Gesture recognizer tool [Swift / iOS]

Didier Brun

Last update: Dec 18, 2022

Related tags

Gesture DBPathRecognizer

Overview

DBPathRecognizer

Demo

Installation

Simply add the file DBPathRecognizer.swift to your project

Basic usage

Start by creating a new DBPathRecognizer instance

// Create the path 8-directions path recognizer with a delta move sensibility of 16 pt
let recognizer = DBPathRecognizer(sliceCount: 8, deltaMove: 16.0)

Note that you can specify a max cost to recognize the gestures. It means that if a gesture has a score greater than costMax, it will be ignored.

let recognizer = DBPathRecognizer(sliceCount: 8, deltaMove: 16.0, costMax: 40)

Add some path model to the recognizer. Each path is defined by a direction-sequence and an associated data object (AnyObject).

recognizer.addModel(PathModel(directions: [7, 1], datas:"A"))
recognizer.addModel(PathModel(directions: [2,6,0,1,2,3,4,0,1,2,3,4], datas:"B"))
recognizer.addModel(PathModel(directions: [4,3,2,1,0], datas:"C"))
recognizer.addModel(PathModel(directions: [4,3,2,1,0,4,3,2,1,0], datas:"E"))

For example, here the model for the letter E :

Record a touch move sequence into the dedicated Path structure :

// Create the path
var path:Path = Path()

// Add a point (from touch location)
path.addPoint(PathPoint(x:100, y:100)) 

// You can also use the convenient method addPointFromRaw(var rawDatas:[Int])
path.addPointFromRaw(rawPoints)

Finally, tell the recognizer to find the best model :

var gesture:PathModel? = self.recognizer!.recognizePath(path)
        
if gesture != nil {
    // The best gesture is recognized
} else {
    // No gesture recognized (score is too low)
}

Custom filter

While adding a model, you can specify a custom filter. The filter callback method, if specified, will let you a last chance to modify / analyze the datas to determine a new score.

For example, the letter D & P have a similar draw-direction-path, however you can discriminate each one by detecting the position of the last point (up -> it's a P, down -> it's a D). The PathInfos struct transmited to the filter function will help you to determine the new score.

Your custom filter function should conform to this signature : ((score:Int, infos:PathInfos) -> newScore:Int) :

recognizer.addModel(PathModel(directions: [2,6,7,0,1,2,3,4], datas:"P", filter:{
            (cost:Int, infos:PathInfos) -> Int in
                // Determine new cost
                return cost
        }));

Free path

In this sample project I've used the Graffiti alphabet for the didactic aspect. However, PathRecognizer is a generic algorithm, you can add any free path to control an interface / game :

You might also like...

The right way to increment/decrement values with a simple gesture on iOS.

Comments

How to use custom filter

Hey Didier (or anyone reading)

I'm trying to use this great library for a game I'm making, but it seems the recognizer is quite inaccurate for me.

So I'm trying to put in some custom filters to better differentiate between the gestures, but I'm having a hard time understanding how to implement them.

Could you give me a sample code of how it would be used, to differentiate between the "B" and "P" as you mentioned in the readme?

Thank you!

opened by sixpercentninja 4
Numbers

Hey there,

Thanks for the amazing library. I have used it in one of my apps. – Do you have a list of the "combinations" for the numbers from 0 to 9?

Cheers, Cesare

opened by csr 2
Fix broken headings in Markdown files

GitHub changed the way Markdown headings are parsed, so this change fixes it.

See bryant1410/readmesfix for more information.

Tackles bryant1410/readmesfix#1

opened by bryant1410 1
How to set recognizer to specific view?

I have modified the constraint on renderView but it still registers touches in whole viewcontroller. How to set it to register touches only within specific view.

Thanks

opened by nbawe 0