Image color picker in javascript that work without canvas in every browser

If you want to create color picker from image in JavaScript you probably will use canvas, but what if you need it work in IE8 as I needed. You can use some server side help to fetch pixels data from the server. I use php for that and GD library. The code is below.

cross-browser color picker

Server side code that return json pixel data

<?php

function rgb($color) {
    $result[] = ($color >> 16) & 0xFF;
    $result[] = ($color >> 8) & 0xFF;
    $result[] = $color & 0xFF;
    return $result;
}

function imagecreatefrom($filename) {
    $path = pathinfo($filename);
    switch($path['extension']) {
        case 'png':
            return imagecreatefrompng($filename);
        case 'jpg':
            return imagecreatefromjpeg($filename);
        case 'gif':
            return imagecreatefromgif($filename);
        default:
            return null;
    }
}

function getImageData($filename) {
    list($width, $height) = getimagesize($filename);
    $image = imagecreatefrom($filename);
    $image_data = array();
    for ($y = 0; $y < $height; ++$y) {
        $row = array();
        for ($x = 0; $x < $width; ++$x) {
            $row[] = rgb(imagecolorat($image, $x, $y));
        }
        $image_data[] = $row;
    }
    return $image_data;
}

if (isset($_GET['filename'])) {
    $filename = $_GET['filename'];
    if (file_exists($filename)) {
        $result = array(
            'error' => null,
            'result' => getImageData($filename)
        );
    } else {
        $result = array(
            'error' => "The file '$filename' don't exist",
            'result' => null
        );
    }
} else {
    $result = array(
        'error' => "You need to put filename",
        'result' => null
    );
}
header('Content-Type: application/json');
echo json_encode($result);

?>

Then you can fetch the data using ajax and add get invidial pixels on mousemove

    var img = $('img');
    $.getJSON('image_data.php', {filename: img.attr('src')}, function(data) {
        if (data.error) {
            alert(data.error);
        } else {
            $('.eyedropper').click(function() {
                picker = true;
                return false;
            });
            img.mousemove(function(e) {
                if (picker) {
                    var x = Math.round(e.pageX - offset.left);
                    var y = Math.round(e.pageY - offset.top);
                    if (x >= 0) {
                        $('.color').css('background-color',
                                        'rgb('+data.result[y][x].join(',')+')');
                    }
                }
            }).click(function(e) {
                picker = false;
            });
        }
    });

Now all you need to have is element with class eyedropper like a link in your html:


<a href="#" class="eyedropper">pick the color</a>

Published by

jcubic

I'm graphic designer and programmer from Poland.

3 thoughts on “Image color picker in javascript that work without canvas in every browser”

  1. Here my code

    [img id=”img” name=”filename” class=”eyedropper” src=”Penguins.jpg”}

    [div style=”width:100px;height:100px;border:1px #000 solid” class=”color” ][/div]

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