/src/libjpeg-turbo.main/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.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2022, D. R. Commander.
 * 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 */
    memcpy(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: 2024-05-15 07:07

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		* libjpeg-turbo Modifications:
7		* Copyright (C) 2022, D. R. Commander.
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
85	0	if (pass_mode != JBUF_PASS_THRU)
86	0	ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
87
88		/* Initialize total-height counter for detecting bottom of image */
89	0	prep->rows_to_go = cinfo->image_height;
90		/* Mark the conversion buffer empty */
91	0	prep->next_buf_row = 0;
92	0	#ifdef CONTEXT_ROWS_SUPPORTED
93		/* Preset additional state variables for context mode.
94		* These aren't used in non-context mode, so we needn't test which mode.
95		*/
96	0	prep->this_row_group = 0;
97		/* 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, int input_rows,
110		int output_rows)
111	0	{
112	0	register int row;
113
114	0	for (row = input_rows; row < output_rows; row++) {
115	0	jcopy_sample_rows(image_data, input_rows - 1, image_data, row, 1,
116	0	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, JSAMPARRAY input_buf,
132		JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail,
133		JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
134		JDIMENSION out_row_groups_avail)
135	0	{
136	0	my_prep_ptr prep = (my_prep_ptr)cinfo->prep;
137	0	int numrows, ci;
138	0	JDIMENSION inrows;
139	0	jpeg_component_info *compptr;
140
141	0	while (*in_row_ctr < in_rows_avail &&
142	0	*out_row_group_ctr < out_row_groups_avail) {
143		/* Do color conversion to fill the conversion buffer. */
144	0	inrows = in_rows_avail - *in_row_ctr;
145	0	numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
146	0	numrows = (int)MIN((JDIMENSION)numrows, inrows);
147	0	(cinfo->cconvert->color_convert) (cinfo, input_buf + in_row_ctr,
148	0	prep->color_buf,
149	0	(JDIMENSION)prep->next_buf_row,
150	0	numrows);
151	0	*in_row_ctr += numrows;
152	0	prep->next_buf_row += numrows;
153	0	prep->rows_to_go -= numrows;
154		/* If at bottom of image, pad to fill the conversion buffer. */
155	0	if (prep->rows_to_go == 0 &&
156	0	prep->next_buf_row < cinfo->max_v_samp_factor) {
157	0	for (ci = 0; ci < cinfo->num_components; ci++) {
158	0	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
159	0	prep->next_buf_row, cinfo->max_v_samp_factor);
160	0	}
161	0	prep->next_buf_row = cinfo->max_v_samp_factor;
162	0	}
163		/* If we've filled the conversion buffer, empty it. */
164	0	if (prep->next_buf_row == cinfo->max_v_samp_factor) {
165	0	(*cinfo->downsample->downsample) (cinfo,
166	0	prep->color_buf, (JDIMENSION)0,
167	0	output_buf, *out_row_group_ctr);
168	0	prep->next_buf_row = 0;
169	0	(*out_row_group_ctr)++;
170	0	}
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	0	if (prep->rows_to_go == 0 && *out_row_group_ctr < out_row_groups_avail) {
175	0	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
176	0	ci++, compptr++) {
177	0	expand_bottom_edge(output_buf[ci], compptr->width_in_blocks * DCTSIZE,
178	0	(int)(out_row_group_ctr compptr->v_samp_factor),
179	0	(int)(out_row_groups_avail * compptr->v_samp_factor));
180	0	}
181	0	*out_row_group_ctr = out_row_groups_avail;
182	0	break; /* can exit outer loop without test */
183	0	}
184	0	}
185	0	}
186
187
188		#ifdef CONTEXT_ROWS_SUPPORTED
189
190		/*
191		* Process some data in the context case.
192		*/
193
194		METHODDEF(void)
195		pre_process_context(j_compress_ptr cinfo, JSAMPARRAY input_buf,
196		JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail,
197		JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
198		JDIMENSION out_row_groups_avail)
199	0	{
200	0	my_prep_ptr prep = (my_prep_ptr)cinfo->prep;
201	0	int numrows, ci;
202	0	int buf_height = cinfo->max_v_samp_factor * 3;
203	0	JDIMENSION inrows;
204
205	0	while (*out_row_group_ctr < out_row_groups_avail) {
206	0	if (*in_row_ctr < in_rows_avail) {
207		/* Do color conversion to fill the conversion buffer. */
208	0	inrows = in_rows_avail - *in_row_ctr;
209	0	numrows = prep->next_buf_stop - prep->next_buf_row;
210	0	numrows = (int)MIN((JDIMENSION)numrows, inrows);
211	0	(cinfo->cconvert->color_convert) (cinfo, input_buf + in_row_ctr,
212	0	prep->color_buf,
213	0	(JDIMENSION)prep->next_buf_row,
214	0	numrows);
215		/* Pad at top of image, if first time through */
216	0	if (prep->rows_to_go == cinfo->image_height) {
217	0	for (ci = 0; ci < cinfo->num_components; ci++) {
218	0	int row;
219	0	for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
220	0	jcopy_sample_rows(prep->color_buf[ci], 0, prep->color_buf[ci],
221	0	-row, 1, cinfo->image_width);
222	0	}
223	0	}
224	0	}
225	0	*in_row_ctr += numrows;
226	0	prep->next_buf_row += numrows;
227	0	prep->rows_to_go -= numrows;
228	0	} else {
229		/* Return for more data, unless we are at the bottom of the image. */
230	0	if (prep->rows_to_go != 0)
231	0	break;
232		/* When at bottom of image, pad to fill the conversion buffer. */
233	0	if (prep->next_buf_row < prep->next_buf_stop) {
234	0	for (ci = 0; ci < cinfo->num_components; ci++) {
235	0	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
236	0	prep->next_buf_row, prep->next_buf_stop);
237	0	}
238	0	prep->next_buf_row = prep->next_buf_stop;
239	0	}
240	0	}
241		/* If we've gotten enough data, downsample a row group. */
242	0	if (prep->next_buf_row == prep->next_buf_stop) {
243	0	(*cinfo->downsample->downsample) (cinfo, prep->color_buf,
244	0	(JDIMENSION)prep->this_row_group,
245	0	output_buf, *out_row_group_ctr);
246	0	(*out_row_group_ctr)++;
247		/* Advance pointers with wraparound as necessary. */
248	0	prep->this_row_group += cinfo->max_v_samp_factor;
249	0	if (prep->this_row_group >= buf_height)
250	0	prep->this_row_group = 0;
251	0	if (prep->next_buf_row >= buf_height)
252	0	prep->next_buf_row = 0;
253	0	prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
254	0	}
255	0	}
256	0	}
257
258
259		/*
260		* Create the wrapped-around downsampling input buffer needed for context mode.
261		*/
262
263		LOCAL(void)
264		create_context_buffer(j_compress_ptr cinfo)
265	0	{
266	0	my_prep_ptr prep = (my_prep_ptr)cinfo->prep;
267	0	int rgroup_height = cinfo->max_v_samp_factor;
268	0	int ci, i;
269	0	jpeg_component_info *compptr;
270	0	JSAMPARRAY true_buffer, fake_buffer;
271
272		/* Grab enough space for fake row pointers for all the components;
273		* we need five row groups' worth of pointers for each component.
274		*/
275	0	fake_buffer = (JSAMPARRAY)
276	0	(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
277	0	(cinfo->num_components * 5 * rgroup_height) *
278	0	sizeof(JSAMPROW));
279
280	0	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
281	0	ci++, compptr++) {
282		/* Allocate the actual buffer space (3 row groups) for this component.
283		* We make the buffer wide enough to allow the downsampler to edge-expand
284		* horizontally within the buffer, if it so chooses.
285		*/
286	0	true_buffer = (*cinfo->mem->alloc_sarray)
287	0	((j_common_ptr)cinfo, JPOOL_IMAGE,
288	0	(JDIMENSION)(((long)compptr->width_in_blocks * DCTSIZE *
289	0	cinfo->max_h_samp_factor) / compptr->h_samp_factor),
290	0	(JDIMENSION)(3 * rgroup_height));
291		/* Copy true buffer row pointers into the middle of the fake row array */
292	0	memcpy(fake_buffer + rgroup_height, true_buffer,
293	0	3 * rgroup_height * sizeof(JSAMPROW));
294		/* Fill in the above and below wraparound pointers */
295	0	for (i = 0; i < rgroup_height; i++) {
296	0	fake_buffer[i] = true_buffer[2 * rgroup_height + i];
297	0	fake_buffer[4 * rgroup_height + i] = true_buffer[i];
298	0	}
299	0	prep->color_buf[ci] = fake_buffer + rgroup_height;
300	0	fake_buffer += 5 * rgroup_height; /* point to space for next component */
301	0	}
302	0	}
303
304		#endif /* CONTEXT_ROWS_SUPPORTED */
305
306
307		/*
308		* Initialize preprocessing controller.
309		*/
310
311		GLOBAL(void)
312		jinit_c_prep_controller(j_compress_ptr cinfo, boolean need_full_buffer)
313	0	{
314	0	my_prep_ptr prep;
315	0	int ci;
316	0	jpeg_component_info *compptr;
317
318	0	if (need_full_buffer) /* safety check */
319	0	ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
320
321	0	prep = (my_prep_ptr)
322	0	(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
323	0	sizeof(my_prep_controller));
324	0	cinfo->prep = (struct jpeg_c_prep_controller *)prep;
325	0	prep->pub.start_pass = start_pass_prep;
326
327		/* Allocate the color conversion buffer.
328		* We make the buffer wide enough to allow the downsampler to edge-expand
329		* horizontally within the buffer, if it so chooses.
330		*/
331	0	if (cinfo->downsample->need_context_rows) {
332		/* Set up to provide context rows */
333	0	#ifdef CONTEXT_ROWS_SUPPORTED
334	0	prep->pub.pre_process_data = pre_process_context;
335	0	create_context_buffer(cinfo);
336		#else
337		ERREXIT(cinfo, JERR_NOT_COMPILED);
338		#endif
339	0	} else {
340		/* No context, just make it tall enough for one row group */
341	0	prep->pub.pre_process_data = pre_process_data;
342	0	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
343	0	ci++, compptr++) {
344	0	prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
345	0	((j_common_ptr)cinfo, JPOOL_IMAGE,
346	0	(JDIMENSION)(((long)compptr->width_in_blocks * DCTSIZE *
347	0	cinfo->max_h_samp_factor) / compptr->h_samp_factor),
348	0	(JDIMENSION)cinfo->max_v_samp_factor);
349	0	}
350	0	}
351	0	}