diff options
Diffstat (limited to 'jpeg/jdmaster.c')
| -rw-r--r-- | jpeg/jdmaster.c | 65 |
1 files changed, 30 insertions, 35 deletions
diff --git a/jpeg/jdmaster.c b/jpeg/jdmaster.c index 6f42d3c5a..62c07671f 100644 --- a/jpeg/jdmaster.c +++ b/jpeg/jdmaster.c @@ -2,7 +2,7 @@ * jdmaster.c * * Copyright (C) 1991-1997, Thomas G. Lane. - * Modified 2002-2013 by Guido Vollbeding. + * 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. * @@ -45,11 +45,23 @@ LOCAL(boolean) use_merged_upsample (j_decompress_ptr cinfo) { #ifdef UPSAMPLE_MERGING_SUPPORTED - /* Merging is the equivalent of plain box-filter upsampling */ - if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling) + /* Merging is the equivalent of plain box-filter upsampling. */ + /* The following condition is only needed if fancy shall select + * a different upsampling method. In our current implementation + * fancy only affects the DCT scaling, thus we can use fancy + * upsampling and merged upsample simultaneously, in particular + * with scaled DCT sizes larger than the default DCTSIZE. + */ +#if 0 + if (cinfo->do_fancy_upsampling) + return FALSE; +#endif + if (cinfo->CCIR601_sampling) return FALSE; /* jdmerge.c only supports YCC=>RGB color conversion */ - if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 || + if ((cinfo->jpeg_color_space != JCS_YCbCr && + cinfo->jpeg_color_space != JCS_BG_YCC) || + cinfo->num_components != 3 || cinfo->out_color_space != JCS_RGB || cinfo->out_color_components != RGB_PIXELSIZE || cinfo->color_transform) @@ -199,30 +211,20 @@ jpeg_calc_output_dimensions (j_decompress_ptr cinfo) * These processes all use a common table prepared by the routine below. * * For most steps we can mathematically guarantee that the initial value - * of x is within MAXJSAMPLE+1 of the legal range, so a table running from - * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial - * limiting step (just after the IDCT), a wildly out-of-range value is - * possible if the input data is corrupt. To avoid any chance of indexing + * of x is within 2*(MAXJSAMPLE+1) of the legal range, so a table running + * from -2*(MAXJSAMPLE+1) to 3*MAXJSAMPLE+2 is sufficient. But for the + * initial limiting step (just after the IDCT), a wildly out-of-range value + * is possible if the input data is corrupt. To avoid any chance of indexing * off the end of memory and getting a bad-pointer trap, we perform the * post-IDCT limiting thus: - * x = range_limit[x & MASK]; + * x = (sample_range_limit - SUBSET)[(x + CENTER) & MASK]; * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit * samples. Under normal circumstances this is more than enough range and * a correct output will be generated; with bogus input data the mask will * cause wraparound, and we will safely generate a bogus-but-in-range output. * For the post-IDCT step, we want to convert the data from signed to unsigned * representation by adding CENTERJSAMPLE at the same time that we limit it. - * So the post-IDCT limiting table ends up looking like this: - * CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE, - * MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), - * 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), - * 0,1,...,CENTERJSAMPLE-1 - * Negative inputs select values from the upper half of the table after - * masking. - * - * We can save some space by overlapping the start of the post-IDCT table - * with the simpler range limiting table. The post-IDCT table begins at - * sample_range_limit + CENTERJSAMPLE. + * This is accomplished with SUBSET = CENTER - CENTERJSAMPLE. * * Note that the table is allocated in near data space on PCs; it's small * enough and used often enough to justify this. @@ -235,25 +237,18 @@ prepare_range_limit_table (j_decompress_ptr cinfo) JSAMPLE * table; int i; - table = (JSAMPLE *) - (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, - (5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE)); - table += (MAXJSAMPLE+1); /* allow negative subscripts of simple table */ + table = (JSAMPLE *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, + JPOOL_IMAGE, (RANGE_CENTER * 2 + MAXJSAMPLE + 1) * SIZEOF(JSAMPLE)); + /* First segment of range limit table: limit[x] = 0 for x < 0 */ + MEMZERO(table, RANGE_CENTER * SIZEOF(JSAMPLE)); + table += RANGE_CENTER; /* allow negative subscripts of table */ cinfo->sample_range_limit = table; - /* First segment of "simple" table: limit[x] = 0 for x < 0 */ - MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE)); - /* Main part of "simple" table: limit[x] = x */ + /* Main part of range limit table: limit[x] = x */ for (i = 0; i <= MAXJSAMPLE; i++) table[i] = (JSAMPLE) i; - table += CENTERJSAMPLE; /* Point to where post-IDCT table starts */ - /* End of simple table, rest of first half of post-IDCT table */ - for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++) + /* End of range limit table: limit[x] = MAXJSAMPLE for x > MAXJSAMPLE */ + for (; i <= MAXJSAMPLE + RANGE_CENTER; i++) table[i] = MAXJSAMPLE; - /* Second half of post-IDCT table */ - MEMZERO(table + (2 * (MAXJSAMPLE+1)), - (2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE)); - MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE), - cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE)); } |