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Using C++11 Lambdas As Qt Slots

I have an old codebase I started writing using the Qt 3.x framework—a little while before Qt4 was released. It’s still alive! I still work on it, keeping up-to-date with Qt and C++ as much as possible, and I still ship the product. Over the years I have moved the codebase along through Qt4 to […]

     

Clustering Markers On Leaflet Maps

So you’re creating an interactive map using Leaflet and have diligently added your 8107 markers to the map. Uh-oh. Definitely slow and pretty much doesn’t provide a user experience. What do we do now? There’s a great plugin for Leaflet called Leaflet.markercluster by Dave Leaver which will save us. This plugin clusters the markers and […]

     

QSignalMapper Example Revisited

Several years ago I wrote a short piece on QSignalMapper to give a quick example of how it can be used. Since then, Qt5 has been released and C++11 is now A Thing. One of the cool things introduced in Qt5 is a new overload for the QObject::connect() method:

This means we can use […]

     

Qt Patches: QGraphicsView & QImageWriter

QGraphicsView Two and a half years ago I wrote about a UX bug with QGraphicsView where it would reset the selection in the view if you tried to extend it with a rubberband selection. I have been using those changes in the version of Qt I maintain for my software. I finally took the time […]

     

Creating An Interactive Map With Leaflet and OpenStreetMap

I’ve known for a while that the interactive map of the world showing some of my bloodstain pattern analysis software customers was kind of slow. I also knew that I was using a very outdated version of Google’s API for displaying the data. Yesterday I decided to take a look at it to see what […]

     

Converting Between cv::Mat and QImage or QPixmap

In a previous article, I outlined how to compile OpenCV for Mac OS X and to build and run a small example. In that post I used OpenCV‘s High-Level GUI (highgui) module to display a simple interface using the Qt framework. This is great if you’re writing a one-off program or are just experimenting with […]

     

Compiling OpenCV On Mac OS X 10.6

A couple of years ago I needed to do some basic image processing and found OpenCV. OpenCV is a BSD-licensed library for digital image processing which implements several hundred computer vision algorithms. Unfortunately compiling it on the Mac was not straightforward—requiring Fink or MacPorts—and the one existing Mac framework was out of date and no […]