How can I calculate the average color of an image using JavaScript?

Get Average Color of Image using JavaScript

Determining the average color of an image is valuable for various applications, but it can be particularly challenging to accomplish this task using JavaScript.

JavaScript Implementation

Fortunately, with the advancements in HTML5, JavaScript developers can leverage the element to extract the average color of an image. The following script demonstrates how this technique can be applied:

<code class="javascript">function getAverageRGB(imgEl) {

    var blockSize = 5, // only visit every 5 pixels
        defaultRGB = {r:0,g:0,b:0}, // for non-supporting envs
        canvas = document.createElement('canvas'),
        context = canvas.getContext &amp;&amp; canvas.getContext('2d'),
        data, width, height,
        i = -4,
        length,
        rgb = {r:0,g:0,b:0},
        count = 0;

    if (!context) {
        return defaultRGB;
    }

    height = canvas.height = imgEl.naturalHeight || imgEl.offsetHeight || imgEl.height;
    width = canvas.width = imgEl.naturalWidth || imgEl.offsetWidth || imgEl.width;

    context.drawImage(imgEl, 0, 0);

    try {
        data = context.getImageData(0, 0, width, height);
    } catch(e) {
        /* security error, img on diff domain */
        return defaultRGB;
    }

    length = data.data.length;

    while ( (i += blockSize * 4) < length ) {
        ++count;
        rgb.r += data.data[i];
        rgb.g += data.data[i+1];
        rgb.b += data.data[i+2];
    }

    // ~~ used to floor values
    rgb.r = ~~(rgb.r/count);
    rgb.g = ~~(rgb.g/count);
    rgb.b = ~~(rgb.b/count);

    return rgb;

}</code>

Usage

To obtain the average color of an image, call the getAverageRGB function, passing the image element as an argument. The function returns an object with the average values for red, green, and blue components.

Limitations

This technique is restricted to images residing on the same domain and is only supported by browsers that feature the HTML5 canvas element. For older versions of Internet Explorer, consider incorporating the excanvas library to enable partial functionality.

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