Web/API/CanvasRenderingContext2D/createImageData

The CanvasRenderingContext2D.createImageData() method of the Canvas 2D API creates a new, blank ImageData object with the specified dimensions. All of the pixels in the new object are transparent black.

Syntax

ImageData ctx.createImageData(width, height);
ImageData ctx.createImageData(imagedata);

Parameters

width

The width to give the new ImageData object. A negative value flips the rectangle around the vertical axis.

height

The height to give the new ImageData object. A negative value flips the rectangle around the horizontal axis.

imagedata

An existing ImageData object from which to copy the width and height. The image itself is not copied.

Return value

A new ImageData object with the specified width and height. The new object is filled with transparent black pixels.

Errors thrown

IndexSizeError

Thrown if either of the width or height arguments is zero.

Examples

Creating a blank ImageData object

This snippet creates a blank ImageData object using the createImageData() method.

HTML

<canvas id="canvas"></canvas>

JavaScript

The generated object is 100 pixels wide and 50 pixels tall, making 5,000 pixels in all. Each pixel within an ImageData object consists of four array values, so the object's data property has  a length of 4 × 5,000, or 20,000.

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');

const imageData = ctx.createImageData(100, 50);
console.log(imageData);
// ImageData { width: 100, height: 50, data: Uint8ClampedArray[20000] }

Filling a blank ImageData object

This example creates and fills a new ImageData object with purple pixels.

HTML

<canvas id="canvas"></canvas>

JavaScript

Since each pixel consists of four values, the for loop iterates by multiples of four. The array values associated with each pixel are R (red), G (green), B (blue), and A (alpha), in that order.

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
const imageData = ctx.createImageData(100, 100);

// Iterate through every pixel
for (let i = 0; i < imageData.data.length; i += 4) {
  // Modify pixel data
  imageData.data[i + 0] = 190;  // R value
  imageData.data[i + 1] = 0;    // G value
  imageData.data[i + 2] = 210;  // B value
  imageData.data[i + 3] = 255;  // A value
}

// Draw image data to the canvas
ctx.putImageData(imageData, 20, 20);

More examples

For more examples using createImageData() and the ImageData object, see Pixel manipulation with canvas and ImageData.data.

Specifications

Specification	Status	Comment
HTML Living StandardThe definition of 'CanvasRenderingContext2D.createImageData' in that specification.	Living Standard

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
createImageData	Chrome Full support Yes	Edge Full support 12	Firefox Full support 2	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support  

Full support

Gecko-specific notes

• Starting with (Firefox 5.0 / Thunderbird 5.0 / SeaMonkey 2.2):
  • createImageData() now correctly returns at least one pixel's worth of image data if a rectangle smaller than one pixel is specified.
  • Specifying non-finite values when calling createImageData() now properly throws a NOT_SUPPORTED_ERR exception.
  • createImageData() now handles negative arguments in accordance with the specification, by flipping the rectangle around the appropriate axis.

See also

• The interface defining this method: CanvasRenderingContext2D
• ImageData
• Pixel manipulation with canvas

CanvasRenderingContext2D.createImageData() by Mozilla Contributors is licensed under CC-BY-SA 2.5.