CSS filter: make color image with transparency white

Question

I have a colored png image with transparency. I would like to use css filter to make the whole image white but leave the transparency as it is. Is that possible in CSS?

Calliecalligraphy

You can try filter. It's currently only supported on webkit browsers, though. – Noemi

I know I can try filter, but what filter should I use? I would like to see the exact css code. – Calliecalligraphy

jsfiddle.net/Paulie_D/zAh8a/3 – Epicedium

Answer 1

You can use

filter: brightness(0) invert(1);

html {
  background: red;
}
p {
  float: left;
  max-width: 50%;
  text-align: center;
}
img {
  display: block;
  max-width: 100%;
}
.filter {
  -webkit-filter: brightness(0) invert(1);
  filter: brightness(0) invert(1);
}

<p>
  Original:
  <img src="https://i.stack.imgur.com/jO8jP.gif" />
</p>
<p>
  Filter:
  <img src="https://i.stack.imgur.com/jO8jP.gif" class="filter" />
</p>

First, brightness(0) makes all image black, except transparent parts, which remain transparent.

Then, invert(1) makes the black parts white.

Noemi

@DanielPerván It works on Firefox 34 with layout.css.filters.enabled set to true. – Noemi

@Gorg Theoretically it should be brightness(infinity). But in practice brightness(10000%) is high enough for the gray resulting from contrast(0) – Noemi

@Noemi 200 IQ developer – Metropolitan

Works with Firefox out of the box as of 60.0.1 (June 2018) – Socher

If brightness value is set larger than 1 (or 100%), like brightness(10000), anti-aliasing will be disabled in Firefox/IE/Edge. So brightness(0) invert(1) is the best solution. – Omentum

@MahmudulHaque You’re replying to a comment from 2014. In those years there have been 33 major versions of Firefox and IE has gone from the second most popular browser in the world to essentially dead. – Gambia

In my case, I was doing transitions on the filter which had some weird results. filter: brightness(3) saturation(0) worked better for me. – Gryphon

Answer 2

To my knowledge, there is sadly no CSS filter to colorise an element (perhaps with the use of some SVG filter magic, but I'm somewhat unfamiliar with that) and even if that wasn't the case, filters are basically only supported by webkit browsers.

With that said, you could still work around this and use a canvas to modify your image. Basically, you can draw an image element onto a canvas and then loop through the pixels, modifying the respective RGBA values to the colour you want.

However, canvases do come with some restrictions. Most importantly, you have to make sure that the image src comes from the same domain as the page. Otherwise the browser won't allow you to read or modify the pixel data of the canvas.

Here's a JSFiddle changing the colour of the JSFiddle logo.

//Base64 source, but any local source will work
var src = "data:image/png;base64,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";
var canvas = document.getElementById("theCanvas");
var ctx = canvas.getContext("2d");
var img = new Image;

//wait for the image to load
img.onload = function() {
    //Draw the original image so that you can fetch the colour data
    ctx.drawImage(img,0,0);
    var imgData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    
    /*
    imgData.data is a one-dimensional array which contains 
    the respective RGBA values for every pixel 
    in the selected region of the context 
    (note i+=4 in the loop)
    */
    
    for (var i = 0; i < imgData.data.length; i+=4) {
			imgData.data[i] = 255; //Red, 0-255
			imgData.data[i+1] = 255; //Green, 0-255
			imgData.data[i+2] = 255; //Blue, 0-255
			/* 
			imgData.data[i+3] contains the alpha value
			which we are going to ignore and leave
			alone with its original value
			*/
    }
    ctx.clearRect(0, 0, canvas.width, canvas.height); //clear the original image
    ctx.putImageData(imgData, 0, 0); //paint the new colorised image
}

//Load the image!
img.src = src;

body {
    background: green;
}

<canvas id="theCanvas"></canvas>

Malvie

Another important caveat is that running a line of javascript per image pixel is going to be prohibitively slow for many purposes – Cobol