[magick-users] Changing the resolution of a Class F TIFF file

[Bogdan Cristea]

On Thu, Dec 11, 2008 at 8:15 PM,
<duc.sequere.aut.de.via.decede at imagemagick.org> wrote:
>> correctly done, since ghfaxviewer cannot display the new image.
>
> TIFF supports a wide variety of image types and some viewers can only deal with
> a subset of the image types.
>
>> convert file.tif -density 200x100 resampled_file.tif
>
> You probably want
>
>  convert file.tif -resample 200x100 resampled_file.tif
>
> Post the output of
>
>  tiffinfo file.tif
>  tiffinfo resampled_file.tif
>
> so wee can determine how resampled_file.tif differs from file.tif.
>

Using 'convert file.tif -resample 200x100 resampled_file.tif' gives a
file which cannot be displayed.

tiffinfo file.tif
TIFF Directory at offset 0x8 (8)
  Subfile Type: multi-page document (2 = 0x2)
  Image Width: 1728 Image Length: 2292
  Resolution: 204, 196 pixels/inch
  Bits/Sample: 1
  Compression Scheme: CCITT Group 4
  Photometric Interpretation: min-is-white
  FillOrder: lsb-to-msb
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 1
  Rows/Strip: 2292
  Planar Configuration: single image plane
  Page Number: 0-0
  Software: ESP Ghostscript 7.07
  DateTime: 2007:02:14 21:32:40
  Group 4 Options: (0 = 0x0)


tiffinfo resampled_file.tif
TIFF Directory at offset 0x3f8be (260286)
  Subfile Type: multi-page document (2 = 0x2)
  Image Width: 1694 Image Length: 1169
  Resolution: 200, 100 pixels/inch
  Bits/Sample: 16
  Compression Scheme: PackBits
  Photometric Interpretation: min-is-black
  FillOrder: lsb-to-msb
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 1
  Rows/Strip: 2
  Planar Configuration: single image plane
  DocumentName: resampled_send_file_mp.tif
  Software: ImageMagick 6.3.5 05/26/08 Q16 http://www.imagemagick.org
  DateTime: 2007:02:14 21:32:40

>From the above output it can be seen that the compression scheme of
the resampled file is PackBits, not a valid compression scheme for a
class F TIFF file, as was the original.

Using 'convert file.tif -density 200x100 resampled_file.tif', seems to
produce the desired output, but, as said in my previous message,
ghfaxviewer has problems viewing this new file.

tiffinfo resampled_file.tif
TIFF Directory at offset 0x1b22 (6946)
  Subfile Type: multi-page document (2 = 0x2)
  Image Width: 1728 Image Length: 2292
  Resolution: 200, 100 pixels/inch
  Bits/Sample: 1
  Compression Scheme: CCITT Group 4
  Photometric Interpretation: min-is-black
  FillOrder: lsb-to-msb
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 1
  Rows/Strip: 2292
  Planar Configuration: single image plane
  DocumentName: resampled_send_file_mp.tif
  Software: ImageMagick 6.3.5 05/26/08 Q16 http://www.imagemagick.org
  DateTime: 2007:02:14 21:32:40

regards
-- 
Bogdan Cristea