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| -rw-r--r-- | directory.html | 1 | ||||
| -rw-r--r-- | giftopnm.html | 8 | ||||
| -rw-r--r-- | pamperspective.html | 51 |
3 files changed, 34 insertions, 26 deletions
diff --git a/directory.html b/directory.html index 68308e4f..fcaf3c53 100644 --- a/directory.html +++ b/directory.html @@ -108,7 +108,6 @@ convert Netpbm format to Portable Network Graphics convert PNG (Portable Network Graphics) to Netpbm formats <DT><B><a href=pngtopnm.html>pngtopnm</a> </B> -<DD> <DD>obsolete version of <b><a href="pngtopam.html">pngtopam</a></b> (kept because it may have fewer bugs) diff --git a/giftopnm.html b/giftopnm.html index a409f3d1..93a68d02 100644 --- a/giftopnm.html +++ b/giftopnm.html @@ -2,7 +2,7 @@ <HTML><HEAD><TITLE>Giftopnm User Manual</TITLE></HEAD> <BODY> <H1>giftopnm</H1> -Updated: 29 January 2007 +Updated: 11 August 2008 <BR> <A HREF="#index">Table Of Contents</A> @@ -73,7 +73,11 @@ the alpha output file. <DT><B>-comments</B> <DD> -Only output GIF89 comment fields. +With this option, <b>giftopnm</b> issues messages showing the GIF comments +(A GIF89 stream can contain comments in comment extensions). +<p> +By default, <b>giftopnm</b> ignores comment extensions. + <DT><B>-image=</B>{<I>N</I>,<B>all</b>} diff --git a/pamperspective.html b/pamperspective.html index f0b5e706..0573f8eb 100644 --- a/pamperspective.html +++ b/pamperspective.html @@ -69,16 +69,21 @@ hyphens may be given in any order. <p><b>pamperspective</b> reads a Netpbm image as input and produces a Netpbm image of the same format as output. -<p>The values <i>upper_left_x</i> ... <i>lower_right_y</i>, that are -required on the command line, specify a quadrilateral in the input -image. <b>pamperspective</b> interprets the input image as a -perspective projection of a three dimensional scene, for example a -photograph. <b>pamperspective</b> assumes the specified quadrilateral -represents a parallelogram in that scene. The output image consists -of this parallelogram, sheared to a rectangle. In this way -<b>pamperspective</b> undoes the effect of a raytracer or scanline +<p><b>pamperspective</b> interprets the input image as a perspective +projection of another image which is in a plane oblique to that of the +input image. For example, a photograph of a painting, taken at an +angle. The arguments <i>upper_left_x</i> ... <i>lower_right_y</i> +specify a quadrilateral in the photograph that <b>pamperspective</b> +assumes corresponds to a parallelogram in the painting. The output +image consists of this parallelogram, sheared to a rectangle. In this +way <b>pamperspective</b> undoes the effect of a raytracer or scanline renderer. +<p>Note that if the input image is a projection of a solid scene, +rather than a plane, the result is like a different camera angle on +that scene, to the extent that the scene is shallow from the other +angle. + <p>The input is from <i>infile</i>, or from Standard Input, if <i>infile</i> is not specified. The output is to Standard Output. @@ -187,13 +192,13 @@ number, <b>pamperspective</b> does not allow this format. <dt><i>system</i>=<b>pixel</b>, <i>unit</i>=<b>image</b></dt> - <dd>(0,0) refers to the centre of the upper left pixel and (1,1) - refers to the centre of the lower right pixel.</dd> + <dd>(0,0) refers to the center of the upper left pixel and (1,1) + refers to the center of the lower right pixel.</dd> <dt><i>system</i>=<b>pixel</b>, <i>unit</i>=<b>pixel</b></dt> - <dd>(0,0) refers to the centre of the upper left pixel and - (<i>width</i>-1,<i>height</i>-1) refers to the centre of the lower + <dd>(0,0) refers to the center of the upper left pixel and + (<i>width</i>-1,<i>height</i>-1) refers to the center of the lower right pixel. Here <i>width</i> and <i>height</i> are the width and height of the input image.</dd> @@ -356,8 +361,8 @@ part. <dt><b>pixel</b></dt> - <dd>The upper left vertex corresponds to the centre of the upper - left pixel and The lower right vertex corresponds to the centre of + <dd>The upper left vertex corresponds to the center of the upper + left pixel and The lower right vertex corresponds to the center of the lower right pixel.</dd> </dl> @@ -367,8 +372,8 @@ part. <dt><b>--interpolation=</b><i>spec</i></dt> - <dd>Usually (centres of) output pixels do not exactly correspond to - (centres of) input pixels. This option determines how the program + <dd>Usually (centers of) output pixels do not exactly correspond to + (centers of) input pixels. This option determines how the program will choose the new pixels. Valid values for <i>spec</i> are: <dl> @@ -397,16 +402,16 @@ so that no part of the input image is missing in the output. There are problems with that: <ul> - <li>If the threedimensional plane defined by the quadrilateral has a + <li>If the three dimensional plane defined by the quadrilateral has a visible horizon in the input image, then the above asks <b>pamperspective</b> to include points that cannot ever be part of the output. - <li>If the horizon is not visible, but close to the border of the input - image, this may result in <em>very</em> large output files. Consider a - picture of a road. If you ask a point close to the horizon to be included, - then this point is far away from the viewer. The output will cover many - kilometers of road, while <b>--detail</b> perhaps makes a pixel equal to a - square centimeter. + <li>If the horizon is not visible, but close to the border of the + input image, this may result in <em>very</em> large output + files. Consider a picture of a road. If you ask for a point close to + the horizon to be included, then this point is far away from the + viewer. The output will cover many kilometers of road, while + <b>--detail</b> perhaps makes a pixel represent a square centimeter. </ul> |