Add option for setting luminance & chrominance quality independently (currently only works if using libjpeg v7 or v8 code base)

git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@248 632fc199-4ca6-4c93-a231-07263d6284db

cdjpeg.h

@@ -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));
 

cjpeg.1

@@ -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
+(Conversion of GIF files to JPEG is usually a bad idea anyway.)
-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.

cjpeg.c

@@ -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)
+      qualityarg = argv[argn];
-	usage();
-      /* Change scale factor in case -qtables is present. */
-      q_scale_factor = jpeg_quality_scaling(quality);
 
     } 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,
+      if (! read_quant_tables(cinfo, qtablefile, force_baseline))
-			      q_scale_factor, force_baseline))
 	usage();
 
     if (qslotsarg != NULL)	/* process -qslots if it was present */

rdswitch.c

@@ -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,
+read_quant_tables (j_compress_ptr cinfo, char * filename, boolean force_baseline)
-		   int scale_factor, 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++;
   }
 
@@ -262,6 +271,46 @@ bogus:
 #endif /* C_MULTISCAN_FILES_SUPPORTED */
 
 
+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