black and white text based on background image with css

Question

I am trying to achieve this effect of a black and white text on a bi-colored header which is always white on a side, and with a background image on the other side (of different colors).

this is the css used for this example, which works only because the image has a solid black background:

.text {
  position: relative;
  color: rgb(255, 255, 255);
  mix-blend-mode: difference;
  text-transform: uppercase;
  font-size: 60px;
}

this doesn't work if the background image doesn't have a solid black background:

in this case i get what i'm supposed to get, but what i want is to get a white text on the left and a black text on the right, as in the first example.

i've been trying css filter, mix-blend-modess, clip-paths, i've seen this https://aerolab.github.io/midnight.js/ (it doesn't suit my case) but i always end up with the wrong result. do your know a way of making a black/white colored text that is aware of a white background and makes the text black and whatever is not a solid white background, switch the color to white?

i hope my explanation was clear, any solutions or even clues are very welcome, even if it needs javascript. thank you!

this is a codepen with the examples: https://codepen.io/vlrprbttst/pen/jOPMzvd?editors=1100

thanks so much!

Answer 1

I tried something that seems to work.

I added one black layer (rgba with alpha 0.8) on top of your image with the same width, then filtered the brightness of your image with filter: brightness(3);

I am not sure whether it renders the image the way you want.

body {
	 margin: 0;
	 padding: 0;
}
header.second {
	 height: 609px;
	 background-image: url("https://thedefiant.net/wp-content/uploads/2019/10/22520100_1600239116694701_7307954682775296386_o.jpg");
	 filter: brightness(3);
	 background-position: center left;
	 background-repeat: no-repeat;
	 background-size: 600px 100%;
	 background-color: #fff;
	 border: 1px solid red;
	 display: flex;
	 align-items: center;
	 padding-left: 390px;
	 position: relative;
}
header.second .mask {
	 position: absolute;
	 left: 0;
	 top: 0;
	 background-color: rgba(0, 0, 0, 0.8);
	 width: 600px;
	 height: 100%;
}
header.second .text {
	 position: relative;
	 color: white;
	 mix-blend-mode: difference;
	 text-transform: uppercase;
	 font-size: 60px;
}
 

<header class="second">
  <div class="mask"></div>
  <div>
    <div class="text" data-title="Sono caduto, ho pianto.">
      Sono caduto, ho pianto.
    </div>
  
    <div class="text" data-title="poi sono risalito">
      poi sono risalito
    </div>
  
    <div class="text" data-title="sei mejo te!">
      sei mejo te! sei mejo te!
    </div>
  </div>
</header>