Klokan Technologies GmbH

Custom style for Google Maps

klokan@klokan.cz (Klokan Petr Přidal) — Fri, 21 May 2010 09:24:00 +0000

I am impressed by the new functionality in Google Maps API V3: StyledMaps

You can create your own dynamic style for Google Maps tiles - and change the look and feel of the base maps which you want to include in your website.

It is quite a natural step, something what open-source projects like Cascadenik and products of other companies such as CloudMade made possible already some time ago. The adoption of this functionality by Google brings this possibility to masses.

If you want to define your own styles for the map you can use the online Style Map Wizard tool. More info and the official announcement is available here.

IIPImage JPEG2000: Free Software for Zoomable High Resolution Online Images

klokan@klokan.cz (Klokan Petr Přidal) — Wed, 13 Jan 2010 14:33:00 +0000

As a technical manager of the OldMapsOnline.org project I am very pleased to post to this blog a note about our results:

Moravian Library and the OldMapsOnline.org project are proud to announce the release of a new version of the open-source IIPImage server software (http://help.oldmapsonline.org/jpeg2000/).

The freely available IIPImage software can be used for stunning online presentations of scanned documents, paintings, maps, books, newspapers, photographs or other high-resolution images on the web directly from JPEG2000 or TIFF files.

The new version allows direct publishing from JPEG2000 images to a wide variety of different client technologies based on AJAX, Adobe Flash or Silverlight. These include popular pan&zoom viewers based on Zoomify or Seadragon technology (including the Seadragon AJAX viewer and the Seadragon iPhone application) as well as it's own AJAX enabled IIPMooViewer. The documents provided by IIPImage can be displayed in any web browser and on a number of platforms - Windows, Mac, Linux or iPhone.

The software is primarily targeted at institutions who operate their own server connected to the Internet and who want to publish large collections of digital images directly from JPEG2000 or
TIFF files.

Institutions who does not have the necessary infrastructure can follow our alternative tutorial at http://help.oldmapsonline.org/publish/ on how to achieve the same using standard web hosting and free software.

IIPImage is a light-weight client-server system for fast and efficient online viewing and zooming of ultra high-resolution images. It is designed to be bandwidth and memory efficient and usable over a slow Internet connection even on gigapixel sized images.
It is available for free, under an open source license (GNU GPL). We recommend installing
the software on a Linux (or other UNIX) server. We have prepared an easy to install binary package for Debian and Ubuntu with step-by-step instructions for installation.

JPEG2000 support has been implemented using the Kakadu library, which provides one of the fastest implementations of the JPEG2000 ISO standard and is redistributable for non-commercial use.

The enhancement of IIPImage was developed by the Moravian Library and the OldMapsOnline.org project with the support of grants from the Ministry of Culture of the Czech Republic.

The Moravian Library (http://www.mzk.cz/), based in Brno, Czech Republic, is a research institution and a legal deposit library. Project OldMapsOnline.org (http://www.oldmapsonline.org/) is a research project of the Moravian Library that aims to develop software to assist in the management, manipulation and visualisation of historical map collections on the web. The project team is designing online tools for publishing, collaborative georeferencing, annotation, 3D visualisation, accuracy analysis and geometadata specification for old maps.

For more information and for the IIPImage JPEG2000 software, see http://help.oldmapsonline.org/jpeg2000/.

Tiles à la Google Maps: Coordinates, Tile Bounds and Projection...

klokan@klokan.cz (Klokan Petr Přidal) — Thu, 27 Nov 2008 07:41:00 +0000

I prepared an online tool I was missing when I started to study how the tiling using Spherical Mercator runs in Google Maps, Virtual Earth, Yahoo Maps, OpenStreeMap and others... This tool can help you to understand how are the tiles referenced and how they are stitched together in the browser.

I think this mashup could be an excellent starting point for people who are interested in this subject, because it contains all the math what you need for overlaying your own geodata from external sources: it can be tiles pre-generated by Maptiler/GDAL2Tiles following the OSGeo TMS recommendations, it can be raster data from WMS servers probably cached by TileCache, or tiles from MSR MapCruncher etc.

The tool is excellent for fast debugging of tiling for particular area, because you can use the search for display the tiles of a given place.

A transparent tile with correct coordinates is displayed for every original map tile by calling Google Chart API service.
Whereever you click the longitude/latitude boundaries of the underlaying tile are displayed in WGS84 datum. Boundaries are also displayed in projected Mercator coordinates (EPSG:900913, EPSG:3785) and in pixels for active zoom level. This information is all you need for generating custom map tiles.

The site contains also a Python script doing the coordinates and bounds calculation offline.

So enjoy this mashup:

Tiles à la Google Maps: Coordinates, Tile Bounds and Projection

BTW This demo is part of the documentation of MapTiler application.

PNG palette with variable alpha: small and great for webbrowser

klokan@klokan.cz (Klokan Petr Přidal) — Wed, 05 Nov 2008 08:01:00 +0000

I am working on the MapTiler/GDAL2Tiles open-source project for user-friendly static tile publishing of maps in the style of Google Maps. This project started as my Google Summer of Code project for OSGEO and results are published in coming GDAL 1.6.

Recently I was testing several optimization of PNG for minimizing the tile size with preserving reasonable image quality as this is crucial for my application. Such optimization speeds up the download and also saves a lot of space on the hard disk. There is plenty of tools available for optimizing the size of PNG: advpng, pngrewrite, pngcrush, pngquant, scolorq, pngnq... I wanted to choose one of them for postprocessing of tiles (or probably later on integrate such optimization directly into GDAL).

The best optimization of the PNG filesize is always based on reduction of the amount of used colors: when you switch from RGB(A) model to palette. What I didn't know before is that PNG supports palette with variable alpha. It means that part of the definition of every color in the palette is also its transparency. It is possible to use functionality usually available only with separate alpha channels but with palette!

After switching to PNG with palette you need just half or even less of the space for your image raster data. Of course conversion from RGBA to palette is lossy operation for images with a lot of colors... but with well chosen algorithm for quantization it can be almost not recognizable for humans. Especially for small tiles like in MapTiler case.

The PNG with the alpha palette is correctly displayed in all latest web-browsers like Firefox 2+, Safari, Explorer 7+ and also in Google Earth.
But wait that is not all! Internet Explorer 5.5 & 6 displays such PNG files with (limited) transparency without HTML hacking! That is just great because it allows you to easily display map overlays in the old browsers by viewers like OpenLayers or Google Maps and still be able to dynamically change opacity for map overlay containing transparent parts!

Well, if it is so great, how to produce such file? There is very nice open-source application for converting standard RGBA PNGs into this PNG8 with alpha palette:

PNGNQ: http://pngnq.sourceforge.net/ (by Stuart Coyle and Greg Roelofs)

It is using The NeuQuant Neural-Net image quantization algorithm (by Anthony Dekker) which was documented in this PDF article. With slightly modified version of this algorithm it converts standard PNG24 with RGBA into PNG8 with alpha palette. It is quite fast.
The result PNG file has usually half of the size of the original.
If you are crazy about the produced png size you can try to compress the file with pngcruch postprocessing step. Sometimes it decrese the size of the result even a bit more.

The documentation at the PNGNQ project page recommends to run:

pngnq -n 256 image.png && pngcrush image-nq8.png smallimage.png

This PNGNQ tool is excellent for post-processing of PNG tiles generated from MapTiler/GDAL2Tiles...

And it seems that the source code of the utility itself as well as of dependencies like NeuQuant algorithm is compatible with BSD license so they have a chance to find a way into GDAL or other open-source tools which are processing maps...

Opacity Control for Google Maps in official demo gallery

klokan@klokan.cz (Klokan Petr Přidal) — Mon, 03 Nov 2008 08:21:00 +0000

One of the results of the MapTiler/GDAL2Tiles is an extension of Google Maps API for new functionality related to tile overlays. In summer I created an Opacity slider control for Google Maps which lets the user drag a slider to change the transparency of a TileLayerOverlay on the map.

Recently I was contacted by Pamela Fox from Google and now she add my control to the official Google Maps API Demo Gallery.

I still should add similar control to OpenLayers, but till now there was no time for that unfortunately. The design of the control is finished (done in SVG in Inkscape, same as the Google one), so only the coding in JavaScript is missing. Christopher Schmidt from OpenLayers recommended to create a new OpenLayers Addin.

iPhone and NOAA BSB, USGS DRG and custom maps

klokan@klokan.cz (Klokan Petr Přidal) — Thu, 04 Sep 2008 08:10:00 +0000

iPhone supports displaying of Google Maps tiles very well by standard Maps.app application. A man can zoom and look around just by finger gestures.

Behind the user interface the Maps.app is loading tiles from Google server and storing them in to SQLite cache file.
Some people proved that you can prepare your own SQLite cache with custom maps and let it use by Maps.app on iPhone.

Then you have a map of your choice and this map is even available off-line, so your iPhone don't need to use internet connection to get the tiles as they are stored in the disk of the phone already.

Such approach was documented for Google Sky tiles for example: http://www.dailyack.com/2007_12_01_archive.html

Nowadays there is even a GUI application for iPhone allowing you to switch prepared maps:
http://code.google.com/p/iphoneofflinemap/

Unfortunatelly the maps are usually prepared in advance on a computer from half legal map sources by software like Global Map Download Tool.

But I don't see a problem to prepare tiles from legally owned maps like NOAA BSB navy charts or USGS DRG topo maps.

Jerry Morrison from Google Inc. in his presentation "Scaling Google Maps from the Big Screen Down to Mobile Phones" mentioned that iPhone uses tiles with size 64x64px, MapTiler should be able to generate such tiles quite well.

I was thinking maybe somebody can push my MapTiler application to generates tiles directly into the SQLite cache database for simple upload into iPhone. Anybody interested?

P.S.
There is now way how to design a 100% web-based map application with iPhone Web Touch API.

Google IP Geolocation

klokan@klokan.cz (Klokan Petr Přidal) — Tue, 26 Aug 2008 16:20:00 +0000

Google just published new AJAX API function ClientLocation for IP Geolocation.

This way you receive an JavaScript object with latitude and longitude and with address (city, region, country and country code) of your visitor.

It is cool and practical for use even without displaying Google Maps, as you can change behavior of your website according location of the visitor.

I wrote a typical example application Google IP Geolocation Map and Address which you can just copy and paste.

What IP database is Google practically using? Anybody knows? Is it their private or they are licensing one from another company?

Is the quality of IP geolocation better then free GeoLite City from MaxMind?

iPhone Touch API ... a way for OpenLayers

klokan@klokan.cz (Klokan Petr Přidal) — Thu, 14 Aug 2008 08:46:00 +0000

It seems that with Apple's web Touch API it is possible to create a website, which will behave same way as iPhone build in Google Maps application. You can react by Javascript on all touch events, so implement zooming by pinching for example, or flicking to another page etc..

This functionality would be really cool in the OpenLayers open-source project

For more info about the possibilities have a look at very nice description and example application of the Apple Touch API.