How to Calculate the Average Color of an Image Using JavaScript?

Get Average Color of Image in JavaScript

Problem:

Is it possible to determine the average color of an image using JavaScript?

Solution:

While it may not be immediately apparent, you can indeed calculate the average color of an image using JavaScript. The key to achieving this is through the utilization of the HTML5 element.

To extract the average color from an image, follow these steps:

1. Create a element and retrieve its 2D context.
2. Draw the image on the canvas using the drawImage() method.
3. Use getImageData() to retrieve the pixel data from the canvas.
4. Iterate through each pixel and accumulate the red, green, and blue values in separate variables.
5. Divide the accumulated values by the total number of pixels to obtain the average color.

Here is an example function that implements the described algorithm:

<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 && 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>

This function takes an image element as input and returns an object containing the average red, green, and blue values as integers.

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