Estrarre numero pagine da un PDF

Introduzione

Un utente di QGIS mi contatta e mi chiede come estrarre il numero di pagine di un PDF usando le espressioni di QGIS.

!!! Abstract "Funzione personalizzata" QGIS ha centinaia di espressioni, per quelle che mancano o per crearne di nuove è possibile aggiungere delle funzioni personalizzate usando PyQGIS

Array nel field calc

Introduzione

Il gruppo Array è stato introdotto in QGIS nella prima versione di QGIS 3.0 Girona nel lontano 2018, nella descrizione leggiamo:

!!! Abstract "GRUPPO ARRAY" Nuovo gruppo che contiene funzioni di espressione per la creazione e la manipolazione di array (noti anche come strutture di dati di elenco). L'ordine dei valori all'interno dell'array è importante, contrariamente alla struttura dei dati "mappa", dove l'ordine delle coppie chiave-valore è irrilevante e i valori sono identificati dalle rispettive chiavi.

Impostazioni di progetto influenzano alcune funzioni

Introduzione

Alcune funzioni di QGIS dipendono dalle impostazioni di progetto, questo significa che le stesse funzioni in progetti diversi possono restituire valori diversi. In questo post vedremo le principali funzioni di QGIS da attenzionare.

!!! Abstract "esempio" $area <> area(@geometry)

Come cercare un valore in funzione di un altro

Introduzione

Alcune volte nasce l'esigenza di cercare un valore in una tabella in funzione di un altro valore presente nella stessa tabella, un po' come fa la funzione cerca verticale di Excel, e utilizzarlo in un altro layer.

!!! Abstract "Funzione" La funzione che permette di fare questa magia è la funzione get_feature

HfcQGIS e la sezione Blog

Introduzione

Benvenuti nel nuovo blog di HfcQGIS!

HfcQGIS è la guida al calcolatore di campi di QGIS per la condivisione di conoscenze ed ora ha il suo Blog!!!.

HfcQGIS è un sito web nato nel 2018 da un'idea di Totò Fiandaca e realizzato con la comunità OpenDataSicilia, un particolare grazie va a Giovan Battista Vitrano che mantiene sempre aggiornato il tema del sito alle ultime novità. L'obiettivo iniziale del sito era quello di fornire una guida completa al calcolatore di campi, un potente strumento che consente di eseguire calcoli sui dati geografici.

Negli anni, HfcQGIS si è evoluto in una piattaforma di condivisione di contenuti per la comunità QGIS. Il sito offre ora una serie di risorse, tra cui:

QField is a community-driven open-source project. It is free to share, use and modify and it will stay like that. The very essence of a community is to help and support each other. And that’s where YOU come into play. To make it work we need your support!

For those who don’t know much about the concept of open source projects, a bit of background. Investing in open-source projects is a technical and ethical decision for OPENGIS.ch. Open source is a technological advantage, as we receive input from many developers worldwide who are motivated to work out the best possible software. It prevents our customers from vendor lock-in and allows complete ownership and control of the developed software. And finally, not only financially independent businesses and people should benefit from professional software but also those who might not have the financial means to pay for features, and licences.

You are not a developer, but you still like to use QField and support it? Good news. You don’t have to be a developer to use, contribute or recommend the app. There are plenty of things that need to be done to help QField to remain the powerful software it is right now and become even better. Here are a few suggestions on how you can give something back.

1. Review the app ★★★★★ in google’s play store or apple’s app store .
2. Let the world know about it! It doesn’t matter if you’re on Twitter, LinkedIn, Instagram or any other social media platform. Show and tell about where QField helped you. We appreciate every post and we promise to like, share and comment.
3. Write about your experience and please let us know. Be it in your blog or as a new success story. Insights into field projects are extremely valuable. It helps us to make the app even more efficient for your work, and it helps others to understand the range of applications for QField.
4. Register for a paid QFieldCloud account . QFieldCloud allows to synchronize and merge the data collected in QField. QFieldCloud is hosted by the makers of QField and by getting an account you help QField too.

Do you want to do something that is more hands-on and directly linked to the app? No problem.

1. Help with the documentation . You can document features, or improve the documentation in English. Read the how-to guide to get started.
2. And if you are multilingual you might consider translating the documentation or the app in your language .
3. Become a beta tester and be the first to report a bug! When something doesn’t work properly it might be a bug. The quicker we know about it, the faster it can be resolved.
4. You can ask and answer questions on gis.stackexchange and help others on the user discussions platform .
5. If you are a developer and you want to get involved in QField development, please refer to the individual documentation for QField , QFieldCloud and QFieldSync .

And now finally for those of you who have the financial means, you can either sponsor a feature or subscribe to one of the monthly sponsorships . By doing so you help get freshly baked QField versions straight to everyone’s devices.

Nothing in it for you? In that case, just drop by to say thank you or have a hot or cold beverage with us next time you meet OPENGIS.ch at a conference and you might make our day!
Want to know more about the idea of community-driven open-source projects and the QGIS project in particular? Check out Nyall Dawson’s blog post about how to effectively get things done in open source !

The international community of QGIS contributors got together in person from 18 to 22 August in parallel to OpenStreetMap State of The Map event and right before the FOSS4G . So there was a lot of open source geo power concentrated in the beautiful city of Florence in those days. It was my first participation and all I knew was that it’s supposed to be an unconference. This means, there is no strict schedule but space and opportunity for everyone to present their work or team up to discuss and hack on specific tasks to bring the QGIS project to the next level.

Introduction and first discussions

We were a group of six OPENGIS.ch members arriving mostly on Thursday, spending the day shopping and moving into our city apartment. In the evening we went to a Bisteccheria to eat the famous Fiorentina steak. It was big and delicious as was the food in general. Though, I am eating vegetarian since to compensate. On Friday we went to the Campus to meet the other contributors. After a warm welcome by the organizer, Rossella and our CEO and QGIS chair Marco Bernasocchi we did an introduction round where everyone mentioned their first QGIS version ever used. At this point, I became aware of the knowledge and experience I was sharing the room with. Besides this, I noticed that there was another company attending with several members, namely Tim Sutton’s Kartoza, which is also contributing a lot to QGIS. The first discussion was about QGIS funding model, vision, communication and on the new website in planning. This discussion then moved into some smaller groups including most of the long term contributors. I was looking around, physically and virtually, and tried to process all the new inputs and to better understand the whole QGIS world. Besides, I noticed my colleague Ivan having problems with compiling QGIS after upgrading to Ubuntu 22.04 which then motivated my other colleague Clemens to implement a docker container to do the compilation. Nevertheless, I postponed my Ubuntu upgrade. That evening we went out all together to have a beer or two and play some pool sessions and table football. Finally, the OPENGIS.ch crew navigated back home pairing a high-precision GNSS sensor with a mobile device running OpenStreetMap in QField . We arrived back home safely and super precise.

First tasks and coffee breaks

There was catering in the main hall covering breakfast, lunch and coffee breaks. It never took long after grabbing a cup of coffee to find yourself in a conversation with either fellow contributors or OpenStreetMap folks. I chatted with a mapper from Japan about mobile apps, an engineer from Colombia about travelling and a freelancer from the Netherlands about GDAL, to name 3 coffees out of many.

QGIS plugins website

After some coffee, Matthias Kuhn, our CTO and high-ranking QGIS contributor, asked me whether I could improve some ugly parts of QGIS plugins website . So I had my first task which I started working on immediately. The task was to make the site more useful on mobile devices which would be achieved by collapsing some unimportant information and even removing other parts. I noticed some quirks in the development workflow, so I also added some pre-commit hooks to the dev setup. Dimas Ciputra from Kartoza helped me finalize the improvements and merge them into master branch on github .

QGIS website downloads section

Regis Haubourg asked to help simplify the QGIS Downloads for Windows section on the main QGIS website. We played around in the browser dev tools until we thought the section looked about right. I then checked out the github repo and started implementing the changes. I need to say the tech stack is not quite easy to develop with currently, but there is a complete rework in planning. Anyway, following the pull request on github a lively discussion started which is ongoing by the time of writing. And this is a good thing and shows how much thought goes into this project.

Presentations

There were many interesting and sometimes spontaneous presentations which always involved lively discussions. Amy Burness from Kartoza presented new styling capabilities for QGIS, Tobias Schmetzer from the Bavarian Center for Applied Energy Research presented the geo data processing and pointed out issues he encountered using QGIS on this and Etienne Trimaille from 3liz talked about qgis-plugins-ci , just to name a few.

Amazing community

On Saturday evening a bus showed up at the campus and took us on a trip up to the hills. After quite a long ride we arrived at a restaurant high up with mind-blowing view of the city. I forgot how many rounds of Tuscan food were served, but it was delicious throughout. An amazing evening with fruitful conversations and many laughs.

The weather was nice and hot, the beers cold, the Tuscan food delicious and the contributors were not only popular Github avatars but really nice people. Thank you QGIS.

Starting with QField 2.2, users can fully rely on animation capabilities that have made their way into QGIS during its last development cycle. This can be a powerful mean to highlight key elements on a map that require special user attention.

The example below demonstrates a scenario where animated raster markers are used to highlight active fires within the visible map extent. Notice how the subtle fire animation helps draw viewers’ eyes to those important markers.

Animated raster markers is a new symbol layer type in QGIS 3.26 that was developed by Nyall Dawson . Supported image formats include GIF, WEBP, and APNG.

The second example below showcases more advanced animated symbology which relies on expressions to animate several symbol properties such as marker size, border width, and color opacity. While more complex than simply adding a GIF marker, the results achieved with data-defined properties animation can be very appealing and integrate perfectly with any type of project.

https://player.vimeo.com/video/732691644

You’ll quickly notice how smooth the animation runs. That is thanks to OPENGIS.ch’s own ninjas having spent time improving the map canvas element’s handling of layers constantly refreshing. This includes automatic skipping of frames on older devices so the app remains responsive.

Oh, we couldn’t help ourselves but take the opportunity to demonstrate how nice the QField feature form layout is these days in the video above ? To know more about other new features in QField 2.2, go and read the release page .

Happy field mapping to all!

The lovely animal markers used in the zoo example above were made by Serbian artist Arsenije Vujovic .