Generate and host your own raster tiles customized with Mapbox Studio

If you have never saw maps hosted in Mapbox platform you would probably agree on the quality of its designs. The business of Mapbox is to host and server geospatial data. For this reason, all the great tools Mapbox facilitates are oriented to help their users to prepare and work with their data.

One of the provided tools is Mapbox Studio. Mapbox Studio (MbS) is a desktop application that allows to create CartoCSS themes that are later used to generate raster tiles. Briefly explained, what MbS does is to download OpenStreetMap data in vector format and render it on the fly applying the specified CartoCSS style.

The result of working with MbS is not a set of tiles but a style, that is, a set of rules that express which colour must be used to render roads, at which levels must labels appears and with which size, which colour must be used for ground, etc. This style can be later uploaded to Mapbox platform so that raster tiles were generated on the cloud and we can consume the tiles paying for the service. (Hope one day I can contract their services, they deserve by their great job).

The question we can make us is: how we can generate the raster tiles locally from a given MbS style?

Well, this article is about that. Continue reading.

Working with Mapbox Studio and create your custom style

Let’s start from the beginning so download Mapbox Studio application and install on your system. Once installed execute it and you will be asked to be connected to the Mapbox platform.

There are two main reasons why Mapbox requires you to register as a user. First, the power of the platform is on the cloud and the goal is you upload all your data to the servers. That includes the styles you create.

Second, MbS retrieves data in vector format from Mapbox servers. When you register as a user you get an API token that identifies your requests. Each time MbS makes a request to extract data it has your token that identifies you as user. This way Mapbox can control if any user is making a bad usage of their platform.
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Once logged in you will be allowed to create new map styles. The easiest way is to start using one of the starter styles created by the great Mapbox designers:

Screen Shot 2015-07-25 at 23.47.38

Here we have chose the Mapbox Outdoors style. In the image you can see the style code (CartoCSS which is inspered by CSS) and the resultant tiles obtaining from painting the vector information with the given style rules:

CartoCSS is a Mapnik stylesheet pre-processor developed by MapBox and inspired by Cascadenik. It is like a CSS language specially developed to style maps.

Screen Shot 2015-07-25 at 23.54.20

Store the style with a new name somewhere on your computer, for example, customstyle. If you look at your disk you will see a customstyle.tm2 folder has been created containing a bunch of files that defines the style rules (take a look they are not dangerous).

Finally, modify some properties, for example @land or @crop colors and save to see the result:

Screen Shot 2015-07-25 at 23.54.47

Great !!! You just have created your first custom style.

Generating raster tiles from MbS style

Looking for a solution I discovered the tessera and tl tools. Tessera is a node based command line application. It is based in some modules from mapbox (concretely tilelive) plus others implemented by the author (Seth Fitzsimmons). The result is we can execute tessera passing a MbS defined style, open a browser pointing to a local address and see a map with the raster tiles generated with our MbS style.

Similarly, tl is a node based command line tool we can execute, passing a set of options, to generate a MBTiles file or a pyramid of tiles following the well known z/x/y.png format.

I know about both tools at the article Converting Mapbox Studio Vector Tiles to Rasters from Azavea Labs.

How to install the tools?

NOTE: You need to have NodeJS installed in your system, along with the npm package manager command line tools.

I don’t like to install global node packages (or at least more than the necessary) so I’m going to install the previous tools in a custom folder:

Inside the directory execute next sentence, which install the tessera and tl packages among others:

You will see a hidden directory named .npm_modules has been created which contains some subdirectories with the same name as the previous packages.

Running tessera

Let’s try to run tessera for the first time. Because it is installed as a local node module execute:

Tessera requires you pass an URI so it can server its content. It accepts URIs from Mapbox hosted file, Mapnik, Tilemill, Mapbox Studio, …

Repeat again indicating the path to our previously created style indicating the protocol tmstyle://.

First seems tessera is working at port 8080 but later we get an error about MAPBOX_ACCESS_TOKEN. If you remember from the first section, Mapbox requires all the requests be signed with the user token. So, you need to get the access token from your account and set it as environment variable before execute tessera:

We are close to make it work. The problem now is our MbS style is using a font we have not installed in our system. One easy, but brute force, solution is to install all Google Web Fonts on your system. For this purpose you can use the Web Font Load installation script. In my case I have installed them in the user’s fonts folder ~/Library/Fonts.

Once fonts were installed try executing tessera again:

That’ s a bit strange, we have just installed the fonts but they are not found. What is happening? Well, tessera uses mapnik to create the raster tiles and it looks for fonts in the folders specified by the environment variable MAPNIK_FONT_PATH, so let define the variable:

and execute the script again:

OMG !!! This seems a never ending story. Now we need to install the Arial Unicode font. Look for it, install in your system and execute tessera again:

Great !!! It seems tessera is working fine. Let’s go to open our browser pointing to http://localhost:8080 and see the result:

A map implemented using Leaflet web mapping library is shown, rendering raster tiles that are created in the fly. Look at the console to see the tessera output information:

We can see how tiles at current zoom, the zoom level 8, has been generated.

At this point we have tessera working but what about generate a local pyramid of tiles for a given zoom levels and a given bounding box?

Generating a custom pyramid of tiles with tl command line tool

Before continue we need to know which bounding box we want to generate, the whole World? or only a piece. In my case I want three zoom levels (7, 8 and 9) wrapping Catalonia.

There are some online tools you can use to get the bbox of a region, but one I like it the Bounding Box Tool from Klokan Technologies.

The tl tool can run three main commands but are only interested in the copy one, which copies data between two providers. In our case the MbS style is one provider and the file system is the other. Run the tl command to see the available options:

So let’s go to execute the command to copy data from our MbS style to the local tiles folder. We want to generate tiles from zoom level 7 to 9 and indicating a bounding box wrapping Catalonia.

Remember the -b options must be indicated as [minLon minLat maxLon maxLat].

Ough !!! That hurts, a segmentation fault. After looking for a while I realised it seems a bug. To solve it go to tl/node_modules/abaculus/node_modules and remove the mapnik folder dependency. It is redundant because there is one installed in parent folder.

Execute the command again and see the output:

The tl tool has created a local tiles directory and generated all the raster tiles for the given zoom levels and bounding box. The output shows in addition the time required to generate each tile.

That’s all. Now we only need to host the tiles at our own servers !!!

 

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From SublimeText to Atom text editor

I have used regularly SublimeText (v2) for the past year. I used it mainly to programming in JavaScript, HTML, CSS and to write in Markdown syntax (I’m sorry but to programming in Java NetBeans continues to be my preferred IDE).

In that time I used a bunch of SublimeText plugins to help me in my day to day:

  • Markdown Editing. Provides a decent Markdown color scheme (light and dark) with more robust syntax highlighting and useful Markdown editing features.
  • Markdown Preview. Preview and build your markdown files quickly in your web browser.
  • Markdown TOC. Search headings in document and insert/update TOC(Table Of Contents) to it.
  • DocBlockr. Simplifies writing DocBlock comments in many languages, one of them JavaScript.

To the previous list we need to attach the spellchecker, autocomplete, minimap, highlight selected text and some more great core features of SublimeText.

A week ago I start using Atom text editor (v1.0.2) so I looked for a list of similar plugins that helps me in my day to day in the same way as previous plugins on SublimeText:

  • Minimap, A preview of the full source code. Replicates the minimap core feature of SublimeText.
  • Highlight Selected: Double click on a word to highlight it throughout the open file. Replicated the highlight selected text core feature of SublimeText.
  • Markdown TOC: Generate/updates TOC (table of contents) of headlines from parsed markdown file.
  • DocBlockr: Designed to make writing documentation faster and easier.

We need to note by default atom.io has support for markdown syntax, autocompletion and spellchecker too.

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The mystery of no flash session variables in Express + Passport auth

Someday I started an application using NodeJS with ExpressJS framework and decided to use passport for authenticate the users. As many other times I wanted to use flash messages so, when user authentication fails, the application shows a message informing about bad credentials. Nothing new on the horizon until…. OMG !!! I can’t see the flash messages !!!

Disclaimer: This is a really stupid history with me as starring.

I like to learn from my errors and because of this I decide to write this post both as a punishment and to ensure I don’t forget it again.

The crime scene

I was working implementing a sign up process, where the user writes its credentials and system creates as a new user or returns an error message like “Sorry, but a username with that email exists” or similar.

Before introduce any code, the flow is as follows:

  • User access the /signup page via GET method.
  • Data is sent to /signup resource via POST method, which is responsible to:
    • Check if data is fine, create a new user and redirected to the /profile page.
    • If a user with the same email exists we redirect again to the /signup page (that is, using the GET method) with a flash message related to bad credentials.

Note: A flash message is a variable stored within a session that is only available once, for the next request. That is if we put a flash variable and renders a page, the flash variable is available but if we render the same (or other) page again the flash variable is not present (it is destroyed).

The approximate code for the previous flow is as follows. First, the next code is responsible to receive the post data and register the user:

The authentication is delegated to passport, which is implemented as:

As you can see, if the user exists we add a flash session message with:  req.flash('signupMessage', 'That email is already taken.'));

On the other side, we show the signup form each time user access to the /signup resource via GET method:

Here we are rendering the signup template passing a message with the value of the signupMessage message. This way if user is redirected to the form, because the signup process fails (that is, the access to the /signup resource via POST), then the error message is shown.

The mystery

The problem was I never get a value for the flash variable. What? Yes, I never get a value for the flash variable.

There was no error, I can’t set and (in the same method) get the flash value, but I can’t get value any value among different resources, that is, between GET /signup and POST /signup.

The solution

After too much time (too many to be recognised publicly) I found my problem was with the way I initialise my sessions. What ? Yes, I said it was my fault due the way I initialise the session. This I did it:

Can you see the problem? Here goes a clue, think I was working with a dev profile, that is, in my local machine accessing resources without HTTPS.

Yes, the problem was to set the  secure: true  and does not access resources via HTTPS.

The express-session middleware documentation says (yes, go to the cookie section):

Please note that secure: true is a recommended option. However, it requires an https-enabled website, i.e., HTTPS is necessary for secure cookies. If secure is set, and you access your site over HTTP, the cookie will not be set. If you have your node.js behind a proxy and are using secure: true, you need to set “trust proxy” in express.

Conclusions

I’m happy to found the problem. Right now, while I write this lines, I’m at a tattoo shop waiting to be tattooed with the previous beautiful sentence.

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Reading/writing compressed and not compressed files in Java

Main reason for this post is trying don’t repeat yourself (DRY) because, often, I fall in the recursive need to read and write compressed and not compressed files (mainly JSON and CSV).

Let’s to see first how to read text files. Note I’m working with (relatively small) text files so:

  1. The read methods returns an String with the whole content.
  2. I’m using BufferedReader to read line by line.

Note: there are more than one way to do things. In the entry Best way to read a text file, where you can find many different ways to read a text file depending on your JDK version and the size of the file.

Similarly to write a String to a file:

To read/write compressed files, that is with binary data, we need to work with streams and buffers. So to read a GZIP compressed file and obtain a String:

and similarly to write a String to a GZip compressed file:

References

Next you can find a couple of great links with Java code for various JDK versions:

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