1 /*
2  * jccoefct.c
3  *
4  * This file was part of the Independent JPEG Group's software:
5  * Copyright (C) 1994-1997, Thomas G. Lane.
6  * It was modified by The libjpeg-turbo Project to include only code and
7  * information relevant to libjpeg-turbo.
8  * For conditions of distribution and use, see the accompanying README.ijg
9  * file.
10  *
11  * This file contains the coefficient buffer controller for compression.
12  * This controller is the top level of the JPEG compressor proper.
13  * The coefficient buffer lies between forward-DCT and entropy encoding steps.
14  */
15 
16 #define JPEG_INTERNALS
17 #include "jinclude.h"
18 #include "jpeglib.h"
19 
20 
21 /* We use a full-image coefficient buffer when doing Huffman optimization,
22  * and also for writing multiple-scan JPEG files.  In all cases, the DCT
23  * step is run during the first pass, and subsequent passes need only read
24  * the buffered coefficients.
25  */
26 #ifdef ENTROPY_OPT_SUPPORTED
27 #define FULL_COEF_BUFFER_SUPPORTED
28 #else
29 #ifdef C_MULTISCAN_FILES_SUPPORTED
30 #define FULL_COEF_BUFFER_SUPPORTED
31 #endif
32 #endif
33 
34 
35 /* Private buffer controller object */
36 
37 typedef struct {
38   struct jpeg_c_coef_controller pub; /* public fields */
39 
40   JDIMENSION iMCU_row_num;      /* iMCU row # within image */
41   JDIMENSION mcu_ctr;           /* counts MCUs processed in current row */
42   int MCU_vert_offset;          /* counts MCU rows within iMCU row */
43   int MCU_rows_per_iMCU_row;    /* number of such rows needed */
44 
45   /* For single-pass compression, it's sufficient to buffer just one MCU
46    * (although this may prove a bit slow in practice).  We allocate a
47    * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
48    * MCU constructed and sent.  In multi-pass modes, this array points to the
49    * current MCU's blocks within the virtual arrays.
50    */
51   JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
52 
53   /* In multi-pass modes, we need a virtual block array for each component. */
54   jvirt_barray_ptr whole_image[MAX_COMPONENTS];
55 } my_coef_controller;
56 
57 typedef my_coef_controller *my_coef_ptr;
58 
59 
60 /* Forward declarations */
61 METHODDEF(boolean) compress_data(j_compress_ptr cinfo, JSAMPIMAGE input_buf);
62 #ifdef FULL_COEF_BUFFER_SUPPORTED
63 METHODDEF(boolean) compress_first_pass(j_compress_ptr cinfo,
64                                        JSAMPIMAGE input_buf);
65 METHODDEF(boolean) compress_output(j_compress_ptr cinfo, JSAMPIMAGE input_buf);
66 #endif
67 
68 
69 LOCAL(void)
start_iMCU_row(j_compress_ptr cinfo)70 start_iMCU_row(j_compress_ptr cinfo)
71 /* Reset within-iMCU-row counters for a new row */
72 {
73   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
74 
75   /* In an interleaved scan, an MCU row is the same as an iMCU row.
76    * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
77    * But at the bottom of the image, process only what's left.
78    */
79   if (cinfo->comps_in_scan > 1) {
80     coef->MCU_rows_per_iMCU_row = 1;
81   } else {
82     if (coef->iMCU_row_num < (cinfo->total_iMCU_rows - 1))
83       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
84     else
85       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
86   }
87 
88   coef->mcu_ctr = 0;
89   coef->MCU_vert_offset = 0;
90 }
91 
92 
93 /*
94  * Initialize for a processing pass.
95  */
96 
97 METHODDEF(void)
start_pass_coef(j_compress_ptr cinfo,J_BUF_MODE pass_mode)98 start_pass_coef(j_compress_ptr cinfo, J_BUF_MODE pass_mode)
99 {
100   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
101 
102   coef->iMCU_row_num = 0;
103   start_iMCU_row(cinfo);
104 
105   switch (pass_mode) {
106   case JBUF_PASS_THRU:
107     if (coef->whole_image[0] != NULL)
108       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
109     coef->pub.compress_data = compress_data;
110     break;
111 #ifdef FULL_COEF_BUFFER_SUPPORTED
112   case JBUF_SAVE_AND_PASS:
113     if (coef->whole_image[0] == NULL)
114       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
115     coef->pub.compress_data = compress_first_pass;
116     break;
117   case JBUF_CRANK_DEST:
118     if (coef->whole_image[0] == NULL)
119       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
120     coef->pub.compress_data = compress_output;
121     break;
122 #endif
123   default:
124     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
125     break;
126   }
127 }
128 
129 
130 /*
131  * Process some data in the single-pass case.
132  * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
133  * per call, ie, v_samp_factor block rows for each component in the image.
134  * Returns TRUE if the iMCU row is completed, FALSE if suspended.
135  *
136  * NB: input_buf contains a plane for each component in image,
137  * which we index according to the component's SOF position.
138  */
139 
140 METHODDEF(boolean)
compress_data(j_compress_ptr cinfo,JSAMPIMAGE input_buf)141 compress_data(j_compress_ptr cinfo, JSAMPIMAGE input_buf)
142 {
143   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
144   JDIMENSION MCU_col_num;       /* index of current MCU within row */
145   JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
146   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
147   int blkn, bi, ci, yindex, yoffset, blockcnt;
148   JDIMENSION ypos, xpos;
149   jpeg_component_info *compptr;
150 
151   /* Loop to write as much as one whole iMCU row */
152   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
153        yoffset++) {
154     for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
155          MCU_col_num++) {
156       /* Determine where data comes from in input_buf and do the DCT thing.
157        * Each call on forward_DCT processes a horizontal row of DCT blocks
158        * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
159        * sequentially.  Dummy blocks at the right or bottom edge are filled in
160        * specially.  The data in them does not matter for image reconstruction,
161        * so we fill them with values that will encode to the smallest amount of
162        * data, viz: all zeroes in the AC entries, DC entries equal to previous
163        * block's DC value.  (Thanks to Thomas Kinsman for this idea.)
164        */
165       blkn = 0;
166       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
167         compptr = cinfo->cur_comp_info[ci];
168         blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width :
169                                                   compptr->last_col_width;
170         xpos = MCU_col_num * compptr->MCU_sample_width;
171         ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */
172         for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
173           if (coef->iMCU_row_num < last_iMCU_row ||
174               yoffset + yindex < compptr->last_row_height) {
175             (*cinfo->fdct->forward_DCT) (cinfo, compptr,
176                                          input_buf[compptr->component_index],
177                                          coef->MCU_buffer[blkn],
178                                          ypos, xpos, (JDIMENSION)blockcnt);
179             if (blockcnt < compptr->MCU_width) {
180               /* Create some dummy blocks at the right edge of the image. */
181               jzero_far((void *)coef->MCU_buffer[blkn + blockcnt],
182                         (compptr->MCU_width - blockcnt) * sizeof(JBLOCK));
183               for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
184                 coef->MCU_buffer[blkn + bi][0][0] =
185                   coef->MCU_buffer[blkn + bi - 1][0][0];
186               }
187             }
188           } else {
189             /* Create a row of dummy blocks at the bottom of the image. */
190             jzero_far((void *)coef->MCU_buffer[blkn],
191                       compptr->MCU_width * sizeof(JBLOCK));
192             for (bi = 0; bi < compptr->MCU_width; bi++) {
193               coef->MCU_buffer[blkn + bi][0][0] =
194                 coef->MCU_buffer[blkn - 1][0][0];
195             }
196           }
197           blkn += compptr->MCU_width;
198           ypos += DCTSIZE;
199         }
200       }
201       /* Try to write the MCU.  In event of a suspension failure, we will
202        * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
203        */
204       if (!(*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
205         /* Suspension forced; update state counters and exit */
206         coef->MCU_vert_offset = yoffset;
207         coef->mcu_ctr = MCU_col_num;
208         return FALSE;
209       }
210     }
211     /* Completed an MCU row, but perhaps not an iMCU row */
212     coef->mcu_ctr = 0;
213   }
214   /* Completed the iMCU row, advance counters for next one */
215   coef->iMCU_row_num++;
216   start_iMCU_row(cinfo);
217   return TRUE;
218 }
219 
220 
221 #ifdef FULL_COEF_BUFFER_SUPPORTED
222 
223 /*
224  * Process some data in the first pass of a multi-pass case.
225  * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
226  * per call, ie, v_samp_factor block rows for each component in the image.
227  * This amount of data is read from the source buffer, DCT'd and quantized,
228  * and saved into the virtual arrays.  We also generate suitable dummy blocks
229  * as needed at the right and lower edges.  (The dummy blocks are constructed
230  * in the virtual arrays, which have been padded appropriately.)  This makes
231  * it possible for subsequent passes not to worry about real vs. dummy blocks.
232  *
233  * We must also emit the data to the entropy encoder.  This is conveniently
234  * done by calling compress_output() after we've loaded the current strip
235  * of the virtual arrays.
236  *
237  * NB: input_buf contains a plane for each component in image.  All
238  * components are DCT'd and loaded into the virtual arrays in this pass.
239  * However, it may be that only a subset of the components are emitted to
240  * the entropy encoder during this first pass; be careful about looking
241  * at the scan-dependent variables (MCU dimensions, etc).
242  */
243 
244 METHODDEF(boolean)
compress_first_pass(j_compress_ptr cinfo,JSAMPIMAGE input_buf)245 compress_first_pass(j_compress_ptr cinfo, JSAMPIMAGE input_buf)
246 {
247   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
248   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
249   JDIMENSION blocks_across, MCUs_across, MCUindex;
250   int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
251   JCOEF lastDC;
252   jpeg_component_info *compptr;
253   JBLOCKARRAY buffer;
254   JBLOCKROW thisblockrow, lastblockrow;
255 
256   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
257        ci++, compptr++) {
258     /* Align the virtual buffer for this component. */
259     buffer = (*cinfo->mem->access_virt_barray)
260       ((j_common_ptr)cinfo, coef->whole_image[ci],
261        coef->iMCU_row_num * compptr->v_samp_factor,
262        (JDIMENSION)compptr->v_samp_factor, TRUE);
263     /* Count non-dummy DCT block rows in this iMCU row. */
264     if (coef->iMCU_row_num < last_iMCU_row)
265       block_rows = compptr->v_samp_factor;
266     else {
267       /* NB: can't use last_row_height here, since may not be set! */
268       block_rows = (int)(compptr->height_in_blocks % compptr->v_samp_factor);
269       if (block_rows == 0) block_rows = compptr->v_samp_factor;
270     }
271     blocks_across = compptr->width_in_blocks;
272     h_samp_factor = compptr->h_samp_factor;
273     /* Count number of dummy blocks to be added at the right margin. */
274     ndummy = (int)(blocks_across % h_samp_factor);
275     if (ndummy > 0)
276       ndummy = h_samp_factor - ndummy;
277     /* Perform DCT for all non-dummy blocks in this iMCU row.  Each call
278      * on forward_DCT processes a complete horizontal row of DCT blocks.
279      */
280     for (block_row = 0; block_row < block_rows; block_row++) {
281       thisblockrow = buffer[block_row];
282       (*cinfo->fdct->forward_DCT) (cinfo, compptr,
283                                    input_buf[ci], thisblockrow,
284                                    (JDIMENSION)(block_row * DCTSIZE),
285                                    (JDIMENSION)0, blocks_across);
286       if (ndummy > 0) {
287         /* Create dummy blocks at the right edge of the image. */
288         thisblockrow += blocks_across; /* => first dummy block */
289         jzero_far((void *)thisblockrow, ndummy * sizeof(JBLOCK));
290         lastDC = thisblockrow[-1][0];
291         for (bi = 0; bi < ndummy; bi++) {
292           thisblockrow[bi][0] = lastDC;
293         }
294       }
295     }
296     /* If at end of image, create dummy block rows as needed.
297      * The tricky part here is that within each MCU, we want the DC values
298      * of the dummy blocks to match the last real block's DC value.
299      * This squeezes a few more bytes out of the resulting file...
300      */
301     if (coef->iMCU_row_num == last_iMCU_row) {
302       blocks_across += ndummy;  /* include lower right corner */
303       MCUs_across = blocks_across / h_samp_factor;
304       for (block_row = block_rows; block_row < compptr->v_samp_factor;
305            block_row++) {
306         thisblockrow = buffer[block_row];
307         lastblockrow = buffer[block_row - 1];
308         jzero_far((void *)thisblockrow,
309                   (size_t)(blocks_across * sizeof(JBLOCK)));
310         for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
311           lastDC = lastblockrow[h_samp_factor - 1][0];
312           for (bi = 0; bi < h_samp_factor; bi++) {
313             thisblockrow[bi][0] = lastDC;
314           }
315           thisblockrow += h_samp_factor; /* advance to next MCU in row */
316           lastblockrow += h_samp_factor;
317         }
318       }
319     }
320   }
321   /* NB: compress_output will increment iMCU_row_num if successful.
322    * A suspension return will result in redoing all the work above next time.
323    */
324 
325   /* Emit data to the entropy encoder, sharing code with subsequent passes */
326   return compress_output(cinfo, input_buf);
327 }
328 
329 
330 /*
331  * Process some data in subsequent passes of a multi-pass case.
332  * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
333  * per call, ie, v_samp_factor block rows for each component in the scan.
334  * The data is obtained from the virtual arrays and fed to the entropy coder.
335  * Returns TRUE if the iMCU row is completed, FALSE if suspended.
336  *
337  * NB: input_buf is ignored; it is likely to be a NULL pointer.
338  */
339 
340 METHODDEF(boolean)
compress_output(j_compress_ptr cinfo,JSAMPIMAGE input_buf)341 compress_output(j_compress_ptr cinfo, JSAMPIMAGE input_buf)
342 {
343   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
344   JDIMENSION MCU_col_num;       /* index of current MCU within row */
345   int blkn, ci, xindex, yindex, yoffset;
346   JDIMENSION start_col;
347   JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
348   JBLOCKROW buffer_ptr;
349   jpeg_component_info *compptr;
350 
351   /* Align the virtual buffers for the components used in this scan.
352    * NB: during first pass, this is safe only because the buffers will
353    * already be aligned properly, so jmemmgr.c won't need to do any I/O.
354    */
355   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
356     compptr = cinfo->cur_comp_info[ci];
357     buffer[ci] = (*cinfo->mem->access_virt_barray)
358       ((j_common_ptr)cinfo, coef->whole_image[compptr->component_index],
359        coef->iMCU_row_num * compptr->v_samp_factor,
360        (JDIMENSION)compptr->v_samp_factor, FALSE);
361   }
362 
363   /* Loop to process one whole iMCU row */
364   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
365        yoffset++) {
366     for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
367          MCU_col_num++) {
368       /* Construct list of pointers to DCT blocks belonging to this MCU */
369       blkn = 0;                 /* index of current DCT block within MCU */
370       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
371         compptr = cinfo->cur_comp_info[ci];
372         start_col = MCU_col_num * compptr->MCU_width;
373         for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
374           buffer_ptr = buffer[ci][yindex + yoffset] + start_col;
375           for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
376             coef->MCU_buffer[blkn++] = buffer_ptr++;
377           }
378         }
379       }
380       /* Try to write the MCU. */
381       if (!(*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
382         /* Suspension forced; update state counters and exit */
383         coef->MCU_vert_offset = yoffset;
384         coef->mcu_ctr = MCU_col_num;
385         return FALSE;
386       }
387     }
388     /* Completed an MCU row, but perhaps not an iMCU row */
389     coef->mcu_ctr = 0;
390   }
391   /* Completed the iMCU row, advance counters for next one */
392   coef->iMCU_row_num++;
393   start_iMCU_row(cinfo);
394   return TRUE;
395 }
396 
397 #endif /* FULL_COEF_BUFFER_SUPPORTED */
398 
399 
400 /*
401  * Initialize coefficient buffer controller.
402  */
403 
404 GLOBAL(void)
jinit_c_coef_controller(j_compress_ptr cinfo,boolean need_full_buffer)405 jinit_c_coef_controller(j_compress_ptr cinfo, boolean need_full_buffer)
406 {
407   my_coef_ptr coef;
408 
409   coef = (my_coef_ptr)
410     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
411                                 sizeof(my_coef_controller));
412   cinfo->coef = (struct jpeg_c_coef_controller *)coef;
413   coef->pub.start_pass = start_pass_coef;
414 
415   /* Create the coefficient buffer. */
416   if (need_full_buffer) {
417 #ifdef FULL_COEF_BUFFER_SUPPORTED
418     /* Allocate a full-image virtual array for each component, */
419     /* padded to a multiple of samp_factor DCT blocks in each direction. */
420     int ci;
421     jpeg_component_info *compptr;
422 
423     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
424          ci++, compptr++) {
425       coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
426         ((j_common_ptr)cinfo, JPOOL_IMAGE, FALSE,
427          (JDIMENSION)jround_up((long)compptr->width_in_blocks,
428                                (long)compptr->h_samp_factor),
429          (JDIMENSION)jround_up((long)compptr->height_in_blocks,
430                                (long)compptr->v_samp_factor),
431          (JDIMENSION)compptr->v_samp_factor);
432     }
433 #else
434     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
435 #endif
436   } else {
437     /* We only need a single-MCU buffer. */
438     JBLOCKROW buffer;
439     int i;
440 
441     buffer = (JBLOCKROW)
442       (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE,
443                                   C_MAX_BLOCKS_IN_MCU * sizeof(JBLOCK));
444     for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
445       coef->MCU_buffer[i] = buffer + i;
446     }
447     coef->whole_image[0] = NULL; /* flag for no virtual arrays */
448   }
449 }
450