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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 */
54  typedef 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  
60  typedef struct {
61    struct jpeg_downsampler pub;	/* public fields */
62  
63    /* Downsampling method pointers, one per component */
64    downsample1_ptr methods[MAX_COMPONENTS];
65  } my_downsampler;
66  
67  typedef my_downsampler * my_downsample_ptr;
68  
69  
70  /*
71   * Initialize for a downsampling pass.
72   */
73  
74  METHODDEF(void)
start_pass_downsample(j_compress_ptr cinfo)75  start_pass_downsample (j_compress_ptr cinfo)
76  {
77    /* no work for now */
78  }
79  
80  
81  /*
82   * Expand a component horizontally from width input_cols to width output_cols,
83   * by duplicating the rightmost samples.
84   */
85  
86  LOCAL(void)
expand_right_edge(JSAMPARRAY image_data,int num_rows,JDIMENSION input_cols,JDIMENSION output_cols)87  expand_right_edge (JSAMPARRAY image_data, int num_rows,
88  		   JDIMENSION input_cols, JDIMENSION output_cols)
89  {
90    register JSAMPROW ptr;
91    register JSAMPLE pixval;
92    register int count;
93    int row;
94    int numcols = (int) (output_cols - input_cols);
95  
96    if (numcols > 0) {
97      for (row = 0; row < num_rows; row++) {
98        ptr = image_data[row] + input_cols;
99        pixval = ptr[-1];		/* don't need GETJSAMPLE() here */
100        for (count = numcols; count > 0; count--)
101  	*ptr++ = pixval;
102      }
103    }
104  }
105  
106  
107  /*
108   * Do downsampling for a whole row group (all components).
109   *
110   * In this version we simply downsample each component independently.
111   */
112  
113  METHODDEF(void)
sep_downsample(j_compress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION in_row_index,JSAMPIMAGE output_buf,JDIMENSION out_row_group_index)114  sep_downsample (j_compress_ptr cinfo,
115  		JSAMPIMAGE input_buf, JDIMENSION in_row_index,
116  		JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)
117  {
118    my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
119    int ci;
120    jpeg_component_info * compptr;
121    JSAMPARRAY in_ptr, out_ptr;
122  
123    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
124         ci++, compptr++) {
125      in_ptr = input_buf[ci] + in_row_index;
126      out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);
127      (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);
128    }
129  }
130  
131  
132  /*
133   * Downsample pixel values of a single component.
134   * One row group is processed per call.
135   * This version handles arbitrary integral sampling ratios, without smoothing.
136   * Note that this version is not actually used for customary sampling ratios.
137   */
138  
139  METHODDEF(void)
int_downsample(j_compress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY output_data)140  int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
141  		JSAMPARRAY input_data, JSAMPARRAY output_data)
142  {
143    int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
144    JDIMENSION outcol, outcol_h;	/* outcol_h == outcol*h_expand */
145    JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
146    JSAMPROW inptr, outptr;
147    INT32 outvalue;
148  
149    h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
150    v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
151    numpix = h_expand * v_expand;
152    numpix2 = numpix/2;
153  
154    /* Expand input data enough to let all the output samples be generated
155     * by the standard loop.  Special-casing padded output would be more
156     * efficient.
157     */
158    expand_right_edge(input_data, cinfo->max_v_samp_factor,
159  		    cinfo->image_width, output_cols * h_expand);
160  
161    inrow = 0;
162    for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
163      outptr = output_data[outrow];
164      for (outcol = 0, outcol_h = 0; outcol < output_cols;
165  	 outcol++, outcol_h += h_expand) {
166        outvalue = 0;
167        for (v = 0; v < v_expand; v++) {
168  	inptr = input_data[inrow+v] + outcol_h;
169  	for (h = 0; h < h_expand; h++) {
170  	  outvalue += (INT32) GETJSAMPLE(*inptr++);
171  	}
172        }
173        *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
174      }
175      inrow += v_expand;
176    }
177  }
178  
179  
180  /*
181   * Downsample pixel values of a single component.
182   * This version handles the special case of a full-size component,
183   * without smoothing.
184   */
185  
186  METHODDEF(void)
fullsize_downsample(j_compress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY output_data)187  fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
188  		     JSAMPARRAY input_data, JSAMPARRAY output_data)
189  {
190    /* Copy the data */
191    jcopy_sample_rows(input_data, 0, output_data, 0,
192  		    cinfo->max_v_samp_factor, cinfo->image_width);
193    /* Edge-expand */
194    expand_right_edge(output_data, cinfo->max_v_samp_factor,
195  		    cinfo->image_width, compptr->width_in_blocks * DCTSIZE);
196  }
197  
198  
199  /*
200   * Downsample pixel values of a single component.
201   * This version handles the common case of 2:1 horizontal and 1:1 vertical,
202   * without smoothing.
203   *
204   * A note about the "bias" calculations: when rounding fractional values to
205   * integer, we do not want to always round 0.5 up to the next integer.
206   * If we did that, we'd introduce a noticeable bias towards larger values.
207   * Instead, this code is arranged so that 0.5 will be rounded up or down at
208   * alternate pixel locations (a simple ordered dither pattern).
209   */
210  
211  METHODDEF(void)
h2v1_downsample(j_compress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY output_data)212  h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
213  		 JSAMPARRAY input_data, JSAMPARRAY output_data)
214  {
215    int outrow;
216    JDIMENSION outcol;
217    JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
218    register JSAMPROW inptr, outptr;
219    register int bias;
220  
221    /* Expand input data enough to let all the output samples be generated
222     * by the standard loop.  Special-casing padded output would be more
223     * efficient.
224     */
225    expand_right_edge(input_data, cinfo->max_v_samp_factor,
226  		    cinfo->image_width, output_cols * 2);
227  
228    for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
229      outptr = output_data[outrow];
230      inptr = input_data[outrow];
231      bias = 0;			/* bias = 0,1,0,1,... for successive samples */
232      for (outcol = 0; outcol < output_cols; outcol++) {
233        *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
234  			      + bias) >> 1);
235        bias ^= 1;		/* 0=>1, 1=>0 */
236        inptr += 2;
237      }
238    }
239  }
240  
241  
242  /*
243   * Downsample pixel values of a single component.
244   * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
245   * without smoothing.
246   */
247  
248  METHODDEF(void)
h2v2_downsample(j_compress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY output_data)249  h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
250  		 JSAMPARRAY input_data, JSAMPARRAY output_data)
251  {
252    int inrow, outrow;
253    JDIMENSION outcol;
254    JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
255    register JSAMPROW inptr0, inptr1, outptr;
256    register int bias;
257  
258    /* Expand input data enough to let all the output samples be generated
259     * by the standard loop.  Special-casing padded output would be more
260     * efficient.
261     */
262    expand_right_edge(input_data, cinfo->max_v_samp_factor,
263  		    cinfo->image_width, output_cols * 2);
264  
265    inrow = 0;
266    for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
267      outptr = output_data[outrow];
268      inptr0 = input_data[inrow];
269      inptr1 = input_data[inrow+1];
270      bias = 1;			/* bias = 1,2,1,2,... for successive samples */
271      for (outcol = 0; outcol < output_cols; outcol++) {
272        *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
273  			      GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
274  			      + bias) >> 2);
275        bias ^= 3;		/* 1=>2, 2=>1 */
276        inptr0 += 2; inptr1 += 2;
277      }
278      inrow += 2;
279    }
280  }
281  
282  
283  #ifdef INPUT_SMOOTHING_SUPPORTED
284  
285  /*
286   * Downsample pixel values of a single component.
287   * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
288   * with smoothing.  One row of context is required.
289   */
290  
291  METHODDEF(void)
h2v2_smooth_downsample(j_compress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY output_data)292  h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
293  			JSAMPARRAY input_data, JSAMPARRAY output_data)
294  {
295    int inrow, outrow;
296    JDIMENSION colctr;
297    JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
298    register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
299    INT32 membersum, neighsum, memberscale, neighscale;
300  
301    /* Expand input data enough to let all the output samples be generated
302     * by the standard loop.  Special-casing padded output would be more
303     * efficient.
304     */
305    expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
306  		    cinfo->image_width, output_cols * 2);
307  
308    /* We don't bother to form the individual "smoothed" input pixel values;
309     * we can directly compute the output which is the average of the four
310     * smoothed values.  Each of the four member pixels contributes a fraction
311     * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
312     * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
313     * output.  The four corner-adjacent neighbor pixels contribute a fraction
314     * SF to just one smoothed pixel, or SF/4 to the final output; while the
315     * eight edge-adjacent neighbors contribute SF to each of two smoothed
316     * pixels, or SF/2 overall.  In order to use integer arithmetic, these
317     * factors are scaled by 2^16 = 65536.
318     * Also recall that SF = smoothing_factor / 1024.
319     */
320  
321    memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
322    neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
323  
324    inrow = 0;
325    for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
326      outptr = output_data[outrow];
327      inptr0 = input_data[inrow];
328      inptr1 = input_data[inrow+1];
329      above_ptr = input_data[inrow-1];
330      below_ptr = input_data[inrow+2];
331  
332      /* Special case for first column: pretend column -1 is same as column 0 */
333      membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
334  		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
335      neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
336  	       GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
337  	       GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
338  	       GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
339      neighsum += neighsum;
340      neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
341  		GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
342      membersum = membersum * memberscale + neighsum * neighscale;
343      *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
344      inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
345  
346      for (colctr = output_cols - 2; colctr > 0; colctr--) {
347        /* sum of pixels directly mapped to this output element */
348        membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
349  		  GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
350        /* sum of edge-neighbor pixels */
351        neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
352  		 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
353  		 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
354  		 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
355        /* The edge-neighbors count twice as much as corner-neighbors */
356        neighsum += neighsum;
357        /* Add in the corner-neighbors */
358        neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
359  		  GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
360        /* form final output scaled up by 2^16 */
361        membersum = membersum * memberscale + neighsum * neighscale;
362        /* round, descale and output it */
363        *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
364        inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
365      }
366  
367      /* Special case for last column */
368      membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
369  		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
370      neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
371  	       GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
372  	       GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
373  	       GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
374      neighsum += neighsum;
375      neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
376  		GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
377      membersum = membersum * memberscale + neighsum * neighscale;
378      *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
379  
380      inrow += 2;
381    }
382  }
383  
384  
385  /*
386   * Downsample pixel values of a single component.
387   * This version handles the special case of a full-size component,
388   * with smoothing.  One row of context is required.
389   */
390  
391  METHODDEF(void)
fullsize_smooth_downsample(j_compress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY output_data)392  fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr,
393  			    JSAMPARRAY input_data, JSAMPARRAY output_data)
394  {
395    int outrow;
396    JDIMENSION colctr;
397    JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
398    register JSAMPROW inptr, above_ptr, below_ptr, outptr;
399    INT32 membersum, neighsum, memberscale, neighscale;
400    int colsum, lastcolsum, nextcolsum;
401  
402    /* Expand input data enough to let all the output samples be generated
403     * by the standard loop.  Special-casing padded output would be more
404     * efficient.
405     */
406    expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
407  		    cinfo->image_width, output_cols);
408  
409    /* Each of the eight neighbor pixels contributes a fraction SF to the
410     * smoothed pixel, while the main pixel contributes (1-8*SF).  In order
411     * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
412     * Also recall that SF = smoothing_factor / 1024.
413     */
414  
415    memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
416    neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
417  
418    for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
419      outptr = output_data[outrow];
420      inptr = input_data[outrow];
421      above_ptr = input_data[outrow-1];
422      below_ptr = input_data[outrow+1];
423  
424      /* Special case for first column */
425      colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
426  	     GETJSAMPLE(*inptr);
427      membersum = GETJSAMPLE(*inptr++);
428      nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
429  		 GETJSAMPLE(*inptr);
430      neighsum = colsum + (colsum - membersum) + nextcolsum;
431      membersum = membersum * memberscale + neighsum * neighscale;
432      *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
433      lastcolsum = colsum; colsum = nextcolsum;
434  
435      for (colctr = output_cols - 2; colctr > 0; colctr--) {
436        membersum = GETJSAMPLE(*inptr++);
437        above_ptr++; below_ptr++;
438        nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
439  		   GETJSAMPLE(*inptr);
440        neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
441        membersum = membersum * memberscale + neighsum * neighscale;
442        *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
443        lastcolsum = colsum; colsum = nextcolsum;
444      }
445  
446      /* Special case for last column */
447      membersum = GETJSAMPLE(*inptr);
448      neighsum = lastcolsum + (colsum - membersum) + colsum;
449      membersum = membersum * memberscale + neighsum * neighscale;
450      *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
451  
452    }
453  }
454  
455  #endif /* INPUT_SMOOTHING_SUPPORTED */
456  
457  
458  /*
459   * Module initialization routine for downsampling.
460   * Note that we must select a routine for each component.
461   */
462  
463  GLOBAL(void)
jinit_downsampler(j_compress_ptr cinfo)464  jinit_downsampler (j_compress_ptr cinfo)
465  {
466    my_downsample_ptr downsample;
467    int ci;
468    jpeg_component_info * compptr;
469    boolean smoothok = TRUE;
470  
471    downsample = (my_downsample_ptr)
472      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
473  				SIZEOF(my_downsampler));
474    cinfo->downsample = (struct jpeg_downsampler *) downsample;
475    downsample->pub.start_pass = start_pass_downsample;
476    downsample->pub.downsample = sep_downsample;
477    downsample->pub.need_context_rows = FALSE;
478  
479    if (cinfo->CCIR601_sampling)
480      ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
481  
482    /* Verify we can handle the sampling factors, and set up method pointers */
483    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
484         ci++, compptr++) {
485      if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
486  	compptr->v_samp_factor == cinfo->max_v_samp_factor) {
487  #ifdef INPUT_SMOOTHING_SUPPORTED
488        if (cinfo->smoothing_factor) {
489  	downsample->methods[ci] = fullsize_smooth_downsample;
490  	downsample->pub.need_context_rows = TRUE;
491        } else
492  #endif
493  	downsample->methods[ci] = fullsize_downsample;
494      } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
495  	       compptr->v_samp_factor == cinfo->max_v_samp_factor) {
496        smoothok = FALSE;
497        downsample->methods[ci] = h2v1_downsample;
498      } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
499  	       compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {
500  #ifdef INPUT_SMOOTHING_SUPPORTED
501        if (cinfo->smoothing_factor) {
502  	downsample->methods[ci] = h2v2_smooth_downsample;
503  	downsample->pub.need_context_rows = TRUE;
504        } else
505  #endif
506  	downsample->methods[ci] = h2v2_downsample;
507      } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
508  	       (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {
509        smoothok = FALSE;
510        downsample->methods[ci] = int_downsample;
511      } else
512        ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
513    }
514  
515  #ifdef INPUT_SMOOTHING_SUPPORTED
516    if (cinfo->smoothing_factor && !smoothok)
517      TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);
518  #endif
519  }
520