Implement arithmetic coding with 12-bit precision

This actually works and apparently always has worked.  It only failed
because the libjpeg code, which did not originally support arithmetic
coding, assumed that optimize_coding should always be TRUE for 12-bit
data precision.

cmakescripts/tjbenchtest.cmake

@@ -35,7 +35,12 @@ if(NOT PRECISION EQUAL 16)
 endif()
 if(PRECISION EQUAL 8)
   run_test(tjbenchtest "-precision;${PRECISION};-progressive;-yuv")
+endif()
+if(NOT PRECISION EQUAL 16)
   run_test(tjbenchtest "-precision;${PRECISION};-arithmetic")
+  run_test(tjbenchtest "-precision;${PRECISION};-progressive;-arithmetic")
+endif()
+if(PRECISION EQUAL 8)
   run_test(tjbenchtest "-precision;${PRECISION};-arithmetic;-yuv")
 endif()
 run_test(tjbenchtest "-precision;${PRECISION};-lossless")
@@ -57,7 +62,12 @@ if(WITH_JAVA)
   endif()
   if(PRECISION EQUAL 8)
     run_test(tjbenchtest "-java;-precision;${PRECISION};-progressive;-yuv")
+  endif()
+  if(NOT PRECISION EQUAL 16)
     run_test(tjbenchtest "-java;-precision;${PRECISION};-arithmetic")
+    run_test(tjbenchtest "-java;-precision;${PRECISION};-progressive;-arithmetic")
+  endif()
+  if(PRECISION EQUAL 8)
     run_test(tjbenchtest "-java;-precision;${PRECISION};-arithmetic;-yuv")
   endif()
   run_test(tjbenchtest "-java;-precision;${PRECISION};-lossless")

doc/html/group___turbo_j_p_e_g.html

@@ -572,7 +572,7 @@ YUV Image Format Notes</h2>
 </div><div class="memdoc">
 
 <p>This option will enable arithmetic entropy coding in the JPEG image generated by this particular transform. </p>
-<p>Arithmetic entropy coding will generally improve compression relative to Huffman entropy coding (the default), but it will reduce decompression performance considerably. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#gad2371c80674584ecc1a7d75e564cf026" title="This option will enable progressive entropy coding in the JPEG image generated by this particular tra...">TJXOPT_PROGRESSIVE</a>. Arithmetic entropy coding is currently only implemented for 8-bit samples. </p>
+<p>Arithmetic entropy coding will generally improve compression relative to Huffman entropy coding (the default), but it will reduce decompression performance considerably. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#gad2371c80674584ecc1a7d75e564cf026" title="This option will enable progressive entropy coding in the JPEG image generated by this particular tra...">TJXOPT_PROGRESSIVE</a>. </p>
 
 </div>
 </div>
@@ -689,7 +689,7 @@ YUV Image Format Notes</h2>
 </div><div class="memdoc">
 
 <p>This option will enable progressive entropy coding in the JPEG image generated by this particular transform. </p>
-<p>Progressive entropy coding will generally improve compression relative to baseline entropy coding (the default), but it will reduce decompression performance considerably. Implies <a class="el" href="group___turbo_j_p_e_g.html#ga6bedf37aa9e1122f3ec9f7302ca59117" title="This option will enable optimized baseline entropy coding in the JPEG image generated by this particu...">TJXOPT_OPTIMIZE</a>. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#gaecaaa3b7e2af812592c015d83207f010" title="This option will enable arithmetic entropy coding in the JPEG image generated by this particular tran...">TJXOPT_ARITHMETIC</a>. </p>
+<p>Progressive entropy coding will generally improve compression relative to baseline entropy coding (the default), but it will reduce decompression performance considerably. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#gaecaaa3b7e2af812592c015d83207f010" title="This option will enable arithmetic entropy coding in the JPEG image generated by this particular tran...">TJXOPT_ARITHMETIC</a>. Implies <a class="el" href="group___turbo_j_p_e_g.html#ga6bedf37aa9e1122f3ec9f7302ca59117" title="This option will enable optimized baseline entropy coding in the JPEG image generated by this particu...">TJXOPT_OPTIMIZE</a> unless <a class="el" href="group___turbo_j_p_e_g.html#gaecaaa3b7e2af812592c015d83207f010" title="This option will enable arithmetic entropy coding in the JPEG image generated by this particular tran...">TJXOPT_ARITHMETIC</a> is also specified. </p>
 
 </div>
 </div>
@@ -874,7 +874,7 @@ YUV Image Format Notes</h2>
 <p><b>Value</b></p><ul>
 <li><code>8</code>, <code>12</code>, or <code>16</code></li>
 </ul>
-<p>12-bit data precision implies <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a8f0af9afc0b36443751f9ee82b760aa6" title="Optimized baseline entropy coding [lossy compression only].">TJPARAM_OPTIMIZE</a>. </p>
+<p>12-bit data precision implies <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a8f0af9afc0b36443751f9ee82b760aa6" title="Optimized baseline entropy coding [lossy compression only].">TJPARAM_OPTIMIZE</a> unless <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a1c756757384308145602c040524aebf7" title="Arithmetic entropy coding.">TJPARAM_ARITHMETIC</a> is set. </p>
 </td></tr>
 <tr><td class="fieldname"><a id="ggaa0f6be63ba78278299c9f5c12031fe82a46a10d46309514907d0c39fcd86c324c"></a>TJPARAM_COLORSPACE&#160;</td><td class="fielddoc"><p>JPEG colorspace. </p>
 <p>The JPEG image uses (decompression) or will use (lossy compression) the specified colorspace.</p>
@@ -912,7 +912,7 @@ YUV Image Format Notes</h2>
 <li><code>0</code> <em>[default for compression, lossless transformation]</em> The lossy JPEG image uses (decompression) or will use (compression, lossless transformation) baseline entropy coding.</li>
 <li><code>1</code> The lossy JPEG image uses (decompression) or will use (compression, lossless transformation) progressive entropy coding. For lossless transformation, this can also be specified using <a class="el" href="group___turbo_j_p_e_g.html#gad2371c80674584ecc1a7d75e564cf026" title="This option will enable progressive entropy coding in the JPEG image generated by this particular tra...">TJXOPT_PROGRESSIVE</a>.</li>
 </ul>
-<p>Progressive entropy coding will generally improve compression relative to baseline entropy coding, but it will reduce compression and decompression performance considerably. Implies <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a8f0af9afc0b36443751f9ee82b760aa6" title="Optimized baseline entropy coding [lossy compression only].">TJPARAM_OPTIMIZE</a>. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a1c756757384308145602c040524aebf7" title="Arithmetic entropy coding.">TJPARAM_ARITHMETIC</a>. </p>
+<p>Progressive entropy coding will generally improve compression relative to baseline entropy coding, but it will reduce compression and decompression performance considerably. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a1c756757384308145602c040524aebf7" title="Arithmetic entropy coding.">TJPARAM_ARITHMETIC</a>. Implies <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a8f0af9afc0b36443751f9ee82b760aa6" title="Optimized baseline entropy coding [lossy compression only].">TJPARAM_OPTIMIZE</a> unless <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a1c756757384308145602c040524aebf7" title="Arithmetic entropy coding.">TJPARAM_ARITHMETIC</a> is also set. </p>
 </td></tr>
 <tr><td class="fieldname"><a id="ggaa0f6be63ba78278299c9f5c12031fe82ac478910e20ecf61b914f9824d80f8167"></a>TJPARAM_SCANLIMIT&#160;</td><td class="fielddoc"><p>Progressive JPEG scan limit for lossy JPEG images [decompression, lossless transformation]. </p>
 <p>Setting this parameter will cause the decompression and transform functions to return an error if the number of scans in a progressive JPEG image exceeds the specified limit. The primary purpose of this is to allow security-critical applications to guard against an exploit of the progressive JPEG format described in <a href="https://libjpeg-turbo.org/pmwiki/uploads/About/TwoIssueswiththeJPEGStandard.pdf" target="_blank">this report</a>.</p>
@@ -926,7 +926,7 @@ YUV Image Format Notes</h2>
 <li><code>0</code> <em>[default for compression, lossless transformation]</em> The lossy JPEG image uses (decompression) or will use (compression, lossless transformation) Huffman entropy coding.</li>
 <li><code>1</code> The lossy JPEG image uses (decompression) or will use (compression, lossless transformation) arithmetic entropy coding. For lossless transformation, this can also be specified using <a class="el" href="group___turbo_j_p_e_g.html#gaecaaa3b7e2af812592c015d83207f010" title="This option will enable arithmetic entropy coding in the JPEG image generated by this particular tran...">TJXOPT_ARITHMETIC</a>.</li>
 </ul>
-<p>Arithmetic entropy coding will generally improve compression relative to Huffman entropy coding, but it will reduce compression and decompression performance considerably. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a1716f242b3859905b4a317dae8cfb75f" title="Progressive entropy coding.">TJPARAM_PROGRESSIVE</a>. Arithmetic entropy coding is currently only implemented for 8-bit samples. </p>
+<p>Arithmetic entropy coding will generally improve compression relative to Huffman entropy coding, but it will reduce compression and decompression performance considerably. Can be combined with <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a1716f242b3859905b4a317dae8cfb75f" title="Progressive entropy coding.">TJPARAM_PROGRESSIVE</a>. </p>
 </td></tr>
 <tr><td class="fieldname"><a id="ggaa0f6be63ba78278299c9f5c12031fe82a249f35f0770792b19f995e603bb17c6f"></a>TJPARAM_LOSSLESS&#160;</td><td class="fielddoc"><p>Lossless JPEG. </p>
 <p><b>Value</b></p><ul>

fuzz/compress12.cc

@@ -83,6 +83,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
     tj3Set(handle, TJPARAM_BOTTOMUP, ti == 0);
     tj3Set(handle, TJPARAM_FASTDCT, ti == 0);
     tj3Set(handle, TJPARAM_PROGRESSIVE, ti == 1 || ti == 3);
+    tj3Set(handle, TJPARAM_ARITHMETIC, ti == 2 || ti == 3);
     tj3Set(handle, TJPARAM_NOREALLOC, ti != 2);
     tj3Set(handle, TJPARAM_RESTARTROWS, ti == 1 || ti == 2 ? 2 : 0);
 

java/TJBench.java

@@ -775,6 +775,7 @@ final class TJBench {
     System.out.println("     (use the CMYK pixel format for packed-pixel source/destination buffers)");
     System.out.println("-precision N = Use N-bit data precision when compressing [N is 8, 12, or 16;");
     System.out.println("     default = 8; if N is 16, then -lossless must also be specified]");
+    System.out.println("     (-precision 12 implies -optimize unless -arithmetic is also specified)");
     System.out.println("-quiet = Output results in tabular rather than verbose format");
     System.out.println("-restart N = When compressing, add a restart marker every N MCU rows (lossy) or");
     System.out.println("     N sample rows (lossless) [default = 0 (no restart markers)].  Append 'B'");
@@ -793,7 +794,6 @@ final class TJBench {
     System.out.println("------------------");
     System.out.println("-arithmetic = Use arithmetic entropy coding in JPEG images generated by");
     System.out.println("     compression and transform operations (can be combined with -progressive)");
-    System.out.println("     ** 8-bit data precision only **");
     System.out.println("-crop WxH+X+Y = Decompress only the specified region of the JPEG image, where W");
     System.out.println("     and H are the width and height of the region (0 = maximum possible width");
     System.out.println("     or height) and X and Y are the left and upper boundary of the region, all");
@@ -804,8 +804,8 @@ final class TJBench {
     System.out.println("-optimize = Use optimized baseline entropy coding in JPEG images generated by");
     System.out.println("     compession and transform operations");
     System.out.println("-progressive = Use progressive entropy coding in JPEG images generated by");
-    System.out.println("     compression and transform operations (implies -optimize; can be combined");
+    System.out.println("     compression and transform operations (can be combined with -arithmetic;");
-    System.out.println("     with -arithmetic)");
+    System.out.println("     implies -optimize unless -arithmetic is also specified)");
     System.out.println("-limitscans = Refuse to decompress or transform progressive JPEG images that");
     System.out.println("     have an unreasonably large number of scans");
     System.out.println("-scale M/N = When decompressing, scale the width/height of the JPEG image by a");
@@ -1087,8 +1087,6 @@ final class TJBench {
 
       if (precision == 16 && !lossless)
         throw new Exception("-lossless must be specified along with -precision 16");
-      if (precision != 8 && arithmetic)
-        throw new Exception("-arithmetic requires 8-bit data precision");
       if (precision != 8 && doYUV)
         throw new Exception("-yuv requires 8-bit data precision");
       if (lossless && doYUV)

java/doc/org/libjpegturbo/turbojpeg/TJ.html

@@ -1367,7 +1367,8 @@ extends java.lang.Object</pre>
  <li> <code>8</code>, <code>12</code>, or <code>16</code>
  </ul>
 
- <p>12-bit data precision implies <a href="#PARAM_OPTIMIZE"><code>PARAM_OPTIMIZE</code></a>.</div>
+ <p>12-bit data precision implies <a href="#PARAM_OPTIMIZE"><code>PARAM_OPTIMIZE</code></a> unless
+ <a href="#PARAM_ARITHMETIC"><code>PARAM_ARITHMETIC</code></a> is set.</div>
 <dl>
 <dt><span class="seeLabel">See Also:</span></dt>
 <dd><a href="../../../constant-values.html#org.libjpegturbo.turbojpeg.TJ.PARAM_PRECISION">Constant Field Values</a></dd>
@@ -1511,8 +1512,9 @@ extends java.lang.Object</pre>
 
  <p>Progressive entropy coding will generally improve compression relative
  to baseline entropy coding, but it will reduce compression and
- decompression performance considerably.  Implies <a href="#PARAM_OPTIMIZE"><code>PARAM_OPTIMIZE</code></a>.
+ decompression performance considerably.  Can be combined with
- Can be combined with <a href="#PARAM_ARITHMETIC"><code>PARAM_ARITHMETIC</code></a>.</div>
+ <a href="#PARAM_ARITHMETIC"><code>PARAM_ARITHMETIC</code></a>.  Implies <a href="#PARAM_OPTIMIZE"><code>PARAM_OPTIMIZE</code></a> unless
+ <a href="#PARAM_ARITHMETIC"><code>PARAM_ARITHMETIC</code></a> is also set.</div>
 <dl>
 <dt><span class="seeLabel">See Also:</span></dt>
 <dd><a href="../../../constant-values.html#org.libjpegturbo.turbojpeg.TJ.PARAM_PROGRESSIVE">Constant Field Values</a></dd>
@@ -1572,8 +1574,7 @@ extends java.lang.Object</pre>
  <p>Arithmetic entropy coding will generally improve compression relative
  to Huffman entropy coding, but it will reduce compression and
  decompression performance considerably.  Can be combined with
- <a href="#PARAM_PROGRESSIVE"><code>PARAM_PROGRESSIVE</code></a>.  Arithmetic entropy coding is currently only
+ <a href="#PARAM_PROGRESSIVE"><code>PARAM_PROGRESSIVE</code></a>.</div>
- implemented for 8-bit samples.</div>
 <dl>
 <dt><span class="seeLabel">See Also:</span></dt>
 <dd><a href="../../../constant-values.html#org.libjpegturbo.turbojpeg.TJ.PARAM_ARITHMETIC">Constant Field Values</a></dd>

java/doc/org/libjpegturbo/turbojpeg/TJTransform.html

@@ -700,8 +700,8 @@ extends java.awt.Rectangle</pre>
  generated by this particular transform.  Progressive entropy coding will
  generally improve compression relative to baseline entropy coding (the
  default), but it will reduce decompression performance considerably.
- Implies <a href="#OPT_OPTIMIZE"><code>OPT_OPTIMIZE</code></a>.  Can be combined with
+ Can be combined with <a href="#OPT_ARITHMETIC"><code>OPT_ARITHMETIC</code></a>.  Implies
- <a href="#OPT_ARITHMETIC"><code>OPT_ARITHMETIC</code></a>.</div>
+ <a href="#OPT_OPTIMIZE"><code>OPT_OPTIMIZE</code></a> unless <a href="#OPT_ARITHMETIC"><code>OPT_ARITHMETIC</code></a> is also specified.</div>
 <dl>
 <dt><span class="seeLabel">See Also:</span></dt>
 <dd><a href="../../../constant-values.html#org.libjpegturbo.turbojpeg.TJTransform.OPT_PROGRESSIVE">Constant Field Values</a></dd>

java/org/libjpegturbo/turbojpeg/TJ.java

@@ -465,7 +465,8 @@ public final class TJ {
    * <li> <code>8</code>, <code>12</code>, or <code>16</code>
    * </ul>
    *
-   * <p>12-bit data precision implies {@link #PARAM_OPTIMIZE}.
+   * <p>12-bit data precision implies {@link #PARAM_OPTIMIZE} unless
+   * {@link #PARAM_ARITHMETIC} is set.
    */
   public static final int PARAM_PRECISION = 7;
   /**
@@ -559,8 +560,9 @@ public final class TJ {
    *
    * <p>Progressive entropy coding will generally improve compression relative
    * to baseline entropy coding, but it will reduce compression and
-   * decompression performance considerably.  Implies {@link #PARAM_OPTIMIZE}.
+   * decompression performance considerably.  Can be combined with
-   * Can be combined with {@link #PARAM_ARITHMETIC}.
+   * {@link #PARAM_ARITHMETIC}.  Implies {@link #PARAM_OPTIMIZE} unless
+   * {@link #PARAM_ARITHMETIC} is also set.
    */
   public static final int PARAM_PROGRESSIVE = 12;
   /**
@@ -601,8 +603,7 @@ public final class TJ {
    * <p>Arithmetic entropy coding will generally improve compression relative
    * to Huffman entropy coding, but it will reduce compression and
    * decompression performance considerably.  Can be combined with
-   * {@link #PARAM_PROGRESSIVE}.  Arithmetic entropy coding is currently only
+   * {@link #PARAM_PROGRESSIVE}.
-   * implemented for 8-bit samples.
    */
   public static final int PARAM_ARITHMETIC = 14;
   /**

java/org/libjpegturbo/turbojpeg/TJTransform.java

@@ -133,8 +133,8 @@ public class TJTransform extends Rectangle {
    * generated by this particular transform.  Progressive entropy coding will
    * generally improve compression relative to baseline entropy coding (the
    * default), but it will reduce decompression performance considerably.
-   * Implies {@link #OPT_OPTIMIZE}.  Can be combined with
+   * Can be combined with {@link #OPT_ARITHMETIC}.  Implies
-   * {@link #OPT_ARITHMETIC}.
+   * {@link #OPT_OPTIMIZE} unless {@link #OPT_ARITHMETIC} is also specified.
    */
   public static final int OPT_PROGRESSIVE = (1 << 5);
   /**

jcarith.c

@@ -914,9 +914,6 @@ jinit_arith_encoder(j_compress_ptr cinfo)
   arith_entropy_ptr entropy;
   int i;
 
-  if (cinfo->data_precision != 8)
-    ERREXIT(cinfo, JERR_NOTIMPL);
-
   entropy = (arith_entropy_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                 sizeof(arith_entropy_encoder));

jcmaster.c

@@ -7,7 +7,7 @@
  * Lossless JPEG Modifications:
  * Copyright (C) 1999, Ken Murchison.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2010, 2016, 2018, 2022, D. R. Commander.
+ * Copyright (C) 2010, 2016, 2018, 2022-2023, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -646,7 +646,7 @@ jinit_c_master_control(j_compress_ptr cinfo, boolean transcode_only)
       (cinfo->progressive_mode && !cinfo->arith_code))
     cinfo->optimize_coding = TRUE; /* assume default tables no good for
                                       progressive mode or lossless mode */
-  if (cinfo->data_precision == 12)
+  if (cinfo->data_precision == 12 && !cinfo->arith_code)
     cinfo->optimize_coding = TRUE; /* assume default tables no good for 12-bit
                                       data precision */
 

jcparam.c

@@ -7,7 +7,7 @@
  * Lossless JPEG Modifications:
  * Copyright (C) 1999, Ken Murchison.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2009-2011, 2018, D. R. Commander.
+ * Copyright (C) 2009-2011, 2018, 2023, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -233,7 +233,7 @@ jpeg_set_defaults(j_compress_ptr cinfo)
    * tables will be computed.  This test can be removed if default tables
    * are supplied that are valid for the desired precision.
    */
-  if (cinfo->data_precision > 8)
+  if (cinfo->data_precision == 12 && !cinfo->arith_code)
     cinfo->optimize_coding = TRUE;
 
   /* By default, use the simpler non-cosited sampling alignment */

jdarith.c

@@ -752,9 +752,6 @@ jinit_arith_decoder(j_decompress_ptr cinfo)
   arith_entropy_ptr entropy;
   int i;
 
-  if (cinfo->data_precision != 8)
-    ERREXIT(cinfo, JERR_NOTIMPL);
-
   entropy = (arith_entropy_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                 sizeof(arith_entropy_decoder));

tjbench.c

@@ -901,6 +901,7 @@ static void usage(char *progName)
   printf("     (use the CMYK pixel format for packed-pixel source/destination buffers)\n");
   printf("-precision N = Use N-bit data precision when compressing [N is 8, 12, or 16;\n");
   printf("     default = 8; if N is 16, then -lossless must also be specified]\n");
+  printf("     (-precision 12 implies -optimize unless -arithmetic is also specified)\n");
   printf("-quiet = Output results in tabular rather than verbose format\n");
   printf("-restart N = When compressing, add a restart marker every N MCU rows (lossy) or\n");
   printf("     N sample rows (lossless) [default = 0 (no restart markers)].  Append 'B'\n");
@@ -919,7 +920,6 @@ static void usage(char *progName)
   printf("------------------\n");
   printf("-arithmetic = Use arithmetic entropy coding in JPEG images generated by\n");
   printf("     compression and transform operations (can be combined with -progressive)\n");
-  printf("     ** 8-bit data precision only **\n");
   printf("-crop WxH+X+Y = Decompress only the specified region of the JPEG image, where W\n");
   printf("     and H are the width and height of the region (0 = maximum possible width\n");
   printf("     or height) and X and Y are the left and upper boundary of the region, all\n");
@@ -930,8 +930,8 @@ static void usage(char *progName)
   printf("-optimize = Use optimized baseline entropy coding in JPEG images generated by\n");
   printf("     compession and transform operations\n");
   printf("-progressive = Use progressive entropy coding in JPEG images generated by\n");
-  printf("     compression and transform operations (implies -optimize; can be combined\n");
+  printf("     compression and transform operations (can be combined with -arithmetic;\n");
-  printf("     with -arithmetic)\n");
+  printf("     implies -optimize unless -arithmetic is also specified)\n");
   printf("-limitscans = Refuse to decompress or transform progressive JPEG images that\n");
   printf("     have an unreasonably large number of scans\n");
   printf("-scale M/N = When decompressing, scale the width/height of the JPEG image by a\n");
@@ -1159,10 +1159,6 @@ int main(int argc, char *argv[])
     printf("ERROR: -lossless must be specified along with -precision 16\n");
     retval = -1;  goto bailout;
   }
-  if (precision != 8 && arithmetic) {
-    printf("ERROR: -arithmetic requires 8-bit data precision\n");
-    retval = -1;  goto bailout;
-  }
   if (precision != 8 && doYUV) {
     printf("ERROR: -yuv requires 8-bit data precision\n");
     retval = -1;  goto bailout;

tjbenchtest.in

@@ -84,10 +84,18 @@ while [ $# -gt 0 ]; do
 		ENTROPYARG=-optimize
 		;;
 	-progressive)
-		ENTROPYARG=-progressive
+		if [ "$ENTROPYARG" = "-arithmetic" ]; then
+			ENTROPYARG=-progressive-arithmetic
+		else
+			ENTROPYARG=-progressive
+		fi
 		;;
 	-arithmetic)
-		ENTROPYARG=-arithmetic
+		if [ "$ENTROPYARG" = "-progressive" ]; then
+			ENTROPYARG=-progressive-arithmetic
+		else
+			ENTROPYARG=-arithmetic
+		fi
 		;;
 	-lossless)
 		LOSSLSARG="-lossless"
@@ -115,13 +123,18 @@ if [ $PRECISION = 8 -a "$YUVARG" = "" ]; then
 		IMAGES="vgl_6434_0018a.${EXT}"
 	elif [ "$ENTROPYARG" = "-progressive" ]; then
 		IMAGES="vgl_6548_0026a.${EXT}"
-	elif [ "$ENTROPYARG" = "-arithmetic" ]; then
+	elif [ "$ENTROPYARG" = "-arithmetic" -o \
+		"$ENTROPYARG" = "-progressive-arithmetic" ]; then
 		IMAGES="big_tree8.${EXT}"
 	fi
 fi
 
 exec >$EXEDIR/tjbenchtest$JAVAARG$YUVARG$ALLOCARG$ENTROPYARG$LOSSLSARG-$PRECISION.log
 
+if [ "$ENTROPYARG" = "-progressive-arithmetic" ]; then
+	ENTROPYARG="-progressive -arithmetic"
+fi
+
 # Standard tests
 for image in $IMAGES; do
 

turbojpeg.c

@@ -2728,8 +2728,10 @@ DLLEXPORT int tj3Transform(tjhandle handle, const unsigned char *jpegBuf,
     if (this->progressive || t[i].options & TJXOPT_PROGRESSIVE)
       jpeg_simple_progression(cinfo);
 #endif
-    if (this->arithmetic || t[i].options & TJXOPT_ARITHMETIC)
+    if (this->arithmetic || t[i].options & TJXOPT_ARITHMETIC) {
       cinfo->arith_code = TRUE;
+      cinfo->optimize_coding = FALSE;
+    }
     if (!(t[i].options & TJXOPT_NOOUTPUT)) {
       jpeg_write_coefficients(cinfo, dstcoefs);
       jcopy_markers_execute(dinfo, cinfo, t[i].options & TJXOPT_COPYNONE ?

turbojpeg.h

@@ -490,7 +490,8 @@ enum TJPARAM {
    * **Value**
    * - `8`, `12`, or `16`
    *
-   * 12-bit data precision implies #TJPARAM_OPTIMIZE.
+   * 12-bit data precision implies #TJPARAM_OPTIMIZE unless #TJPARAM_ARITHMETIC
+   * is set.
    */
   TJPARAM_PRECISION,
   /**
@@ -566,8 +567,8 @@ enum TJPARAM {
    *
    * Progressive entropy coding will generally improve compression relative to
    * baseline entropy coding, but it will reduce compression and decompression
-   * performance considerably.  Implies #TJPARAM_OPTIMIZE.  Can be combined
+   * performance considerably.  Can be combined with #TJPARAM_ARITHMETIC.
-   * with #TJPARAM_ARITHMETIC.
+   * Implies #TJPARAM_OPTIMIZE unless #TJPARAM_ARITHMETIC is also set.
    */
   TJPARAM_PROGRESSIVE,
   /**
@@ -602,7 +603,6 @@ enum TJPARAM {
    * Arithmetic entropy coding will generally improve compression relative to
    * Huffman entropy coding, but it will reduce compression and decompression
    * performance considerably.  Can be combined with #TJPARAM_PROGRESSIVE.
-   * Arithmetic entropy coding is currently only implemented for 8-bit samples.
    */
   TJPARAM_ARITHMETIC,
   /**
@@ -863,7 +863,8 @@ enum TJXOP {
  * generated by this particular transform.  Progressive entropy coding will
  * generally improve compression relative to baseline entropy coding (the
  * default), but it will reduce decompression performance considerably.
- * Implies #TJXOPT_OPTIMIZE.  Can be combined with #TJXOPT_ARITHMETIC.
+ * Can be combined with #TJXOPT_ARITHMETIC.  Implies #TJXOPT_OPTIMIZE unless
+ * #TJXOPT_ARITHMETIC is also specified.
  */
 #define TJXOPT_PROGRESSIVE  (1 << 5)
 /**
@@ -877,8 +878,7 @@ enum TJXOP {
  * generated by this particular transform.  Arithmetic entropy coding will
  * generally improve compression relative to Huffman entropy coding (the
  * default), but it will reduce decompression performance considerably.  Can be
- * combined with #TJXOPT_PROGRESSIVE.  Arithmetic entropy coding is currently
+ * combined with #TJXOPT_PROGRESSIVE.
- * only implemented for 8-bit samples.
  */
 #define TJXOPT_ARITHMETIC  (1 << 7)
 /**