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1 files changed, 8 insertions, 7 deletions
diff --git a/giftopnm.html b/giftopnm.html index a4a82b48..4e41f607 100644 --- a/giftopnm.html +++ b/giftopnm.html @@ -2,7 +2,7 @@ <HTML><HEAD><TITLE>Giftopnm User Manual</TITLE></HEAD> <BODY> <H1>giftopnm</H1> -Updated: 25 May 2012 +Updated: 13 September 2012 <BR> <A HREF="#index">Table Of Contents</A> @@ -52,12 +52,13 @@ Netpbm output image has the wrong aspect ratio. In this case, <DL COMPACT> <DT><B>--alphaout=</B><I>alpha-filename</I> -<DD><B>giftopnm </B> creates a PBM file containing the alpha channel values in -the input image. If the input image doesn't contain an alpha channel, -the <I>alpha-filename</I> file contains all zero (transparent) alpha values. -If you don't specify <B>--alphaout</B>, <B>giftopnm</B> does not generate an -alpha file, and if the input image has an alpha channel, <B>giftopnm</B> -simply discards it. +<DD><B>giftopnm </B> creates a PBM file containing the transparency +information from the input image. This "alpha image" is the same +dimensions as the input image, and each pixel of the alpha image tells whether +the corresponding pixel of the input image is transparent. Black means +transparent; white means opaque. If you don't specify <B>--alphaout</B>, +<B>giftopnm</B> does not generate an alpha file, and if the input image has an +alpha channel, <B>giftopnm</B> simply discards it. <P>If you specify <B>-</B> as the filename, <B>giftopnm</B> writes the alpha output to Standard Output and discards the image. |