Document convert_primaries option in toktx. (#765)

tools/toktx/toktx.cc

@@ -254,6 +254,17 @@ Create a KTX file from JPEG, PNG or netpbm format files.
  @b --assign_oetf are specified, conversion will be performed from the
  assigned transfer function to the transfer function specified by this
  option, if different.
+ <dt>--convert_primaries &lt;primaries&gt;</dt>
+ <dd>Convert the image images to the specified color primaries, if
+ different from the color primaries of the input file(s) or the one
+ specified by --assign-primaries. If both this and --assign-primaries
+ are specified, conversion will be performed from the assigned primaries
+ to the primaries specified by this option, if different. This option is
+ not allowed to be specified when --assign-primaries is set to 'none'.
+ Case insensitive.
+ Possible options are:
+ bt709 | srgb | bt601-ebu | bt601-smpte | bt2020 | ciexyz | aces |
+ acescc | ntsc1953 | pal525 | displayp3 | adobergb</dd>
  <dt>--linear</dt>
  <dd>Deprecated. Use @b --assign_oetf linear.</dd>
  <dt>--srgb</dt>
@@ -634,6 +645,17 @@ toktxApp::usage()
  " --assign_oetf are specified, conversion will be performed from\n"
  " the assigned transfer function to the transfer function specified\n"
  " by this option, if different.\n"
+ " --convert_primaries <primaries> \n"
+ " Convert the image image(s) to the specified color primaries,\n"
+ " if different from the color primaries of the input file(s) or the\n"
+ " one specified by --assign-primaries. If both this and\n"
+ " --assign-primaries are specified, conversion will be performed\n"
+ " from the assigned primaries to the primaries specified by this\n"
+ " option, if different. This option is not allowed to be specified\n"
+ " when --assign-primaries is set to 'none'. Case insensitive.\n"
+ " Possible options are: bt709 | srgb | bt601-ebu | bt601-smpte |\n"
+ " bt2020 | ciexyz | aces | acescc | ntsc1953 | pal525 |\n"
+ " displayp3 | adobergb.\n"
  " --linear Deprecated. Use --assign_oetf linear.\n"
  " --srgb Deprecated. Use --assign_oetf srgb.\n"
  " --swizzle <swizzle>\n"