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source: trunk/JPGPROC/source/gbmsrc/gbmerr.c@ 2

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Last change on this file since 2 was 2, checked in by stevenhl, 8 years ago
Import sources from cwmm-full.zip dated 2005-03-21
File size: 33.4 KB

Line
1	/*
2
3	gbmerr.c - Error diffusion Module
4
5	*/
6
7	/...sincludes:0:/
8	#include <stdio.h>
9	#include <stddef.h>
10	#include <stdlib.h>
11	#include <string.h>
12	#include "gbm.h"
13
14	/...vgbm\46\h:0:/
15	/...e/
16	/...svars:0:/
17	static BOOLEAN inited = FALSE;
18
19	/*
20	Tables used for quick saturated addition and subtraction.
21	*/
22
23	static byte usat[256+256+256];
24	#define U_SAT_ADD(a,b) usat[(a)+(b)+256]
25
26	static short ssat[256+256+256+256];
27	#define S_SAT_ADD(a,b) ssat[(a)+(b)+512]
28
29	/*
30	For 6Rx6Gx6B, 7Rx8Gx4B palettes etc.
31	*/
32
33	static byte index4[0x100];
34	static byte index6[0x100];
35	static byte index7[0x100];
36	static byte index8[0x100];
37	static byte index16[0x100];
38	static byte scale4[] = { 0, 85, 170, 255 };
39	static byte scale6[] = { 0, 51, 102, 153, 204, 255 };
40	static byte scale7[] = { 0, 43, 85, 128, 170, 213, 255 };
41	static byte scale8[] = { 0, 36, 73, 109, 146, 182, 219, 255 };
42	static byte scale16[] = { 0, 17, 34, 51, 68, 85, 102, 119, 136,
43	153, 170, 187, 204, 221, 238, 255 };
44
45	static word randtab[0x100];
46	static int randinx = 0;
47	/...e/
48	/...sinit:0:/
49	/*
50	This function initialises this module.
51	It does this by preparing the quick saturated addition and subraction tables.
52	*/
53
54	/...snearest_inx:0:/
55	#ifndef abs
56	#define abs(x) (((x)>=0)?(x):-(x))
57	#endif
58
59	static byte nearest_inx(byte value, const byte ab[], unsigned short cb)
60	{
61	byte b, inx, inx_min;
62	short diff, diff_min;
63
64	b = ab[0];
65	diff_min = abs((short) value - (short) b);
66	inx_min = 0;
67	for ( inx = 1; (unsigned short) inx < cb; inx++ )
68	{
69	b = ab[inx];
70	diff = abs((short) value - (short) b);
71	if ( diff < diff_min )
72	{
73	diff_min = diff;
74	inx_min = inx;
75	}
76	}
77	return inx_min;
78	}
79	/...e/
80
81	static void init(void)
82	{
83	int i;
84
85	if ( inited )
86	return;
87
88	memset(usat, 0, 0x100);
89	for ( i = 0; i < 0x100; i++ )
90	usat[i + 0x100] = (byte) i;
91	memset(usat + 0x200, 0xff, 0x100);
92
93	for ( i = -0x200; i < -0x100; i++ )
94	ssat[i + 0x200] = -0x100;
95	for ( i = -0x100; i < 0x100; i++ )
96	ssat[i + 0x200] = i;
97	for ( i = 0x100; i < 0x200; i++ )
98	ssat[i + 0x200] = 0xff;
99
100	/* For 7 Red x 8 Green x 4 Blue palettes etc. */
101
102	for ( i = 0; i < 0x100; i++ )
103	{
104	index4 [i] = nearest_inx((byte) i, scale4 , sizeof(scale4 ));
105	index6 [i] = nearest_inx((byte) i, scale6 , sizeof(scale6 ));
106	index7 [i] = nearest_inx((byte) i, scale7 , sizeof(scale7 ));
107	index8 [i] = nearest_inx((byte) i, scale8 , sizeof(scale8 ));
108	index16[i] = nearest_inx((byte) i, scale16, sizeof(scale16));
109	}
110
111	/* For faster random number calculation */
112
113	for ( i = 0; i < 0x100; i++ )
114	randtab [i] = (word) (rand() % (51*0x100));
115
116	inited = TRUE;
117	}
118	/...e/
119	/...serrdiff:0:/
120	static BOOLEAN errdiff(
121	const GBM gbm, const byte src, byte *dest,
122	int dest_bpp,
123	void (errdiff_line)(byte src, byte dest, short errs, int cx)
124	)
125	{
126	int stride_src = ((gbm->w * 3 + 3) & ~3);
127	int stride_dest = ((gbm->w * dest_bpp + 31) / 32) * 4;
128	byte *buf;
129	short *errs;
130	int y;
131
132	if ( (buf = malloc((size_t) stride_src + 3)) == NULL )
133	return FALSE;
134
135	if ( (errs = malloc((size_t) ((gbm->w + 1) * 3 * sizeof(short)))) == NULL )
136	{
137	free(buf);
138	return FALSE;
139	}
140
141	memset(errs, 0, (gbm->w + 1) * 3 * sizeof(short));
142
143	for ( y = 0; y < gbm->h; y++ )
144	{
145	memcpy(buf, src + y * stride_src, stride_src);
146	(errdiff_line)(buf, dest + y stride_dest, errs, gbm->w);
147	}
148
149	free(buf);
150	free(errs);
151
152	return TRUE;
153	}
154	/...e/
155
156	/...sgbm_errdiff_line_24 \45\ error diffuse to fewer bits per pixel one line:0:/
157	/*
158	This function takes a line of RGB data, a destination buffer and a buffer of
159	error terms and performs one lines worth (a given # of pixels) of error
160	diffusion.
161	*/
162
163	void gbm_errdiff_line_24(byte src, byte dest, short *errs, int cx, byte rm, byte gm, byte bm)
164	{
165	int x, ptr = 0;
166
167	init();
168
169	/* Step 1: Add error terms to newly supplied line */
170
171	for ( x = 0; x < cx * 3; x++ )
172	src[x] = U_SAT_ADD((int) src[x], (int) errs[x]);
173
174	/* Step 2: Zero out error terms */
175
176	memset(errs, 0, cx * 3 * sizeof(errs[0]));
177
178	/* Step 3: Go along data, finding nearest colour and propagating error */
179
180	randinx = rand();
181
182	for ( x = 0; x < cx; x++ )
183	{
184	byte b = *src++;
185	byte g = *src++;
186	byte r = *src++;
187	byte bi = (b & bm);
188	byte gi = (g & gm);
189	byte ri = (r & rm);
190	int be = b - (int) bi;
191	int ge = g - (int) gi;
192	int re = r - (int) ri;
193	word rn = randtab[(byte) (randinx++)];
194	int right = (rn >> 8);
195	int down = ((rn & 0xff) % (63 - right));
196	int be1 = ((be * right) >> 6);
197	int ge1 = ((ge * right) >> 6);
198	int re1 = ((re * right) >> 6);
199	int be2 = ((be * down ) >> 6);
200	int ge2 = ((ge * down ) >> 6);
201	int re2 = ((re * down ) >> 6);
202	int be3 = be - be1 - be2;
203	int ge3 = ge - ge1 - ge2;
204	int re3 = re - re1 - re2;
205
206	*dest++ = bi;
207	*dest++ = gi;
208	*dest++ = ri;
209
210	src[0] = U_SAT_ADD((int) src[0], be1);
211	src[1] = U_SAT_ADD((int) src[1], ge1);
212	src[2] = U_SAT_ADD((int) src[2], re1);
213
214	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be2);
215	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge2);
216	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re2);
217
218	ptr += 3;
219
220	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be3);
221	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge3);
222	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re3);
223	}
224	}
225	/...e/
226	/...sgbm_errdiff_24 \45\ error diffuse to fewer bits per pixel:0:/
227	BOOLEAN gbm_errdiff_24(const GBM gbm, const byte data24, byte *data24a, byte rm, byte gm, byte bm)
228	{
229	int stride = ((gbm->w * 3 + 3) & ~3);
230	byte *buf;
231	short *errs;
232	int y;
233
234	if ( (buf = malloc((size_t) (stride + 3))) == NULL )
235	return FALSE;
236
237	if ( (errs = malloc((size_t) ((gbm->w + 1) * 3 * sizeof(short)))) == NULL )
238	{
239	free(buf);
240	return FALSE;
241	}
242
243	memset(errs, 0, (gbm->w + 1) * 3 * sizeof(short));
244
245	for ( y = 0; y < gbm->h; y++ )
246	{
247	memcpy(buf, data24 + y * stride, stride);
248	gbm_errdiff_line_24(buf, data24a + y * stride, errs, gbm->w, rm, gm, bm);
249	}
250
251	free(buf);
252	free(errs);
253
254	return TRUE;
255	}
256	/...e/
257
258	/...sgbm_errdiff_pal_6R6G6B \45\ return 6Rx6Gx6B palette:0:/
259	/*
260	This function makes the palette for the 6 red x 6 green x 6 blue palette.
261	216 palette entrys used. Remaining 40 left blank.
262	*/
263
264	void gbm_errdiff_pal_6R6G6B(GBMRGB *gbmrgb)
265	{
266	byte volatile r; /* C-Set/2 optimiser fix */
267	byte volatile g;
268	byte volatile b;
269
270	init();
271	memset(gbmrgb, 0x80, 0x100 * sizeof(GBMRGB));
272	for ( r = 0; r < 6; r++ )
273	for ( g = 0; g < 6; g++ )
274	for ( b = 0; b < 6; b++ )
275	{
276	gbmrgb->r = scale6[r];
277	gbmrgb->g = scale6[g];
278	gbmrgb->b = scale6[b];
279	gbmrgb++;
280	}
281	}
282	/...e/
283	/...sgbm_errdiff_line_6R6G6B \45\ error diffuse to 6Rx6Gx6B one line:0:/
284	/*
285	This function takes a line of RGB data, a destination buffer and a buffer of
286	error terms and performs one lines worth (a given # of pixels) of error
287	diffusion.
288	*/
289
290	void gbm_errdiff_line_6R6G6B(byte src, byte dest, short *errs, int cx)
291	{
292	int x, ptr = 0;
293
294	init();
295
296	/* Step 1: Add error terms to newly supplied line */
297
298	for ( x = 0; x < cx * 3; x++ )
299	src[x] = U_SAT_ADD((int) src[x], (int) errs[x]);
300
301	/* Step 2: Zero out error terms */
302
303	memset(errs, 0, (cx + 1) * 3 * sizeof(errs[0]));
304
305	/* Step 3: Go along data, finding nearest colour and propagating error */
306
307	randinx = rand();
308
309	for ( x = 0; x < cx; x++ )
310	{
311	byte b = *src++;
312	byte g = *src++;
313	byte r = *src++;
314	byte bi = index6[b];
315	byte gi = index6[g];
316	byte ri = index6[r];
317	int be = b - ((int) scale6[bi]);
318	int ge = g - ((int) scale6[gi]);
319	int re = r - ((int) scale6[ri]);
320	word rn = randtab[(byte) (randinx++)];
321	int right = (int) (rn >> 8);
322	int down = (int) ((rn & 0xff) % (63 - right));
323	int be1 = ((be * right) >> 6);
324	int ge1 = ((ge * right) >> 6);
325	int re1 = ((re * right) >> 6);
326	int be2 = ((be * down ) >> 6);
327	int ge2 = ((ge * down ) >> 6);
328	int re2 = ((re * down ) >> 6);
329	int be3 = be - be1 - be2;
330	int ge3 = ge - ge1 - ge2;
331	int re3 = re - re1 - re2;
332
333	dest++ = (byte) (6 (6 * ri + gi) + bi);
334
335	src[0] = U_SAT_ADD((int) src[0], be1);
336	src[1] = U_SAT_ADD((int) src[1], ge1);
337	src[2] = U_SAT_ADD((int) src[2], re1);
338
339	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be2);
340	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge2);
341	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re2);
342
343	ptr += 3;
344
345	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be3);
346	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge3);
347	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re3);
348	}
349	}
350	/...e/
351	/...sgbm_errdiff_6R6G6B \45\ error diffuse to 6Rx6Gx6B:0:/
352	BOOLEAN gbm_errdiff_6R6G6B(const GBM gbm, const byte data24, byte *data8)
353	{
354	return errdiff(gbm, data24, data8, 8, gbm_errdiff_line_6R6G6B);
355	}
356	/...e/
357
358	/...sgbm_errdiff_pal_7R8G4B \45\ return 7Rx8Gx4B palette:0:/
359	/*
360	This function makes the palette for the 7 red x 8 green x 4 blue palette.
361	224 palette entrys used. Remaining 32 left blank.
362	Colours calculated to match those used by 8514/A PM driver.
363	*/
364
365	void gbm_errdiff_pal_7R8G4B(GBMRGB *gbmrgb)
366	{
367	byte volatile r; /* C-Set/2 optimiser fix */
368	byte volatile g;
369	byte volatile b;
370
371	init();
372
373	memset(gbmrgb, 0x80, 0x100 * sizeof(GBMRGB));
374	for ( r = 0; r < 7; r++ )
375	for ( g = 0; g < 8; g++ )
376	for ( b = 0; b < 4; b++ )
377	{
378	gbmrgb->r = scale7[r];
379	gbmrgb->g = scale8[g];
380	gbmrgb->b = scale4[b];
381	gbmrgb++;
382	}
383	}
384	/...e/
385	/...sgbm_errdiff_line_7R8G4B \45\ error diffuse to 7Rx8Gx4B one line:0:/
386	/*
387	This function takes a line of RGB data, a destination buffer and a buffer of
388	error terms and performs one lines worth (a given # of pixels) of error
389	diffusion.
390	*/
391
392	void gbm_errdiff_line_7R8G4B(byte src, byte dest, short *errs, int cx)
393	{
394	int x, ptr = 0;
395
396	init();
397
398	/* Step 1: Add error terms to newly supplied line */
399
400	for ( x = 0; x < cx * 3; x++ )
401	src[x] = U_SAT_ADD((int) src[x], (int) errs[x]);
402
403	/* Step 2: Zero out error terms */
404
405	memset(errs, 0, (cx + 1) * 3 * sizeof(errs[0]));
406
407	/* Step 3: Go along data, finding nearest colour and propagating error */
408
409	randinx = rand();
410
411	for ( x = 0; x < cx; x++ )
412	{
413	byte b = *src++;
414	byte g = *src++;
415	byte r = *src++;
416	byte bi = index4[b];
417	byte gi = index8[g];
418	byte ri = index7[r];
419	int be = b - ((int) scale4[bi]);
420	int ge = g - ((int) scale8[gi]);
421	int re = r - ((int) scale7[ri]);
422	word rn = randtab[(byte) (randinx++)];
423	int right = (rn >> 8);
424	int down = ((rn & 0xff) % (63 - right));
425	int be1 = ((be * right) >> 6);
426	int ge1 = ((ge * right) >> 6);
427	int re1 = ((re * right) >> 6);
428	int be2 = ((be * down ) >> 6);
429	int ge2 = ((ge * down ) >> 6);
430	int re2 = ((re * down ) >> 6);
431	int be3 = be - be1 - be2;
432	int ge3 = ge - ge1 - ge2;
433	int re3 = re - re1 - re2;
434
435	dest++ = (byte) (4 (8 * ri + gi) + bi);
436
437	src[0] = U_SAT_ADD((int) src[0], be1);
438	src[1] = U_SAT_ADD((int) src[1], ge1);
439	src[2] = U_SAT_ADD((int) src[2], re1);
440
441	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be2);
442	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge2);
443	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re2);
444
445	ptr += 3;
446
447	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be3);
448	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge3);
449	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re3);
450	}
451	}
452	/...e/
453	/...sgbm_errdiff_7R8G4B \45\ error diffuse to 7Rx8Gx4B:0:/
454	BOOLEAN gbm_errdiff_7R8G4B(const GBM gbm, const byte data24, byte *data8)
455	{
456	return errdiff(gbm, data24, data8, 8, gbm_errdiff_line_7R8G4B);
457	}
458	/...e/
459
460	/...sgbm_errdiff_pal_VGA \45\ return default VGA palette:0:/
461	/*
462	This function makes the palette for the 16 colour VGA palette.
463	*/
464
465	static GBMRGB gbmrgb_vga[] =
466	{
467	0, 0, 0,
468	128, 0, 0,
469	0,128, 0,
470	128,128, 0,
471	0, 0,128,
472	128, 0,128,
473	0,128,128,
474	128,128,128,
475	204,204,204,
476	255, 0, 0,
477	0,255, 0,
478	255,255, 0,
479	0, 0,255,
480	255, 0,255,
481	0,255,255,
482	255,255,255,
483	};
484
485	void gbm_errdiff_pal_VGA(GBMRGB *gbmrgb)
486	{
487	init();
488	memcpy((char ) gbmrgb, (char ) gbmrgb_vga, sizeof(gbmrgb_vga));
489	}
490	/...e/
491	/...sgbm_errdiff_line_VGA \45\ error diffuse to default VGA palette one line:0:/
492	/*
493	This function takes a line of RGB data, a destination buffer and a buffer of
494	error terms and performs one lines worth (a given # of pixels) of error
495	diffusion.
496	*/
497
498	/...scalc_nearest:0:/
499	/*
500	This function, when given am RGB colour, finds the VGA palette entry closest
501	to it. We deliberately bias away from the two grey palette entries.
502	*/
503
504	static byte calc_nearest(byte r, byte g, byte b)
505	{
506	long min_dist = 3L * 256L * 256L * 10L;
507	byte bi, bi_min;
508
509	for ( bi = 0; bi < 0x10; bi++ )
510	{
511	long b_dist = ((long) b - (long) gbmrgb_vga[bi].b);
512	long g_dist = ((long) g - (long) gbmrgb_vga[bi].g);
513	long r_dist = ((long) r - (long) gbmrgb_vga[bi].r);
514	long dist = r_dist * r_dist + g_dist * g_dist + b_dist * b_dist;
515
516	if ( bi == 7 \|\| bi == 8 )
517	/* Bias away from this colour */
518	dist <<= 3;
519
520	if ( dist < min_dist )
521	{
522	min_dist = dist;
523	bi_min = bi;
524	}
525	}
526	return bi_min;
527	}
528	/...e/
529	/...snearest_colour:0:/
530	/*
531	This function finds the closest VGA palette colour to a given RGB value.
532	It uses a lookup table to avoid performing distance calculations to the
533	16 palette entrys. The table is pre-calculated.
534	*/
535
536	/...squick lookup table:0:/
537	/...v_gbmerr\46\c \45\ used to make quick_tab:0:/
538
539	static byte quick_tab[16][16][16] =
540	{
541	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
542	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
543	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
544	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
545	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
546	2,2,2,2,255,6,6,6,6,6,6,6,6,255,12,12,
547	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,12,
548	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
549	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
550	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,14,
551	2,2,2,2,255,6,6,6,6,6,6,6,6,255,14,14,
552	2,2,2,2,255,6,6,6,6,6,6,6,255,14,14,14,
553	10,10,10,10,255,6,6,6,6,6,6,255,14,14,14,14,
554	10,10,10,10,10,255,6,6,6,6,255,14,14,14,14,14,
555	10,10,10,10,10,10,255,6,6,255,14,14,14,14,14,14,
556	10,10,10,10,10,10,10,255,255,14,14,14,14,14,14,14,
557	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
558	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
559	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
560	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
561	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
562	2,2,2,2,255,6,6,6,6,6,6,6,6,255,12,12,
563	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,12,
564	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
565	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
566	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,14,
567	2,2,2,2,255,6,6,6,6,6,6,6,6,255,14,14,
568	2,2,2,2,255,6,6,6,6,6,6,6,255,14,14,14,
569	10,10,10,10,255,6,6,6,6,6,6,255,14,14,14,14,
570	10,10,10,10,10,255,6,6,6,6,255,14,14,14,14,14,
571	10,10,10,10,10,10,255,6,6,255,14,14,14,14,14,14,
572	10,10,10,10,10,10,10,255,255,14,14,14,14,14,14,14,
573	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
574	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
575	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
576	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
577	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
578	2,2,2,2,255,6,6,6,6,6,6,6,6,255,12,12,
579	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,12,
580	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
581	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
582	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,14,
583	2,2,2,2,255,6,6,6,6,6,6,6,6,255,14,14,
584	2,2,2,2,255,6,6,6,6,6,6,6,255,14,14,14,
585	10,10,10,10,255,6,6,6,6,6,6,255,14,14,14,14,
586	10,10,10,10,10,255,6,6,6,6,255,14,14,14,14,14,
587	10,10,10,10,10,10,255,6,6,255,14,14,14,14,14,14,
588	10,10,10,10,10,10,10,255,255,14,14,14,14,14,14,14,
589	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
590	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
591	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
592	0,0,0,0,255,4,4,4,4,4,4,4,12,12,12,12,
593	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
594	2,2,2,2,255,6,6,6,6,6,6,6,6,255,12,12,
595	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,12,
596	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
597	2,2,2,2,255,6,6,6,6,6,6,6,6,6,6,255,
598	2,2,2,2,255,6,6,6,6,6,6,6,6,6,255,14,
599	2,2,2,2,255,6,6,6,6,6,6,6,6,255,14,14,
600	2,2,2,2,255,6,6,6,6,6,6,6,255,14,14,14,
601	10,10,10,10,255,6,6,6,6,6,6,255,14,14,14,14,
602	10,10,10,10,10,255,6,6,6,6,255,14,14,14,14,14,
603	10,10,10,10,10,10,255,6,6,255,14,14,14,14,14,14,
604	10,10,10,10,10,10,10,255,255,14,14,14,14,14,14,14,
605	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
606	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
607	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
608	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
609	255,255,255,255,255,255,255,255,255,255,255,255,255,12,12,12,
610	255,255,255,255,255,6,6,6,6,6,6,6,6,255,12,12,
611	255,255,255,255,255,6,6,6,6,6,6,6,6,6,255,12,
612	255,255,255,255,255,6,6,6,6,6,6,6,6,6,6,255,
613	255,255,255,255,255,6,6,6,6,6,6,6,6,6,6,255,
614	255,255,255,255,255,6,6,6,6,6,6,6,6,6,255,14,
615	255,255,255,255,255,6,6,6,6,6,6,6,6,255,14,14,
616	255,255,255,255,255,6,6,6,6,6,6,6,255,14,14,14,
617	255,255,255,255,255,6,6,6,6,6,6,255,14,14,14,14,
618	10,10,10,10,10,255,6,6,6,6,255,14,14,14,14,14,
619	10,10,10,10,10,10,255,6,6,255,14,14,14,14,14,14,
620	10,10,10,10,10,10,10,255,255,14,14,14,14,14,14,14,
621	1,1,1,1,255,5,5,5,5,5,5,5,5,255,12,12,
622	1,1,1,1,255,5,5,5,5,5,5,5,5,255,12,12,
623	1,1,1,1,255,5,5,5,5,5,5,5,5,255,12,12,
624	1,1,1,1,255,5,5,5,5,5,5,5,5,255,12,12,
625	255,255,255,255,255,5,5,5,5,5,5,5,5,255,12,12,
626	3,3,3,3,3,255,255,255,255,255,255,255,255,255,12,12,
627	3,3,3,3,3,255,6,6,6,6,6,6,6,6,255,12,
628	3,3,3,3,3,255,6,255,255,6,6,6,6,6,6,255,
629	3,3,3,3,3,255,6,255,255,6,6,6,6,6,6,255,
630	3,3,3,3,3,255,6,6,6,6,6,6,6,6,255,14,
631	3,3,3,3,3,255,6,6,6,6,6,6,6,255,14,14,
632	3,3,3,3,3,255,6,6,6,6,6,6,255,14,14,14,
633	3,3,3,3,3,255,6,6,6,6,6,255,14,14,14,14,
634	255,255,255,255,255,255,6,6,6,6,255,14,14,14,14,14,
635	10,10,10,10,10,10,255,6,6,255,14,14,14,14,14,14,
636	10,10,10,10,10,10,10,255,255,14,14,14,14,14,14,14,
637	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,12,
638	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,12,
639	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,12,
640	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,12,
641	255,255,255,255,255,5,5,5,5,5,5,5,5,5,255,12,
642	3,3,3,3,3,255,5,5,5,5,5,5,5,5,255,12,
643	3,3,3,3,3,3,255,255,255,255,255,255,255,255,255,12,
644	3,3,3,3,3,3,255,255,255,255,255,6,6,6,6,255,
645	3,3,3,3,3,3,255,255,255,255,255,6,6,6,6,255,
646	3,3,3,3,3,3,255,255,255,255,255,6,6,6,255,14,
647	3,3,3,3,3,3,255,255,255,255,6,6,6,255,14,14,
648	3,3,3,3,3,3,255,6,6,6,6,6,255,14,14,14,
649	3,3,3,3,3,3,255,6,6,6,6,255,14,14,14,14,
650	3,3,3,3,3,3,255,6,6,6,255,14,14,14,14,14,
651	255,255,255,255,255,255,255,6,6,255,14,14,14,14,14,14,
652	10,10,10,10,10,10,10,255,255,14,14,14,14,14,14,14,
653	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
654	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
655	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
656	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
657	255,255,255,255,255,5,5,5,5,5,5,5,5,5,5,255,
658	3,3,3,3,3,255,5,255,255,5,5,5,5,5,5,255,
659	3,3,3,3,3,3,255,255,255,255,255,5,5,5,5,255,
660	3,3,3,3,3,255,255,7,7,7,255,255,255,255,255,255,
661	3,3,3,3,3,255,255,7,7,7,255,6,6,6,6,255,
662	3,3,3,3,3,3,255,7,7,255,255,6,6,6,255,14,
663	3,3,3,3,3,3,255,255,255,255,255,6,6,255,14,14,
664	3,3,3,3,3,3,3,255,6,6,6,6,255,14,14,14,
665	3,3,3,3,3,3,3,255,6,6,6,255,14,14,14,14,
666	3,3,3,3,3,3,3,255,6,6,255,14,14,14,14,14,
667	3,3,3,3,3,3,3,255,6,255,14,14,14,14,14,14,
668	255,255,255,255,255,255,255,255,255,14,14,14,14,14,14,14,
669	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
670	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
671	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
672	1,1,1,1,255,5,5,5,5,5,5,5,5,5,5,255,
673	255,255,255,255,255,5,5,5,5,5,5,5,5,5,5,255,
674	3,3,3,3,3,255,5,255,255,5,5,5,5,5,5,255,
675	3,3,3,3,3,3,255,255,255,255,255,5,5,5,5,255,
676	3,3,3,3,3,255,255,7,7,7,255,5,5,5,5,255,
677	3,3,3,3,3,255,255,7,7,7,255,255,255,255,255,255,
678	3,3,3,3,3,3,255,7,7,7,255,255,255,255,255,15,
679	3,3,3,3,3,3,255,255,255,255,255,255,255,255,15,15,
680	3,3,3,3,3,3,3,3,255,255,255,255,255,15,15,15,
681	3,3,3,3,3,3,3,3,255,255,255,255,15,15,15,15,
682	3,3,3,3,3,3,3,3,255,255,255,15,15,15,15,15,
683	3,3,3,3,3,3,3,3,255,255,15,15,15,15,15,15,
684	255,255,255,255,255,255,255,255,255,15,15,15,15,15,15,15,
685	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,13,
686	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,13,
687	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,13,
688	1,1,1,1,255,5,5,5,5,5,5,5,5,5,255,13,
689	255,255,255,255,255,5,5,5,5,5,5,5,5,5,255,13,
690	3,3,3,3,3,255,5,5,5,5,5,5,5,5,255,13,
691	3,3,3,3,3,3,255,255,255,255,255,5,5,5,255,13,
692	3,3,3,3,3,3,255,7,7,255,255,5,5,5,255,13,
693	3,3,3,3,3,3,255,7,7,7,255,255,255,255,255,15,
694	3,3,3,3,3,3,255,255,7,7,255,255,255,15,15,15,
695	3,3,3,3,3,3,255,255,255,255,255,255,15,15,15,15,
696	3,3,3,3,3,3,3,3,255,255,255,15,15,15,15,15,
697	3,3,3,3,3,3,3,3,255,255,15,15,15,15,15,15,
698	3,3,3,3,3,3,3,3,255,15,15,15,15,15,15,15,
699	255,255,255,255,255,255,255,255,255,15,15,15,15,15,15,15,
700	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
701	1,1,1,1,255,5,5,5,5,5,5,5,5,255,13,13,
702	1,1,1,1,255,5,5,5,5,5,5,5,5,255,13,13,
703	1,1,1,1,255,5,5,5,5,5,5,5,5,255,13,13,
704	1,1,1,1,255,5,5,5,5,5,5,5,5,255,13,13,
705	255,255,255,255,255,5,5,5,5,5,5,5,5,255,13,13,
706	3,3,3,3,3,255,5,5,5,5,5,5,5,255,13,13,
707	3,3,3,3,3,3,255,255,255,255,5,5,5,255,13,13,
708	3,3,3,3,3,3,255,255,255,255,255,5,5,255,13,13,
709	3,3,3,3,3,3,255,255,255,255,255,255,255,255,15,15,
710	3,3,3,3,3,3,255,255,255,255,255,255,15,15,15,15,
711	3,3,3,3,3,3,3,255,255,255,255,255,255,255,15,15,
712	3,3,3,3,3,3,3,3,255,255,255,255,255,255,255,15,
713	3,3,3,3,3,3,3,3,255,15,255,255,255,255,255,15,
714	255,255,255,255,255,255,255,255,255,15,255,255,255,255,15,15,
715	11,11,11,11,11,11,11,11,15,15,15,255,255,15,15,15,
716	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
717	1,1,1,1,255,5,5,5,5,5,5,5,255,13,13,13,
718	1,1,1,1,255,5,5,5,5,5,5,5,255,13,13,13,
719	1,1,1,1,255,5,5,5,5,5,5,5,255,13,13,13,
720	1,1,1,1,255,5,5,5,5,5,5,5,255,13,13,13,
721	255,255,255,255,255,5,5,5,5,5,5,5,255,13,13,13,
722	3,3,3,3,3,255,5,5,5,5,5,5,255,13,13,13,
723	3,3,3,3,3,3,255,5,5,5,5,5,255,13,13,13,
724	3,3,3,3,3,3,3,255,5,5,5,5,255,13,13,13,
725	3,3,3,3,3,3,3,3,255,255,255,255,255,15,15,15,
726	3,3,3,3,3,3,3,3,255,255,255,15,15,15,15,15,
727	3,3,3,3,3,3,3,3,255,255,255,255,255,255,255,15,
728	3,3,3,3,3,3,3,3,255,15,255,255,8,255,255,15,
729	255,255,255,255,255,255,255,255,255,15,255,8,8,8,255,15,
730	11,11,11,11,11,11,11,11,15,15,255,255,8,255,255,15,
731	11,11,11,11,11,11,11,11,15,15,255,255,255,255,15,15,
732	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
733	9,9,9,9,255,5,5,5,5,5,5,255,13,13,13,13,
734	9,9,9,9,255,5,5,5,5,5,5,255,13,13,13,13,
735	9,9,9,9,255,5,5,5,5,5,5,255,13,13,13,13,
736	9,9,9,9,255,5,5,5,5,5,5,255,13,13,13,13,
737	255,255,255,255,255,5,5,5,5,5,5,255,13,13,13,13,
738	3,3,3,3,3,255,5,5,5,5,5,255,13,13,13,13,
739	3,3,3,3,3,3,255,5,5,5,5,255,13,13,13,13,
740	3,3,3,3,3,3,3,255,5,5,5,255,13,13,13,13,
741	3,3,3,3,3,3,3,3,255,255,255,255,15,15,15,15,
742	3,3,3,3,3,3,3,3,255,255,15,15,15,15,15,15,
743	3,3,3,3,3,3,3,3,255,15,255,255,255,255,255,15,
744	255,255,255,255,255,255,255,255,255,15,255,8,8,8,255,15,
745	11,11,11,11,11,11,11,11,15,15,255,8,8,8,255,15,
746	11,11,11,11,11,11,11,11,15,15,255,8,8,255,255,15,
747	11,11,11,11,11,11,11,11,15,15,255,255,255,255,15,15,
748	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
749	9,9,9,9,9,255,5,5,5,5,255,13,13,13,13,13,
750	9,9,9,9,9,255,5,5,5,5,255,13,13,13,13,13,
751	9,9,9,9,9,255,5,5,5,5,255,13,13,13,13,13,
752	9,9,9,9,9,255,5,5,5,5,255,13,13,13,13,13,
753	9,9,9,9,9,255,5,5,5,5,255,13,13,13,13,13,
754	255,255,255,255,255,255,5,5,5,5,255,13,13,13,13,13,
755	3,3,3,3,3,3,255,5,5,5,255,13,13,13,13,13,
756	3,3,3,3,3,3,3,255,5,5,255,13,13,13,13,13,
757	3,3,3,3,3,3,3,3,255,255,255,15,15,15,15,15,
758	3,3,3,3,3,3,3,3,255,15,15,15,15,15,15,15,
759	255,255,255,255,255,255,255,255,255,15,255,255,255,255,15,15,
760	11,11,11,11,11,11,11,11,15,15,255,255,8,255,255,15,
761	11,11,11,11,11,11,11,11,15,15,255,8,8,255,255,15,
762	11,11,11,11,11,11,11,11,15,15,255,255,255,255,255,15,
763	11,11,11,11,11,11,11,11,15,15,15,255,255,255,15,15,
764	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
765	9,9,9,9,9,9,255,5,5,255,13,13,13,13,13,13,
766	9,9,9,9,9,9,255,5,5,255,13,13,13,13,13,13,
767	9,9,9,9,9,9,255,5,5,255,13,13,13,13,13,13,
768	9,9,9,9,9,9,255,5,5,255,13,13,13,13,13,13,
769	9,9,9,9,9,9,255,5,5,255,13,13,13,13,13,13,
770	9,9,9,9,9,9,255,5,5,255,13,13,13,13,13,13,
771	255,255,255,255,255,255,255,5,5,255,13,13,13,13,13,13,
772	3,3,3,3,3,3,3,255,5,255,13,13,13,13,13,13,
773	3,3,3,3,3,3,3,3,255,255,15,15,15,15,15,15,
774	255,255,255,255,255,255,255,255,255,15,15,15,15,15,15,15,
775	11,11,11,11,11,11,11,11,15,15,15,255,255,15,15,15,
776	11,11,11,11,11,11,11,11,15,15,255,255,255,255,15,15,
777	11,11,11,11,11,11,11,11,15,15,255,255,255,255,15,15,
778	11,11,11,11,11,11,11,11,15,15,15,255,255,255,15,15,
779	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
780	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
781	9,9,9,9,9,9,9,255,255,13,13,13,13,13,13,13,
782	9,9,9,9,9,9,9,255,255,13,13,13,13,13,13,13,
783	9,9,9,9,9,9,9,255,255,13,13,13,13,13,13,13,
784	9,9,9,9,9,9,9,255,255,13,13,13,13,13,13,13,
785	9,9,9,9,9,9,9,255,255,13,13,13,13,13,13,13,
786	9,9,9,9,9,9,9,255,255,13,13,13,13,13,13,13,
787	9,9,9,9,9,9,9,255,255,13,13,13,13,13,13,13,
788	255,255,255,255,255,255,255,255,255,13,13,13,13,13,13,13,
789	255,255,255,255,255,255,255,255,255,15,15,15,15,15,15,15,
790	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
791	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
792	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
793	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
794	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
795	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
796	11,11,11,11,11,11,11,11,15,15,15,15,15,15,15,15,
797	};
798	/...e/
799
800	static byte nearest_colour(byte r, byte g, byte b)
801	{
802	byte i;
803
804	if ( (i = quick_tab[r >> 4][g >> 4][b >> 4]) != (byte) 0xff )
805	return i;
806
807	return calc_nearest(r, g, b);
808	}
809	/...e/
810
811	void gbm_errdiff_line_VGA(byte src, byte dest, short *errs, int cx)
812	{
813	BOOLEAN left = TRUE;
814	int x, ptr = 0;
815
816	init();
817
818	/* Step 1: Add error terms to newly supplied line */
819
820	for ( x = 0; x < cx * 3; x++ )
821	src[x] = U_SAT_ADD((int) src[x], (int) errs[x]);
822
823	/* Step 2: Zero out error terms */
824
825	memset(errs, 0, (cx + 1) * 3 * sizeof(errs[0]));
826
827	/* Step 3: Go along data, finding nearest colour and propagating error */
828
829	randinx = rand();
830
831	for ( x = 0; x < cx; x++ )
832	{
833	byte b = *src++;
834	byte g = *src++;
835	byte r = *src++;
836	byte bi = nearest_colour(r, g, b);
837	int be = (int) b - (int) gbmrgb_vga[bi].b;
838	int ge = (int) g - (int) gbmrgb_vga[bi].g;
839	int re = (int) r - (int) gbmrgb_vga[bi].r;
840	word rn = randtab[(byte) (randinx++)];
841	int right = (rn >> 8);
842	int down = ((rn & 0xff) % (63 - right));
843	int be1 = ((be * right) >> 6);
844	int ge1 = ((ge * right) >> 6);
845	int re1 = ((re * right) >> 6);
846	int be2 = ((be * down ) >> 6);
847	int ge2 = ((ge * down ) >> 6);
848	int re2 = ((re * down ) >> 6);
849	int be3 = be - be1 - be2;
850	int ge3 = ge - ge1 - ge2;
851	int re3 = re - re1 - re2;
852
853	if ( left )
854	*dest = (byte) (bi << 4);
855	else
856	*dest++ \|= bi;
857
858	left = !left;
859
860	src[0] = U_SAT_ADD((int) src[0], be1);
861	src[1] = U_SAT_ADD((int) src[1], ge1);
862	src[2] = U_SAT_ADD((int) src[2], re1);
863
864	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be2);
865	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge2);
866	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re2);
867
868	ptr += 3;
869
870	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be3);
871	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge3);
872	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re3);
873	}
874	}
875	/...e/
876	/...sgbm_errdiff_VGA \45\ error diffuse to default VGA palette:0:/
877	BOOLEAN gbm_errdiff_VGA(const GBM gbm, const byte data24, byte *data4)
878	{
879	return errdiff(gbm, data24, data4, 4, gbm_errdiff_line_VGA);
880	}
881	/...e/
882
883	/...sgbm_errdiff_pal_8 \45\ return default 8 colour palette:0:/
884	/*
885	This function makes the palette for the 16 colour 8 colour palette.
886	*/
887
888	static GBMRGB gbmrgb_8[] =
889	{
890	0, 0, 0,
891	0, 0,255,
892	0,255, 0,
893	0,255,255,
894	255, 0, 0,
895	255, 0,255,
896	255,255, 0,
897	255,255,255,
898	0, 0, 0,
899	0, 0, 0,
900	0, 0, 0,
901	0, 0, 0,
902	0, 0, 0,
903	0, 0, 0,
904	0, 0, 0,
905	0, 0, 0,
906	};
907
908	void gbm_errdiff_pal_8(GBMRGB *gbmrgb)
909	{
910	init();
911	memcpy((char ) gbmrgb, (char ) gbmrgb_8, sizeof(gbmrgb_8));
912	}
913	/...e/
914	/...sgbm_errdiff_line_8 \45\ error diffuse to default 8 colour palette one line:0:/
915	/*
916	This function takes a line of RGB data, a destination buffer and a buffer of
917	error terms and performs one lines worth (a given # of pixels) of error
918	diffusion.
919	*/
920
921	void gbm_errdiff_line_8(byte src, byte dest, short *errs, int cx)
922	{
923	BOOLEAN left = TRUE;
924	int x, ptr = 0;
925
926	init();
927
928	/* Step 1: Add error terms to newly supplied line */
929
930	for ( x = 0; x < cx * 3; x++ )
931	src[x] = U_SAT_ADD((int) src[x], (int) errs[x]);
932
933	/* Step 2: Zero out error terms */
934
935	memset(errs, 0, (cx + 1) * 3 * sizeof(errs[0]));
936
937	/* Step 3: Go along data, finding nearest colour and propagating error */
938
939	randinx = rand();
940
941	for ( x = 0; x < cx; x++ )
942	{
943	byte b = *src++;
944	byte g = *src++;
945	byte r = *src++;
946	byte bi = ((r&0x80U)>>5) \| ((g&0x80U)>>6) \| ((b&0x80U)>>7);
947	int be = (int) b - (int) gbmrgb_8[bi].b;
948	int ge = (int) g - (int) gbmrgb_8[bi].g;
949	int re = (int) r - (int) gbmrgb_8[bi].r;
950	word rn = randtab[(byte) (randinx++)];
951	int right = (rn >> 8);
952	int down = ((rn & 0xff) % (63 - right));
953	int be1 = ((be * right) >> 6);
954	int ge1 = ((ge * right) >> 6);
955	int re1 = ((re * right) >> 6);
956	int be2 = ((be * down ) >> 6);
957	int ge2 = ((ge * down ) >> 6);
958	int re2 = ((re * down ) >> 6);
959	int be3 = be - be1 - be2;
960	int ge3 = ge - ge1 - ge2;
961	int re3 = re - re1 - re2;
962
963	if ( left )
964	*dest = (byte) (bi << 4);
965	else
966	*dest++ \|= bi;
967
968	left = !left;
969
970	src[0] = U_SAT_ADD((int) src[0], be1);
971	src[1] = U_SAT_ADD((int) src[1], ge1);
972	src[2] = U_SAT_ADD((int) src[2], re1);
973
974	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be2);
975	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge2);
976	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re2);
977
978	ptr += 3;
979
980	errs[ptr ] = S_SAT_ADD((int) errs[ptr ], be3);
981	errs[ptr + 1] = S_SAT_ADD((int) errs[ptr + 1], ge3);
982	errs[ptr + 2] = S_SAT_ADD((int) errs[ptr + 2], re3);
983	}
984	}
985	/...e/
986	/...sgbm_errdiff_8 \45\ error diffuse to default 8 colour palette:0:/
987	BOOLEAN gbm_errdiff_8(const GBM gbm, const byte data24, byte *data4)
988	{
989	return errdiff(gbm, data24, data4, 4, gbm_errdiff_line_8);
990	}
991	/...e/
992
993	/...sgbm_errdiff_pal_4G \45\ return 4 bit greyscale palette:0:/
994	/*
995	This function makes the palette for the 16 colour VGA palette.
996	*/
997
998	void gbm_errdiff_pal_4G(GBMRGB *gbmrgb)
999	{
1000	int i;
1001
1002	init();
1003	for ( i = 0; i < 0x10; i++ )
1004	{
1005	gbmrgb[i].r = scale16[i];
1006	gbmrgb[i].g = scale16[i];
1007	gbmrgb[i].b = scale16[i];
1008	}
1009	}
1010	/...e/
1011	/...sgbm_errdiff_line_4G \45\ error diffuse to 4 bit greyscale palette one line:0:/
1012	/*
1013	This function takes a line of RGB data, a destination buffer and a buffer of
1014	error terms and performs one lines worth (a given # of pixels) of error
1015	diffusion.
1016	*/
1017
1018	void gbm_errdiff_line_4G(byte src, byte dest, short *errs, int cx)
1019	{
1020	BOOLEAN left = TRUE;
1021	int x, ptr = 0;
1022	byte *pb;
1023
1024	init();
1025
1026	/* Step 1: Add error terms to newly supplied line */
1027
1028	for ( x = 0, pb = src; x < cx; x++ )
1029	{
1030	byte b = *pb++;
1031	byte g = *pb++;
1032	byte r = *pb++;
1033
1034	src[x] = (byte) (((word) r * 77U + (word) g * 150U + (word) b * 29U) >> 8);
1035	src[x] = U_SAT_ADD((int) src[x], (int) errs[x]);
1036	}
1037
1038	/* Step 2: Zero out error terms */
1039
1040	memset(errs, 0, (cx + 1) * sizeof(errs[0]));
1041
1042	/* Step 3: Go along data, finding nearest colour and propagating error */
1043
1044	randinx = rand();
1045
1046	for ( x = 0; x < cx; x++ )
1047	{
1048	byte grey = *src++;
1049	byte inx = index16[grey];
1050	int err = (int) grey - (int) scale16[inx];
1051	word rn = randtab[(byte) (randinx++)];
1052	int right = (rn >> 8);
1053	int down = ((rn & 0xff) % (63 - right));
1054	int err1 = ((err * right) >> 6);
1055	int err2 = ((err * down ) >> 6);
1056	int err3 = err - err1 - err2;
1057
1058	if ( left )
1059	*dest = (byte) (inx << 4);
1060	else
1061	*dest++ \|= inx;
1062
1063	left = !left;
1064
1065	src[0] = U_SAT_ADD((int) src[0], err1);
1066
1067	errs[ptr] = S_SAT_ADD((int) errs[ptr], err2);
1068
1069	ptr++;
1070
1071	errs[ptr] = S_SAT_ADD((int) errs[ptr], err3);
1072	}
1073	}
1074	/...e/
1075	/...sgbm_errdiff_4G \45\ error diffuse to 4 bit greyscale palette:0:/
1076	BOOLEAN gbm_errdiff_4G(const GBM gbm, const byte data24, byte *data4)
1077	{
1078	return errdiff(gbm, data24, data4, 4, gbm_errdiff_line_4G);
1079	}
1080	/...e/
1081
1082	/...sgbm_errdiff_pal_BW \45\ return black and white palette:0:/
1083	/*
1084	This function returns the b/w palette.
1085	(We consider the image to be likely black on white,
1086	hence the ordering of the palette entries).
1087	*/
1088
1089	static GBMRGB gbmrgb_bw[] =
1090	{
1091	255,255,255,
1092	0,0,0,
1093	};
1094
1095	void gbm_errdiff_pal_BW(GBMRGB *gbmrgb)
1096	{
1097	init();
1098	memcpy((char ) gbmrgb, (char ) gbmrgb_bw, sizeof(gbmrgb_bw));
1099	}
1100	/...e/
1101	/...sgbm_errdiff_line_BW \45\ error diffuse to black and white one line:0:/
1102	/*
1103	This function takes a line of RGB data, a destination buffer and a buffer of
1104	error terms and performs one lines worth (a given # of pixels) of error
1105	diffusion.
1106	*/
1107
1108	void gbm_errdiff_line_BW(byte src, byte dest, short *errs, int cx)
1109	{
1110	int x, bit = 0, ptr = 0;
1111	byte *pb;
1112
1113	init();
1114
1115	/* Step 1: Add error terms to newly supplied line */
1116
1117	for ( x = 0, pb = src; x < cx; x++ )
1118	{
1119	byte b = *pb++;
1120	byte g = *pb++;
1121	byte r = *pb++;
1122
1123	src[x] = (byte) (((word) r * 77U + (word) g * 150U + (word) b * 29U) >> 8);
1124	src[x] = U_SAT_ADD((int) src[x], (int) errs[x]);
1125	}
1126
1127	/* Step 2: Zero out error terms */
1128
1129	memset(errs, 0, (cx + 1) * sizeof(errs[0]));
1130
1131	/* Step 3: Go along data, finding nearest colour and propagating error */
1132
1133	memset(dest, 0, (unsigned) (cx + 7) >> 3);
1134
1135	randinx = rand();
1136
1137	for ( x = 0; x < cx; x++ )
1138	{
1139	byte grey = *src++;
1140	byte inx = (byte) (grey < 0x80);
1141	int err = (int) grey - (int) gbmrgb_bw[inx].b;
1142	word rn = randtab[(byte) (randinx++)];
1143	int right = (rn >> 8);
1144	int down = ((rn & 0xff) % (63 - right));
1145	int err1 = ((err * right) >> 6);
1146	int err2 = ((err * down ) >> 6);
1147	int err3 = err - err1 - err2;
1148
1149	if ( inx )
1150	*dest \|= (0x80U >> bit);
1151
1152	if ( ++bit == 8 )
1153	{
1154	bit = 0;
1155	dest++;
1156	}
1157
1158	src[0] = U_SAT_ADD((int) src[0], err1);
1159
1160	errs[ptr] = S_SAT_ADD((int) errs[ptr], err2);
1161
1162	ptr++;
1163
1164	errs[ptr] = S_SAT_ADD((int) errs[ptr], err3);
1165	}
1166	}
1167	/...e/
1168	/...sgbm_errdiff_BW \45\ error diffuse to black and white:0:/
1169	BOOLEAN gbm_errdiff_BW(const GBM gbm, const byte data24, byte *data1)
1170	{
1171	return errdiff(gbm, data24, data1, 1, gbm_errdiff_line_BW);
1172	}
1173	/...e/

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