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Pamfixtrunc User Manual(0)                          Pamfixtrunc User Manual(0)

       pamfixtrunc - repair a Netpbm image whose file is truncated




       This program is part of Netpbm(1).

       pamfixtrunc  reads as much as it can of a Netpbm image that may be truncated (i.e. the file may not contain the
       last part of the image) and writes out a valid Netpbm image that is just missing the bottom rows of the  origi-
       nal (pre-truncation) image.

       The  header  of  a Netpbm image implies how large the image must be (how many bytes the file must contain).  If
       the file is actually smaller than that, a Netpbm program that tries to read the image fails, with an error mes-
       sage telling you that it couldn't read the whole file.  The data in the file is arranged in row order, from top
       to bottom, and the most common reason for the file being smaller than its header says it should be  is  because
       the bottommost rows are simply missing.  So pamfixtrunc assumes that is the case and generates a new image with
       just the rows that are readable.  (technically, that means the output's header indicates a  smaller  number  of
       rows and omits any partial last row).

       The  most  common way for a Netpbm file to be small is that something interrupted the program that generated it
       before it was finished writing the file.  For example, the program ran out of its own input  or  encountered  a
       bug or ran out of space in which to write the output.

       Another problem pamfixtrunc deals with is where the file isn't actually too small, but due to a system error, a
       byte in the middle of it cannot be read (think of a disk storage failure).  pamfixtrunc reads the input sequen-
       tially  until it can't read any further, for any reason.  So it treats such an image as a truncated one, ignor-
       ing all data after the unreadable byte.

       But be aware that an image file is sometimes too small because of a bug in the program that generated  it,  and
       in  that  case  it  is  not simply a matter of the bottom of the image missing, so pamfixtrunc simply creates a
       valid Netpbm image containing a garbage picture.

       pamfixtrunc looks at only on the first image in a multi-image stream.

       If you want to test an image file to see if it is corrupted by being too small, use pamfile --allimages  .   It
       fails with an error message if the file is too small.

       If you want to cut the bottom off a valid Netpbm image, use pamcut.

       pnm(1), pam(1), pamcut(1), pamfile(1),

       pamfixtrunc was new in Netpbm 10.38 (March 2007).

netpbm documentation            06 January 2006     Pamfixtrunc User Manual(0)