This block uses SVG’s linearGradient element and D3 selections to create a linear gradient. Rather than having just two colors, this gradient uses a six-color rainbow spectrum.
Drag the circles to change the gradient’s orientation.
<html>
<head>
<style>
body {
margin: 0;
}
.position-circle {
stroke: #000;
stroke-width: 2px;
fill: #3a403d;
cursor: all-scroll;
}
</style>
</head>
<body>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
var width = window.innerWidth, height = window.innerHeight;
var colors = ["#ff0000", "#ffb400", "#fff800", "#02ff00", "#005fff", "#9a01ff"];
var position = [[.1, .1], [.9, .9]];
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
var defs = svg.append("defs");
var gradient = defs.append("linearGradient")
.attr("id", "linear-gradient");
colors.forEach(function(d, i){
gradient.append("stop")
.attr("offset", i / (colors.length - 1) * 100 + "%")
.attr("stop-color", colors[i]);
});
svg.append("rect")
.attr("class", "gradient-rectangle")
.attr("x", "0")
.attr("y", "0")
.attr("width", width)
.attr("height", height)
.style("fill", "url(#linear-gradient)");
changeOrientation(position);
position.forEach(function(d, i){
svg.append("circle")
.attr("class", "position-circle")
.attr("data-which", i)
.attr("cx", width * position[i][0])
.attr("cy", height * position[i][1])
.attr("r", "20")
.call(d3.drag(d)
.on("drag", function(){
var x = d3.event.x, y = d3.event.y;
d3.select(this).attr("cx", x);
d3.select(this).attr("cy", y);
if (d3.select(this).attr("data-which") == 0) {
position[0][0] = x / width;
position[0][1] = y / height;
} else {
position[1][0] = x / width;
position[1][1] = y / height;
}
changeOrientation(position);
}));
});
function changeOrientation(position){
gradient
.attr("x1", position[0][0] * 100 + "%")
.attr("y1", position[0][1] * 100 + "%")
.attr("x2", position[1][0] * 100 + "%")
.attr("y2", position[1][1] * 100 + "%");
}
</script>
</body>
</html>