how to get rgb values of image in fabric.js on mouse move. I used getFill() method of image object, but it is returning (0,0,0). Please help me
FabricJS does not have a native method for getting the pixel colors.
The workaround is to use native html5 canvas to fetch the pixel data:
Create your Fabric image objects. Be sure to specify crossOrigin
as 'anonymous' otherwise the canvas will be tainted with a security violation and then the pixel data will be unavailable.
Listen on Fabric's 'mouse:move' event. When it fires, get the current mouse position and use native canvas's context.getImageData
to fetch that pixel's color array.
Good luck with your project!
Here's annotatede code and a Demo:
// create a Fabric.Canvas
var canvas = new fabric.Canvas("canvas");
// get a reference to <p id=results></p>
// (used to report pixel color under mouse)
var results = document.getElementById('results');
// get references to the html canvas element & its context
var canvasElement = document.getElementById('canvas');
var ctx = canvasElement.getContext("2d");
// create a test Fabric.Image
addFabricImage('https://cdn.pixabay.com/photo/2019/12/12/05/34/afro-4689826_1280.jpg');
// listen for mouse:move events
canvas.on('mouse:move', function(e) {
// get the current mouse position
var mouse = canvas.getPointer(e.e);
var x = parseInt(mouse.x);
var y = parseInt(mouse.y);
// get the color array for the pixel under the mouse
var px = ctx.getImageData(x, y, 1, 1).data;
// report that pixel data
results.innerHTML = 'At [' + x + ' / ' + y + ']: Red/Green/Blue/Alpha = [' + px[0] + ' / ' + px[1] + ' / ' + px[2] + ' / ' + px[3] + ']';
});
// create a Fabric.Image at x,y using a specified imgSrc
function addFabricImage(imgSrc, x, y) {
// create a new javascript Image object using imgSrc
var img = new Image();
// be sure to set crossOrigin or else
// cross-domain imgSrc's will taint the canvas
// and then we can't get the pixel data
// IMPORTANT!: the source domain must be properly configured
// to allow crossOrigin='anonymous'
img.crossOrigin = 'anonymous';
// when the Image object is fully loaded,
// use it to create a new fabric.Image object
img.onload = function() {
var fabImg = new fabric.Image(this, {
left: 30,
top: 30
});
canvas.add(fabImg);
}
// use imgSrc as the image source
img.src = imgSrc;
}
body {
background-color: ivory;
}
canvas {
border: 1px solid red;
}
<script src="http://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.4.0/fabric.min.js"></script>
<p id="results">Move mouse over canvas</p>
<canvas id=canvas width=300 height=300></canvas>
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