diff options
Diffstat (limited to 'pamtogif.html')
| -rw-r--r-- | pamtogif.html | 27 |
1 files changed, 20 insertions, 7 deletions
diff --git a/pamtogif.html b/pamtogif.html index 6d720817..1c1f0ac7 100644 --- a/pamtogif.html +++ b/pamtogif.html @@ -2,7 +2,7 @@ <html><head><title>Pamtogif User Manual</title></head> <body> <h1>pamtogif</h1> -Updated: 05 June 2021 +Updated: 09 June 2021 <br> <a href="#index">Table Of Contents</a> @@ -56,11 +56,14 @@ multiple GIF images into an animated GIF, use <a href="http://www.lcdf.org/gifsicle/"><b>gifsicle</b></a> (not part of the Netpbm package). -<p><b>pamtogif</b> creates either an original GIF87 format GIF file or -the newer GIF89 format. It creates GIF89 when you request features -that were new with GIF89, to wit the <b>-transparent</b> or -<b>-comment</b> options. Otherwise, it creates GIF87. Really old GIF -readers conceivably could not recognize GIF89. +<p><b>pamtogif</b> creates either an original GIF87 format GIF file or the + newer GIF89 format. It creates GIF89 when the output needs to have features + that were new with GIF89, to wit transparency or comments. Otherwise, it + creates GIF87. Really old GIF readers conceivably could not recognize + GIF89. The output needs to have transparency when either the input has a + transparency information or you specify the <b>-transparent</b> option. It + needs to have comments when you specify the + <b>-comment</b> option. <p><b>pamtogif</b> generates a GIF image with a single image block, which means the image cannot have more than 256 colors in it (it contains a single @@ -69,12 +72,22 @@ more colors than that (<b>ppmhist</b> can tell you), you can use <b>pnmquant</b> to reduce it to 256. Or use the more complex but faster method described under the <b>-mapfile</b> option. -<p>If your input image is a PAM with transparency information, <b>ppmtogif</b> +<p>If your input image is a PAM with transparency information, <b>pamtogif</b> uses one entry in the GIF colormap specifically for the transparent pixels, so you can have at most 255 opaque colors. In contrast, if you use the <b>-transparent</b> option, one of the colors from the input becomes transparent, so the limit is still 256. +<p><b>pamtogif</b> recognizes transparency information in the input by the + tuple type being <b>RGB_ALPHA</b>, <B>GRAYSCALE_ALPHA</B>, or + <b>BLACKANDWHITE_ALPHA</b>. This is the case for any image that has + transparency information and was created by a Netpbm program that + manipulates visual images. If, on the other hand, you have a PAM generated + some other way, but you know the planes have the same meaning as implied by + these tuple types, you can make <b>pamtogif</b> process the transparency + information by changing the tuple type accordingly before you pass it + to <b>pamtogif</b>. You can use <b>pamstack</b> to change the tuple type. + <p><b>pamtogif</b> was new in Netpbm 10.37 (December 2006). In older Netpbm, use <b>ppmtogif</b>. |