jcmainct.c

Go to the documentation of this file.

/*
 * jcmainct.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * Modified 2003-2012 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 the main buffer controller for compression.
 * The main buffer lies between the pre-processor and the JPEG
 * compressor proper; it holds downsampled data in the JPEG colorspace.
 */
 
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
 
 
/* Note: currently, there is no operating mode in which a full-image buffer
 * is needed at this step.  If there were, that mode could not be used with
 * "raw data" input, since this module is bypassed in that case.  However,
 * we've left the code here for possible use in special applications.
 */
#undef FULL_MAIN_BUFFER_SUPPORTED
 
 
/* Private buffer controller object */
 
typedef struct {
  struct jpeg_c_main_controller pub; /* public fields */
 
  JDIMENSION cur_iMCU_row;  /* number of current iMCU row */
  JDIMENSION rowgroup_ctr;  /* counts row groups received in iMCU row */
  boolean suspended;        /* remember if we suspended output */
  J_BUF_MODE pass_mode;     /* current operating mode */
 
  /* If using just a strip buffer, this points to the entire set of buffers
   * (we allocate one for each component).  In the full-image case, this
   * points to the currently accessible strips of the virtual arrays.
   */
  JSAMPARRAY buffer[MAX_COMPONENTS];
 
#ifdef FULL_MAIN_BUFFER_SUPPORTED
  /* If using full-image storage, this array holds pointers to virtual-array
   * control blocks for each component.  Unused if not full-image storage.
   */
  jvirt_sarray_ptr whole_image[MAX_COMPONENTS];
#endif
} my_main_controller;
 
typedef my_main_controller * my_main_ptr;
 
 
/* Forward declarations */
METHODDEF(void) process_data_simple_main
    JPP((j_compress_ptr cinfo, JSAMPARRAY input_buf,
         JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail));
#ifdef FULL_MAIN_BUFFER_SUPPORTED
METHODDEF(void) process_data_buffer_main
    JPP((j_compress_ptr cinfo, JSAMPARRAY input_buf,
         JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail));
#endif
 
 
/*
 * Initialize for a processing pass.
 */
 
METHODDEF(void)
start_pass_main (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
{
  my_main_ptr mainp = (my_main_ptr) cinfo->main;
 
  /* Do nothing in raw-data mode. */
  if (cinfo->raw_data_in)
    return;
 
  mainp->cur_iMCU_row = 0;  /* initialize counters */
  mainp->rowgroup_ctr = 0;
  mainp->suspended = FALSE;
  mainp->pass_mode = pass_mode; /* save mode for use by process_data */
 
  switch (pass_mode) {
  case JBUF_PASS_THRU:
#ifdef FULL_MAIN_BUFFER_SUPPORTED
    if (mainp->whole_image[0] != NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif
    mainp->pub.process_data = process_data_simple_main;
    break;
#ifdef FULL_MAIN_BUFFER_SUPPORTED
  case JBUF_SAVE_SOURCE:
  case JBUF_CRANK_DEST:
  case JBUF_SAVE_AND_PASS:
    if (mainp->whole_image[0] == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    mainp->pub.process_data = process_data_buffer_main;
    break;
#endif
  default:
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    break;
  }
}
 
 
/*
 * Process some data.
 * This routine handles the simple pass-through mode,
 * where we have only a strip buffer.
 */
 
METHODDEF(void)
process_data_simple_main (j_compress_ptr cinfo,
              JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
              JDIMENSION in_rows_avail)
{
  my_main_ptr mainp = (my_main_ptr) cinfo->main;
 
  while (mainp->cur_iMCU_row < cinfo->total_iMCU_rows) {
    /* Read input data if we haven't filled the main buffer yet */
    if (mainp->rowgroup_ctr < (JDIMENSION) cinfo->min_DCT_v_scaled_size)
      (*cinfo->prep->pre_process_data) (cinfo,
                    input_buf, in_row_ctr, in_rows_avail,
                    mainp->buffer, &mainp->rowgroup_ctr,
                    (JDIMENSION) cinfo->min_DCT_v_scaled_size);
 
    /* If we don't have a full iMCU row buffered, return to application for
     * more data.  Note that preprocessor will always pad to fill the iMCU row
     * at the bottom of the image.
     */
    if (mainp->rowgroup_ctr != (JDIMENSION) cinfo->min_DCT_v_scaled_size)
      return;
 
    /* Send the completed row to the compressor */
    if (! (*cinfo->coef->compress_data) (cinfo, mainp->buffer)) {
      /* If compressor did not consume the whole row, then we must need to
       * suspend processing and return to the application.  In this situation
       * we pretend we didn't yet consume the last input row; otherwise, if
       * it happened to be the last row of the image, the application would
       * think we were done.
       */
      if (! mainp->suspended) {
    (*in_row_ctr)--;
    mainp->suspended = TRUE;
      }
      return;
    }
    /* We did finish the row.  Undo our little suspension hack if a previous
     * call suspended; then mark the main buffer empty.
     */
    if (mainp->suspended) {
      (*in_row_ctr)++;
      mainp->suspended = FALSE;
    }
    mainp->rowgroup_ctr = 0;
    mainp->cur_iMCU_row++;
  }
}
 
 
#ifdef FULL_MAIN_BUFFER_SUPPORTED
 
/*
 * Process some data.
 * This routine handles all of the modes that use a full-size buffer.
 */
 
METHODDEF(void)
process_data_buffer_main (j_compress_ptr cinfo,
              JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
              JDIMENSION in_rows_avail)
{
  my_main_ptr mainp = (my_main_ptr) cinfo->main;
  int ci;
  jpeg_component_info *compptr;
  boolean writing = (mainp->pass_mode != JBUF_CRANK_DEST);
 
  while (mainp->cur_iMCU_row < cinfo->total_iMCU_rows) {
    /* Realign the virtual buffers if at the start of an iMCU row. */
    if (mainp->rowgroup_ctr == 0) {
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    mainp->buffer[ci] = (*cinfo->mem->access_virt_sarray)
      ((j_common_ptr) cinfo, mainp->whole_image[ci], mainp->cur_iMCU_row *
       ((JDIMENSION) (compptr->v_samp_factor * cinfo->min_DCT_v_scaled_size)),
       (JDIMENSION) (compptr->v_samp_factor * cinfo->min_DCT_v_scaled_size),
       writing);
      }
      /* In a read pass, pretend we just read some source data. */
      if (! writing) {
    *in_row_ctr += (JDIMENSION)
      (cinfo->max_v_samp_factor * cinfo->min_DCT_v_scaled_size);
    mainp->rowgroup_ctr = (JDIMENSION) cinfo->min_DCT_v_scaled_size;
      }
    }
 
    /* If a write pass, read input data until the current iMCU row is full. */
    /* Note: preprocessor will pad if necessary to fill the last iMCU row. */
    if (writing) {
      (*cinfo->prep->pre_process_data) (cinfo,
                    input_buf, in_row_ctr, in_rows_avail,
                    mainp->buffer, &mainp->rowgroup_ctr,
                    (JDIMENSION) cinfo->min_DCT_v_scaled_size);
      /* Return to application if we need more data to fill the iMCU row. */
      if (mainp->rowgroup_ctr < (JDIMENSION) cinfo->min_DCT_v_scaled_size)
    return;
    }
 
    /* Emit data, unless this is a sink-only pass. */
    if (mainp->pass_mode != JBUF_SAVE_SOURCE) {
      if (! (*cinfo->coef->compress_data) (cinfo, mainp->buffer)) {
    /* If compressor did not consume the whole row, then we must need to
     * suspend processing and return to the application.  In this situation
     * we pretend we didn't yet consume the last input row; otherwise, if
     * it happened to be the last row of the image, the application would
     * think we were done.
     */
    if (! mainp->suspended) {
      (*in_row_ctr)--;
      mainp->suspended = TRUE;
    }
    return;
      }
      /* We did finish the row.  Undo our little suspension hack if a previous
       * call suspended; then mark the main buffer empty.
       */
      if (mainp->suspended) {
    (*in_row_ctr)++;
    mainp->suspended = FALSE;
      }
    }
 
    /* If get here, we are done with this iMCU row.  Mark buffer empty. */
    mainp->rowgroup_ctr = 0;
    mainp->cur_iMCU_row++;
  }
}
 
#endif /* FULL_MAIN_BUFFER_SUPPORTED */
 
 
/*
 * Initialize main buffer controller.
 */
 
GLOBAL(void)
jinit_c_main_controller (j_compress_ptr cinfo, boolean need_full_buffer)
{
  my_main_ptr mainp;
  int ci;
  jpeg_component_info *compptr;
 
  mainp = (my_main_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                SIZEOF(my_main_controller));
  cinfo->main = &mainp->pub;
  mainp->pub.start_pass = start_pass_main;
 
  /* We don't need to create a buffer in raw-data mode. */
  if (cinfo->raw_data_in)
    return;
 
  /* Create the buffer.  It holds downsampled data, so each component
   * may be of a different size.
   */
  if (need_full_buffer) {
#ifdef FULL_MAIN_BUFFER_SUPPORTED
    /* Allocate a full-image virtual array for each component */
    /* Note we pad the bottom to a multiple of the iMCU height */
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     ci++, compptr++) {
      mainp->whole_image[ci] = (*cinfo->mem->request_virt_sarray)
    ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
     compptr->width_in_blocks * ((JDIMENSION) compptr->DCT_h_scaled_size),
     ((JDIMENSION) jround_up((long) compptr->height_in_blocks,
                 (long) compptr->v_samp_factor)) *
     ((JDIMENSION) cinfo->min_DCT_v_scaled_size),
     (JDIMENSION) (compptr->v_samp_factor * compptr->DCT_v_scaled_size));
    }
#else
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif
  } else {
#ifdef FULL_MAIN_BUFFER_SUPPORTED
    mainp->whole_image[0] = NULL; /* flag for no virtual arrays */
#endif
    /* Allocate a strip buffer for each component */
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     ci++, compptr++) {
      mainp->buffer[ci] = (*cinfo->mem->alloc_sarray)
    ((j_common_ptr) cinfo, JPOOL_IMAGE,
     compptr->width_in_blocks * ((JDIMENSION) compptr->DCT_h_scaled_size),
     (JDIMENSION) (compptr->v_samp_factor * compptr->DCT_v_scaled_size));
    }
  }
}