/* * 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);    }  }}