On Mon, 2 Feb 2009, Anthony Thyssen wrote: > On Sun, 01 Feb 2009 08:58:36 -0500 (Eastern Standard Time) > [email protected] wrote: > > | I am trying to convert 16-bit GRAY files to 8-bit JPEG or PNG format. > | Since the original images are actually 12-bit, I assume that I need to > | right-shift each pixel, so I'm using a command like > | > | convert -size 512x512+3416 -depth 16 -evaluate RightShift 4 -endian LSB > gray:c_vf1169.fre c_vf1169_rs4_lsb.png > | > | The effect seems to be that the high-order byte is simply ignored when > | the right-shift is done. Could someone please explain what I'm doing > | wrong? I'm using IM 6.2.4 Q16 as distributed by Debian. > | > | I apologize if this is really obvious, but I haven't been able to > | figure it out or find an answer. > | > perhaps the 12 bit values in 16 bit integers are already right shifted?
The 12 bits are indeed right shifted in their 16-bit representation. What I wanted to do was to right shift the 12 bits into an 8-bit value for use in an 8-bit PNG. In looking into this further in response to your response, I've discovered that PNG does support 16-bit greyscale, but I don't want that. I've tried some additional manoeuvres but without success, and I haven't figured out how to tell IM whether to produce 8-bit or 16-bit PNG. - Robert _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
