A direct path connecting two locations

Question

A direct path connecting two locations

Using an HTML canvas, I have implemented a connect-the-dots application where users can draw lines between multiple points from 1 to N upon touchstart.

Currently, there is validation in place to ensure that users can only draw lines connecting dots from point 1 to point 2 (..n). However, the issue lies in the lack of validation for straight lines. I am seeking an algorithm to address this problem. Here is my initial thought process:

To determine if a line is straight between two points (x1,y1) and (x2,y2), calculate all coordinates using the slope formula y = mx + b.
During touchmove events, verify that the x,y coordinates correspond to one of the calculated points from the previous step before drawing the line.

I am open to suggestions for better approaches or alternative methods to achieve this desired functionality. Any input would be greatly appreciated!

javascript algorithm geometry

Answer 1

Answer №1

Edit: My initial interpretation of the question was off, it appears.

When it comes to validating the path: I believe it would be more practical to have a function that determines if a point is valid rather than computing all values in advance. Something along these lines could work:

function createPointValidator(x1, y1, x2, y2) {
    var slope = (y2 - y1) / (x2 - x1);
    return function (x, y) {
        return (y - y1) == slope * (x - x1);
    }
}

With this function, you can then use it like so for two points:

var isValid = createPointValidator(x1, y1, x2, y2);
var x = getX(), y = getY();// Assuming getX and getY fetch the user's new point.
if (isValid(x, y)) {
    // Draw
}

This method also offers some flexibility—you can adjust the function to allow for less precision to cater to those who may not draw perfectly straight lines but are close enough.

Precision: In line with my earlier comment, you can tweak the function to make it less strict. A suggested modification can be made like this:

We currently use the formula (y - y1) == slope * (x - x1), which is equivalent to

(slope * (x - x1)) - (y - y1) == 0

. By altering the zero to a positive number, we can consider points "near" the valid line as follows:

Math.abs((slope * (x - x1)) - (y - y1)) <= n

In this scenario, changing the value of n adjusts how closely a point must align with the line to be considered valid.

I am confident that this adjustment functions as intended, aiding in accommodating users who may draw slightly askew lines. However, it would be wise for someone to review my calculations.

Answer 2

Edit: My initial interpretation of the question was off, it appears.

When it comes to validating the path: I believe it would be more practical to have a function that determines if a point is valid rather than computing all values in advance. Something along these lines could work:

function createPointValidator(x1, y1, x2, y2) {
    var slope = (y2 - y1) / (x2 - x1);
    return function (x, y) {
        return (y - y1) == slope * (x - x1);
    }
}

With this function, you can then use it like so for two points:

var isValid = createPointValidator(x1, y1, x2, y2);
var x = getX(), y = getY();// Assuming getX and getY fetch the user's new point.
if (isValid(x, y)) {
    // Draw
}

This method also offers some flexibility—you can adjust the function to allow for less precision to cater to those who may not draw perfectly straight lines but are close enough.

Precision: In line with my earlier comment, you can tweak the function to make it less strict. A suggested modification can be made like this:

We currently use the formula (y - y1) == slope * (x - x1), which is equivalent to

(slope * (x - x1)) - (y - y1) == 0

. By altering the zero to a positive number, we can consider points "near" the valid line as follows:

Math.abs((slope * (x - x1)) - (y - y1)) <= n

In this scenario, changing the value of n adjusts how closely a point must align with the line to be considered valid.

I am confident that this adjustment functions as intended, aiding in accommodating users who may draw slightly askew lines. However, it would be wise for someone to review my calculations.

Answer 3

Answer №2

function createLineGraph(x1, y1, x2, y2, color) {

    var distance = Math.ceil(Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));
    var lineAngle = Math.atan2(y2-y1, x2-x1)*180/Math.PI;
    var xShift = distance - Math.abs(x2-x1);
    var yShift = Math.abs(y1-y2)/2;

    var newDiv = document.createElement('div');
    newDiv.style.backgroundColor = color;
    newDiv.style.position = 'absolute';
    newDiv.style.left = (x1 - xShift/2) + 'px';
    newDiv.style.top = (Math.min(y1,y2) + yShift) + 'px';
    newDiv.style.width = distance+'px';
    newDiv.style.height = '3px';
    newDiv.style.WebkitTransform = 'rotate('+lineAngle+'deg)';
    newDiv.style.MozTransform = 'rotate('+lineAngle+'deg)';

}

// Written by Gina Smith

Answer 4

function createLineGraph(x1, y1, x2, y2, color) {

    var distance = Math.ceil(Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));
    var lineAngle = Math.atan2(y2-y1, x2-x1)*180/Math.PI;
    var xShift = distance - Math.abs(x2-x1);
    var yShift = Math.abs(y1-y2)/2;

    var newDiv = document.createElement('div');
    newDiv.style.backgroundColor = color;
    newDiv.style.position = 'absolute';
    newDiv.style.left = (x1 - xShift/2) + 'px';
    newDiv.style.top = (Math.min(y1,y2) + yShift) + 'px';
    newDiv.style.width = distance+'px';
    newDiv.style.height = '3px';
    newDiv.style.WebkitTransform = 'rotate('+lineAngle+'deg)';
    newDiv.style.MozTransform = 'rotate('+lineAngle+'deg)';

}

// Written by Gina Smith

A direct path connecting two locations

Answer №1

Answer №2

Similar questions

Cutting an in-memory Base64 PNG using ONLY JavaScript on the client side without relying on canvas

Continue moving the division to the left

Changing Text to Number in JavaScript

'Redux' has not been declared ... along with ReactRedux and ReactDOM

An array of Promise<Employee> cannot be used as a parameter for an array of type Employee[]

A guide to implementing child level filtering of JSON data with Lodash

Troubleshooting: Issue with AngularJS Image onload directive - "this" reference not functioning properly?

The JavaScript function is not returning the correct string when implemented in an HTML

Embed Text inside an HTML Canvas

A versatile multi-select jQuery widget featuring the ability to choose options within a specific opt

Ways to dynamically fetch data by merging the response outcome with a dynamic parameter from the route in Vue.js

Feeling puzzled by the code snippet for vuejs-templates using webpack-simple?

Tips for bringing in pictures from outside directories in react

Why does a React error keep popping up when trying to set a background-image in my CSS?

The hidden DIV containing an ASP.NET CheckBox consistently yields a value of false

Utilizing Node.js to iterate through arrays grouped by categories

Unexpected format of _id is returned by Mongolian DeadBeef .toArray() method

Limiting the input of a user to a maximum of a five-digit integer with a maximum of two decimal points using Angular 2 and ngModel

Container struggling to contain overflowing grid content items

Having trouble using a setTimeout() callback to display a Bootstrap Vue modal programmatically