Rafael Sanches

July 23, 2009

Retrieve driving directions from google maps with server-side HTTP calls and show results with static maps for WAP

Filed under: maps — Tags: , , , , , , , , , — mufumbo @ 8:32 am

Edit may 2010: Google has released the directions API. Documentation is available here.

Mobile phones are not famous for supporting javascript. A problem arises when you need to use google API to retrieve the driver directions for a mobile site, or when you just don’t want your site to be overloaded with the complete maps toolkit to show a simple map.

Google provides a good directions-static demo but, unfortunately, it’s javascript-only. They don’t have any example or documentation about how to generate the directions through server side HTTP call.

The driving direction API doesn’t seem to be 100%. I wasn’t able to find examples of how to use the directions API with google maps API-V3 javascript, it seems that it’s not ready yet. I’ve founded this issue tracking in gmaps-api-issues (by the way, the most voted issue) that says that there isn’t support for google maps directions through server side http calls.

Putting all together: I have decided to check what HTTP calls the directions API of google maps API-V2 does and to use it in the server side. I don’t know if it’s forbidden in the terms of service, but it works!

Basically, my PHP server-side is doing the exact same thing that the google directions-static demo is doing in javascript (checkout the source code of the page). It retrieves the answer from the server and write the coordinates information in the  static maps URL.

Note that HttpHelper::doGET downloads the string, you can substitute that part with CURL or fopen. Here is the code to make the HTTP calls to get the driving directions and to create the static map image link:

<?php
class GoogleGeo {
    public static function buildStaticMap($center, $markers=array(), $width=400, $height=400, $zoom=12, $directions=null) {
        $strMarkers = "";
        foreach($markers as $marker) {
            if (!empty($strMarkers)) $strMarkers .= '|';
            $strMarkers .= urlencode($marker);
        }
        if ($width > 640) $width = 640;
        if (!empty($center)) {
            $center = "&center=".$center;
        }
        if (!empty($strMarkers)) {
            $strMarkers = "&markers=".$strMarkers;
        }
        if ($zoom > 0) {
            $zoom = "&zoom=$zoom";
        }

        $steps = "";
        if (!empty($directions)) {
            foreach($directions['Directions']['Routes'][0]['Steps'] as $step) {
                $lat = $step['Point']['coordinates'][1];
                $lon = $step['Point']['coordinates'][0];
                if (!empty($steps)) $steps .= "|";
                $steps .= $lat.",".$lon;
            }
            if (!empty($steps)) {
                $steps .= "|".$directions['Directions']['Routes'][0]['End']['coordinates'][1].",".$directions['Directions']['Routes'][0]['End']['coordinates'][0];
                $steps = "&path=rgb:0x0000ff,weight:5|".$steps;
            }
        }

        $staticMap = "http://maps.google.com/staticmap?maptype=mobile&size=".$width."x$height&maptype=roadmap&key=".GOOGLE_MAPS_KEY."&sensor=false$strMarkers$center$zoom$steps";
        return $staticMap;
    }

    public static function retrieveDirections ($from, $to) {
        $params = array('key' => GOOGLE_MAPS_KEY, 'output' => 'json', 'q' => "from: $from to: $to");
        $url = "http://maps.google.com/maps/nav";
        $result = HttpHelper::doGET($url, $params);
        $result = json_decode($result, true);
        return $result;
    }
}
?>

A example how to use this code is:

<?php
...
    /* FROM and TO coordinates */
    $markers = array("37.262568,-121.962232,redr", "37.229898,-121.971853,blueg");
    /* Get the driving directions from google api */
    $directions = GoogleGeo::retrieveDirections("485 Alberto Way, Suite 210. Los Gatos, CA 95032", "14109 Winchester Bl, Los Gatos, CA");
    /* Create the map image url with the directions coordinates */
    $staticMap = GoogleGeo::buildStaticMap(null, $markers, 640, 240, null, $directions);
....
?>

In this way you will have $staticMap with a value similar to the image urls in the directions-static demo. In this case it will be:

http://maps.google.com/staticmap?maptype=mobile&size=640×240&maptype=roadmap&key=YOUR_GOOGLE_KEY&sensor=false&markers=37.262568%2C-121.962232%2Credr|37.229898%2C-121.971853%2Cblueg&path=rgb:0x0000ff,weight:5|37.22898,-121.97104|37.22818,-121.97112|37.22597,-121.97231|37.22892,-121.98063|37.23713,-121.97714|37.26301,-121.96088|37.262282,-121.961628

The variable $directions will contain a array with the complete direction steps, so you can easily loop through it and print it out on your WAP application.

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May 7, 2009

Install ffmpeg for alembik transcoding server with 51.40.4 on ubuntu

Filed under: transcoding, Uncategorized — Tags: , , , , , , , , , , , — mufumbo @ 12:31 pm

I find the alembik transcode server a cool piece of software, but I found lots of caveats when started to use it.

The most difficult part is that alembik supports only two versions of libavcodec for ffmpeg, so you must compile it from the sources, since they are quite old.
That happens because ffmpeg changes the parameters from version to version and the alembik team had choosen both 51.40.4 and 51.48.0 to be supported. I think that in the future it will be possible to have an external “.properties” file, so I hope that it will not be necessary to compile ffmpeg by hand, every time.

I’ve used this references:
http://sourceforge.net/mailarchive/message.php?msg_name=48A176CC.8080300%40kimiasol.com (here i’ve found the rpm of a ffmpeg with libavcodec version 51.40.4 to download)
http://juliensimon.blogspot.com/2008/12/howto-compiling-ffmpeg-x264-mp3-xvid.html (this post teach how to install libamr from mediubuntu repository)

install both amr, you can install also from mediubuntu repo.

$ wget http://ftp.penguin.cz/pub/users/utx/amr/amrnb-6.1.0.4.tar.bz2
$ wget http://ftp.penguin.cz/pub/users/utx/amr/amrwb-7.0.0.1.tar.bz2
$ sudo apt-get install g++ nasm zlib1g-dev libx264-dev libfaad-dev faad liba52-0.7.4-dev libgsm1-dev libmp3lame-dev \
libtheora-dev libvorbis-dev libxvidcore4-dev libfaac-dev libimlib2-dev libfreetype6-dev

Use an aplication to convert the rpm to tar and decompress it (with alien or something else):

$ wget http://dag.wieers.com/rpm/packages/ffmpeg/ffmpeg-0.4.9-0.9.20070530.rf.src.rpm

$ ./configure --enable-libmp3lame --enable-libogg --enable-libvorbis --enable-libamr-nb --enable-libfaad --enable-libfaac \
--enable-libgsm --enable-xvid --enable-x264 --enable-liba52 --enable-liba52bin --enable-pp --enable-shared --enable-pthreads \
--enable-libtheora --enable-gpl --disable-strip --enable-libfaadbin --prefix=/usr/local --enable-swscaler --enable-libamr-wb

Install it as a package or with “make && make install” and settup alembik with “ffmpeg.version=51.40.4”

August 22, 2008

How to correctly make Javascript onclick links and keep in mind SEO and compatibility

Filed under: javascript, seo — Tags: — mufumbo @ 8:44 am

Today I have faced a common problem with web developers: How to correctly make Javascript onclick links keep in mind SEO and compatibility.

My solution was very simple, first of all, never use:

<a href="javascript:void(0)" onclick="some_function('someparameter')">Text</a>

This is the worst way of having javascript links. As discussed in this post this is a known issue of IE and why the use of the javascript pseudo-protocol for the value of HREF attributes is actively discouraged.

Suppose that you have an ajax box with tabs that allows you to refresh the content of the tabs with ajax. What would be the best way of assign onclick events to refresh the content with ajax?

What I did was:

  • When the page is loaded the first tab is loaded in the server side, without ajax. In this way search engines can crawl the contents.
  • The link on the tabs points to the HREF of the current page with a parameter that permits to change the pre-selected tab in the server side when the page is loaded. Ex: ?sec=onlineusers loads the page with the tab of onlineusers pre-selected and ?sec=lastusersers load the page with lastusers pre-selected.
  • The link on the tabs have the event onclick associated with a function and it returns false.

Code speaking:
<a href="?tabselection=onlineusers" onClick="changeTab('onlineusers');return false;">Online Users</a>
<a href="?tabselection=lastusers" onClick="changeTab('lastusers');return false;">Last registered users</a>

What are the advantages of this solution?

  • If the user have javascript disabled he can still have a fully functional website.
  • Search engines and mobile phones can navigate without problem.
  • It is compatible with all browsers.

For those who have already a website running, the simpliest way of having compatibility is to link the HREF to a page like “/noJavaScriptEnabled.html” and return false in the onclick event. Doing like this seems to be better than use the “javascript:void(0)” or point to the anchor “#”.

May 14, 2008

database replication tools

Filed under: performance, programming — Tags: — mufumbo @ 9:32 pm

Today I was searching about replication architecturesand found a very interesting presentation: Portable Scale-Out Benchmarks for MySQL that refers to GORDA – “Open Replication of Databases“. The following tools are the result of my search on that topic:

ESCADA is a opensource implementation of the GORDA replication server interface. It provides a full range of database replication options across a multiple database management systems, in a single inter-operable and evolutive package. Target application scenarios include:

  • Asynchronous master-slave replication, the no-frills industry standard approach.
  • Consistent multi-master/update everywhere replication for scalable and high performance shared-nothing clusters.
  • Zero data-loss inter-cluster replication over WAN for mission critical applications and disaster recovery.

SEQUOIA is a database cluster middleware that allows any Java application to transparently access a cluster of databases through JDBC. You do not have to modify client applications, application servers or database server software. You just have to ensure that all database accesses are performed through JDBC.

SEQUOIA allows to achieve scalability, high availability and failover for database tiers. It instantiates the concept of Redundant Array of Inexpensive Databases (RAIDb). The database is distributed and replicated among several nodes and SEQUOIA load balance the queries between these nodes. The server can be accessed from a generic JDBC driver, used by the clients. The client drivers forward the SQL requests to the SEQUOIA controller that balances them on a cluster of replicate d databases (reads are load balanced and writes are broadcasted).

Slony-I is a “master to multiple slaves” replication system supporting cascading (e.g. – a node can feed another node which feeds another node…) and failover.

The big picture for the development of Slony-I is that it is a master-slave replication system that includes all features and capabilities needed to replicate large databases to a reasonably limited number of slave systems.

May 10, 2008

simple script to merge commits from a bugzilla id

Filed under: maintainability, programming — Tags: , , , , — mufumbo @ 9:15 pm

Today i have made my first PERL script!

For me it is very painful when it arrives the time to merge, into another branch, all the commits that i have done in the “trunk”. I have searched a little and did not find anything that could magically solve all my problems. I know that it’s better to create a separated branch when there are lot’s of commits, but there are some cases that a super-simple functionality can explode into a big ball of mud.

Practically the script merge all the commits of a bugzilla id to another branch. If someone knows a standard way to do this; please tell me!

The script take three inputs:

  1. The starting revision ID to filter the search.
  2. The SVN address of the source.
  3. The search string to filter the results. Here you put your bugzilla bug id.

Commands that are executed when you launch the script:

  1. Go to the directory of the destination branch.
  2. To execute the script simply do:
  3. svn_search_merge.pl 0 https://svn.example.com/main/trunk/ “1: “
  4. Note that “1: ” is the bugzilla bug id. What happens next is:
  5. svn log -r 1:HEAD https://svn.example.com/main/trunk/
  6. With that command we get the log of all commits from the revision 1 to the HEAD. After it’s just matter of check if the string “1: ” is inside the log. Then we simply execute:
  7. svn merge -r (ACTUAL_REVISION-1):ACTUAL_REVISION https://svn.example.com/main/trunk/

Source code of the script:

#!/usr/bin/perl

# Simple script to merge commits from a source branch to the current destination directory.
# https://mufumbo.wordpress.com/2008/05/10/simple-script-to-merge-commits-from-a-bugzilla-id/
#
# Example:
# $ cd my-branch-destination/
# $ svn_search_merge.pl 3000 https://svn.example.com/main/trunk/ "bug 673"
# Where 3000 is the starting revision and "bug 673" is the string to match in the comments.
#
use strict;
use warnings;

my $prev_revision = shift;
my $svnHost = shift;
my $searchStr = shift;

print "Starting Revision: $prev_revision\n";
print "SVN addr: $svnHost\n";
print "Search pattern: $searchStr\n";

my $buffer;
$buffer = `svn log -r $prev_revision:HEAD $svnHost`;
my $shouldContinue = "y";
LOGS: foreach my $changelog_entry (split(/----+/m, $buffer)) {
    if($changelog_entry =~ m/($searchStr)/) {
            #my (undef, $info, undef, $comment) = split(/\n/, $changelog_entry);
            #next unless $info =~ m/^r/;

        print "\n--------------------------------------------------";
        print $changelog_entry;
        my $revisionId = substr($changelog_entry, 2, 5);
        $revisionId =~ s/^\s+//;
        $revisionId =~ s/\s+$//;

        if ($shouldContinue ne 'a') {
            PROMPT: while(1) {
                print "\nShould continue with merge of revision '$revisionId'? (Yes,Always,Skip,Exit): ";
                $shouldContinue = &lt;&gt;;
                chomp($shouldContinue);

                last PROMPT if $shouldContinue eq 'y';
                last PROMPT if $shouldContinue eq 'a';
                next LOGS if $shouldContinue eq 's';
                die("User requested to stop.") if $shouldContinue eq 'e';
            }
        }
        else {
            print "\nAuto merging '$revisionId'\n";
        }

        my $pRevisionId = $revisionId-1;
        my $mergeBuffer = `svn merge -r $pRevisionId:$revisionId $svnHost`;
        print $mergeBuffer;
    }
}
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