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HTML canvas createImageData() Method

❮ Canvas API


Create a 100*100 pixels ImageData object where every pixel is red, and put it onto the canvas:



const canvas = document.getElementById("myCanvas");
const ctx = canvas.getContext("2d");
const imgData = ctx.createImageData(100, 100);
for (let i = 0; i < imgData.data.length; i += 4)
  imgData.data[i+0] = 255;
  imgData.data[i+1] = 0;
  imgData.data[i+2] = 0;
  imgData.data[i+3] = 255;
ctx.putImageData(imgData, 10, 10);
Try it Yourself »


The createImageData() method creates a new, blank ImageData object. The new object's pixel values are transparent black by default.

For every pixel in an ImageData object there are four pieces of information, the RGBA values:

R - The color red (from 0-255)
G - The color green (from 0-255)
B - The color blue (from 0-255)
A - The alpha channel (from 0-255; 0 is transparent and 255 is fully visible)

So, transparent black indicates: (0, 0, 0, 0).

The color/alpha information is held in an array, and since the array contains 4 pieces of information for every pixel, the array's size is 4 times the size of the ImageData object: width*height*4. (An easier way to find the size of the array, is to use ImageDataObject.data.length)

The array containing the color/alpha information is stored in the data property of the ImageData object.

Tip: After you have manipulated the color/alpha information in the array, you can copy the image data back onto the canvas with the putImageData() method.


The syntax for making the first pixel in the ImageData object red:

imgData = ctx.createImageData(100, 100);

imgData.data[0] = 255;
imgData.data[1] = 0;
imgData.data[2] = 0;
imgData.data[3] = 255;

The syntax for making the second pixel in the ImageData object green:

imgData = ctx.createImageData(100, 100);

imgData.data[4] = 0;
imgData.data[5] = 255;
imgData.data[6] = 0;
imgData.data[7] = 255;

JavaScript Syntax

There are two versions of the createImageData() method:

1. This creates a new ImageData object with the specified dimensions (in pixels):

JavaScript syntax: var imgData = context.createImageData(width, height);

2. This creates a new ImageData object with the same dimensions as the object specified by anotherImageData (this does not copy the image data):

JavaScript syntax: var imgData = context.createImageData(imageData);

Parameter Values

Parameter Description
width The width of the new ImageData object, in pixels
height The height of the new ImageData object, in pixels
imageData anotherImageData object

Browser Support

The <canvas> element is an HTML5 standard (2014).

createImageData() is supported in all modern browsers:

Chrome Edge Firefox Safari Opera IE
Yes Yes Yes Yes Yes 9-11

❮ Canvas API