/src/ghostpdl/obj/jcprepct.c

Source (jump to first uncovered line)
/*
 * jcprepct.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * Modified 2003-2020 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 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++) {
  numrows = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
      cinfo->min_DCT_v_scaled_size;
  expand_bottom_edge(output_buf[ci],
         compptr->width_in_blocks * compptr->DCT_h_scaled_size,
         (int) (*out_row_group_ctr * numrows),
         (int) (out_row_groups_avail * numrows));
      }
      *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],
            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 *
          cinfo->min_DCT_h_scaled_size *
          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 = &prep->pub;
  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 *
      cinfo->min_DCT_h_scaled_size *
      cinfo->max_h_samp_factor) / compptr->h_samp_factor),
   (JDIMENSION) cinfo->max_v_samp_factor);
    }
  }
}

Coverage Report

Created: 2025-06-24 07:01

Line	Count	Source (jump to first uncovered line)
1		/*
2		* jcprepct.c
3		*
4		* Copyright (C) 1994-1996, Thomas G. Lane.
5		* Modified 2003-2020 by Guido Vollbeding.
6		* This file is part of the Independent JPEG Group's software.
7		* For conditions of distribution and use, see the accompanying README file.
8		*
9		* This file contains the compression preprocessing controller.
10		* This controller manages the color conversion, downsampling,
11		* and edge expansion steps.
12		*
13		* Most of the complexity here is associated with buffering input rows
14		* as required by the downsampler. See the comments at the head of
15		* jcsample.c for the downsampler's needs.
16		*/
17
18		#define JPEG_INTERNALS
19		#include "jinclude.h"
20		#include "jpeglib.h"
21
22
23		/* At present, jcsample.c can request context rows only for smoothing.
24		* In the future, we might also need context rows for CCIR601 sampling
25		* or other more-complex downsampling procedures. The code to support
26		* context rows should be compiled only if needed.
27		*/
28		#ifdef INPUT_SMOOTHING_SUPPORTED
29		#define CONTEXT_ROWS_SUPPORTED
30		#endif
31
32
33		/*
34		* For the simple (no-context-row) case, we just need to buffer one
35		* row group's worth of pixels for the downsampling step. At the bottom of
36		* the image, we pad to a full row group by replicating the last pixel row.
37		* The downsampler's last output row is then replicated if needed to pad
38		* out to a full iMCU row.
39		*
40		* When providing context rows, we must buffer three row groups' worth of
41		* pixels. Three row groups are physically allocated, but the row pointer
42		* arrays are made five row groups high, with the extra pointers above and
43		* below "wrapping around" to point to the last and first real row groups.
44		* This allows the downsampler to access the proper context rows.
45		* At the top and bottom of the image, we create dummy context rows by
46		* copying the first or last real pixel row. This copying could be avoided
47		* by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
48		* trouble on the compression side.
49		*/
50
51
52		/* Private buffer controller object */
53
54		typedef struct {
55		struct jpeg_c_prep_controller pub; /* public fields */
56
57		/* Downsampling input buffer. This buffer holds color-converted data
58		* until we have enough to do a downsample step.
59		*/
60		JSAMPARRAY color_buf[MAX_COMPONENTS];
61
62		JDIMENSION rows_to_go; /* counts rows remaining in source image */
63		int next_buf_row; /* index of next row to store in color_buf */
64
65		#ifdef CONTEXT_ROWS_SUPPORTED /* only needed for context case */
66		int this_row_group; /* starting row index of group to process */
67		int next_buf_stop; /* downsample when we reach this index */
68		#endif
69		} my_prep_controller;
70
71		typedef my_prep_controller * my_prep_ptr;
72
73
74		/*
75		* Initialize for a processing pass.
76		*/
77
78		METHODDEF(void)
79		start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
80	6.12k	{
81	6.12k	my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
82
83	6.12k	if (pass_mode != JBUF_PASS_THRU)
84	0	ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
85
86		/* Initialize total-height counter for detecting bottom of image */
87	6.12k	prep->rows_to_go = cinfo->image_height;
88		/* Mark the conversion buffer empty */
89	6.12k	prep->next_buf_row = 0;
90		#ifdef CONTEXT_ROWS_SUPPORTED
91		/* Preset additional state variables for context mode.
92		* These aren't used in non-context mode, so we needn't test which mode.
93		*/
94		prep->this_row_group = 0;
95		/* Set next_buf_stop to stop after two row groups have been read in. */
96		prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
97		#endif
98	6.12k	}
99
100
101		/*
102		* Expand an image vertically from height input_rows to height output_rows,
103		* by duplicating the bottom row.
104		*/
105
106		LOCAL(void)
107		expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
108		int input_rows, int output_rows)
109	5.73k	{
110	5.73k	register int row;
111
112	40.0k	for (row = input_rows; row < output_rows; row++) {
113	34.3k	jcopy_sample_rows(image_data + input_rows - 1,
114	34.3k	image_data + row,
115	34.3k	1, num_cols);
116	34.3k	}
117	5.73k	}
118
119
120		/*
121		* Process some data in the simple no-context case.
122		*
123		* Preprocessor output data is counted in "row groups". A row group
124		* is defined to be v_samp_factor sample rows of each component.
125		* Downsampling will produce this much data from each max_v_samp_factor
126		* input rows.
127		*/
128
129		METHODDEF(void)
130		pre_process_data (j_compress_ptr cinfo,
131		JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
132		JDIMENSION in_rows_avail,
133		JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
134		JDIMENSION out_row_groups_avail)
135	608k	{
136	608k	my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
137	608k	int numrows, ci;
138	608k	JDIMENSION inrows;
139	608k	jpeg_component_info * compptr;
140
141	1.18M	while (*in_row_ctr < in_rows_avail &&
142	1.18M	*out_row_group_ctr < out_row_groups_avail) {
143		/* Do color conversion to fill the conversion buffer. */
144	577k	inrows = in_rows_avail - *in_row_ctr;
145	577k	numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
146	577k	numrows = (int) MIN((JDIMENSION) numrows, inrows);
147	577k	(cinfo->cconvert->color_convert) (cinfo, input_buf + in_row_ctr,
148	577k	prep->color_buf,
149	577k	(JDIMENSION) prep->next_buf_row,
150	577k	numrows);
151	577k	*in_row_ctr += numrows;
152	577k	prep->next_buf_row += numrows;
153	577k	prep->rows_to_go -= numrows;
154		/* If at bottom of image, pad to fill the conversion buffer. */
155	577k	if (prep->rows_to_go == 0 &&
156	577k	prep->next_buf_row < cinfo->max_v_samp_factor) {
157	2.93k	for (ci = 0; ci < cinfo->num_components; ci++) {
158	1.92k	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
159	1.92k	prep->next_buf_row, cinfo->max_v_samp_factor);
160	1.92k	}
161	1.00k	prep->next_buf_row = cinfo->max_v_samp_factor;
162	1.00k	}
163		/* If we've filled the conversion buffer, empty it. */
164	577k	if (prep->next_buf_row == cinfo->max_v_samp_factor) {
165	289k	(*cinfo->downsample->downsample) (cinfo,
166	289k	prep->color_buf, (JDIMENSION) 0,
167	289k	output_buf, *out_row_group_ctr);
168	289k	prep->next_buf_row = 0;
169	289k	(*out_row_group_ctr)++;
170	289k	}
171		/* If at bottom of image, pad the output to a full iMCU height.
172		* Note we assume the caller is providing a one-iMCU-height output buffer!
173		*/
174	577k	if (prep->rows_to_go == 0 &&
175	577k	*out_row_group_ctr < out_row_groups_avail) {
176	5.67k	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
177	3.80k	ci++, compptr++) {
178	3.80k	numrows = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
179	3.80k	cinfo->min_DCT_v_scaled_size;
180	3.80k	expand_bottom_edge(output_buf[ci],
181	3.80k	compptr->width_in_blocks * compptr->DCT_h_scaled_size,
182	3.80k	(int) (out_row_group_ctr numrows),
183	3.80k	(int) (out_row_groups_avail * numrows));
184	3.80k	}
185	1.87k	*out_row_group_ctr = out_row_groups_avail;
186	1.87k	break; /* can exit outer loop without test */
187	1.87k	}
188	577k	}
189	608k	}
190
191
192		#ifdef CONTEXT_ROWS_SUPPORTED
193
194		/*
195		* Process some data in the context case.
196		*/
197
198		METHODDEF(void)
199		pre_process_context (j_compress_ptr cinfo,
200		JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
201		JDIMENSION in_rows_avail,
202		JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
203		JDIMENSION out_row_groups_avail)
204		{
205		my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
206		int numrows, ci;
207		int buf_height = cinfo->max_v_samp_factor * 3;
208		JDIMENSION inrows;
209
210		while (*out_row_group_ctr < out_row_groups_avail) {
211		if (*in_row_ctr < in_rows_avail) {
212		/* Do color conversion to fill the conversion buffer. */
213		inrows = in_rows_avail - *in_row_ctr;
214		numrows = prep->next_buf_stop - prep->next_buf_row;
215		numrows = (int) MIN((JDIMENSION) numrows, inrows);
216		(cinfo->cconvert->color_convert) (cinfo, input_buf + in_row_ctr,
217		prep->color_buf,
218		(JDIMENSION) prep->next_buf_row,
219		numrows);
220		/* Pad at top of image, if first time through */
221		if (prep->rows_to_go == cinfo->image_height) {
222		for (ci = 0; ci < cinfo->num_components; ci++) {
223		int row;
224		for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
225		jcopy_sample_rows(prep->color_buf[ci],
226		prep->color_buf[ci] - row,
227		1, cinfo->image_width);
228		}
229		}
230		}
231		*in_row_ctr += numrows;
232		prep->next_buf_row += numrows;
233		prep->rows_to_go -= numrows;
234		} else {
235		/* Return for more data, unless we are at the bottom of the image. */
236		if (prep->rows_to_go != 0)
237		break;
238		/* When at bottom of image, pad to fill the conversion buffer. */
239		if (prep->next_buf_row < prep->next_buf_stop) {
240		for (ci = 0; ci < cinfo->num_components; ci++) {
241		expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
242		prep->next_buf_row, prep->next_buf_stop);
243		}
244		prep->next_buf_row = prep->next_buf_stop;
245		}
246		}
247		/* If we've gotten enough data, downsample a row group. */
248		if (prep->next_buf_row == prep->next_buf_stop) {
249		(*cinfo->downsample->downsample) (cinfo,
250		prep->color_buf,
251		(JDIMENSION) prep->this_row_group,
252		output_buf, *out_row_group_ctr);
253		(*out_row_group_ctr)++;
254		/* Advance pointers with wraparound as necessary. */
255		prep->this_row_group += cinfo->max_v_samp_factor;
256		if (prep->this_row_group >= buf_height)
257		prep->this_row_group = 0;
258		if (prep->next_buf_row >= buf_height)
259		prep->next_buf_row = 0;
260		prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
261		}
262		}
263		}
264
265
266		/*
267		* Create the wrapped-around downsampling input buffer needed for context mode.
268		*/
269
270		LOCAL(void)
271		create_context_buffer (j_compress_ptr cinfo)
272		{
273		my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
274		int rgroup_height = cinfo->max_v_samp_factor;
275		int ci, i;
276		jpeg_component_info * compptr;
277		JSAMPARRAY true_buffer, fake_buffer;
278
279		/* Grab enough space for fake row pointers for all the components;
280		* we need five row groups' worth of pointers for each component.
281		*/
282		fake_buffer = (JSAMPARRAY) (*cinfo->mem->alloc_small)
283		((j_common_ptr) cinfo, JPOOL_IMAGE,
284		(cinfo->num_components * 5 * rgroup_height) * SIZEOF(JSAMPROW));
285
286		for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
287		ci++, compptr++) {
288		/* Allocate the actual buffer space (3 row groups) for this component.
289		* We make the buffer wide enough to allow the downsampler to edge-expand
290		* horizontally within the buffer, if it so chooses.
291		*/
292		true_buffer = (*cinfo->mem->alloc_sarray)
293		((j_common_ptr) cinfo, JPOOL_IMAGE,
294		(JDIMENSION) (((long) compptr->width_in_blocks *
295		cinfo->min_DCT_h_scaled_size *
296		cinfo->max_h_samp_factor) / compptr->h_samp_factor),
297		(JDIMENSION) (3 * rgroup_height));
298		/* Copy true buffer row pointers into the middle of the fake row array */
299		MEMCOPY(fake_buffer + rgroup_height, true_buffer,
300		3 * rgroup_height * SIZEOF(JSAMPROW));
301		/* Fill in the above and below wraparound pointers */
302		for (i = 0; i < rgroup_height; i++) {
303		fake_buffer[i] = true_buffer[2 * rgroup_height + i];
304		fake_buffer[4 * rgroup_height + i] = true_buffer[i];
305		}
306		prep->color_buf[ci] = fake_buffer + rgroup_height;
307		fake_buffer += 5 * rgroup_height; /* point to space for next component */
308		}
309		}
310
311		#endif /* CONTEXT_ROWS_SUPPORTED */
312
313
314		/*
315		* Initialize preprocessing controller.
316		*/
317
318		GLOBAL(void)
319		jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
320	6.12k	{
321	6.12k	my_prep_ptr prep;
322	6.12k	int ci;
323	6.12k	jpeg_component_info * compptr;
324
325	6.12k	if (need_full_buffer) /* safety check */
326	0	ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
327
328	6.12k	prep = (my_prep_ptr) (*cinfo->mem->alloc_small)
329	6.12k	((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_prep_controller));
330	6.12k	cinfo->prep = &prep->pub;
331	6.12k	prep->pub.start_pass = start_pass_prep;
332
333		/* Allocate the color conversion buffer.
334		* We make the buffer wide enough to allow the downsampler to edge-expand
335		* horizontally within the buffer, if it so chooses.
336		*/
337	6.12k	if (cinfo->downsample->need_context_rows) {
338		/* Set up to provide context rows */
339		#ifdef CONTEXT_ROWS_SUPPORTED
340		prep->pub.pre_process_data = pre_process_context;
341		create_context_buffer(cinfo);
342		#else
343	0	ERREXIT(cinfo, JERR_NOT_COMPILED);
344	0	#endif
345	6.12k	} else {
346		/* No context, just make it tall enough for one row group */
347	6.12k	prep->pub.pre_process_data = pre_process_data;
348	18.4k	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
349	12.3k	ci++, compptr++) {
350	12.3k	prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
351	12.3k	((j_common_ptr) cinfo, JPOOL_IMAGE,
352	12.3k	(JDIMENSION) (((long) compptr->width_in_blocks *
353	12.3k	cinfo->min_DCT_h_scaled_size *
354	12.3k	cinfo->max_h_samp_factor) / compptr->h_samp_factor),
355	12.3k	(JDIMENSION) cinfo->max_v_samp_factor);
356	12.3k	}
357	6.12k	}
358	6.12k	}