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HTML5 canvas imagedata data Attribute

HTML5 track Tag Reference HTML5 canvas reference

Example

Create a 50*50 pixels imagedata object where every pixel is red:

Canvas

JavaScript:

var ctx=c.getContext("2d");
var imgData=ctx.createImageData(50,50);
for (i=0; i<imgData.width*imgData.height*4;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 »

Definition and Usage

The data attribute represents an array containing information of every pixel of an imagedata object.

For every pixel in the imagedata object there are 4 pieces of information, the rgba values:
1. The color red (0-255)
2. The color green (0-255)
3. The color blue (0-255)
4. The alpha strength (0-255) where 0 is transparent and 255 is fully visible

The information is held in an array, and since the array contains 4 pieces of information of every pixel, the array's size is 4 times the size of the rectangle: width*height*4.

You can change the information in the array, and put the new drawings back on the canvas, using the putImageData method.

JavaScript Syntax

JavaScript syntax:	imageData.data[0]=255;

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;

Browser Support

The data attribute is supported in all major browsers.

Attribute Values

Values	Description
array	Specifies rgba values of the imagedata object