Monochrome HDR

[dukesook]

I interested in writing 10/12/14/16-bit monochrome HEIFs. Is the existing heif_chroma_monochrome suited for this? Or would new chromas be requried:

enum heif_chroma
{
  heif_chroma_undefined = 99,
  heif_chroma_monochrome = 0,
  ...
  ...
  ...
  heif_chroma_monochrome_HDR_BE = 16,
  heif_chroma_monochrome_HDR_LE = 17,

};

[farindk]

You can simply process 16bit monochrome by using heif_chroma_monochrome and adding a single heif_channel_Y with 10-16 bits. The plane then points to uint16_t.

It works out of the box with PNG 16bit input (use -b # to specify the output bit depth). JPEG2000 works up to 16 bit, H.265 with 10 and 12 bits (because of encoder limitations). I just tested with ISO23001-17, but it does not work correctly. There seems to be a bug.

Another bug seems to be in the 16bit PNG writer. I got a

libpng error: profile 'unknown': 'GRAY': Gray color space not permitted on RGB PNG

[dukesook]

Sounds good, I'll see if I can find the ISO23001-17 bug.

[farindk]

Here is the relevant code: https://github.com/strukturag/libheif/blob/a5c6d3a972e5a43eeb2c0a971911fd69885eec62/libheif/image-items/unc_image.cc#L254-L259

It simply does not seem to consider bytes per pixel and only works with 8 bit. Looks like the same problem is also in the planar RGB writer. Interleaved RGB seems to be ok.

I'll reopen the issue until this and the PNG writer is fixed.