diff options
Diffstat (limited to 'jpeg/jdct.h')
| -rw-r--r-- | jpeg/jdct.h | 29 |
1 files changed, 26 insertions, 3 deletions
diff --git a/jpeg/jdct.h b/jpeg/jdct.h index 360dec80c..bcfedfcfd 100644 --- a/jpeg/jdct.h +++ b/jpeg/jdct.h @@ -2,6 +2,7 @@ * jdct.h * * Copyright (C) 1994-1996, Thomas G. Lane. + * Modified 2002-2017 by Guido Vollbeding. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README file. * @@ -78,13 +79,15 @@ typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */ * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could * be quite far out of range if the input data is corrupt, so a bulletproof * range-limiting step is required. We use a mask-and-table-lookup method - * to do the combined operations quickly. See the comments with + * to do the combined operations quickly, assuming that RANGE_CENTER + * (defined in jpegint.h) is a power of 2. See the comments with * prepare_range_limit_table (in jdmaster.c) for more info. */ -#define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit + CENTERJSAMPLE) +#define RANGE_MASK (RANGE_CENTER * 2 - 1) +#define RANGE_SUBSET (RANGE_CENTER - CENTERJSAMPLE) -#define RANGE_MASK (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */ +#define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit - RANGE_SUBSET) /* Short forms of external names for systems with brain-damaged linkers. */ @@ -391,3 +394,23 @@ EXTERN(void) jpeg_idct_1x2 #ifndef MULTIPLY16V16 /* default definition */ #define MULTIPLY16V16(var1,var2) ((var1) * (var2)) #endif + +/* Like RIGHT_SHIFT, but applies to a DCTELEM. + * We assume that int right shift is unsigned if INT32 right shift is. + */ + +#ifdef RIGHT_SHIFT_IS_UNSIGNED +#define ISHIFT_TEMPS DCTELEM ishift_temp; +#if BITS_IN_JSAMPLE == 8 +#define DCTELEMBITS 16 /* DCTELEM may be 16 or 32 bits */ +#else +#define DCTELEMBITS 32 /* DCTELEM must be 32 bits */ +#endif +#define IRIGHT_SHIFT(x,shft) \ + ((ishift_temp = (x)) < 0 ? \ + (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \ + (ishift_temp >> (shft))) +#else +#define ISHIFT_TEMPS +#define IRIGHT_SHIFT(x,shft) ((x) >> (shft)) +#endif |