1 /*
2  * jdcolor.c
3  *
4  * Copyright (C) 1991-1997, 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 output colorspace conversion routines.
9  */
10 
11 #define JPEG_INTERNALS
12 #include "jinclude.h"
13 #include "jpeglib.h"
14 
15 
16 /* Private subobject */
17 
18 typedef struct {
19   struct jpeg_color_deconverter pub; /* public fields */
20 
21   /* Private state for YCC->RGB conversion */
22   int * Cr_r_tab;		/* => table for Cr to R conversion */
23   int * Cb_b_tab;		/* => table for Cb to B conversion */
24   INT32 * Cr_g_tab;		/* => table for Cr to G conversion */
25   INT32 * Cb_g_tab;		/* => table for Cb to G conversion */
26 } my_color_deconverter;
27 
28 typedef my_color_deconverter * my_cconvert_ptr;
29 
30 
31 /**************** YCbCr -> RGB conversion: most common case **************/
32 
33 /*
34  * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
35  * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
36  * The conversion equations to be implemented are therefore
37  *	R = Y                + 1.40200 * Cr
38  *	G = Y - 0.34414 * Cb - 0.71414 * Cr
39  *	B = Y + 1.77200 * Cb
40  * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
41  * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
42  *
43  * To avoid floating-point arithmetic, we represent the fractional constants
44  * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
45  * the products by 2^16, with appropriate rounding, to get the correct answer.
46  * Notice that Y, being an integral input, does not contribute any fraction
47  * so it need not participate in the rounding.
48  *
49  * For even more speed, we avoid doing any multiplications in the inner loop
50  * by precalculating the constants times Cb and Cr for all possible values.
51  * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
52  * for 12-bit samples it is still acceptable.  It's not very reasonable for
53  * 16-bit samples, but if you want lossless storage you shouldn't be changing
54  * colorspace anyway.
55  * The Cr=>R and Cb=>B values can be rounded to integers in advance; the
56  * values for the G calculation are left scaled up, since we must add them
57  * together before rounding.
58  */
59 
60 #define SCALEBITS	16	/* speediest right-shift on some machines */
61 #define ONE_HALF	((INT32) 1 << (SCALEBITS-1))
62 #define FIX(x)		((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
63 
64 
65 /*
66  * Initialize tables for YCC->RGB colorspace conversion.
67  */
68 
69 LOCAL(void)
build_ycc_rgb_table(j_decompress_ptr cinfo)70 build_ycc_rgb_table (j_decompress_ptr cinfo)
71 {
72   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
73   int i;
74   INT32 x;
75   SHIFT_TEMPS
76 
77   cconvert->Cr_r_tab = (int *)
78     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
79 				(MAXJSAMPLE+1) * SIZEOF(int));
80   cconvert->Cb_b_tab = (int *)
81     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
82 				(MAXJSAMPLE+1) * SIZEOF(int));
83   cconvert->Cr_g_tab = (INT32 *)
84     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
85 				(MAXJSAMPLE+1) * SIZEOF(INT32));
86   cconvert->Cb_g_tab = (INT32 *)
87     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
88 				(MAXJSAMPLE+1) * SIZEOF(INT32));
89 
90   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
91     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
92     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
93     /* Cr=>R value is nearest int to 1.40200 * x */
94     cconvert->Cr_r_tab[i] = (int)
95 		    RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
96     /* Cb=>B value is nearest int to 1.77200 * x */
97     cconvert->Cb_b_tab[i] = (int)
98 		    RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
99     /* Cr=>G value is scaled-up -0.71414 * x */
100     cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x;
101     /* Cb=>G value is scaled-up -0.34414 * x */
102     /* We also add in ONE_HALF so that need not do it in inner loop */
103     cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
104   }
105 }
106 
107 
108 /*
109  * Convert some rows of samples to the output colorspace.
110  *
111  * Note that we change from noninterleaved, one-plane-per-component format
112  * to interleaved-pixel format.  The output buffer is therefore three times
113  * as wide as the input buffer.
114  * A starting row offset is provided only for the input buffer.  The caller
115  * can easily adjust the passed output_buf value to accommodate any row
116  * offset required on that side.
117  */
118 
119 METHODDEF(void)
ycc_rgb_convert(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION input_row,JSAMPARRAY output_buf,int num_rows)120 ycc_rgb_convert (j_decompress_ptr cinfo,
121 		 JSAMPIMAGE input_buf, JDIMENSION input_row,
122 		 JSAMPARRAY output_buf, int num_rows)
123 {
124   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
125   register int y, cb, cr;
126   register JSAMPROW outptr;
127   register JSAMPROW inptr0, inptr1, inptr2;
128   register JDIMENSION col;
129   JDIMENSION num_cols = cinfo->output_width;
130   /* copy these pointers into registers if possible */
131   register JSAMPLE * range_limit = cinfo->sample_range_limit;
132   register int * Crrtab = cconvert->Cr_r_tab;
133   register int * Cbbtab = cconvert->Cb_b_tab;
134   register INT32 * Crgtab = cconvert->Cr_g_tab;
135   register INT32 * Cbgtab = cconvert->Cb_g_tab;
136   SHIFT_TEMPS
137 
138   while (--num_rows >= 0) {
139     inptr0 = input_buf[0][input_row];
140     inptr1 = input_buf[1][input_row];
141     inptr2 = input_buf[2][input_row];
142     input_row++;
143     outptr = *output_buf++;
144     for (col = 0; col < num_cols; col++) {
145       y  = GETJSAMPLE(inptr0[col]);
146       cb = GETJSAMPLE(inptr1[col]);
147       cr = GETJSAMPLE(inptr2[col]);
148       /* Range-limiting is essential due to noise introduced by DCT losses. */
149       outptr[RGB_RED] =   range_limit[y + Crrtab[cr]];
150       outptr[RGB_GREEN] = range_limit[y +
151 			      ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
152 						 SCALEBITS))];
153       outptr[RGB_BLUE] =  range_limit[y + Cbbtab[cb]];
154       outptr += RGB_PIXELSIZE;
155     }
156   }
157 }
158 
159 
160 /**************** Cases other than YCbCr -> RGB **************/
161 
162 
163 /*
164  * Color conversion for no colorspace change: just copy the data,
165  * converting from separate-planes to interleaved representation.
166  */
167 
168 METHODDEF(void)
null_convert(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION input_row,JSAMPARRAY output_buf,int num_rows)169 null_convert (j_decompress_ptr cinfo,
170 	      JSAMPIMAGE input_buf, JDIMENSION input_row,
171 	      JSAMPARRAY output_buf, int num_rows)
172 {
173   register JSAMPROW inptr, outptr;
174   register JDIMENSION count;
175   register int num_components = cinfo->num_components;
176   JDIMENSION num_cols = cinfo->output_width;
177   int ci;
178 
179   while (--num_rows >= 0) {
180     for (ci = 0; ci < num_components; ci++) {
181       inptr = input_buf[ci][input_row];
182       outptr = output_buf[0] + ci;
183       for (count = num_cols; count > 0; count--) {
184 	*outptr = *inptr++;	/* needn't bother with GETJSAMPLE() here */
185 	outptr += num_components;
186       }
187     }
188     input_row++;
189     output_buf++;
190   }
191 }
192 
193 
194 /*
195  * Color conversion for grayscale: just copy the data.
196  * This also works for YCbCr -> grayscale conversion, in which
197  * we just copy the Y (luminance) component and ignore chrominance.
198  */
199 
200 METHODDEF(void)
grayscale_convert(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION input_row,JSAMPARRAY output_buf,int num_rows)201 grayscale_convert (j_decompress_ptr cinfo,
202 		   JSAMPIMAGE input_buf, JDIMENSION input_row,
203 		   JSAMPARRAY output_buf, int num_rows)
204 {
205   jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0,
206 		    num_rows, cinfo->output_width);
207 }
208 
209 
210 /*
211  * Convert grayscale to RGB: just duplicate the graylevel three times.
212  * This is provided to support applications that don't want to cope
213  * with grayscale as a separate case.
214  */
215 
216 METHODDEF(void)
gray_rgb_convert(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION input_row,JSAMPARRAY output_buf,int num_rows)217 gray_rgb_convert (j_decompress_ptr cinfo,
218 		  JSAMPIMAGE input_buf, JDIMENSION input_row,
219 		  JSAMPARRAY output_buf, int num_rows)
220 {
221   register JSAMPROW inptr, outptr;
222   register JDIMENSION col;
223   JDIMENSION num_cols = cinfo->output_width;
224 
225   while (--num_rows >= 0) {
226     inptr = input_buf[0][input_row++];
227     outptr = *output_buf++;
228     for (col = 0; col < num_cols; col++) {
229       /* We can dispense with GETJSAMPLE() here */
230       outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col];
231       outptr += RGB_PIXELSIZE;
232     }
233   }
234 }
235 
236 
237 /*
238  * Adobe-style YCCK->CMYK conversion.
239  * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
240  * conversion as above, while passing K (black) unchanged.
241  * We assume build_ycc_rgb_table has been called.
242  */
243 
244 METHODDEF(void)
ycck_cmyk_convert(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION input_row,JSAMPARRAY output_buf,int num_rows)245 ycck_cmyk_convert (j_decompress_ptr cinfo,
246 		   JSAMPIMAGE input_buf, JDIMENSION input_row,
247 		   JSAMPARRAY output_buf, int num_rows)
248 {
249   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
250   register int y, cb, cr;
251   register JSAMPROW outptr;
252   register JSAMPROW inptr0, inptr1, inptr2, inptr3;
253   register JDIMENSION col;
254   JDIMENSION num_cols = cinfo->output_width;
255   /* copy these pointers into registers if possible */
256   register JSAMPLE * range_limit = cinfo->sample_range_limit;
257   register int * Crrtab = cconvert->Cr_r_tab;
258   register int * Cbbtab = cconvert->Cb_b_tab;
259   register INT32 * Crgtab = cconvert->Cr_g_tab;
260   register INT32 * Cbgtab = cconvert->Cb_g_tab;
261   SHIFT_TEMPS
262 
263   while (--num_rows >= 0) {
264     inptr0 = input_buf[0][input_row];
265     inptr1 = input_buf[1][input_row];
266     inptr2 = input_buf[2][input_row];
267     inptr3 = input_buf[3][input_row];
268     input_row++;
269     outptr = *output_buf++;
270     for (col = 0; col < num_cols; col++) {
271       y  = GETJSAMPLE(inptr0[col]);
272       cb = GETJSAMPLE(inptr1[col]);
273       cr = GETJSAMPLE(inptr2[col]);
274       /* Range-limiting is essential due to noise introduced by DCT losses. */
275       outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])];	/* red */
276       outptr[1] = range_limit[MAXJSAMPLE - (y +			/* green */
277 			      ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
278 						 SCALEBITS)))];
279       outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])];	/* blue */
280       /* K passes through unchanged */
281       outptr[3] = inptr3[col];	/* don't need GETJSAMPLE here */
282       outptr += 4;
283     }
284   }
285 }
286 
287 
288 /*
289  * Empty method for start_pass.
290  */
291 
292 METHODDEF(void)
start_pass_dcolor(j_decompress_ptr cinfo)293 start_pass_dcolor (j_decompress_ptr cinfo)
294 {
295   /* no work needed */
296 }
297 
298 
299 /*
300  * Module initialization routine for output colorspace conversion.
301  */
302 
303 GLOBAL(void)
jinit_color_deconverter(j_decompress_ptr cinfo)304 jinit_color_deconverter (j_decompress_ptr cinfo)
305 {
306   my_cconvert_ptr cconvert;
307   int ci;
308 
309   cconvert = (my_cconvert_ptr)
310     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
311 				SIZEOF(my_color_deconverter));
312   cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
313   cconvert->pub.start_pass = start_pass_dcolor;
314 
315   /* Make sure num_components agrees with jpeg_color_space */
316   switch (cinfo->jpeg_color_space) {
317   case JCS_GRAYSCALE:
318     if (cinfo->num_components != 1)
319       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
320     break;
321 
322   case JCS_RGB:
323   case JCS_YCbCr:
324     if (cinfo->num_components != 3)
325       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
326     break;
327 
328   case JCS_CMYK:
329   case JCS_YCCK:
330     if (cinfo->num_components != 4)
331       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
332     break;
333 
334   default:			/* JCS_UNKNOWN can be anything */
335     if (cinfo->num_components < 1)
336       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
337     break;
338   }
339 
340   /* Set out_color_components and conversion method based on requested space.
341    * Also clear the component_needed flags for any unused components,
342    * so that earlier pipeline stages can avoid useless computation.
343    */
344 
345   switch (cinfo->out_color_space) {
346   case JCS_GRAYSCALE:
347     cinfo->out_color_components = 1;
348     if (cinfo->jpeg_color_space == JCS_GRAYSCALE ||
349 	cinfo->jpeg_color_space == JCS_YCbCr) {
350       cconvert->pub.color_convert = grayscale_convert;
351       /* For color->grayscale conversion, only the Y (0) component is needed */
352       for (ci = 1; ci < cinfo->num_components; ci++)
353 	cinfo->comp_info[ci].component_needed = FALSE;
354     } else
355       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
356     break;
357 
358   case JCS_RGB:
359     cinfo->out_color_components = RGB_PIXELSIZE;
360     if (cinfo->jpeg_color_space == JCS_YCbCr) {
361       cconvert->pub.color_convert = ycc_rgb_convert;
362       build_ycc_rgb_table(cinfo);
363     } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
364       cconvert->pub.color_convert = gray_rgb_convert;
365     } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) {
366       cconvert->pub.color_convert = null_convert;
367     } else
368       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
369     break;
370 
371   case JCS_CMYK:
372     cinfo->out_color_components = 4;
373     if (cinfo->jpeg_color_space == JCS_YCCK) {
374       cconvert->pub.color_convert = ycck_cmyk_convert;
375       build_ycc_rgb_table(cinfo);
376     } else if (cinfo->jpeg_color_space == JCS_CMYK) {
377       cconvert->pub.color_convert = null_convert;
378     } else
379       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
380     break;
381 
382   default:
383     /* Permit null conversion to same output space */
384     if (cinfo->out_color_space == cinfo->jpeg_color_space) {
385       cinfo->out_color_components = cinfo->num_components;
386       cconvert->pub.color_convert = null_convert;
387     } else			/* unsupported non-null conversion */
388       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
389     break;
390   }
391 
392   if (cinfo->quantize_colors)
393     cinfo->output_components = 1; /* single colormapped output component */
394   else
395     cinfo->output_components = cinfo->out_color_components;
396 }
397