The Tor Browser: media/libjpeg/jidctred.c@b8a032363ba2 (annotated)

media/libjpeg/jidctred.c@b8a032363ba2 (annotated)

media/libjpeg/jidctred.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /*
  * jidctred.c
  *
  * Copyright (C) 1994-1998, Thomas G. Lane.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains inverse-DCT routines that produce reduced-size output:
  * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
  *
  * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
  * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
  * with an 8-to-4 step that produces the four averages of two adjacent outputs
  * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
  * These steps were derived by computing the corresponding values at the end
  * of the normal LL&M code, then simplifying as much as possible.
  *
  * 1x1 is trivial: just take the DC coefficient divided by 8.
  *
  * See jidctint.c for additional comments.
  */
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "jdct.h"		/* Private declarations for DCT subsystem */
 #ifdef IDCT_SCALING_SUPPORTED
 /*
  * This module is specialized to the case DCTSIZE = 8.
  */
 #if DCTSIZE != 8
   Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
 #endif
 /* Scaling is the same as in jidctint.c. */
 #if BITS_IN_JSAMPLE == 8
 #define CONST_BITS  13
 #define PASS1_BITS  2
 #else
 #define CONST_BITS  13
 #define PASS1_BITS  1		/* lose a little precision to avoid overflow */
 #endif
 /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
  * causing a lot of useless floating-point operations at run time.
  * To get around this we use the following pre-calculated constants.
  * If you change CONST_BITS you may want to add appropriate values.
  * (With a reasonable C compiler, you can just rely on the FIX() macro...)
  */
 #if CONST_BITS == 13
 #define FIX_0_211164243  ((INT32)  1730)	/* FIX(0.211164243) */
 #define FIX_0_509795579  ((INT32)  4176)	/* FIX(0.509795579) */
 #define FIX_0_601344887  ((INT32)  4926)	/* FIX(0.601344887) */
 #define FIX_0_720959822  ((INT32)  5906)	/* FIX(0.720959822) */
 #define FIX_0_765366865  ((INT32)  6270)	/* FIX(0.765366865) */
 #define FIX_0_850430095  ((INT32)  6967)	/* FIX(0.850430095) */
 #define FIX_0_899976223  ((INT32)  7373)	/* FIX(0.899976223) */
 #define FIX_1_061594337  ((INT32)  8697)	/* FIX(1.061594337) */
 #define FIX_1_272758580  ((INT32)  10426)	/* FIX(1.272758580) */
 #define FIX_1_451774981  ((INT32)  11893)	/* FIX(1.451774981) */
 #define FIX_1_847759065  ((INT32)  15137)	/* FIX(1.847759065) */
 #define FIX_2_172734803  ((INT32)  17799)	/* FIX(2.172734803) */
 #define FIX_2_562915447  ((INT32)  20995)	/* FIX(2.562915447) */
 #define FIX_3_624509785  ((INT32)  29692)	/* FIX(3.624509785) */
 #else
 #define FIX_0_211164243  FIX(0.211164243)
 #define FIX_0_509795579  FIX(0.509795579)
 #define FIX_0_601344887  FIX(0.601344887)
 #define FIX_0_720959822  FIX(0.720959822)
 #define FIX_0_765366865  FIX(0.765366865)
 #define FIX_0_850430095  FIX(0.850430095)
 #define FIX_0_899976223  FIX(0.899976223)
 #define FIX_1_061594337  FIX(1.061594337)
 #define FIX_1_272758580  FIX(1.272758580)
 #define FIX_1_451774981  FIX(1.451774981)
 #define FIX_1_847759065  FIX(1.847759065)
 #define FIX_2_172734803  FIX(2.172734803)
 #define FIX_2_562915447  FIX(2.562915447)
 #define FIX_3_624509785  FIX(3.624509785)
 #endif
 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
  * For 8-bit samples with the recommended scaling, all the variable
  * and constant values involved are no more than 16 bits wide, so a
  * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
  * For 12-bit samples, a full 32-bit multiplication will be needed.
  */
 #if BITS_IN_JSAMPLE == 8
 #define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
 #else
 #define MULTIPLY(var,const)  ((var) * (const))
 #endif
 /* Dequantize a coefficient by multiplying it by the multiplier-table
  * entry; produce an int result.  In this module, both inputs and result
  * are 16 bits or less, so either int or short multiply will work.
  */
 #define DEQUANTIZE(coef,quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))
 /*
  * Perform dequantization and inverse DCT on one block of coefficients,
  * producing a reduced-size 4x4 output block.
  */
 GLOBAL(void)
 jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	       JCOEFPTR coef_block,
 	       JSAMPARRAY output_buf, JDIMENSION output_col)
 {
   INT32 tmp0, tmp2, tmp10, tmp12;
   INT32 z1, z2, z3, z4;
   JCOEFPTR inptr;
   ISLOW_MULT_TYPE * quantptr;
   int * wsptr;
   JSAMPROW outptr;
   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   int ctr;
   int workspace[DCTSIZE*4];	/* buffers data between passes */
   SHIFT_TEMPS
   /* Pass 1: process columns from input, store into work array. */
   inptr = coef_block;
   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   wsptr = workspace;
   for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
     /* Don't bother to process column 4, because second pass won't use it */
     if (ctr == DCTSIZE-4)
       continue;
     if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
 	inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
 	inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
       /* AC terms all zero; we need not examine term 4 for 4x4 output */
       int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
       wsptr[DCTSIZE*0] = dcval;
       wsptr[DCTSIZE*1] = dcval;
       wsptr[DCTSIZE*2] = dcval;
       wsptr[DCTSIZE*3] = dcval;
       continue;
     }
     /* Even part */
     tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
     tmp0 <<= (CONST_BITS+1);
     z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
     z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
     tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
     tmp10 = tmp0 + tmp2;
     tmp12 = tmp0 - tmp2;
     /* Odd part */
     z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
     z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
     z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
     z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
     tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
 	 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
 	 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
 	 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
     tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
 	 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
 	 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
 	 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
     /* Final output stage */
     wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
     wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
     wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
     wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
   }
   /* Pass 2: process 4 rows from work array, store into output array. */
   wsptr = workspace;
   for (ctr = 0; ctr < 4; ctr++) {
     outptr = output_buf[ctr] + output_col;
     /* It's not clear whether a zero row test is worthwhile here ... */
 #ifndef NO_ZERO_ROW_TEST
     if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
 	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
       /* AC terms all zero */
       JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
 				  & RANGE_MASK];
       outptr[0] = dcval;
       outptr[1] = dcval;
       outptr[2] = dcval;
       outptr[3] = dcval;
       wsptr += DCTSIZE;		/* advance pointer to next row */
       continue;
     }
 #endif
     /* Even part */
     tmp0 = ((INT32) wsptr[0]) << (CONST_BITS+1);
     tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065)
 	 + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865);
     tmp10 = tmp0 + tmp2;
     tmp12 = tmp0 - tmp2;
     /* Odd part */
     z1 = (INT32) wsptr[7];
     z2 = (INT32) wsptr[5];
     z3 = (INT32) wsptr[3];
     z4 = (INT32) wsptr[1];
     tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
 	 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
 	 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
 	 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
     tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
 	 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
 	 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
 	 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
     /* Final output stage */
     outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
 					  CONST_BITS+PASS1_BITS+3+1)
 			    & RANGE_MASK];
     outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
 					  CONST_BITS+PASS1_BITS+3+1)
 			    & RANGE_MASK];
     outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
 					  CONST_BITS+PASS1_BITS+3+1)
 			    & RANGE_MASK];
     outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
 					  CONST_BITS+PASS1_BITS+3+1)
 			    & RANGE_MASK];
     wsptr += DCTSIZE;		/* advance pointer to next row */
   }
 }
 /*
  * Perform dequantization and inverse DCT on one block of coefficients,
  * producing a reduced-size 2x2 output block.
  */
 GLOBAL(void)
 jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	       JCOEFPTR coef_block,
 	       JSAMPARRAY output_buf, JDIMENSION output_col)
 {
   INT32 tmp0, tmp10, z1;
   JCOEFPTR inptr;
   ISLOW_MULT_TYPE * quantptr;
   int * wsptr;
   JSAMPROW outptr;
   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   int ctr;
   int workspace[DCTSIZE*2];	/* buffers data between passes */
   SHIFT_TEMPS
   /* Pass 1: process columns from input, store into work array. */
   inptr = coef_block;
   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   wsptr = workspace;
   for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
     /* Don't bother to process columns 2,4,6 */
     if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
       continue;
     if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
 	inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
       /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
       int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
       wsptr[DCTSIZE*0] = dcval;
       wsptr[DCTSIZE*1] = dcval;
       continue;
     }
     /* Even part */
     z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
     tmp10 = z1 << (CONST_BITS+2);
     /* Odd part */
     z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
     tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
     z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
     tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
     z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
     tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
     z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
     tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
     /* Final output stage */
     wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
     wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
   }
   /* Pass 2: process 2 rows from work array, store into output array. */
   wsptr = workspace;
   for (ctr = 0; ctr < 2; ctr++) {
     outptr = output_buf[ctr] + output_col;
     /* It's not clear whether a zero row test is worthwhile here ... */
 #ifndef NO_ZERO_ROW_TEST
     if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
       /* AC terms all zero */
       JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
 				  & RANGE_MASK];
       outptr[0] = dcval;
       outptr[1] = dcval;
       wsptr += DCTSIZE;		/* advance pointer to next row */
       continue;
     }
 #endif
     /* Even part */
     tmp10 = ((INT32) wsptr[0]) << (CONST_BITS+2);
     /* Odd part */
     tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
 	 + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
 	 + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
 	 + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
     /* Final output stage */
     outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
 					  CONST_BITS+PASS1_BITS+3+2)
 			    & RANGE_MASK];
     outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
 					  CONST_BITS+PASS1_BITS+3+2)
 			    & RANGE_MASK];
     wsptr += DCTSIZE;		/* advance pointer to next row */
   }
 }
 /*
  * Perform dequantization and inverse DCT on one block of coefficients,
  * producing a reduced-size 1x1 output block.
  */
 GLOBAL(void)
 jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	       JCOEFPTR coef_block,
 	       JSAMPARRAY output_buf, JDIMENSION output_col)
 {
   int dcval;
   ISLOW_MULT_TYPE * quantptr;
   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   SHIFT_TEMPS
   /* We hardly need an inverse DCT routine for this: just take the
    * average pixel value, which is one-eighth of the DC coefficient.
    */
   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
   dcval = (int) DESCALE((INT32) dcval, 3);
   output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
 }
 #endif /* IDCT_SCALING_SUPPORTED */

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media/libjpeg/jidctred.c@b8a032363ba2 (annotated)

media/libjpeg/jidctred.c