diff options
| -rw-r--r-- | cdjpeg.h | 5 | ||||
| -rw-r--r-- | cjpeg.1 | 40 | ||||
| -rw-r--r-- | cjpeg.c | 28 | ||||
| -rw-r--r-- | rdswitch.c | 55 |
4 files changed, 98 insertions, 30 deletions
@@ -104,6 +104,7 @@ typedef struct cdjpeg_progress_mgr * cd_progress_ptr; #define jinit_write_targa jIWrTarga #define read_quant_tables RdQTables #define read_scan_script RdScnScript +#define set_quality_ratings SetQRates #define set_quant_slots SetQSlots #define set_sample_factors SetSFacts #define read_color_map RdCMap @@ -131,8 +132,10 @@ EXTERN(djpeg_dest_ptr) jinit_write_targa JPP((j_decompress_ptr cinfo)); /* cjpeg support routines (in rdswitch.c) */ EXTERN(boolean) read_quant_tables JPP((j_compress_ptr cinfo, char * filename, - int scale_factor, boolean force_baseline)); + boolean force_baseline)); EXTERN(boolean) read_scan_script JPP((j_compress_ptr cinfo, char * filename)); +EXTERN(boolean) set_quality_ratings JPP((j_compress_ptr cinfo, char *arg, + boolean force_baseline)); EXTERN(boolean) set_quant_slots JPP((j_compress_ptr cinfo, char *arg)); EXTERN(boolean) set_sample_factors JPP((j_compress_ptr cinfo, char *arg)); @@ -1,4 +1,4 @@ -.TH CJPEG 1 "20 March 1998" +.TH CJPEG 1 "30 December 2009" .SH NAME cjpeg \- compress an image file to a JPEG file .SH SYNOPSIS @@ -36,7 +36,7 @@ though for brevity these are not mentioned below. .PP The basic switches are: .TP -.BI \-quality " N" +.BI \-quality " N[,...]" Scale quantization tables to adjust image quality. Quality is 0 (worst) to 100 (best); default is 75. (See below for more info.) .TP @@ -109,6 +109,34 @@ other JPEG programs may be unable to decode the resulting file. Use if you need to ensure compatibility at low quality values.) .PP The +.B \-quality +option has been extended in IJG version 7 for support of separate quality +settings for luminance and chrominance (or in general, for every provided +quantization table slot). This feature is useful for high-quality +applications which cannot accept the damage of color data by coarse +subsampling settings. You can now easily reduce the color data amount more +smoothly with finer control without separate subsampling. The resulting file +is fully compliant with standard JPEG decoders. +Note that the +.B \-quality +ratings refer to the quantization table slots, and that the last value is +replicated if there are more q-table slots than parameters. The default +q-table slots are 0 for luminance and 1 for chrominance with default tables as +given in the JPEG standard. This is compatible with the old behaviour in case +that only one parameter is given, which is then used for both luminance and +chrominance (slots 0 and 1). More or custom quantization tables can be set +with +.B \-qtables +and assigned to components with +.B \-qslots +parameter (see the "wizard" switches below). +.B Caution: +You must explicitly add +.BI \-sample " 1x1" +for efficient separate color +quality selection, since the default value used by library is 2x2! +.PP +The .B \-progressive switch creates a "progressive JPEG" file. In this type of JPEG file, the data is stored in multiple scans of increasing quality. If the file is being @@ -117,9 +145,6 @@ scan to display a low-quality image very quickly, and can then improve the display with each subsequent scan. The final image is exactly equivalent to a standard JPEG file of the same quality setting, and the total file size is about the same --- often a little smaller. -.B Caution: -progressive JPEG is not yet widely implemented, so many decoders will be -unable to view a progressive JPEG file at all. .PP Switches for advanced users: .TP @@ -279,8 +304,7 @@ Independent JPEG Group Arithmetic coding is not supported for legal reasons. .PP GIF input files are no longer supported, to avoid the Unisys LZW patent. -Use a Unisys-licensed program if you need to read a GIF file. (Conversion -of GIF files to JPEG is usually a bad idea anyway.) +(Conversion of GIF files to JPEG is usually a bad idea anyway.) .PP Not all variants of BMP and Targa file formats are supported. .PP @@ -288,5 +312,3 @@ The .B \-targa switch is not a bug, it's a feature. (It would be a bug if the Targa format designers had not been clueless.) -.PP -Still not as fast as we'd like. @@ -2,6 +2,7 @@ * cjpeg.c * * Copyright (C) 1991-1998, Thomas G. Lane. + * Modified 2003-2008 by Guido Vollbeding. * Copyright (C) 2010, D. R. Commander. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README file. @@ -151,7 +152,7 @@ usage (void) #endif fprintf(stderr, "Switches (names may be abbreviated):\n"); - fprintf(stderr, " -quality N Compression quality (0..100; 5-95 is useful range)\n"); + fprintf(stderr, " -quality N[,...] Compression quality (0..100; 5-95 is useful range)\n"); fprintf(stderr, " -grayscale Create monochrome JPEG file\n"); #ifdef ENTROPY_OPT_SUPPORTED fprintf(stderr, " -optimize Optimize Huffman table (smaller file, but slow compression)\n"); @@ -211,21 +212,16 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv, { int argn; char * arg; - int quality; /* -quality parameter */ - int q_scale_factor; /* scaling percentage for -qtables */ boolean force_baseline; boolean simple_progressive; + char * qualityarg = NULL; /* saves -quality parm if any */ char * qtablefile = NULL; /* saves -qtables filename if any */ char * qslotsarg = NULL; /* saves -qslots parm if any */ char * samplearg = NULL; /* saves -sample parm if any */ char * scansarg = NULL; /* saves -scans parm if any */ /* Set up default JPEG parameters. */ - /* Note that default -quality level need not, and does not, - * match the default scaling for an explicit -qtables argument. - */ - quality = 75; /* default -quality value */ - q_scale_factor = 100; /* default to no scaling for -qtables */ + force_baseline = FALSE; /* by default, allow 16-bit quantizers */ simple_progressive = FALSE; is_targa = FALSE; @@ -333,13 +329,10 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv, #endif } else if (keymatch(arg, "quality", 1)) { - /* Quality factor (quantization table scaling factor). */ + /* Quality ratings (quantization table scaling factors). */ if (++argn >= argc) /* advance to next argument */ usage(); - if (sscanf(argv[argn], "%d", &quality) != 1) - usage(); - /* Change scale factor in case -qtables is present. */ - q_scale_factor = jpeg_quality_scaling(quality); + qualityarg = argv[argn]; } else if (keymatch(arg, "qslots", 2)) { /* Quantization table slot numbers. */ @@ -387,7 +380,7 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv, * default sampling factors. */ - } else if (keymatch(arg, "scans", 2)) { + } else if (keymatch(arg, "scans", 4)) { /* Set scan script. */ #ifdef C_MULTISCAN_FILES_SUPPORTED if (++argn >= argc) /* advance to next argument */ @@ -427,11 +420,12 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv, /* Set quantization tables for selected quality. */ /* Some or all may be overridden if -qtables is present. */ - jpeg_set_quality(cinfo, quality, force_baseline); + if (qualityarg != NULL) /* process -quality if it was present */ + if (! set_quality_ratings(cinfo, qualityarg, force_baseline)) + usage(); if (qtablefile != NULL) /* process -qtables if it was present */ - if (! read_quant_tables(cinfo, qtablefile, - q_scale_factor, force_baseline)) + if (! read_quant_tables(cinfo, qtablefile, force_baseline)) usage(); if (qslotsarg != NULL) /* process -qslots if it was present */ @@ -9,6 +9,7 @@ * command-line switches. Switches processed here are: * -qtables file Read quantization tables from text file * -scans file Read scan script from text file + * -quality N[,N,...] Set quality ratings * -qslots N[,N,...] Set component quantization table selectors * -sample HxV[,HxV,...] Set component sampling factors */ @@ -69,9 +70,12 @@ read_text_integer (FILE * file, long * result, int * termchar) } +#if JPEG_LIB_VERSION < 70 +static int q_scale_factor = 100; +#endif + GLOBAL(boolean) -read_quant_tables (j_compress_ptr cinfo, char * filename, - int scale_factor, boolean force_baseline) +read_quant_tables (j_compress_ptr cinfo, char * filename, boolean force_baseline) /* Read a set of quantization tables from the specified file. * The file is plain ASCII text: decimal numbers with whitespace between. * Comments preceded by '#' may be included in the file. @@ -108,7 +112,12 @@ read_quant_tables (j_compress_ptr cinfo, char * filename, } table[i] = (unsigned int) val; } - jpeg_add_quant_table(cinfo, tblno, table, scale_factor, force_baseline); +#if JPEG_LIB_VERSION >= 70 + jpeg_add_quant_table(cinfo, tblno, table, cinfo->q_scale_factor[tblno], + force_baseline); +#else + jpeg_add_quant_table(cinfo, tblno, table, q_scale_factor, force_baseline); +#endif tblno++; } @@ -263,6 +272,46 @@ bogus: GLOBAL(boolean) +set_quality_ratings (j_compress_ptr cinfo, char *arg, boolean force_baseline) +/* Process a quality-ratings parameter string, of the form + * N[,N,...] + * If there are more q-table slots than parameters, the last value is replicated. + */ +{ + int val = 75; /* default value */ + int tblno; + char ch; + + for (tblno = 0; tblno < NUM_QUANT_TBLS; tblno++) { + if (*arg) { + ch = ','; /* if not set by sscanf, will be ',' */ + if (sscanf(arg, "%d%c", &val, &ch) < 1) + return FALSE; + if (ch != ',') /* syntax check */ + return FALSE; + /* Convert user 0-100 rating to percentage scaling */ +#if JPEG_LIB_VERSION >= 70 + cinfo->q_scale_factor[tblno] = jpeg_quality_scaling(val); +#endif + while (*arg && *arg++ != ',') /* advance to next segment of arg string */ + ; + } else { + /* reached end of parameter, set remaining factors to last value */ +#if JPEG_LIB_VERSION >= 70 + cinfo->q_scale_factor[tblno] = jpeg_quality_scaling(val); +#endif + } + } +#if JPEG_LIB_VERSION >= 70 + jpeg_default_qtables(cinfo, force_baseline); +#else + jpeg_set_quality(cinfo, val, force_baseline); +#endif + return TRUE; +} + + +GLOBAL(boolean) set_quant_slots (j_compress_ptr cinfo, char *arg) /* Process a quantization-table-selectors parameter string, of the form * N[,N,...] |