Legacy ImageMagick Discussions Archive

I'm new to the forum.... I've been using ImageMagick-6.5.7-Q16 for some months. I get error messages when trying to break a 3000 x 1600 pixel 16 bit tif file into a series of twenty 600x400 pixel image blocks. The summarized error is: unknown field with tag 50838 (0xc696) TIFF Read Directory. Tiff warnings 703. This error occurs after:

> convert 750.tif -depth 16 -type Grayscale -crop 600x400@ 750a.tif

So, I converted my image, 750.tif, which is a 16 bit tiff image into a FITS image using ImageJ. I then use the following code in ImageMagick:

I've tried:

> convert 750.fits -depth 16 -type Grayscale-type Grayscale -crop 600x400@ 750a.fits

and also:

> convert 750.fits -crop 600x400@ 750a.fits

Both work, producing twenty image blocks in fits format. However, the resulting image blocks show a reduced greyscale spread. Instead of running from 0 to 32768 as the original tiff and my fits converted images created using ImageJ are, I find the greyscale restricted to 23802 to 32120.

This greyscale restriction appears to occur automatically. I want to eliminate it and get block images with the full grayscale spread from 0 to 32768 or the equivalent.

Is there a way to do this? Could someone explain what is happening with this restricted grayscale I am seeing.... is it a sort of auto-stretch or something?

Rick

The summarized error is: unknown field with tag 50838 (0xc696) TIFF Read Directory. Tiff warnings 703

That is a warning, not an error. Don't worry about it. The command has worked.

Thanks yes... you are correct. When working with the fits format, all the pixel block images carved out of the original image appeared as individual files. I was confused because working in the tiff format only one file was produced, but it contained all 20 image blocks and could be opened in ImageJ and saved as an image sequence. Also, the dynamic range was preserved... so everything works. The tif warning had no effect on the result... Thanks again...

Rick