1/*
2 * jcparam.c
3 *
4 * Copyright (C) 1991-1998, 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 optional default-setting code for the JPEG compressor.
9 * Applications do not have to use this file, but those that don't use it
10 * must know a lot more about the innards of the JPEG code.
11 */
12
13#define JPEG_INTERNALS
14#include "jinclude.h"
15#include "jpeglib.h"
16
17
18/*
19 * Quantization table setup routines
20 */
21
22GLOBAL(void)
23jpeg_add_quant_table (j_compress_ptr cinfo, int which_tbl,
24 const unsigned int *basic_table,
25 int scale_factor, boolean force_baseline)
26/* Define a quantization table equal to the basic_table times
27 * a scale factor (given as a percentage).
28 * If force_baseline is TRUE, the computed quantization table entries
29 * are limited to 1..255 for JPEG baseline compatibility.
30 */
31{
32 JQUANT_TBL ** qtblptr;
33 int i;
34 long temp;
35
36 /* Safety check to ensure start_compress not called yet. */
37 if (cinfo->global_state != CSTATE_START)
38 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
39
40 if (which_tbl < 0 || which_tbl >= NUM_QUANT_TBLS)
41 ERREXIT1(cinfo, JERR_DQT_INDEX, which_tbl);
42
43 qtblptr = & cinfo->quant_tbl_ptrs[which_tbl];
44
45 if (*qtblptr == NULL)
46 *qtblptr = jpeg_alloc_quant_table((j_common_ptr) cinfo);
47
48 for (i = 0; i < DCTSIZE2; i++) {
49 temp = ((long) basic_table[i] * scale_factor + 50L) / 100L;
50 /* limit the values to the valid range */
51 if (temp <= 0L) temp = 1L;
52 if (temp > 32767L) temp = 32767L; /* max quantizer needed for 12 bits */
53 if (force_baseline && temp > 255L)
54 temp = 255L; /* limit to baseline range if requested */
55 (*qtblptr)->quantval[i] = (UINT16) temp;
56 }
57
58 /* Initialize sent_table FALSE so table will be written to JPEG file. */
59 (*qtblptr)->sent_table = FALSE;
60}
61
62
63GLOBAL(void)
64jpeg_set_linear_quality (j_compress_ptr cinfo, int scale_factor,
65 boolean force_baseline)
66/* Set or change the 'quality' (quantization) setting, using default tables
67 * and a straight percentage-scaling quality scale. In most cases it's better
68 * to use jpeg_set_quality (below); this entry point is provided for
69 * applications that insist on a linear percentage scaling.
70 */
71{
72 /* These are the sample quantization tables given in JPEG spec section K.1.
73 * The spec says that the values given produce "good" quality, and
74 * when divided by 2, "very good" quality.
75 */
76 static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = {
77 16, 11, 10, 16, 24, 40, 51, 61,
78 12, 12, 14, 19, 26, 58, 60, 55,
79 14, 13, 16, 24, 40, 57, 69, 56,
80 14, 17, 22, 29, 51, 87, 80, 62,
81 18, 22, 37, 56, 68, 109, 103, 77,
82 24, 35, 55, 64, 81, 104, 113, 92,
83 49, 64, 78, 87, 103, 121, 120, 101,
84 72, 92, 95, 98, 112, 100, 103, 99
85 };
86 static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = {
87 17, 18, 24, 47, 99, 99, 99, 99,
88 18, 21, 26, 66, 99, 99, 99, 99,
89 24, 26, 56, 99, 99, 99, 99, 99,
90 47, 66, 99, 99, 99, 99, 99, 99,
91 99, 99, 99, 99, 99, 99, 99, 99,
92 99, 99, 99, 99, 99, 99, 99, 99,
93 99, 99, 99, 99, 99, 99, 99, 99,
94 99, 99, 99, 99, 99, 99, 99, 99
95 };
96
97 /* Set up two quantization tables using the specified scaling */
98 jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl,
99 scale_factor, force_baseline);
100 jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl,
101 scale_factor, force_baseline);
102}
103
104
105GLOBAL(int)
106jpeg_quality_scaling (int quality)
107/* Convert a user-specified quality rating to a percentage scaling factor
108 * for an underlying quantization table, using our recommended scaling curve.
109 * The input 'quality' factor should be 0 (terrible) to 100 (very good).
110 */
111{
112 /* Safety limit on quality factor. Convert 0 to 1 to avoid zero divide. */
113 if (quality <= 0) quality = 1;
114 if (quality > 100) quality = 100;
115
116 /* The basic table is used as-is (scaling 100) for a quality of 50.
117 * Qualities 50..100 are converted to scaling percentage 200 - 2*Q;
118 * note that at Q=100 the scaling is 0, which will cause jpeg_add_quant_table
119 * to make all the table entries 1 (hence, minimum quantization loss).
120 * Qualities 1..50 are converted to scaling percentage 5000/Q.
121 */
122 if (quality < 50)
123 quality = 5000 / quality;
124 else
125 quality = 200 - quality*2;
126
127 return quality;
128}
129
130
131GLOBAL(void)
132jpeg_set_quality (j_compress_ptr cinfo, int quality, boolean force_baseline)
133/* Set or change the 'quality' (quantization) setting, using default tables.
134 * This is the standard quality-adjusting entry point for typical user
135 * interfaces; only those who want detailed control over quantization tables
136 * would use the preceding three routines directly.
137 */
138{
139 /* Convert user 0-100 rating to percentage scaling */
140 quality = jpeg_quality_scaling(quality);
141
142 /* Set up standard quality tables */
143 jpeg_set_linear_quality(cinfo, quality, force_baseline);
144}
145
146
147/*
148 * Huffman table setup routines
149 */
150
151LOCAL(void)
152add_huff_table (j_compress_ptr cinfo,
153 JHUFF_TBL **htblptr, const UINT8 *bits, const UINT8 *val)
154/* Define a Huffman table */
155{
156 int nsymbols, len;
157
158 if (*htblptr == NULL)
159 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
160
161 /* Copy the number-of-symbols-of-each-code-length counts */
162 MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));
163
164 /* Validate the counts. We do this here mainly so we can copy the right
165 * number of symbols from the val[] array, without risking marching off
166 * the end of memory. jchuff.c will do a more thorough test later.
167 */
168 nsymbols = 0;
169 for (len = 1; len <= 16; len++)
170 nsymbols += bits[len];
171 if (nsymbols < 1 || nsymbols > 256)
172 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
173
174 MEMCOPY((*htblptr)->huffval, val, nsymbols * SIZEOF(UINT8));
175
176 /* Initialize sent_table FALSE so table will be written to JPEG file. */
177 (*htblptr)->sent_table = FALSE;
178}
179
180
181LOCAL(void)
182std_huff_tables (j_compress_ptr cinfo)
183/* Set up the standard Huffman tables (cf. JPEG standard section K.3) */
184/* IMPORTANT: these are only valid for 8-bit data precision! */
185{
186 static const UINT8 bits_dc_luminance[17] =
187 { /* 0-base */ 0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };
188 static const UINT8 val_dc_luminance[] =
189 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
190
191 static const UINT8 bits_dc_chrominance[17] =
192 { /* 0-base */ 0, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
193 static const UINT8 val_dc_chrominance[] =
194 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
195
196 static const UINT8 bits_ac_luminance[17] =
197 { /* 0-base */ 0, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d };
198 static const UINT8 val_ac_luminance[] =
199 { 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
200 0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
201 0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,
202 0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,
203 0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,
204 0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,
205 0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
206 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
207 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
208 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
209 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
210 0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
211 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
212 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
213 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,
214 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,
215 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4,
216 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2,
217 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea,
218 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
219 0xf9, 0xfa };
220
221 static const UINT8 bits_ac_chrominance[17] =
222 { /* 0-base */ 0, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77 };
223 static const UINT8 val_ac_chrominance[] =
224 { 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,
225 0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,
226 0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,
227 0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0,
228 0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,
229 0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26,
230 0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38,
231 0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
232 0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
233 0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
234 0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
235 0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
236 0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96,
237 0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5,
238 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4,
239 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3,
240 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2,
241 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda,
242 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,
243 0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
244 0xf9, 0xfa };
245
246 add_huff_table(cinfo, &cinfo->dc_huff_tbl_ptrs[0],
247 bits_dc_luminance, val_dc_luminance);
248 add_huff_table(cinfo, &cinfo->ac_huff_tbl_ptrs[0],
249 bits_ac_luminance, val_ac_luminance);
250 add_huff_table(cinfo, &cinfo->dc_huff_tbl_ptrs[1],
251 bits_dc_chrominance, val_dc_chrominance);
252 add_huff_table(cinfo, &cinfo->ac_huff_tbl_ptrs[1],
253 bits_ac_chrominance, val_ac_chrominance);
254}
255
256
257/*
258 * Default parameter setup for compression.
259 *
260 * Applications that don't choose to use this routine must do their
261 * own setup of all these parameters. Alternately, you can call this
262 * to establish defaults and then alter parameters selectively. This
263 * is the recommended approach since, if we add any new parameters,
264 * your code will still work (they'll be set to reasonable defaults).
265 */
266
267GLOBAL(void)
268jpeg_set_defaults (j_compress_ptr cinfo)
269{
270 int i;
271
272 /* Safety check to ensure start_compress not called yet. */
273 if (cinfo->global_state != CSTATE_START)
274 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
275
276 /* Allocate comp_info array large enough for maximum component count.
277 * Array is made permanent in case application wants to compress
278 * multiple images at same param settings.
279 */
280 if (cinfo->comp_info == NULL)
281 cinfo->comp_info = (jpeg_component_info *)
282 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
283 MAX_COMPONENTS * SIZEOF(jpeg_component_info));
284
285 /* Initialize everything not dependent on the color space */
286
287 cinfo->data_precision = BITS_IN_JSAMPLE;
288 /* Set up two quantization tables using default quality of 75 */
289 jpeg_set_quality(cinfo, 75, TRUE);
290 /* Set up two Huffman tables */
291 std_huff_tables(cinfo);
292
293 /* Initialize default arithmetic coding conditioning */
294 for (i = 0; i < NUM_ARITH_TBLS; i++) {
295 cinfo->arith_dc_L[i] = 0;
296 cinfo->arith_dc_U[i] = 1;
297 cinfo->arith_ac_K[i] = 5;
298 }
299
300 /* Default is no multiple-scan output */
301 cinfo->scan_info = NULL;
302 cinfo->num_scans = 0;
303
304 /* Expect normal source image, not raw downsampled data */
305 cinfo->raw_data_in = FALSE;
306
307 /* Use Huffman coding, not arithmetic coding, by default */
308 cinfo->arith_code = FALSE;
309
310 /* By default, don't do extra passes to optimize entropy coding */
311 cinfo->optimize_coding = FALSE;
312 /* The standard Huffman tables are only valid for 8-bit data precision.
313 * If the precision is higher, force optimization on so that usable
314 * tables will be computed. This test can be removed if default tables
315 * are supplied that are valid for the desired precision.
316 */
317 if (cinfo->data_precision > 8)
318 cinfo->optimize_coding = TRUE;
319
320 /* By default, use the simpler non-cosited sampling alignment */
321 cinfo->CCIR601_sampling = FALSE;
322
323 /* No input smoothing */
324 cinfo->smoothing_factor = 0;
325
326 /* DCT algorithm preference */
327 cinfo->dct_method = JDCT_DEFAULT;
328
329 /* No restart markers */
330 cinfo->restart_interval = 0;
331 cinfo->restart_in_rows = 0;
332
333 /* Fill in default JFIF marker parameters. Note that whether the marker
334 * will actually be written is determined by jpeg_set_colorspace.
335 *
336 * By default, the library emits JFIF version code 1.01.
337 * An application that wants to emit JFIF 1.02 extension markers should set
338 * JFIF_minor_version to 2. We could probably get away with just defaulting
339 * to 1.02, but there may still be some decoders in use that will complain
340 * about that; saying 1.01 should minimize compatibility problems.
341 */
342 cinfo->JFIF_major_version = 1; /* Default JFIF version = 1.01 */
343 cinfo->JFIF_minor_version = 1;
344 cinfo->density_unit = 0; /* Pixel size is unknown by default */
345 cinfo->X_density = 1; /* Pixel aspect ratio is square by default */
346 cinfo->Y_density = 1;
347
348 /* Choose JPEG colorspace based on input space, set defaults accordingly */
349
350 jpeg_default_colorspace(cinfo);
351}
352
353
354/*
355 * Select an appropriate JPEG colorspace for in_color_space.
356 */
357
358GLOBAL(void)
359jpeg_default_colorspace (j_compress_ptr cinfo)
360{
361 switch (cinfo->in_color_space) {
362 case JCS_GRAYSCALE:
363 jpeg_set_colorspace(cinfo, JCS_GRAYSCALE);
364 break;
365 case JCS_RGB:
366 jpeg_set_colorspace(cinfo, JCS_YCbCr);
367 break;
368 case JCS_YCbCr:
369 jpeg_set_colorspace(cinfo, JCS_YCbCr);
370 break;
371 case JCS_CMYK:
372 jpeg_set_colorspace(cinfo, JCS_CMYK); /* By default, no translation */
373 break;
374 case JCS_YCCK:
375 jpeg_set_colorspace(cinfo, JCS_YCCK);
376 break;
377 case JCS_UNKNOWN:
378 jpeg_set_colorspace(cinfo, JCS_UNKNOWN);
379 break;
380 default:
381 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
382 }
383}
384
385
386/*
387 * Set the JPEG colorspace, and choose colorspace-dependent default values.
388 */
389
390GLOBAL(void)
391jpeg_set_colorspace (j_compress_ptr cinfo, J_COLOR_SPACE colorspace)
392{
393 jpeg_component_info * compptr;
394 int ci;
395
396#define SET_COMP(index,id,hsamp,vsamp,quant,dctbl,actbl) \
397 (compptr = &cinfo->comp_info[index], \
398 compptr->component_id = (id), \
399 compptr->h_samp_factor = (hsamp), \
400 compptr->v_samp_factor = (vsamp), \
401 compptr->quant_tbl_no = (quant), \
402 compptr->dc_tbl_no = (dctbl), \
403 compptr->ac_tbl_no = (actbl) )
404
405 /* Safety check to ensure start_compress not called yet. */
406 if (cinfo->global_state != CSTATE_START)
407 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
408
409 /* For all colorspaces, we use Q and Huff tables 0 for luminance components,
410 * tables 1 for chrominance components.
411 */
412
413 cinfo->jpeg_color_space = colorspace;
414
415 cinfo->write_JFIF_header = FALSE; /* No marker for non-JFIF colorspaces */
416 cinfo->write_Adobe_marker = FALSE; /* write no Adobe marker by default */
417
418 switch (colorspace) {
419 case JCS_GRAYSCALE:
420 cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */
421 cinfo->num_components = 1;
422 /* JFIF specifies component ID 1 */
423 SET_COMP(0, 1, 1,1, 0, 0,0);
424 break;
425 case JCS_RGB:
426 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag RGB */
427 cinfo->num_components = 3;
428 SET_COMP(0, 0x52 /* 'R' */, 1,1, 0, 0,0);
429 SET_COMP(1, 0x47 /* 'G' */, 1,1, 0, 0,0);
430 SET_COMP(2, 0x42 /* 'B' */, 1,1, 0, 0,0);
431 break;
432 case JCS_YCbCr:
433 cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */
434 cinfo->num_components = 3;
435 /* JFIF specifies component IDs 1,2,3 */
436 /* We default to 2x2 subsamples of chrominance */
437 SET_COMP(0, 1, 2,2, 0, 0,0);
438 SET_COMP(1, 2, 1,1, 1, 1,1);
439 SET_COMP(2, 3, 1,1, 1, 1,1);
440 break;
441 case JCS_CMYK:
442 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag CMYK */
443 cinfo->num_components = 4;
444 SET_COMP(0, 0x43 /* 'C' */, 1,1, 0, 0,0);
445 SET_COMP(1, 0x4D /* 'M' */, 1,1, 0, 0,0);
446 SET_COMP(2, 0x59 /* 'Y' */, 1,1, 0, 0,0);
447 SET_COMP(3, 0x4B /* 'K' */, 1,1, 0, 0,0);
448 break;
449 case JCS_YCCK:
450 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag YCCK */
451 cinfo->num_components = 4;
452 SET_COMP(0, 1, 2,2, 0, 0,0);
453 SET_COMP(1, 2, 1,1, 1, 1,1);
454 SET_COMP(2, 3, 1,1, 1, 1,1);
455 SET_COMP(3, 4, 2,2, 0, 0,0);
456 break;
457 case JCS_UNKNOWN:
458 cinfo->num_components = cinfo->input_components;
459 if (cinfo->num_components < 1 || cinfo->num_components > MAX_COMPONENTS)
460 ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
461 MAX_COMPONENTS);
462 for (ci = 0; ci < cinfo->num_components; ci++) {
463 SET_COMP(ci, ci, 1,1, 0, 0,0);
464 }
465 break;
466 default:
467 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
468 }
469}
470
471
472#ifdef C_PROGRESSIVE_SUPPORTED
473
474LOCAL(jpeg_scan_info *)
475fill_a_scan (jpeg_scan_info * scanptr, int ci,
476 int Ss, int Se, int Ah, int Al)
477/* Support routine: generate one scan for specified component */
478{
479 scanptr->comps_in_scan = 1;
480 scanptr->component_index[0] = ci;
481 scanptr->Ss = Ss;
482 scanptr->Se = Se;
483 scanptr->Ah = Ah;
484 scanptr->Al = Al;
485 scanptr++;
486 return scanptr;
487}
488
489LOCAL(jpeg_scan_info *)
490fill_scans (jpeg_scan_info * scanptr, int ncomps,
491 int Ss, int Se, int Ah, int Al)
492/* Support routine: generate one scan for each component */
493{
494 int ci;
495
496 for (ci = 0; ci < ncomps; ci++) {
497 scanptr->comps_in_scan = 1;
498 scanptr->component_index[0] = ci;
499 scanptr->Ss = Ss;
500 scanptr->Se = Se;
501 scanptr->Ah = Ah;
502 scanptr->Al = Al;
503 scanptr++;
504 }
505 return scanptr;
506}
507
508LOCAL(jpeg_scan_info *)
509fill_dc_scans (jpeg_scan_info * scanptr, int ncomps, int Ah, int Al)
510/* Support routine: generate interleaved DC scan if possible, else N scans */
511{
512 int ci;
513
514 if (ncomps <= MAX_COMPS_IN_SCAN) {
515 /* Single interleaved DC scan */
516 scanptr->comps_in_scan = ncomps;
517 for (ci = 0; ci < ncomps; ci++)
518 scanptr->component_index[ci] = ci;
519 scanptr->Ss = scanptr->Se = 0;
520 scanptr->Ah = Ah;
521 scanptr->Al = Al;
522 scanptr++;
523 } else {
524 /* Noninterleaved DC scan for each component */
525 scanptr = fill_scans(scanptr, ncomps, 0, 0, Ah, Al);
526 }
527 return scanptr;
528}
529
530
531/*
532 * Create a recommended progressive-JPEG script.
533 * cinfo->num_components and cinfo->jpeg_color_space must be correct.
534 */
535
536GLOBAL(void)
537jpeg_simple_progression (j_compress_ptr cinfo)
538{
539 int ncomps = cinfo->num_components;
540 int nscans;
541 jpeg_scan_info * scanptr;
542
543 /* Safety check to ensure start_compress not called yet. */
544 if (cinfo->global_state != CSTATE_START)
545 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
546
547 /* Figure space needed for script. Calculation must match code below! */
548 if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {
549 /* Custom script for YCbCr color images. */
550 nscans = 10;
551 } else {
552 /* All-purpose script for other color spaces. */
553 if (ncomps > MAX_COMPS_IN_SCAN)
554 nscans = 6 * ncomps; /* 2 DC + 4 AC scans per component */
555 else
556 nscans = 2 + 4 * ncomps; /* 2 DC scans; 4 AC scans per component */
557 }
558
559 /* Allocate space for script.
560 * We need to put it in the permanent pool in case the application performs
561 * multiple compressions without changing the settings. To avoid a memory
562 * leak if jpeg_simple_progression is called repeatedly for the same JPEG
563 * object, we try to re-use previously allocated space, and we allocate
564 * enough space to handle YCbCr even if initially asked for grayscale.
565 */
566 if (cinfo->script_space == NULL || cinfo->script_space_size < nscans) {
567 cinfo->script_space_size = MAX(nscans, 10);
568 cinfo->script_space = (jpeg_scan_info *)
569 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
570 cinfo->script_space_size * SIZEOF(jpeg_scan_info));
571 }
572 scanptr = cinfo->script_space;
573 cinfo->scan_info = scanptr;
574 cinfo->num_scans = nscans;
575
576 if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {
577 /* Custom script for YCbCr color images. */
578 /* Initial DC scan */
579 scanptr = fill_dc_scans(scanptr, ncomps, 0, 1);
580 /* Initial AC scan: get some luma data out in a hurry */
581 scanptr = fill_a_scan(scanptr, 0, 1, 5, 0, 2);
582 /* Chroma data is too small to be worth expending many scans on */
583 scanptr = fill_a_scan(scanptr, 2, 1, 63, 0, 1);
584 scanptr = fill_a_scan(scanptr, 1, 1, 63, 0, 1);
585 /* Complete spectral selection for luma AC */
586 scanptr = fill_a_scan(scanptr, 0, 6, 63, 0, 2);
587 /* Refine next bit of luma AC */
588 scanptr = fill_a_scan(scanptr, 0, 1, 63, 2, 1);
589 /* Finish DC successive approximation */
590 scanptr = fill_dc_scans(scanptr, ncomps, 1, 0);
591 /* Finish AC successive approximation */
592 scanptr = fill_a_scan(scanptr, 2, 1, 63, 1, 0);
593 scanptr = fill_a_scan(scanptr, 1, 1, 63, 1, 0);
594 /* Luma bottom bit comes last since it's usually largest scan */
595 scanptr = fill_a_scan(scanptr, 0, 1, 63, 1, 0);
596 } else {
597 /* All-purpose script for other color spaces. */
598 /* Successive approximation first pass */
599 scanptr = fill_dc_scans(scanptr, ncomps, 0, 1);
600 scanptr = fill_scans(scanptr, ncomps, 1, 5, 0, 2);
601 scanptr = fill_scans(scanptr, ncomps, 6, 63, 0, 2);
602 /* Successive approximation second pass */
603 scanptr = fill_scans(scanptr, ncomps, 1, 63, 2, 1);
604 /* Successive approximation final pass */
605 scanptr = fill_dc_scans(scanptr, ncomps, 1, 0);
606 scanptr = fill_scans(scanptr, ncomps, 1, 63, 1, 0);
607 }
608}
609
610#endif /* C_PROGRESSIVE_SUPPORTED */
611