# pamtogif - convert a Netpbm image to a GIF image - man(1) - [phpMan] > **TLDR:** Convert a Netpbm image into an unanimated GIF image. > - Convert a Netpbm image into an unanimated GIF image: `pamtogif {{path/to/image.pam}} > {{path/to/output.gif}}` - Mark the specified color as transparent in the output GIF file: `pamtogif {{-t|-transparent}} {{color}} {{path/to/image.pam}} > {{path/to/output.gif}}` - Include the specified text as a comment in the output GIF file: `pamtogif {{-c|-comment}} "{{Hello World!}}" {{path/to/image.pam}} > {{path/to/output.gif}}` *Source: tldr-pages* --- _Pamtogif_ _User_ [_Manual_(1)](https://www.chedong.com/phpMan.php/man/Manual/1/markdown) General Commands Manual _Pamtogif_ _User_ [_Manual_(1)](https://www.chedong.com/phpMan.php/man/Manual/1/markdown) ## NAME pamtogif - convert a Netpbm image to a GIF image ## SYNOPSIS ### pamtogif [**-interlace**] [**-sort**] [**-mapfile=_**mapfile_] [**-transparent=**[**=**]_color_] [**-alphacolor=_**color_] [**-comment=_**text_] [**-noclear**] [**-nolzw**] [**-aspect=_**fraction_] [**-verbose**] [_netpbmfile_] All options can be abbreviated to their shortest unique prefix. You may use two hyphens in‐ stead of one to designate an option. You may use either white space or an equals sign be‐ tween an option name and its value. ## DESCRIPTION This program is part of [**Netpbm**(1)](https://www.chedong.com/phpMan.php/man/Netpbm/1/markdown). **pamtogif **reads a Netpbm image as input and produces a GIF file as output. This program creates only individual GIF images. To combine multiple GIF images into an ani‐ mated GIF, use [**gifsicle**]() (not part of the Netpbm package). **pamtogif **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 **-transparent **option. It needs to have comments when you specify the **-comment **option. **pamtogif **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 color map with a maximum size of 256). If the image you want to convert has more colors than that (**ppmhist **can tell you), you can use **pnmquant **to reduce it to 256. Or use the more complex but faster method described under the ### -mapfile If your input image is a PAM with transparency information, **pamtogif **uses one entry in the GIF colormap specifically for the transparent pixels, so you can have at most 255 opaque col‐ ors. In contrast, if you use the **-transparent **option, one of the colors from the input be‐ comes transparent, so the limit is still 256. **pamtogif **recognizes transparency information in the input by the tuple type being **RGB_ALPHA**, **GRAYSCALE_ALPHA**, or **BLACKANDWHITE_ALPHA**. 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 **pamtogif **process the transparency information by changing the tuple type accordingly before you pass it to **pamtogif**. You can use **pamstack **to change the tuple type. **pamtogif **was new in Netpbm 10.37 (December 2006). In older Netpbm, use **ppmtogif**. ## OPTIONS In addition to the options common to all programs based on libnetpbm (most notably **-quiet**, see [ Common Options](index.html#commonoptions) ), **pamtogif **recognizes the following command line options: ### -interlace Produce an interlaced GIF file. ### -sort This does _not_ produce the sorted color map which is part of the GIF format. That kind of sorted color map is one where the colors are sorted according to how important they are, and the GIF header tells the viewer that it is sorted that way. Its purpose is to allow the viewer to use fewer colors than are in the color map if it is not capable of displaying all the colors. What this option produces is a color map sorted by red value, then green, then blue. That can be useful in analyzing GIF images, particularly those made with two versions of the program, because it removes some of the variability. ### -mapfile=_ Use the colors found in the file _mapfile_ to create the colormap in the GIF file, in‐ stead of the colors from _netpbmfile_. _mapfile_ can be any PPM file; all that matters is the colors in it. If the colors in _netpbmfile_ do not match those in _mapfile_, **pamtogif** matches them to a "best match." You can obtain a much better result by using **pnmremap** to change the colors in the input to those in the map file. The _mapfile_ file is not a palette file, just an image whose colors you want to use. The order of colors in the GIF palette have nothing to do with where they appear in the _mapfile_ image, and duplication of colors in the image is irrelevant. The map file's depth must match the number of color components in the input (which is not necessarily the same as the input's depth -- the input might have a transparency plane in addition). If your map file does not, or it _might_ not, run your input through **pnmremap **using the same map file so that it does. You can use **-mapfile **to speed up conversion of an image where you already have a map file because of earlier processing of your image. For example, it is common to start with an image that has more than 256 colors and remap its colors to a set of 256 col‐ ors so that **pamgtogif **can convert it (a GIF can have only 256 colors; **pamtogif **without **-mapfile **fails on any image that has more than that) with **pnmquant**. When you do this, **pnmquant **generates a palette to do the color quantization, then **pamtogif **generates an identical palette from the quantized image. You can save computation by generating the palette once: $ pnmcolormap 256 myimage.ppm >/tmp/colormap.ppm $ pamtogif myimage.ppm -mapfile=/tmp/colormap.ppm >output.gif ### -transparent=_ **pamtogif **marks the specified color as transparent in the GIF image. If you don't specify **-transparent**, **pamtogif **does not mark any color transparent (ex‐ cept as indicated by the transparency information in the input file). Specify the color (_color_) as described for the argument of the **pnm_parsecolor() **li‐ brary routine . If the color you specify is not present in the image, **pamtogif **selects instead the color in the image that is closest to the one you specify. Closeness is measured as a Cartesian distance between colors in RGB space. If multiple colors are equidistant, **pamtogif **chooses one of them arbitrarily. However, if you prefix your color specification with "=", e.g. **-transparent==red**, only the exact color you specify will be transparent. If that color does not appear in the image, there will be no transparency. **pamtogif **issues an information message when this is the case. When you specify **-transparent**, **pamtogif **ignores explicit transparency information (the "alpha channel") in the input image. ### -alphacolor=_ This specifies the foreground color for transparent pixels. A viewer may use the foreground color for a transparent pixel if it chooses not to have another color "show through.". The default is black. This applies only to pixels that are transparent in the GIF because they are transpar‐ ent in the Netpbm input. If a GIF pixel is transparent because of the **-transparent** option, the foreground color is the color indicated by that option. Note that in GIF, all transparent pixels have the same foreground color. (There is only one entry in the GIF colormap for transparent pixels). Specify the color (_color_) as described for the argument of the **pnm_parsecolor() **li‐ brary routine . ### -comment=_ Include a comment in the GIF output with comment text _text_. Without this option, there are no comments in the output. Note that in a command shell, you'll have to use quotation marks around _text_ if it contains characters (e.g. space) that would make the shell think it is multiple argu‐ ments: $ pamtogif -comment "this is a comment" xxx.gif ### -noclear This option causes the output not to contain any GIF clear codes. In GIF, the stream defines codes that represent strings of pixels as it goes. The stream contains definitions of codes mixed in with the references to those codes that describe the pixels of the image. GIF specifies a maximum number of codes that can be defined; when the stream has defined that many, the stream can either just use those for the rest of the image or include a clear code, deleting all the string codes so that the stream can start over defining new ones. By far the most common choice is the clear code. This usually results in a smaller stream because the set of strings of pixels that occur in an image vary over the parts of the image. Hardly any GIF encoders produce streams that don't use the clear code. But it is conceivable that a stream could be smaller without the use of the clear code because it saves the stream having to redefine the same string codes over and over. It could even avoid a thrashing situation where the stream continually defines a set of strings that never get used again before the maximum is reached. The default is to use the clear codes. This option was new in Netpbm 10.82 (March 2018). Before that, the program aways uses the clear codes. ### -nolzw This option is mainly of historical interest -- it involves use of a patent that is now expired. This option causes the GIF output, and thus **pamtogif**, not to use LZW (Lempel-Ziv) com‐ pression. As a result, the image file is larger and, before the patent expired, no royalties would be owed to the holder of the patent on LZW. See the section LICENSE below. LZW is a method for combining the information from multiple pixels into a single GIF code. With the **-nolzw **option, **pamtogif **creates one GIF code per pixel, so it is not doing any compression and not using LZW. However, any GIF decoder, whether it uses an LZW decompressor or not, will correctly decode this uncompressed format. An LZW de‐ compressor would see this as a particular case of LZW compression. Note that if someone uses an LZW decompressor such as the one in **giftopnm **or pretty much any graphics display program to process the output of **pamtogif -nolzw **, he is then using the LZW patent. But the patent holder expressed far less interest in en‐ forcing the patent on decoding than on encoding. ### -aspect=_ This is the aspect ratio of the pixels of the image. Its only effect is to record that information in the GIF for use by whatever interprets the GIF. Note that this feature of GIF is hardly ever used and most GIF decoders ignore this information and assume pixels are square. Pixels in a Netpbm image do not have aspect ratios; there is always a one-one corre‐ spondence between GIF pixels and Netpbm pixels. The aspect ratio is the quotient of width divided by height. GIF allows aspect ratios from 0.25 (1:4) to 4 (4:1) in increments of 1/64. **pamtogif **implements a natural ex‐ tension of GIF that allows an aspect ratio up to 4 14/64. If you specify anything outside this range, **pamtogif **fails. **pamtogif **rounds _fraction_ to the nearest 1/64. The default is square (1.0). This option was new in Netpbm 10.38 (March 2007). Before that, the pixels are always square. ### -verbose This option causes **pamtogif **to display information about the conversion process and the image it produces. ## SEE ALSO [**giftopnm**(1)](https://www.chedong.com/phpMan.php/man/giftopnm/1/markdown), [**pnmremap**(1)](https://www.chedong.com/phpMan.php/man/pnmremap/1/markdown), [**ppmtogif**(1)](https://www.chedong.com/phpMan.php/man/ppmtogif/1/markdown), **gifsicle **[]() , [**pnm**(1)](https://www.chedong.com/phpMan.php/man/pnm/1/markdown), [**pam**(1)](https://www.chedong.com/phpMan.php/man/pam/1/markdown). ## HISTORY **pamtogif **was new in Netpbm 10.37 (December 2006). It replaced **ppmtogif**, which created GIF images for Pbmplus/Netpbm users since 1989. The main outward change in the conversion from **ppmtogif **to **pamtogif **was that **pamtogif **was able to use transparency information ("alpha channel") in PAM input, whereas with **ppmtogif**, one had to supply the transparency mask in a separate pseudo-PGM image (via the **-alpha **op‐ tion). Jef Poskanzer wrote **ppmtogif **in 1989, and it has always been a cornerstone of Pbmplus/Netpbm because GIF is such a popular image format. Jef based the LZW encoding on GIFENCOD by David Rowley <<_mgardi@watdcsu.waterloo.edu_>>. Jef included GIFENCOD's GIFCOMPR.C file pretty much whole. Rowley, in turn, adapted the LZW compression code from classic Unix **compress**, which used techniques described in IEEE Computer, June 1984. Jef's **ppmtogif **notably lacked the ability to use a transparency mask with it. You could cre‐ ate transparent pixels in a GIF, but only with the **-transparent **option, which allowed one to specify that all pixels of a certain color in the input were to be transparent. Bryan Hen‐ derson added the **-alpha **option in July 2001 so you could supply a mask image that indicates exactly which pixels are to be transparent, and those pixels could have the same color as other opaque ones. Bryan Henderson added another significant piece of code and function in October 2001: the ability to generate a GIF without using the LZW patent -- an uncompressed GIF. This was very important to many people at the time because the GIF patent was still in force, and this al‐ lowed them to make an image that any GIF viewer could display, royalty-free. Bryan adapted code from the Independent JPEG Group's **djpeg **for that. There is no code in **pamtogif **from Jef's original, but Jef may still hold copyright over it because of the way in which it evolved. Virtually all of the code in **pamtogif **was written by Bryan Henderson and contributed to the public domain. ## LICENSE If you use **pamtogif **without the **-nolzw **option, you are using a patent on the LZW compression method which is owned by Unisys. The patent has expired (in 2003 in the US and in 2004 else‐ where), so it doesn't matter. While the patent was in force, most people who used **pamtogif** and similar programs did so without a license from Unisys to do so. Unisys typically asked $5000 for a license for trivial use of the patent. Unisys never enforced the patent against trivial users. Rumor has it that IBM also owns or owned a patent covering **pamtogif**. A replacement for the GIF format that never required any patents to use is the PNG format. ## DOCUMENT SOURCE This manual page was generated by the Netpbm tool 'makeman' from HTML source. The master documentation is at **** netpbm documentation 09 June 2021 _Pamtogif_ _User_ [_Manual_(1)](https://www.chedong.com/phpMan.php/man/Manual/1/markdown)