html - Javascript colorbar - best way to create it - Stack Overflow

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I have a list of colours (created from values) and want to display them in a colourbar (as a legend what each colour means). Something like this.

One way would be a table with 1 row / n columns (n = 25-100), each column representing one colour. Is there any better way to do this?

I have a list of colours (created from values) and want to display them in a colourbar (as a legend what each colour means). Something like this.

One way would be a table with 1 row / n columns (n = 25-100), each column representing one colour. Is there any better way to do this?

• javascript
• html

Share Improve this question Follow edited May 23, 2017 at 11:48 CommunityBot 111 silver badge asked Aug 28, 2011 at 13:30 Horst WalterHorst Walter 14.1k3434 gold badges137137 silver badges239239 bronze badges 2

• Use an image, way better than tables. The position of the mouse pointer hover the image will determine wich color you're dealing with. – yoda Commented Aug 28, 2011 at 13:36
• I would need to create the image dynamically. I have the colour table, which is dynamically created. – Horst Walter Commented Aug 28, 2011 at 13:57

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1 Answer 1

Sorted by: Reset to default 8

Canvas is a powerful API for this: http://jsfiddle/pimvdb/eGjak/89/.

var cv  = document.getElementById('cv'),
    ctx = cv.getContext('2d');

for(var i = 0; i <= 255; i++) { // fill strokes
    ctx.beginPath();

    var color = 'rgb(100, ' + i + ', ' + i + ')';
    ctx.fillStyle = color;

    ctx.fillRect(i * 2, 0, 2, 50);
}

cv.onclick = function(e) {
    var x = e.offsetX, // mouse x
        y = e.offsetY, // mouse y
        p = ctx.getImageData(x, y, 1, 1),
        x = p.data; // pixel at mouse (x, y) - contains [r, g, b, a]

    alert('Color: rgb(' + x[0] + ', ' + x[1] + ', ' + x[2] + ')');
};

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