From 08aa778e94e16817ed35b74a85d77526d0f378e3 Mon Sep 17 00:00:00 2001 From: giraffedata Date: Mon, 29 Jan 2007 02:02:48 +0000 Subject: "miscellaneous update" git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@216 9d0c8265-081b-0410-96cb-a4ca84ce46f8 --- giftopnm.html | 40 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 38 insertions(+), 2 deletions(-) (limited to 'giftopnm.html') diff --git a/giftopnm.html b/giftopnm.html index 3a3d2f2e..60a2ebe9 100644 --- a/giftopnm.html +++ b/giftopnm.html @@ -2,7 +2,7 @@ Giftopnm User Manual

giftopnm

-Updated: 6 August 2006 +Updated: 29 January 2007
Table Of Contents @@ -16,6 +16,7 @@ giftopnm - convert a GIF file into a PNM image [-verbose] [-comments] [-image={N,all}] +[-repair] [-quitearly] [GIFfile] @@ -98,9 +99,44 @@ not do the same for the images after it; see -quitearly.

The all value was added in Netpbm 10.16 (June 2003). Earlier giftopnm can extract only one image. +

-repair + +

This option makes giftopnm try to salvage what it can from an +invalid GIF input. + +

In particular, when giftopnm detects that the GIF input is +invalid so that it is impossible to determine what the pixels are +intended to be, it produces a single arbitrary color for all further +pixels in the image. giftopnm processes the image from top to +bottom, left to right, so this means the bottommost pixels will be +this padding. + +

giftopnm issues warning messages when it salvages an image +in this way. + +

Without this option, giftopnm fails when it detects invalid +GIF input. Any output it produces is arbitrary, and typically is not +a valid PNM image. + +

It is fairly common for an image to be corrupted such that is +started off as a valid GIF, but had the end of the file cut off. An +interrupted network transfer tends to do this. In this case, +giftopnm's salvage operation will produce a valid PNM image of +the proer dimensions, but with a single arbitrary color for the pixels +that were left out of the file. If the truncation is in the middle of +a row, giftopnm produces arbitrary pixels for the entire +truncated row. + +

This option was new in Netpbm 10.38 (March 2007). From 10.32 through +10.37, giftopnm always fails if it detects invalid GIF input. +Before 10.32, it succeeds in the case of a truncated image, and replaces +the missing pixels with arbitrary colors, not necessarily all the same +(The pre-10.32 behavior wasn't actually intended by the design). + +

-quitearly -

This options makes giftopnm stop reading its input file as soon +

This option makes giftopnm stop reading its input file as soon as it has converted and output the images from the input that you requested. By default, giftopnm reads until the end of the GIF stream, ignoring any data after the images you requested. -- cgit 1.4.1