## Thursday, November 29, 2012

### kartograph tutorial II: going interactive

In my last post I showed how to create a cool SVG map using Kartograph, to be opened and edited with an Inkscape-like program.
The elections were celebrated and CiU won again, but with less votes. I could either update the map or play with the same data. The fun with Kartograph is using the generated SVG to create interactive web pages using Kartograph.js, so this is what I'll do.
The web page will be able to:
• Generate the map not only for the first position, but also for the others
• Query every municipality to know which were the results there.
As usual, the code is available to download, and at the working web page too.

This second example has a continuation post: Kartograph tutorial III: Symbols

Changes to the SVG
In the other post, we used the SVG only to draw, but now we need to add data to it, so we can query it.
So change the municipalities layer at the file elections.json from:
   "municipalities":{
"src": "./mun_out.shp"
}


to:
   "municipalities":{
"src": "./mun_out.shp",
"attributes": {"winner": "Winner","ciu": "CiU","psc":"PSC-PSOE","erc":"ERC","pp":"PP","icv":"ICV-EUiA","cs":"C's","name":"Name"}
}

This will add the attributes set in the shapefile geometries to the SVG geometries.
To generate the SVG again, just type:
kartograph -o elections.svg elections.json

### Viewing the map in a web page

Even though is quite simple, I haven't found any really basic working example, so here it is:

<html>
<script src="jquery-1.8.3.min.js"></script>
<script src="raphael-min.js"></script>
<script src="kartograph.min.js"></script>
<script language="JavaScript">
var map = Kartograph.map('#map', 600, 0);

}
</script>

<div id="map"></div>
</body>
</html>

1. Include jquery, raphael and kartograph
2. The map must be created when the page loads, so the function loadMap() is called at the body tag , using the onLoad event.
3. Kartograph.map('#map', 600, 0) creates the map at the div tag with the id map. X size will be 600 px, and the aspect ratio will be respected, because the y size is 0. When an other y is set, strange things happen with the png borders.
4. loadMap draws the map from the file elections.svg. Then, executes a function. In this case, the function loads all the layers one by one, using the method addLayer(LayerNameInTheSVG)
5. padding: -30 removes the strange lines from the vectors in the borders by padding the image. Try without using it to understand what happens.

This renders the SVG without any styling or interaction. But is the basic way to start any Kartograph.js project.

### CSS Styling

There are two ways to add styles to the map. We will use both, to show them.
The first one, is to use a separate css file, as in the last post.
Adding the css file is quite tricky, because of the IExplorer compatibility. Now, the loadMap call would look like:

map.loadMap('elections.svg', function() {
map.addLayer('world');
   ...
});
})

So, the only thing that the loadMap method does, is calling the loadCss method, which will do all the stuff.

The css file is also different than the one used before. To style the layer world, the css section will be:
#map svg path.world {
stroke: #fff;
fill: #cccccf;
fill-opacity: .7;
}

Tip1: Be careful, Chrome doesn't reload your css even though you use ctrl-F5!
Tip2: Do not separate the CSS elements with comas (look at the example). With the python example, this didn't matter.
The other way is using the style method from the layer, as we will see in the final part of the post.

If we want the web page to show a tooltip with the result when the mouse is over a municipality, just add a tooltip to the desired layer (municipalities, in this case). The function in loadCSS will be now:
map.loadCSS('elections.css', function() {
...

\$.fn.qtip.defaults.style.classes = 'qtip-light';

map.getLayer('municipalities').tooltips(function(data) {

return [data.name, 'CiU: <b>' + data.ciu + '</b><br/>PSC-PSOE: <b>'+ data.psc + '</b><br/>ERC: <b>' + data.erc+'</b><br/>PP: <b>'+data.pp+'</b><br/>ICV-EUA: <b>'+data.icv+'</b><br/>C\'s: <b>'+data.cs+'</b>'];
});
});

A function is called as a parameter to the tooltips method of the layer municipalities. This function returns what we want to be shown in the tooltip. The data parameter has all the attributes in the SVG geometries. In this case, a list with the results is shown.
The other line in the code just sets the style of the tooltip. The official documentation has more information about the options.
Also, the tooltips styles and javascript must be included in the header, adding:

<script src="jquery.qtip.js"></script>

### Setting the colors in the map

Finally, the map will be colored. By default, depending on the winner party, but with a combo box to choose the position.
So first, a function is created to sort the results in every municipality, and set the style with a different color for every party:

function setColors(value){
map.getLayer('municipalities').style('fill', function(data) {

var positions = new Array();
positions[0] = parseInt(data.ciu);
positions[1] = parseInt(data.psc);
positions[2] = parseInt(data.erc);
positions[3] = parseInt(data.pp);
positions[4] = parseInt(data.icv);
positions[5] = parseInt(data.cs);

positions.sort(function(a,b) { return b-a; });

var bgColor;
if (positions[value-1] == parseInt(data.ciu)){
bgColor = "#99edff";
} else if (positions[value-1] == parseInt(data.psc)){
bgColor = "#ff9999";
} else if (positions[value-1] == parseInt(data.erc)){
bgColor = "#EDE61A";
} else if (positions[value-1] == parseInt(data.pp)){
bgColor = "#005aff";
} else if (positions[value-1] == parseInt(data.icv)){
bgColor = "#74ff74";
} else if (positions[value-1] == parseInt(data.cs)){
bgColor = "#ff7b00";
}

return bgColor;
});
}
First, we set the style to the layer with the method style. the first argument is the property to change, fill in this case. The second parameter is the value to set. In this case, it will depend of the function that chooses the position. Things to look at:
• value is the position to show (from 1 to 5)
• To sort the positions in the array in descending order, use the sort() method, with a function to order the elements as numbers. See why here.
• Then, check which party corresponds to the number of votes at the desired position, and set the color.
This function will be called at the beginning to show the first position by default:
setColors(1);

and a select element is created to select the position and change the colors when the option is changed:
<select onChange="changePos(this)">

<option value="1">1st position</option>

<option value="2">2nd position</option>
<option value="3">3rd position</option>
<option value="4">4th position</option>
<option value="5">5th position</option>
</select>

An auxiliar function is created to get the option value:
function changePos(sel){
var value = sel.options[sel.selectedIndex].value;
setColors(value);
}

That's all!
The best is to download the code or look at the working web.
Of course, some styling is still needed to do a deliverable web page, but the main idea is already done.

## Saturday, November 24, 2012

### Kartograph tutorial: Electoral map

Tomorrow I will be all the day at the polling station, since I've been chosen as a member.
The last two weeks I was playing with the amazing Kartograph software, so it was a good moment to experiment with electoral maps (the first time for me).

In this example, I will explain step by step how to create the map above. It's quite similar to this tutorial, but I want to continue in a new post, going interactive.
Kartograph creates vector SVG images, which you can edit later with Inkscape or Illustrator, so gives much more flexibility than systems generating PNG like files, much more difficult to modify.
As in all the posts, you can get all the files used in the example.
This example has two continuation posts:

### Getting the data

As usual, getting the data is not so easy. The Catalan government has a good open data web site, where I found:
• A file with a really descriptive name, bm50mv33sh1fc1r170.zip, with all the administrative boundaries (provinces, comarques, and municipalities).
• Lots of files with election results. I choose the 2010 elections, since they where to the Catalan parliament, like the ones tomorrow. As you can see on the map, the party CiU won with a very big majority, so the map is not as interesting as it could be.
I have used the municipalities to draw the map because the result is more diverse than using bigger zones. Actually, the real  constituency is the province, but CiU won everywhere, and a plain blue map is quite boring.
So I've had to join the two files to get one file with the geometries and the results. The process is quite long and dirty (why didn't they use an id? I had to join with the names), so I won't explain how to do it, but put the result at the data files. You can find this file here.

Then, to decorate the map, I used the following files
• World boundaries from Natural Earth (ne_10m_admin_0_countries.zip), to draw the coast line outside Catalonia
• From VMAP, the layers Trees, Crops, and DepthContours, to decorate the map outside the electoral  constituencies.
Since the layers are worldwide, so very big, I have used these ogr commands to clip:
ogr2ogr -clipsrc -3 37 4 44 Trees2.shp Trees.shp
and to simplify:
ogr2ogr -simplify 10 munis.shp bm50mv33sh1fpm1r170.shp
Doing so, the time to generate the map is divided by five or more.

### Installing Kartograph

Since we only need kartograph.py for this tutorial,  first, download it from the github page clicking at the zip icon.
In a linux system, uncompress and execute
python setup install
as a super user.
That's all, if you have the GDAL python bindings installed.

### Creating the map

To create a map with Kartograph, you will need a configuration file in JSON format, which will have three basic sections:

#### Projection

To set the projection, there used to be a web page named Visual map configurator, that doesn't work any more. But don't worry, you can use the Map Projections page. Just choose the projection that fits you more, change the parameters and click the gear icon:
A dialog will open, and the lines that are interesting in this case are, in the image example, like:
"proj": "sinusoidal",
"lon0": 20
This will be translated in our json file as:
"proj": {
"id": "sinusoidal",
"lon0": 20
}

#### Bounds:

The part of the world we want to represent is set here. It's quite well explained at the documentation, but it can be a bit confusing, and not all the options work with all the projections.
In our example, I have used:
  "bounds": {
"mode": "bbox",
"data": [-0, 40, 4, 43],
"crop": [-3, 37, 5, 44]
} 

• mode: How the bounds are expressed. BBOX is the basic option, but you can also set it defining the points you want to enter in the map, or even the features in a layer. If the layers are in different projections, other modes can be a little tricky.
• data: In our case, the bounding box. In other modes, the layer name, the points, or whatever.
• crop: Is an optional label. Our svg will be clipped at the bounds set at data, but all the data in the files will be processed. If the files include all the world, this takes a long time, and generates much bigger SVG outputs. With crop, only the features inside the BBOX will be included.

#### Layers:

As the name suggests, the layers to include.
   "municipalities":{
"src": "./mun_out.shp"
}

There are also two special layer, graticule and sea. The first draws the meridians ans parallels, while the second does nothing more than giving a feature to draw the background:
   "background": {"special": "sea"},
"graticule":{ "special": "graticule", "latitudes": 1, "longitudes": 1}


All the layers  will be drawn in the order indicated at the json file, so this must be well chosen to select which layer hides what.

#### Styling

This is the nice part. Without styling, the SVG can be used directly with Inkscape or Kartograph.js, but is possible to generate styled maps directly with kartograph.py.
You can give the style either in the json file or in a separate css file, which seems cleaner. The names given to the layer are the ones to be used in the css as the id. So to give a style to the municipalities layer, add
#municipalities {
fill: #FFF;
stroke: #882222;
stroke-width: 0.5px;
stroke-opacity: 0.4;
}

The general options are at the documentation again. CSS for SVG is a little different from the one used in traditional html.
Since we want to paint the municipalities in a different color depending of the party who won the elections, we will use filters, like this one:
#municipalities[Winner=CiU]{
fill: #99edff;
}


It would be nice to compare different fields i.e. CiU > PSOE, but this is not possible (at least, I haven't found how to do it), so I had to calculate the winner and put it in a field (called Winner, as you can see in the example)

#### Drawing

There are two options to draw the map. A command line program is installed with the setup, called kartograph.
To draw the styled map, just type
kartograph elections.json --style elections.css -o elections.svg
But you can also include all this in a python program, so could generate the data and then the map. In our case, the code would be
from kartograph import Kartograph
import sys
K = Kartograph()
K.generate(cfg, outfile='elections.svg', format='svg', stylesheet=css) 

Finally, I edited the svg file with Inkscape to put the titles and legend. Is just to show that the idea is generating a base svg and from there, draw the pretty final map.

### Configuration files

To draw the map in the example, I have used the following files:
elections.json
{
"proj": {
"id": "sinusoidal",
"lon0": 20
},
"layers": {
"background": {"special": "sea"},
"graticule":{ "special": "graticule", "latitudes": 1, "longitudes": 1, "styles": { "stroke-width": "0.3px" } },
"world":{
},
"trees":{
"src": "data/Trees2.shp",
"simplify": true
},
"crops":{
"src": "data/Crops2.shp",
"simplify": true
},
"depth": {
"src": "data/DepthContours2.shp",
"simplify": true
},
"municipalities":{
"src": "./mun_out.shp"
}
},
"bounds": {
"mode": "bbox",
"data": [-0, 40, 4, 43],
"crop": [-3, 37, 5, 44]
}
}

elections.css
#background {
fill: #e8f9fb;
stroke: none;
},
#world {
fill: #f5f3f2;
stroke: none;
},
#graticule {
stroke-width: 0.3px;
},
#municipalities {
fill: #FFF;
stroke: #882222;
stroke-width: 0.5px;
stroke-opacity: 0.4;
},
#municipalities-label {
font-family: Arial;
font-size: 13px;
},
#municipalities[Winner=CiU]{
fill: #99edff;
},
#municipalities[Winner=PSC-PSOE]{
fill: #ff9999;
},
#municipalities[Winner=ERC]{
fill: #EDE61A;
},
#depth {
stroke: #223366;
stroke-width: 0.5px;
stroke-opacity: 0.4;
},
#trees {
fill: #d2f8c0;
stroke: none;
},
#crops {
fill: #fcf8d8;
stroke: none;
}

## What's next

If I have time, I'll try my first Kartograph.js example. From the svg generated, is possible to create cool interactive maps.

## Saturday, November 10, 2012

### Fast tip: Changing the geotransform with GDAL python

Preparing the next post, I have found a file with a wrong geotransform, but not an easy tool to do it.
Coding it is as easy as opening the datasource with the update option and setting the new geotransform as follows:
ds = gdal.Open( fileIn, GA_Update )
ds.SetGeoTransform(geotransform)
ds = None

Where the geotransform must be a tuple like (-180.5, 1.0, 0.0, 90.5, 0.0, -1.0). Take a look to the documentation for more information.

I have created a small program to make it even easier, called changeGeotransform.py:
from osgeo import gdal
from osgeo.gdalconst import *
import sys

def changeGeotransform(fileIn, geotransform):
"""
Takes a dataset, and changes its original geotransform to an arbitrary geotransform
"""
ds = gdal.Open( fileIn, GA_Update )
#Exit if there is an error opening the dataset. GDAL will output the error message
if ds is None:
sys.exit()
ds.SetGeoTransform(geotransform)
ds = None

def helpText():
print "To change the file Geotransform, the command is python changeGeotransform  , where the new geotransform must be like '(left_value,delta_x,rotation_x,top_value,rotation_y,delta_y)'"
sys.exit()
def geotransformError(inputGeotransform):
print "Error reading the geotransform: " + inputGeotransform + " it must be like (-180.5, 1.0, 0.0, 90.5, 0.0, -1.0)"
sys.exit()

if __name__ == "__main__":
"""
Program mainline
"""
# Parse command line arguments.
argv = gdal.GeneralCmdLineProcessor( sys.argv )
if len(argv) != 3:
helpText()
fileIn = argv[1]
try:
geotransform = eval(argv[2])
except Exception, ex:
geotransformError(argv[2])
if type(geotransform) != type(()):
geotransformError(argv[2])
changeGeotransform(fileIn, geotransform)

To execute, just type:
python changeGeotransform file_name new_geotransform
where the new geotransform must be like:
(left_value,delta_x,rotation_x,top_value,rotation_y,delta_y)
The program basically tests if the inputs are correct and executes the code I have commented before.
Of course, only the files with drivers able to write the format can be changed. Type  gdalinfo --formats to know which drivers do you have installed.