SVG to PNG conversion using Ruby + cairo + rsvg on Mac OS X Snow Leopard + MacPorts

A way to convert a SVG file to PNG file using Ruby + cairo + rsvg on Mac OS X Snow Leopard + MacPorts is confirmed.

A quick way to get tiled images 'untiled'.

A way to get tlled images 'untiled', using RMagick. An experiment on OpenStreetMap tiles for Pacifico Yokoyama.

A way to remove pairs of the same (but with different orientation) geometries from a (small) LineString collection

Say you have a small collection of LineString geometries, and you want to remove pairs of same geometries with different directions. Here are some solutions using JTS (JTS Topology Suite) from Ruby, using Rjb (Ruby Java Bridge.)

Yet another way to keep Java classes in Ruby, using OpenStruct

Yet another way to keep Java classes in Ruby, using OpenStruct;

What is the actual mathematical expression for Google Mercator? Confirm it through Safari's Web Inspector on OpenLayers and Proj4js

Thanks to http://www.spatialreference.org/ , it is very easy to check the WKT definitions for WGS84 and "Google Mercator" projection. But the actual mathematical expression to convert Google Mercator to WGS84 is not so easy to check, although the expression is published at http://en.wikipedia.org/wiki/Mercator_projection#Mathematics_of_the_projection . This entry shows how we can check the expression on existing JavaScript code using Web Inspector of Safari or Chrome.
This is the English version of http://d.hatena.ne.jp/hfu/20100906/1283778909 .

経緯度とGoogle Mercatorとの変換式を確認してみる（OpenLayers & Proj4js）。

既存の JavaScript プログラムに埋め込まれた、経緯度とGoogle Mercatorとの変換式（特にメルカトルから経緯度への逆変換式）を確認してみました。Safari の Web インスペクタを使って簡単に調べてみます。

ST_AsSVG も魔法ではない。（ST_AsSVG がポリゴンに対してやっていること）

PostGIS に含まれている便利な関数 ST_AsSVG ですが、魔法ではないので特別なことはしていません。穴あきポリゴンに対する ST_AsSVG の動きを追ってみます。