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| -rw-r--r-- | pamtogif.html | 40 | ||||
| -rw-r--r-- | pamtopng.html | 4 |
2 files changed, 11 insertions, 33 deletions
diff --git a/pamtogif.html b/pamtogif.html index c861a3e2..6d720817 100644 --- a/pamtogif.html +++ b/pamtogif.html @@ -2,7 +2,7 @@ <html><head><title>Pamtogif User Manual</title></head> <body> <h1>pamtogif</h1> -Updated: 22 March 2007 +Updated: 05 June 2021 <br> <a href="#index">Table Of Contents</a> @@ -62,12 +62,12 @@ 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>The GIF format is not capable of representing an image with more than -256 colors in it (it contains a color map with a maximum size of 256). -If the image you want to convert has 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><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 +color map with a maximum size of 256). If the image you want to convert has +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> uses one entry in the GIF colormap specifically for the transparent pixels, @@ -172,7 +172,7 @@ in RGB space. If multiple colors are equidistant, <b>pamtogif</b> chooses one of them arbitrarily. <p>However, if you prefix your color specification with "=", -e.g. <b>-transparent==red</b>, only the exact color you specify will +e.g. <b>-transparent==red</b>, only the exact color you specify will be transparent. If that color does not appear in the image, there will be no transparency. <b>pamtogif</b> issues an information message when this is the case. @@ -181,30 +181,6 @@ message when this is the case. explicit transparency information (the "alpha channel") in the input image. -<dt><b>-alpha=</b><i>pgmfile</i> - -<dd>There is no <b>-alpha</b> option. <b>pamtogif</b>'s predecessor had -such an option because it was not capable of taking PAM input that contains -a transparency (alpha) plane, so one used this option to supply a -transparency plane as a separate PGM file. - - This option names a PGM file that contains a transparency mask for the -image. <b>pamtogif</b> creates fully transparent pixels wherever the -transparency mask indicates transparency greater than 50%. The color of -those pixels is that specified by the <b>-alphacolor</b> -option, or black by default. - -<p>To do this, <b>pamtogif</b> creates an entry in the GIF colormap in -addition to the entries for colors that are actually in the image. It -marks that colormap entry as transparent and uses that colormap index -in the output image to create a transparent pixel. - -<p> The transparency image must be the same dimensions as the input -image, but may have any maxval. White means opaque and black means -transparent. - -<p> You cannot specify both <b>-transparent</b> and <b>-alpha</b>. - <dt><b>-alphacolor=</b><i>color</i> <dd>This specifies the foreground color for transparent pixels. A diff --git a/pamtopng.html b/pamtopng.html index ea697bb8..acb6d3e2 100644 --- a/pamtopng.html +++ b/pamtopng.html @@ -132,7 +132,9 @@ command line options: <dt><b>-transparent=</b><i>color</i> <dd> -<b>pamtopng</b> marks the specified color as transparent in the PNG image. +<b>pamtopng</b> marks the specified color as transparent in the PNG image -- +Every pixel of this color is fully transparent. This causes <b>pamtopng</b> to +include a tRNS chunk in the image identifying that color. <p>Specify the color (<i>color</i>) as described for the <a href="libnetpbm_image.html#colorname">argument of the <b>pnm_parsecolor()</b> library routine</a>. E.g. <b>red</b> or <b>rgb:ff/00/0d</b>. |