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diff --git a/graphics/gimp-wideangle-plugin/wideangle.html b/graphics/gimp-wideangle-plugin/wideangle.html new file mode 100644 index 0000000000..0e4682febf --- /dev/null +++ b/graphics/gimp-wideangle-plugin/wideangle.html @@ -0,0 +1,72 @@ +<html><head><title>Gimp Wideangle Filter</title></head> +<body> +<h1>Gimp Wideangle Filter</h1> +<p>The Wideangle plugin is licensed under the GPL.<br/> +The source code is available <a href="wideangle.c">here</a>. Latest version is +1.0.10.<br/> +<b>gimptool --install wideangle.c</b> will compile the plugin and install +it in your local Gimp plugins directory.<br/> +The plugin appears in the <b>Filters/Distorts</b> menu as +<b>Wideangle...</b>.</p> +<p>The Wideangle filter is used to correct (or simulate) the distortion +typically seen on photographs taken with a wideangle lens. There are six +controls. +<dl> +<dt>X Shift</dt> +<dd>Adjusts the centre of the effect, from the left edge of the image (at -100.0), +through the centre (at 0.0), to the right edge (at 100.0).</dd> +<dt>Y Shift</dt> +<dd>Adjusts the centre of the effect, from the top edge of the image (at -100.0), +through the centre (at 0.0), to the bottom edge (at 100.0).</dd> +<dt>Main</dt> +<dd>Controls the amount of distortion. Negative values correct wideangle (barrel) +distortion, while positive values create it (or correct pincushion distortion).</dd> +<dt>Edge</dt> +<dd>Like the <b>Main</b> control, but the <b>Edge</b> control has more effect +at the edges of the image than at the centre.</dd> +<dt>Zoom</dt> +<dd>Zooms the entire image in or out.</dd> +<dt>Brighten</dt> +<dd>Adjusts the image brightness up or down with distance from the centre. +Can be used to remove (or create) vignetting, the darkening of the corners +of an image.</dd> +</dl> +</p> + +<p>The <b>Do Preview</b> toggle enables and disables the preview window. +The preview can show either an overview of the whole image, or a detail view +which shows a 5x5 array of full resolution closeups. The overview is useful for +casual use, while the detail view +allows you to create a precisely calibrated preset for a particular lens. To create +a lens preset, use +a photo of a grid pattern. Start by adjusting the <b>Main</b> control until the +lines of the grid are as straight as possible. Use the <b>Shift</b> controls, if +necessary, to correct for any asymmetry. Finally, if the best setting of the +<b>Main</b> control leaves a "wiggle" in the lines, use the <b>Edge</b> +control to remove it. (You may need to readjust the <b>Main</b> control a little.) +Once you have the correct settings for a particular lens, you should be able +to save the settings as a new preset and use them for all images taken with that +lens.</p> + +<p>Or just play around.</p> + +<p>The preset controls allow you to reset everything, select a previously defined +preset, or save the current settings (if they've been altered) under a new name. +Preset names can contain (fairly) arbitrary characters. If you mess up the presets, +they are stored in a text file under your Gimp user +directory in the <code>wideangle</code> subdirectory.</p> + +<p>Regardless of the Gimp's settings, the Wideangle filter always uses cubic +interpolation. This is not a bug, it's a feature.</p> + +<p><b>What's with the pop up menu on the "select" button?</b></p> + +<p>I originally had a regular option menu to select presets. However this had +a drawback, namely that the displayed option was only correct until a control +was adjusted. A pop up menu, although not the normal choice, provides exactly +the correct model to the user.</p> + +<p>Written by David Hodson. Many thanks for suggestions and improvements +to Lars Clausen. (But bugs are still my fault.)</p> + +</body></html> |