source: branches/kmk/libjpeg/jcsample.c @ 355

Last change on this file since 355 was 283, checked in by rbri, 12 years ago

JPEG plugin: libjpeg updated to version 7

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1/*
2 * jcsample.c
3 *
4 * Copyright (C) 1991-1996, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains downsampling routines.
9 *
10 * Downsampling input data is counted in "row groups".  A row group
11 * is defined to be max_v_samp_factor pixel rows of each component,
12 * from which the downsampler produces v_samp_factor sample rows.
13 * A single row group is processed in each call to the downsampler module.
14 *
15 * The downsampler is responsible for edge-expansion of its output data
16 * to fill an integral number of DCT blocks horizontally.  The source buffer
17 * may be modified if it is helpful for this purpose (the source buffer is
18 * allocated wide enough to correspond to the desired output width).
19 * The caller (the prep controller) is responsible for vertical padding.
20 *
21 * The downsampler may request "context rows" by setting need_context_rows
22 * during startup.  In this case, the input arrays will contain at least
23 * one row group's worth of pixels above and below the passed-in data;
24 * the caller will create dummy rows at image top and bottom by replicating
25 * the first or last real pixel row.
26 *
27 * An excellent reference for image resampling is
28 *   Digital Image Warping, George Wolberg, 1990.
29 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
30 *
31 * The downsampling algorithm used here is a simple average of the source
32 * pixels covered by the output pixel.  The hi-falutin sampling literature
33 * refers to this as a "box filter".  In general the characteristics of a box
34 * filter are not very good, but for the specific cases we normally use (1:1
35 * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
36 * nearly so bad.  If you intend to use other sampling ratios, you'd be well
37 * advised to improve this code.
38 *
39 * A simple input-smoothing capability is provided.  This is mainly intended
40 * for cleaning up color-dithered GIF input files (if you find it inadequate,
41 * we suggest using an external filtering program such as pnmconvol).  When
42 * enabled, each input pixel P is replaced by a weighted sum of itself and its
43 * eight neighbors.  P's weight is 1-8*SF and each neighbor's weight is SF,
44 * where SF = (smoothing_factor / 1024).
45 * Currently, smoothing is only supported for 2h2v sampling factors.
46 */
47
48#define JPEG_INTERNALS
49#include "jinclude.h"
50#include "jpeglib.h"
51
52
53/* Pointer to routine to downsample a single component */
54typedef JMETHOD(void, downsample1_ptr,
55                (j_compress_ptr cinfo, jpeg_component_info * compptr,
56                 JSAMPARRAY input_data, JSAMPARRAY output_data));
57
58/* Private subobject */
59
60typedef struct {
61  struct jpeg_downsampler pub;  /* public fields */
62
63  /* Downsampling method pointers, one per component */
64  downsample1_ptr methods[MAX_COMPONENTS];
65
66  /* Height of an output row group for each component. */
67  int rowgroup_height[MAX_COMPONENTS];
68
69  /* These arrays save pixel expansion factors so that int_downsample need not
70   * recompute them each time.  They are unused for other downsampling methods.
71   */
72  UINT8 h_expand[MAX_COMPONENTS];
73  UINT8 v_expand[MAX_COMPONENTS];
74} my_downsampler;
75
76typedef my_downsampler * my_downsample_ptr;
77
78
79/*
80 * Initialize for a downsampling pass.
81 */
82
83METHODDEF(void)
84start_pass_downsample (j_compress_ptr cinfo)
85{
86  /* no work for now */
87}
88
89
90/*
91 * Expand a component horizontally from width input_cols to width output_cols,
92 * by duplicating the rightmost samples.
93 */
94
95LOCAL(void)
96expand_right_edge (JSAMPARRAY image_data, int num_rows,
97                   JDIMENSION input_cols, JDIMENSION output_cols)
98{
99  register JSAMPROW ptr;
100  register JSAMPLE pixval;
101  register int count;
102  int row;
103  int numcols = (int) (output_cols - input_cols);
104
105  if (numcols > 0) {
106    for (row = 0; row < num_rows; row++) {
107      ptr = image_data[row] + input_cols;
108      pixval = ptr[-1];         /* don't need GETJSAMPLE() here */
109      for (count = numcols; count > 0; count--)
110        *ptr++ = pixval;
111    }
112  }
113}
114
115
116/*
117 * Do downsampling for a whole row group (all components).
118 *
119 * In this version we simply downsample each component independently.
120 */
121
122METHODDEF(void)
123sep_downsample (j_compress_ptr cinfo,
124                JSAMPIMAGE input_buf, JDIMENSION in_row_index,
125                JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)
126{
127  my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
128  int ci;
129  jpeg_component_info * compptr;
130  JSAMPARRAY in_ptr, out_ptr;
131
132  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
133       ci++, compptr++) {
134    in_ptr = input_buf[ci] + in_row_index;
135    out_ptr = output_buf[ci] +
136              (out_row_group_index * downsample->rowgroup_height[ci]);
137    (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);
138  }
139}
140
141
142/*
143 * Downsample pixel values of a single component.
144 * One row group is processed per call.
145 * This version handles arbitrary integral sampling ratios, without smoothing.
146 * Note that this version is not actually used for customary sampling ratios.
147 */
148
149METHODDEF(void)
150int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
151                JSAMPARRAY input_data, JSAMPARRAY output_data)
152{
153  my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
154  int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
155  JDIMENSION outcol, outcol_h;  /* outcol_h == outcol*h_expand */
156  JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
157  JSAMPROW inptr, outptr;
158  INT32 outvalue;
159
160  h_expand = downsample->h_expand[compptr->component_index];
161  v_expand = downsample->v_expand[compptr->component_index];
162  numpix = h_expand * v_expand;
163  numpix2 = numpix/2;
164
165  /* Expand input data enough to let all the output samples be generated
166   * by the standard loop.  Special-casing padded output would be more
167   * efficient.
168   */
169  expand_right_edge(input_data, cinfo->max_v_samp_factor,
170                    cinfo->image_width, output_cols * h_expand);
171
172  inrow = outrow = 0;
173  while (inrow < cinfo->max_v_samp_factor) {
174    outptr = output_data[outrow];
175    for (outcol = 0, outcol_h = 0; outcol < output_cols;
176         outcol++, outcol_h += h_expand) {
177      outvalue = 0;
178      for (v = 0; v < v_expand; v++) {
179        inptr = input_data[inrow+v] + outcol_h;
180        for (h = 0; h < h_expand; h++) {
181          outvalue += (INT32) GETJSAMPLE(*inptr++);
182        }
183      }
184      *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
185    }
186    inrow += v_expand;
187    outrow++;
188  }
189}
190
191
192/*
193 * Downsample pixel values of a single component.
194 * This version handles the special case of a full-size component,
195 * without smoothing.
196 */
197
198METHODDEF(void)
199fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
200                     JSAMPARRAY input_data, JSAMPARRAY output_data)
201{
202  /* Copy the data */
203  jcopy_sample_rows(input_data, 0, output_data, 0,
204                    cinfo->max_v_samp_factor, cinfo->image_width);
205  /* Edge-expand */
206  expand_right_edge(output_data, cinfo->max_v_samp_factor, cinfo->image_width,
207                    compptr->width_in_blocks * compptr->DCT_h_scaled_size);
208}
209
210
211/*
212 * Downsample pixel values of a single component.
213 * This version handles the common case of 2:1 horizontal and 1:1 vertical,
214 * without smoothing.
215 *
216 * A note about the "bias" calculations: when rounding fractional values to
217 * integer, we do not want to always round 0.5 up to the next integer.
218 * If we did that, we'd introduce a noticeable bias towards larger values.
219 * Instead, this code is arranged so that 0.5 will be rounded up or down at
220 * alternate pixel locations (a simple ordered dither pattern).
221 */
222
223METHODDEF(void)
224h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
225                 JSAMPARRAY input_data, JSAMPARRAY output_data)
226{
227  int inrow;
228  JDIMENSION outcol;
229  JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
230  register JSAMPROW inptr, outptr;
231  register int bias;
232
233  /* Expand input data enough to let all the output samples be generated
234   * by the standard loop.  Special-casing padded output would be more
235   * efficient.
236   */
237  expand_right_edge(input_data, cinfo->max_v_samp_factor,
238                    cinfo->image_width, output_cols * 2);
239
240  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
241    outptr = output_data[inrow];
242    inptr = input_data[inrow];
243    bias = 0;                   /* bias = 0,1,0,1,... for successive samples */
244    for (outcol = 0; outcol < output_cols; outcol++) {
245      *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
246                              + bias) >> 1);
247      bias ^= 1;                /* 0=>1, 1=>0 */
248      inptr += 2;
249    }
250  }
251}
252
253
254/*
255 * Downsample pixel values of a single component.
256 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
257 * without smoothing.
258 */
259
260METHODDEF(void)
261h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
262                 JSAMPARRAY input_data, JSAMPARRAY output_data)
263{
264  int inrow, outrow;
265  JDIMENSION outcol;
266  JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
267  register JSAMPROW inptr0, inptr1, outptr;
268  register int bias;
269
270  /* Expand input data enough to let all the output samples be generated
271   * by the standard loop.  Special-casing padded output would be more
272   * efficient.
273   */
274  expand_right_edge(input_data, cinfo->max_v_samp_factor,
275                    cinfo->image_width, output_cols * 2);
276
277  inrow = outrow = 0;
278  while (inrow < cinfo->max_v_samp_factor) {
279    outptr = output_data[outrow];
280    inptr0 = input_data[inrow];
281    inptr1 = input_data[inrow+1];
282    bias = 1;                   /* bias = 1,2,1,2,... for successive samples */
283    for (outcol = 0; outcol < output_cols; outcol++) {
284      *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
285                              GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
286                              + bias) >> 2);
287      bias ^= 3;                /* 1=>2, 2=>1 */
288      inptr0 += 2; inptr1 += 2;
289    }
290    inrow += 2;
291    outrow++;
292  }
293}
294
295
296#ifdef INPUT_SMOOTHING_SUPPORTED
297
298/*
299 * Downsample pixel values of a single component.
300 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
301 * with smoothing.  One row of context is required.
302 */
303
304METHODDEF(void)
305h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
306                        JSAMPARRAY input_data, JSAMPARRAY output_data)
307{
308  int inrow, outrow;
309  JDIMENSION colctr;
310  JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
311  register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
312  INT32 membersum, neighsum, memberscale, neighscale;
313
314  /* Expand input data enough to let all the output samples be generated
315   * by the standard loop.  Special-casing padded output would be more
316   * efficient.
317   */
318  expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
319                    cinfo->image_width, output_cols * 2);
320
321  /* We don't bother to form the individual "smoothed" input pixel values;
322   * we can directly compute the output which is the average of the four
323   * smoothed values.  Each of the four member pixels contributes a fraction
324   * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
325   * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
326   * output.  The four corner-adjacent neighbor pixels contribute a fraction
327   * SF to just one smoothed pixel, or SF/4 to the final output; while the
328   * eight edge-adjacent neighbors contribute SF to each of two smoothed
329   * pixels, or SF/2 overall.  In order to use integer arithmetic, these
330   * factors are scaled by 2^16 = 65536.
331   * Also recall that SF = smoothing_factor / 1024.
332   */
333
334  memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
335  neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
336
337  inrow = outrow = 0;
338  while (inrow < cinfo->max_v_samp_factor) {
339    outptr = output_data[outrow];
340    inptr0 = input_data[inrow];
341    inptr1 = input_data[inrow+1];
342    above_ptr = input_data[inrow-1];
343    below_ptr = input_data[inrow+2];
344
345    /* Special case for first column: pretend column -1 is same as column 0 */
346    membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
347                GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
348    neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
349               GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
350               GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
351               GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
352    neighsum += neighsum;
353    neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
354                GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
355    membersum = membersum * memberscale + neighsum * neighscale;
356    *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
357    inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
358
359    for (colctr = output_cols - 2; colctr > 0; colctr--) {
360      /* sum of pixels directly mapped to this output element */
361      membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
362                  GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
363      /* sum of edge-neighbor pixels */
364      neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
365                 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
366                 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
367                 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
368      /* The edge-neighbors count twice as much as corner-neighbors */
369      neighsum += neighsum;
370      /* Add in the corner-neighbors */
371      neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
372                  GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
373      /* form final output scaled up by 2^16 */
374      membersum = membersum * memberscale + neighsum * neighscale;
375      /* round, descale and output it */
376      *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
377      inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
378    }
379
380    /* Special case for last column */
381    membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
382                GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
383    neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
384               GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
385               GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
386               GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
387    neighsum += neighsum;
388    neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
389                GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
390    membersum = membersum * memberscale + neighsum * neighscale;
391    *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
392
393    inrow += 2;
394    outrow++;
395  }
396}
397
398
399/*
400 * Downsample pixel values of a single component.
401 * This version handles the special case of a full-size component,
402 * with smoothing.  One row of context is required.
403 */
404
405METHODDEF(void)
406fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr,
407                            JSAMPARRAY input_data, JSAMPARRAY output_data)
408{
409  int inrow;
410  JDIMENSION colctr;
411  JDIMENSION output_cols = compptr->width_in_blocks * compptr->DCT_h_scaled_size;
412  register JSAMPROW inptr, above_ptr, below_ptr, outptr;
413  INT32 membersum, neighsum, memberscale, neighscale;
414  int colsum, lastcolsum, nextcolsum;
415
416  /* Expand input data enough to let all the output samples be generated
417   * by the standard loop.  Special-casing padded output would be more
418   * efficient.
419   */
420  expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
421                    cinfo->image_width, output_cols);
422
423  /* Each of the eight neighbor pixels contributes a fraction SF to the
424   * smoothed pixel, while the main pixel contributes (1-8*SF).  In order
425   * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
426   * Also recall that SF = smoothing_factor / 1024.
427   */
428
429  memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
430  neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
431
432  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
433    outptr = output_data[inrow];
434    inptr = input_data[inrow];
435    above_ptr = input_data[inrow-1];
436    below_ptr = input_data[inrow+1];
437
438    /* Special case for first column */
439    colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
440             GETJSAMPLE(*inptr);
441    membersum = GETJSAMPLE(*inptr++);
442    nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
443                 GETJSAMPLE(*inptr);
444    neighsum = colsum + (colsum - membersum) + nextcolsum;
445    membersum = membersum * memberscale + neighsum * neighscale;
446    *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
447    lastcolsum = colsum; colsum = nextcolsum;
448
449    for (colctr = output_cols - 2; colctr > 0; colctr--) {
450      membersum = GETJSAMPLE(*inptr++);
451      above_ptr++; below_ptr++;
452      nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
453                   GETJSAMPLE(*inptr);
454      neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
455      membersum = membersum * memberscale + neighsum * neighscale;
456      *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
457      lastcolsum = colsum; colsum = nextcolsum;
458    }
459
460    /* Special case for last column */
461    membersum = GETJSAMPLE(*inptr);
462    neighsum = lastcolsum + (colsum - membersum) + colsum;
463    membersum = membersum * memberscale + neighsum * neighscale;
464    *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
465
466  }
467}
468
469#endif /* INPUT_SMOOTHING_SUPPORTED */
470
471
472/*
473 * Module initialization routine for downsampling.
474 * Note that we must select a routine for each component.
475 */
476
477GLOBAL(void)
478jinit_downsampler (j_compress_ptr cinfo)
479{
480  my_downsample_ptr downsample;
481  int ci;
482  jpeg_component_info * compptr;
483  boolean smoothok = TRUE;
484  int h_in_group, v_in_group, h_out_group, v_out_group;
485
486  downsample = (my_downsample_ptr)
487    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
488                                SIZEOF(my_downsampler));
489  cinfo->downsample = (struct jpeg_downsampler *) downsample;
490  downsample->pub.start_pass = start_pass_downsample;
491  downsample->pub.downsample = sep_downsample;
492  downsample->pub.need_context_rows = FALSE;
493
494  if (cinfo->CCIR601_sampling)
495    ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
496
497  /* Verify we can handle the sampling factors, and set up method pointers */
498  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
499       ci++, compptr++) {
500    /* Compute size of an "output group" for DCT scaling.  This many samples
501     * are to be converted from max_h_samp_factor * max_v_samp_factor pixels.
502     */
503    h_out_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) /
504                  cinfo->min_DCT_h_scaled_size;
505    v_out_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
506                  cinfo->min_DCT_v_scaled_size;
507    h_in_group = cinfo->max_h_samp_factor;
508    v_in_group = cinfo->max_v_samp_factor;
509    downsample->rowgroup_height[ci] = v_out_group; /* save for use later */
510    if (h_in_group == h_out_group && v_in_group == v_out_group) {
511#ifdef INPUT_SMOOTHING_SUPPORTED
512      if (cinfo->smoothing_factor) {
513        downsample->methods[ci] = fullsize_smooth_downsample;
514        downsample->pub.need_context_rows = TRUE;
515      } else
516#endif
517        downsample->methods[ci] = fullsize_downsample;
518    } else if (h_in_group == h_out_group * 2 &&
519               v_in_group == v_out_group) {
520      smoothok = FALSE;
521      downsample->methods[ci] = h2v1_downsample;
522    } else if (h_in_group == h_out_group * 2 &&
523               v_in_group == v_out_group * 2) {
524#ifdef INPUT_SMOOTHING_SUPPORTED
525      if (cinfo->smoothing_factor) {
526        downsample->methods[ci] = h2v2_smooth_downsample;
527        downsample->pub.need_context_rows = TRUE;
528      } else
529#endif
530        downsample->methods[ci] = h2v2_downsample;
531    } else if ((h_in_group % h_out_group) == 0 &&
532               (v_in_group % v_out_group) == 0) {
533      smoothok = FALSE;
534      downsample->methods[ci] = int_downsample;
535      downsample->h_expand[ci] = (UINT8) (h_in_group / h_out_group);
536      downsample->v_expand[ci] = (UINT8) (v_in_group / v_out_group);
537    } else
538      ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
539  }
540
541#ifdef INPUT_SMOOTHING_SUPPORTED
542  if (cinfo->smoothing_factor && !smoothok)
543    TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);
544#endif
545}
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