/src/mozilla-central/media/libjpeg/jcprepct.c

Source (jump to first uncovered line)
/*
 * jcprepct.c
 *
 * This file is part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * It was modified by The libjpeg-turbo Project to include only code relevant
 * to libjpeg-turbo.
 * For conditions of distribution and use, see the accompanying README.ijg
 * 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);
    }
  }
}

Coverage Report

Created: 2018-09-25 14:53

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