Allow disabling prog/opt/lossless if prev. enabled

- Due to an oversight, a113506d17
  (libjpeg-turbo 1.4 beta1) effectively made the call to
  std_huff_tables() in jpeg_set_defaults() a no-op if the Huffman tables
  were previously defined, which made it impossible to disable Huffman
  table optimization or progressive mode if they were previously enabled
  in the same API instance.  std_huff_tables() retains its previous
  behavior for decompression instances, but it now force-enables the
  standard (baseline) Huffman tables for compression instances.

- Due to another oversight, there was no way to disable lossless mode
  if it was previously enabled in a particular API instance.
  jpeg_set_defaults() now accomplishes this, which makes
  TJ*PARAM_LOSSLESS behave as intended/documented.

- Due to yet another oversight, setCompDefaults() in the TurboJPEG API
  library permanently modified the value of TJ*PARAM_SUBSAMP when
  generating a lossless JPEG image, which affected subsequent lossy
  compression operations.  This issue was hidden by the issue above and
  thus does not need to be publicly documented.

Fixes #792

ChangeLog.md

@@ -8,6 +8,17 @@
 transform value greater than 7 resulted in an error ("Parameter value out of
 range".)
 
+2. Fixed a regression introduced by 1.4 beta1[3] that prevented
+`jpeg_set_defaults()` from resetting the Huffman tables to default (baseline)
+values if Huffman table optimization or progressive mode was previously enabled
+in the same libjpeg instance.
+
+3. Fixed an issue whereby lossless JPEG compression could not be disabled if it
+was previously enabled in a libjpeg or TurboJPEG instance.
+`jpeg_set_defaults()` now disables lossless JPEG compression in a libjpeg
+instance, and setting `TJPARAM_LOSSLESS`/`TJ.PARAM_LOSSLESS` to `0` now
+disables lossless JPEG compression in a TurboJPEG instance.
+
 
 3.0.4
 =====

jcparam.c

@@ -7,7 +7,7 @@
  * Lossless JPEG Modifications:
  * Copyright (C) 1999, Ken Murchison.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2009-2011, 2018, 2023, D. R. Commander.
+ * Copyright (C) 2009-2011, 2018, 2023-2024, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -220,6 +220,9 @@ jpeg_set_defaults(j_compress_ptr cinfo)
   cinfo->scan_info = NULL;
   cinfo->num_scans = 0;
 
+  /* Default is lossy output */
+  cinfo->master->lossless = FALSE;
+
   /* Expect normal source image, not raw downsampled data */
   cinfo->raw_data_in = FALSE;
 

jstdhuff.c

@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1998, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2013, 2022, D. R. Commander.
+ * Copyright (C) 2013, 2022, 2024, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -25,7 +25,7 @@ add_huff_table(j_common_ptr cinfo, JHUFF_TBL **htblptr, const UINT8 *bits,
 
   if (*htblptr == NULL)
     *htblptr = jpeg_alloc_huff_table(cinfo);
-  else
+  else if (cinfo->is_decompressor)
     return;
 
   /* Copy the number-of-symbols-of-each-code-length counts */

turbojpeg.c

@@ -328,6 +328,8 @@ static int getPixelFormat(int pixelSize, int flags)
 
 static void setCompDefaults(tjinstance *this, int pixelFormat)
 {
+  int subsamp = this->subsamp;
+
   this->cinfo.in_color_space = pf2cs[pixelFormat];
   this->cinfo.input_components = tjPixelSize[pixelFormat];
   jpeg_set_defaults(&this->cinfo);
@@ -344,9 +346,9 @@ static void setCompDefaults(tjinstance *this, int pixelFormat)
     jpeg_enable_lossless(&this->cinfo, this->losslessPSV, this->losslessPt);
 #endif
     if (pixelFormat == TJPF_GRAY)
-      this->subsamp = TJSAMP_GRAY;
+      subsamp = TJSAMP_GRAY;
-    else if (this->subsamp != TJSAMP_GRAY)
+    else if (subsamp != TJSAMP_GRAY)
-      this->subsamp = TJSAMP_444;
+      subsamp = TJSAMP_444;
     return;
   }
 
@@ -365,7 +367,7 @@ static void setCompDefaults(tjinstance *this, int pixelFormat)
   case TJCS_YCCK:
     jpeg_set_colorspace(&this->cinfo, JCS_YCCK);  break;
   default:
-    if (this->subsamp == TJSAMP_GRAY)
+    if (subsamp == TJSAMP_GRAY)
       jpeg_set_colorspace(&this->cinfo, JCS_GRAYSCALE);
     else if (pixelFormat == TJPF_CMYK)
       jpeg_set_colorspace(&this->cinfo, JCS_YCCK);
@@ -380,16 +382,16 @@ static void setCompDefaults(tjinstance *this, int pixelFormat)
 #endif
   this->cinfo.arith_code = this->arithmetic;
 
-  this->cinfo.comp_info[0].h_samp_factor = tjMCUWidth[this->subsamp] / 8;
+  this->cinfo.comp_info[0].h_samp_factor = tjMCUWidth[subsamp] / 8;
   this->cinfo.comp_info[1].h_samp_factor = 1;
   this->cinfo.comp_info[2].h_samp_factor = 1;
   if (this->cinfo.num_components > 3)
-    this->cinfo.comp_info[3].h_samp_factor = tjMCUWidth[this->subsamp] / 8;
+    this->cinfo.comp_info[3].h_samp_factor = tjMCUWidth[subsamp] / 8;
-  this->cinfo.comp_info[0].v_samp_factor = tjMCUHeight[this->subsamp] / 8;
+  this->cinfo.comp_info[0].v_samp_factor = tjMCUHeight[subsamp] / 8;
   this->cinfo.comp_info[1].v_samp_factor = 1;
   this->cinfo.comp_info[2].v_samp_factor = 1;
   if (this->cinfo.num_components > 3)
-    this->cinfo.comp_info[3].v_samp_factor = tjMCUHeight[this->subsamp] / 8;
+    this->cinfo.comp_info[3].v_samp_factor = tjMCUHeight[subsamp] / 8;
 }