Re: [OpenJPEG] Writing JP2 openjpegv2, Colour specification box, ICC profile issue with greater than 3 bands

[szuk...@arcor.de]

I downloaded the latest OpenJPEG v2 revision 2223 and did not find 'meth' in the lines
given.

winfried

----- Original Nachricht ----
Von: Will K <willk...@gmail.com>
An: open...@googlegroups.com
Datum: 15.11.2012 16:25
Betreff: [OpenJPEG] Writing JP2 openjpegv2, Colour specification box, ICC
profile issue with greater than 3 bands

> I downloaded the latest OpenJpeg v2 source. I am writing JP2 images with
> greater than 3 bands. In jp2.c line 1427 the meth is set to 2 for bands
> greater than 3. This requires an ICC profiles to be written. The library
> just sets it to NULL in line 722. If I write JP2 this way, other JP2
> readers get upset. The ECW SDK reader errors and crashes and Photoshop
> display a ICC profile error but does recover and open the file. I took a
> quick look at the ICC profile specs and I didn't see anything about higher
> bands covered. My current solution is to just change jp2.c to set the meth
> to 1 and the color space to RGBs for bands greater than 3. When I write
> this way the ECW SDK opens it fine and so does Photoshop. Is there any
> problem with this solution?
>

[Will K]

Sorry I gave the wrong line number.  The line is 2161.  It code looks like this:

 

 if ((image->numcomps == 1 || image->numcomps == 3) && (jp2->bpc != 255)) {
  jp2->meth = 1; /* METH: Enumerated colourspace */
 } else {
  jp2->meth = 2; /* METH: Restricted ICC profile */
 }
 if (jp2->meth == 1) {
  if (image->color_space == 1)
   jp2->enumcs = 16; /* sRGB as defined by IEC 61966–2–1 */
  else if (image->color_space == 2)
   jp2->enumcs = 17; /* greyscale */
  else if (image->color_space == 3)
   jp2->enumcs = 18; /* YUV */
 } else {
  jp2->enumcs = 0;  /* PROFILE (??) */
 }

 Anyway, when numComps is greater than 3 jp2->meth gets set to 2.  Later in the code the Meth 2 should write an ICC Profile, but it writes out a 0 instead.  I think it is best to not set meth 2 unless a real ICC profile is going to actually be written.  I don't now the actual requirement about 4 band imagery, but the ECW and Photoshop JP2 readers do not seem to care if the ICC profile is there.