/* * jccoefct.c * * Copyright (C) 1994-1997, 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 coefficient buffer controller for compression. * This controller is the top level of the JPEG compressor proper. * The coefficient buffer lies between forward-DCT and entropy encoding steps. */#define JPEG_INTERNALS#include "jinclude.h"#include "jpeglib.h"/* We use a full-image coefficient buffer when doing Huffman optimization, * and also for writing multiple-scan JPEG files.  In all cases, the DCT * step is run during the first pass, and subsequent passes need only read * the buffered coefficients. */#ifdef ENTROPY_OPT_SUPPORTED#define FULL_COEF_BUFFER_SUPPORTED#else#ifdef C_MULTISCAN_FILES_SUPPORTED#define FULL_COEF_BUFFER_SUPPORTED#endif#endif/* 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 */  /* For single-pass compression, it's sufficient to buffer just one MCU   * (although this may prove a bit slow in practice).  We allocate a   * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each   * MCU constructed and sent.  (On 80x86, the workspace is FAR even though   * it's not really very big; this is to keep the module interfaces unchanged   * when a large coefficient buffer is necessary.)   * In multi-pass modes, this array points to the current MCU's blocks   * within the virtual arrays.   */  JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];  /* In multi-pass modes, we need a virtual block array for each component. */  jvirt_barray_ptr whole_image[MAX_COMPONENTS];} my_coef_controller;typedef my_coef_controller * my_coef_ptr;/* Forward declarations */METHODDEF(boolean) compress_data    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));#ifdef FULL_COEF_BUFFER_SUPPORTEDMETHODDEF(boolean) compress_first_pass    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));METHODDEF(boolean) compress_output    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));#endifLOCAL(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;  coef->iMCU_row_num = 0;  start_iMCU_row(cinfo);  switch (pass_mode) {  case JBUF_PASS_THRU:    if (coef->whole_image[0] != NULL)      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);    coef->pub.compress_data = compress_data;    break;#ifdef FULL_COEF_BUFFER_SUPPORTED  case JBUF_SAVE_AND_PASS:    if (coef->whole_image[0] == NULL)      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);    coef->pub.compress_data = compress_first_pass;    break;  case JBUF_CRANK_DEST:    if (coef->whole_image[0] == NULL)      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);    coef->pub.compress_data = compress_output;    break;#endif  default:    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);    break;  }}/* * Process some data in the single-pass case. * 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 image. * Returns TRUE if the iMCU row is completed, FALSE if suspended. * * NB: input_buf contains a plane for each component in image, * which we index according to the component's SOF position. */METHODDEF(boolean)compress_data (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, bi, ci, yindex, yoffset, blockcnt;  JDIMENSION ypos, xpos;  jpeg_component_info *compptr;  /* Loop to write as much as 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 <= last_MCU_col;	 MCU_col_num++) {      /* Determine where data comes from in input_buf and do the DCT thing.       * Each call on forward_DCT processes a horizontal row of DCT blocks       * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks       * sequentially.  Dummy blocks at the right or bottom edge are filled in       * specially.  The data in them does not matter for image reconstruction,       * so we fill them with values that will encode to the smallest amount of       * data, viz: all zeroes in the AC entries, DC entries equal to previous       * block's DC value.  (Thanks to Thomas Kinsman for this idea.)       */      blkn = 0;      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {	compptr = cinfo->cur_comp_info[ci];	blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width						: compptr->last_col_width;	xpos = MCU_col_num * compptr->MCU_sample_width;	ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {	  if (coef->iMCU_row_num < last_iMCU_row ||	      yoffset+yindex < compptr->last_row_height) {	    (*cinfo->fdct->forward_DCT) (cinfo, compptr,					 input_buf[compptr->component_index],					 coef->MCU_buffer[blkn],					 ypos, xpos, (JDIMENSION) blockcnt);	    if (blockcnt < compptr->MCU_width) {	      /* Create some dummy blocks at the right edge of the image. */	      jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],			(compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));	      for (bi = blockcnt; bi < compptr->MCU_width; bi++) {		coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];	      }	    }	  } else {	    /* Create a row of dummy blocks at the bottom of the image. */	    jzero_far((void FAR *) coef->MCU_buffer[blkn],		      compptr->MCU_width * SIZEOF(JBLOCK));	    for (bi = 0; bi < compptr->MCU_width; bi++) {	      coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];	    }	  }	  blkn += compptr->MCU_width;	  ypos += DCTSIZE;	}      }      /* Try to write the MCU.  In event of a suspension failure, we will       * re-DCT the MCU on restart (a bit inefficient, could be fixed...)       */      if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->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;}#ifdef FULL_COEF_BUFFER_SUPPORTED/* * Process some data in the first pass of a multi-pass case. * We process the equivalent of one fully interleaved MCU row ("iMCU" row)