be avoided

 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the

 * trouble on the compression side.

 */





/* Private buffer controller object */



typedef struct {

  struct jpeg_c_prep_controller pub; /* public fields */



  /* Downsampling input buffer.  This buffer holds color-converted data

   * until we have enough to do a downsample step.

   */

  JSAMPARRAY color_buf[MAX_COMPONENTS];



  JDIMENSION rows_to_go;        /* counts rows remaining in source image */

  int next_buf_row;             /* index of next row to store in color_buf */



#ifdef CONTEXT_ROWS_SUPPORTED   /* only needed for context case */

  int this_row_group;           /* starting row index of group to process */

  int next_buf_stop;            /* downsample when we reach this index */

#endif

} my_prep_controller;



typedef my_prep_controller * my_prep_ptr;





/*

 * Initialize for a processing pass.

 */



METHODDEF(void)

start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)

{

  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;



  if (pass_mode != JBUF_PASS_THRU)

    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);



  /* Initialize total-height counter for detecting bottom of image */

  prep->rows_to_go = cinfo->image_height;

  /* Mark the conversion buffer empty */

  prep->next_buf_row = 0;

#ifdef CONTEXT_ROWS_SUPPORTED

  /* Preset additional state variables for context mode.

   * These aren't used in non-context mode, so we needn't test which mode.

   */

  prep->this_row_group = 0;

  /* Set next_buf_stop to stop after two row groups have been read in. */

  prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;

#endif

}





/*

 * Expand an image vertically from height input_rows to height output_rows,

 * by duplicating the bottom row.

 */



LOCAL(void)

expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,

                    int input_rows, int output_rows)

{

  register int row;



  for (row = input_rows; row < output_rows; row++) {

    jcopy_sample_rows(image_data, input_rows-1, image_data, row,

                      1, num_cols);

  }

}





/*

 * Process some data in the simple no-context case.

 *

 * Preprocessor output data is counted in "row groups".  A row group

 * is defined to be v_samp_factor sample rows of each component.

 * Downsampling will produce this much data from each max_v_samp_factor

 * input rows.

 */



METHODDEF(void)

pre_process_data (j_compress_ptr cinfo,

                  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,

                  JDIMENSION in_rows_avail,

                  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,

                  JDIMENSION out_row_groups_avail)

{

  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

  int numrows, ci;

  JDIMENSION inrows;

  jpeg_component_info * compptr;



  while (*in_row_ctr < in_rows_avail &&

         *out_row_group_ctr < out_row_groups_avail) {

    /* Do color conversion to fill the conversion buffer. */

    inrows = in_rows_avail - *in_row_ctr;

    numrows = cinfo->max_v_samp_factor - prep->next_buf_row;

    numrows = (int) MIN((JDIMENSION) numrows, inrows);

    (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,

                                       prep->color_buf,

                                       (JDIMENSION) prep->next_buf_row,

                                       numrows);

    *in_row_ctr += numrows;

    prep->next_buf_row += numrows;

    prep->rows_to_go -= numrows;

    /* If at bottom of image, pad to fill the conversion buffer. */

    if (prep->rows_to_go == 0 &&

        prep->next_buf_row < cinfo->max_v_samp_factor) {

      for (ci = 0; ci < cinfo->num_components; ci++) {

        expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,

                           prep->next_buf_row, cinfo->max_v_samp_factor);

      }

      prep->next_buf_row = cinfo->max_v_samp_factor;

    }

    /* If we've filled the conversion buffer, empty it. */

    if (prep->next_buf_row == cinfo->max_v_samp_factor) {

      (*cinfo->downsample->downsample) (cinfo,

                                        prep->color_buf, (JDIMENSION) 0,

                                        output_buf, *out_row_group_ctr);

      prep->next_buf_row = 0;

      (*out_row_group_ctr)++;

    }

    /* If at bottom of image, pad the output to a full iMCU height.

     * Note we assume the caller is providing a one-iMCU-height output buffer!

     */

    if (prep->rows_to_go == 0 &&

        *out_row_group_ctr < out_row_groups_avail) {

      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

           ci++, compptr++) {

        expand_bottom_edge(output_buf[ci],

                           compptr->width_in_blocks * DCTSIZE,

                           (int) (*out_row_group_ctr * compptr->v_samp_factor),

                           (int) (out_row_groups_avail * compptr->v_samp_factor));

      }

      *out_row_group_ctr = out_row_groups_avail;

      break;                    /* can exit outer loop without test */

    }

  }

}





#ifdef CONTEXT_ROWS_SUPPORTED



/*

 * Process some data in the context case.

 */



METHODDEF(void)

pre_process_context (j_compress_ptr cinfo,

                     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,

                     JDIMENSION in_rows_avail,

                     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,

                     JDIMENSION out_row_groups_avail)

{

  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

  int numrows, ci;

  int buf_height = cinfo->max_v_samp_factor * 3;

  JDIMENSION inrows;



  while (*out_row_group_ctr < out_row_groups_avail) {

    if (*in_row_ctr < in_rows_avail) {

      /* Do color conversion to fill the conversion buffer. */

      inrows = in_rows_avail - *in_row_ctr;

      numrows = prep->next_buf_stop - prep->next_buf_row;

      numrows = (int) MIN((JDIMENSION) numrows, inrows);

      (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,

                                         prep->color_buf,

                                         (JDIMENSION) prep->next_buf_row,

                                         numrows);

      /* Pad at top of image, if first time through */

      if (prep->rows_to_go == cinfo->image_height) {

        for (ci = 0; ci < cinfo->num_components; ci++) {

          int row;

          for (row = 1; row <= cinfo->max_v_samp_factor; row++) {

            jcopy_sample_rows(prep->color_buf[ci], 0,

                              prep->color_buf[ci], -row,

                              1, cinfo->image_width);

          }

        }

      }

      *in_row_ctr += numrows;

      prep->next_buf_row += numrows;

      prep->rows_to_go -= numrows;

    } else {

      /* Return for more data, unless we are at the bottom of the image. */

      if (prep->rows_to_go != 0)

        break;

      /* When at bottom of image, pad to fill the conversion buffer. */

      if (prep->next_buf_row < prep->next_buf_stop) {

        for (ci = 0; ci < cinfo->num_components; ci++) {

          expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,

                             prep->next_buf_row, prep->next_buf_stop);

        }

        prep->next_buf_row = prep->next_buf_stop;

      }

    }

    /* If we've gotten enough data, downsample a row group. */

    if (prep->next_buf_row == prep->next_buf_stop) {

      (*cinfo->downsample->downsample) (cinfo,

                                        prep->color_buf,

                                        (JDIMENSION) prep->this_row_group,

                                        output_buf, *out_row_group_ctr);

      (*out_row_group_ctr)++;

      /* Advance pointers with wraparound as necessary. */

      prep->this_row_group += cinfo->max_v_samp_factor;

      if (prep->this_row_group >= buf_height)

        prep->this_row_group = 0;

      if (prep->next_buf_row >= buf_height)

        prep->next_buf_row = 0;

      prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;

    }

  }

}





/*

 * Create the wrapped-around downsampling input buffer needed for context mode.

 */



LOCAL(void)

create_context_buffer (j_compress_ptr cinfo)

{

  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

  int rgroup_height = cinfo->max_v_samp_factor;

  int ci, i;

  jpeg_component_info * compptr;

  JSAMPARRAY true_buffer, fake_buffer;



  /* Grab enough space for fake row pointers for all the components;

   * we need five row groups' worth of pointers for each component.

   */

  fake_buffer = (JSAMPARRAY)

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

                                (cinfo->num_components * 5 * rgroup_height) *

                                SIZEOF(JSAMPROW));



  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* Allocate the actual buffer space (3 row groups) for this component.

     * We make the buffer wide enough to allow the downsampler to edge-expand

     * horizontally within the buffer, if it so chooses.

     */

    true_buffer = (*cinfo->mem->alloc_sarray)

      ((j_common_ptr) cinfo, JPOOL_IMAGE,

       (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *

                      cinfo->max_h_samp_factor) / compptr->h_samp_factor),

       (JDIMENSION) (3 * rgroup_height));

    /* Copy true buffer row pointers into the middle of the fake row array */

    MEMCOPY(fake_buffer + rgroup_height, true_buffer,

            3 * rgroup_height * SIZEOF(JSAMPROW));

    /* Fill in the above and below wraparound pointers */

    for (i = 0; i < rgroup_height; i++) {

      fake_buffer[i] = true_buffer[2 * rgroup_height + i];

      fake_buffer[4 * rgroup_height + i] = true_buffer[i];

    }

    prep->color_buf[ci] = fake_buffer + rgroup_height;

    fake_buffer += 5 * rgroup_height; /* point to space for next component */

  }

}



#endif /* CONTEXT_ROWS_SUPPORTED */





/*

 * Initialize preprocessing controller.

 */



GLOBAL(void)

jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)

{

  my_prep_ptr prep;

  int ci;

  jpeg_component_info * compptr;



  if (need_full_buffer)         /* safety check */

    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);



  prep = (my_prep_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

                                SIZEOF(my_prep_controller));

  cinfo->prep = (struct jpeg_c_prep_controller *) prep;

  prep->pub.start_pass = start_pass_prep;



  /* Allocate the color conversion buffer.

   * We make the buffer wide enough to allow the downsampler to edge-expand

   * horizontally within the buffer, if it so chooses.

   */

  if (cinfo->downsample->need_context_rows) {

    /* Set up to provide context rows */

#ifdef CONTEXT_ROWS_SUPPORTED

    prep->pub.pre_process_data = pre_process_context;

    create_context_buffer(cinfo);

#else

    ERREXIT(cinfo, JERR_NOT_COMPILED);

#endif

  } else {

    /* No context, just make it tall enough for one row group */

    prep->pub.pre_process_data = pre_process_data;

    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

         ci++, compptr++) {

      prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)

        ((j_common_ptr) cinfo, JPOOL_IMAGE,

         (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *

                        cinfo->max_h_samp_factor) / compptr->h_samp_factor),

         (JDIMENSION) cinfo->max_v_samp_factor);

    }

  }

}