Felipe Barriga Richards Blog

After some time thinking I’ve decided to release the source code of OLHeatmap as GPLv2 to incentive others developers to join and help in the project.
Here is the original post showing OLHeatmap working and here is the project link in SourceForge (the guys at savannah.gnu.org take too long to approve a project…): http://olheatmap.sourceforge.net

After been working sometime with OpenLayers I figure out how to make heatmaps generated in the user browser. Now I’m using OpenStreetMap for both map and data. As is based on OpenLayers you can use any map (including Google Maps) and get data from other places.

There are some similar projects: gheat (server side), Google Maps – Heatmap (server side, not dynamic) and HeatMapAPI (server side and need an API key). If you know another API/Library to make Heatmaps please send me an email.

Currently you can watch the following demo videos (try to watch them on HD and fullscreen):
Read it all..

To convert PDF to big images like maps you can try with Gimp but it eat too much memory and is a bit slow.
The other option is to use ImageMagick:

If the output image is to small you can try to change the pixel density (dpi) which is 72dpi by default to a bigger one.
Here is an example using 500dpi, 8 bits of color (256), inverting the colors (negate) and saving it in PNG format:

The sample file is here: http://www.osornochile.cl/webimo/documentos/base_actualizado_diciembre_2009.pdf
The PDF size is 7.5M and the output PNG size is 59M.