[GM-help] 16-bit jpeg -> 8-bit jpeg conversion

[Albert C. <gra...@ml...>]

Some weird things are happening with a 16-bit jpeg image. Maybe I'm
misunderstanding something. A copy of the 16-bit jpeg is at:
  ftp://support.thewrittenword.com/outgoing/16bit.jpeg

I'm using GM 1.1.2

$ gm display 16bit.jpeg
[right click]
[select "Image Info"]
...
Depth: 16 bits-per-pixel component
Channel Depths:
  Red:      16 bits
  Green:    16 bits
  Blue:     16 bits
...

$ gm identify -verbose 16bit.jpeg
  Depth: 8 bits-per-pixel component
  Channel Depths:
    Cyan:     8 bits
    Magenta:  8 bits
    Yellow:   8 bits
    Black:    8 bits

Huh? Why is the 'gm display' Image Info output different from the 'gm
identify -verbose' output?

Should the following convert the 16-bit JPEG to an 8-bit JPEG? It
doesn't. It remains 16-bit.
  $ gm convert -depth 8 16bit.jpeg 8bit.jpeg

I've duplicated these results with IM 6.1.9.

-- 
albert chin (ch...@th...)