• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /*
2  * jccoefct.c
3  *
4  * Copyright (C) 1994-1997, 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 the coefficient buffer controller for compression.
9  * This controller is the top level of the JPEG compressor proper.
10  * The coefficient buffer lies between forward-DCT and entropy encoding steps.
11  */
12 
13 #define JPEG_INTERNALS
14 #include "jinclude.h"
15 #include "jpeglib.h"
16 
17 
18 /* We use a full-image coefficient buffer when doing Huffman optimization,
19  * and also for writing multiple-scan JPEG files.  In all cases, the DCT
20  * step is run during the first pass, and subsequent passes need only read
21  * the buffered coefficients.
22  */
23 #ifdef ENTROPY_OPT_SUPPORTED
24 #define FULL_COEF_BUFFER_SUPPORTED
25 #else
26 #ifdef C_MULTISCAN_FILES_SUPPORTED
27 #define FULL_COEF_BUFFER_SUPPORTED
28 #endif
29 #endif
30 
31 
32 /* Private buffer controller object */
33 
34 typedef struct {
35   struct jpeg_c_coef_controller pub; /* public fields */
36 
37   JDIMENSION iMCU_row_num;	/* iMCU row # within image */
38   JDIMENSION mcu_ctr;		/* counts MCUs processed in current row */
39   int MCU_vert_offset;		/* counts MCU rows within iMCU row */
40   int MCU_rows_per_iMCU_row;	/* number of such rows needed */
41 
42   /* For single-pass compression, it's sufficient to buffer just one MCU
43    * (although this may prove a bit slow in practice).  We allocate a
44    * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
45    * MCU constructed and sent.  (On 80x86, the workspace is FAR even though
46    * it's not really very big; this is to keep the module interfaces unchanged
47    * when a large coefficient buffer is necessary.)
48    * In multi-pass modes, this array points to the current MCU's blocks
49    * 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
62     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
63 #ifdef FULL_COEF_BUFFER_SUPPORTED
64 METHODDEF(boolean) compress_first_pass
65     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
66 METHODDEF(boolean) compress_output
67     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
68 #endif
69 
70 
71 LOCAL(void)
start_iMCU_row(j_compress_ptr cinfo)72 start_iMCU_row (j_compress_ptr cinfo)
73 /* Reset within-iMCU-row counters for a new row */
74 {
75   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
76 
77   /* In an interleaved scan, an MCU row is the same as an iMCU row.
78    * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
79    * But at the bottom of the image, process only what's left.
80    */
81   if (cinfo->comps_in_scan > 1) {
82     coef->MCU_rows_per_iMCU_row = 1;
83   } else {
84     if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
85       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
86     else
87       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
88   }
89 
90   coef->mcu_ctr = 0;
91   coef->MCU_vert_offset = 0;
92 }
93 
94 
95 /*
96  * Initialize for a processing pass.
97  */
98 
99 METHODDEF(void)
start_pass_coef(j_compress_ptr cinfo,J_BUF_MODE pass_mode)100 start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
101 {
102   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
103 
104   coef->iMCU_row_num = 0;
105   start_iMCU_row(cinfo);
106 
107   switch (pass_mode) {
108   case JBUF_PASS_THRU:
109     if (coef->whole_image[0] != NULL)
110       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
111     coef->pub.compress_data = compress_data;
112     break;
113 #ifdef FULL_COEF_BUFFER_SUPPORTED
114   case JBUF_SAVE_AND_PASS:
115     if (coef->whole_image[0] == NULL)
116       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
117     coef->pub.compress_data = compress_first_pass;
118     break;
119   case JBUF_CRANK_DEST:
120     if (coef->whole_image[0] == NULL)
121       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
122     coef->pub.compress_data = compress_output;
123     break;
124 #endif
125   default:
126     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
127     break;
128   }
129 }
130 
131 
132 /*
133  * Process some data in the single-pass case.
134  * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
135  * per call, ie, v_samp_factor block rows for each component in the image.
136  * Returns TRUE if the iMCU row is completed, FALSE if suspended.
137  *
138  * NB: input_buf contains a plane for each component in image,
139  * which we index according to the component's SOF position.
140  */
141 
142 METHODDEF(boolean)
compress_data(j_compress_ptr cinfo,JSAMPIMAGE input_buf)143 compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
144 {
145   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
146   JDIMENSION MCU_col_num;	/* index of current MCU within row */
147   JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
148   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
149   int blkn, bi, ci, yindex, yoffset, blockcnt;
150   JDIMENSION ypos, xpos;
151   jpeg_component_info *compptr;
152 
153   /* Loop to write as much as one whole iMCU row */
154   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
155        yoffset++) {
156     for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
157 	 MCU_col_num++) {
158       /* Determine where data comes from in input_buf and do the DCT thing.
159        * Each call on forward_DCT processes a horizontal row of DCT blocks
160        * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
161        * sequentially.  Dummy blocks at the right or bottom edge are filled in
162        * specially.  The data in them does not matter for image reconstruction,
163        * so we fill them with values that will encode to the smallest amount of
164        * data, viz: all zeroes in the AC entries, DC entries equal to previous
165        * block's DC value.  (Thanks to Thomas Kinsman for this idea.)
166        */
167       blkn = 0;
168       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
169 	compptr = cinfo->cur_comp_info[ci];
170 	blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
171 						: compptr->last_col_width;
172 	xpos = MCU_col_num * compptr->MCU_sample_width;
173 	ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */
174 	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
175 	  if (coef->iMCU_row_num < last_iMCU_row ||
176 	      yoffset+yindex < compptr->last_row_height) {
177 	    (*cinfo->fdct->forward_DCT) (cinfo, compptr,
178 					 input_buf[compptr->component_index],
179 					 coef->MCU_buffer[blkn],
180 					 ypos, xpos, (JDIMENSION) blockcnt);
181 	    if (blockcnt < compptr->MCU_width) {
182 	      /* Create some dummy blocks at the right edge of the image. */
183 	      jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
184 			(compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
185 	      for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
186 		coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
187 	      }
188 	    }
189 	  } else {
190 	    /* Create a row of dummy blocks at the bottom of the image. */
191 	    jzero_far((void FAR *) coef->MCU_buffer[blkn],
192 		      compptr->MCU_width * SIZEOF(JBLOCK));
193 	    for (bi = 0; bi < compptr->MCU_width; bi++) {
194 	      coef->MCU_buffer[blkn+bi][0][0] = 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 FAR *) 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 FAR *) 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