2019-03-07-15:32于公司：
最近在搞TMS，碰到了颜色选择器，想了解下用原生JS如何实现。记录下：
效果如下：
image.png
先上源码稍后来分析，到时候搞成react版本
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
body {
background: #535353;
padding: 0;
margin: 0;
}
canvas {
cursor: crosshair;
}
#cur {
width: 3px;
height: 3px;
outline: 2px solid #535353;
margin-left: -1px;
margin-top: -1px;
position: absolute;
}
.wrapper {
position: relative;
}
#color_show {
width: 50px;
height: 50px;
background: #f00;
}
.panel {
width: 200px;
height: 200px;
position: fixed;
top: 20px;
right: 20px;
background-color: #fff;
padding: 10px;
text-align: center;
line-height: 2em;
}
</style>
</head>
<body>
<div class="wrapper">
<canvas id="canvas" width="600" height="600"></canvas>
<em id="cur"></em>
<div class="panel">
<div id="color_show"></div>
<label>
rgb <input type="text" class="color_input" value="" id="rgb_value">
</label><br>
<label>
hex <input type="text" class="color_input" value="" id="hex_value">
</label>
</div>
</div>
<script>
(function() {
var width = 256;
var can = document.getElementById('canvas');
var ctx = can.getContext('2d');
var curColor = 'rgba(255,0,0,1)';
var cur = document.getElementById('cur');
var rgbValue = document.getElementById('rgb_value');
var hexValue = document.getElementById('hex_value');
var colorShow = document.getElementById('color_show');
var aColorInput = document.getElementsByClassName('color_input');
function colorBar() {
var gradientBar = ctx.createLinearGradient(0, 0, 0, width);
gradientBar.addColorStop(0, '#f00');
gradientBar.addColorStop(1 / 6, '#f0f');
gradientBar.addColorStop(2 / 6, '#00f');
gradientBar.addColorStop(3 / 6, '#0ff');
gradientBar.addColorStop(4 / 6, '#0f0');
gradientBar.addColorStop(5 / 6, '#ff0');
gradientBar.addColorStop(1, '#f00');
ctx.fillStyle = gradientBar;
ctx.fillRect(0, 0, 20, width);
}
function rgb2hex(rgb) {
var aRgb = rgb instanceof Array ? rgb : (rgb.split(',') || [0, 0, 0]);
var temp;
return [
(temp = Number(aRgb[0]).toString(16)).length == 1 ? ('0' + temp) : temp,
(temp = Number(aRgb[1]).toString(16)).length == 1 ? ('0' + temp) : temp,
(temp = Number(aRgb[2]).toString(16)).length == 1 ? ('0' + temp) : temp,
].join('');
}
function hex2rgb(hex) {
if(hex.length == 3) {
hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2];
}
return [
parseInt(hex[0] + hex[1], 16),
parseInt(hex[2] + hex[3], 16),
parseInt(hex[4] + hex[5], 16),
].join();
}
function putCurDom(color) {
if(/([0-9a-f]{3}|[0-9a-f]{6})/i.test(color)) {
// hex
color = hex2rgb(color);
} else if(color instanceof Array) {
color = color.join(',');
} else if(/\d{1,3}(\,\d{1,3}){2}/i.test(color)) {
} else {
return;
}
}
function colorBox(color) {
// 底色填充，也就是（举例红色）到白色
var gradientBase = ctx.createLinearGradient(30, 0, width + 30, 0);
gradientBase.addColorStop(1, color);
gradientBase.addColorStop(0, 'rgba(255,255,255,1)');
ctx.fillStyle = gradientBase;
ctx.fillRect(30, 0, width, width);
// 第二次填充，黑色到透明
var my_gradient1 = ctx.createLinearGradient(0, 0, 0, width);
my_gradient1.addColorStop(0, 'rgba(0,0,0,0)');
my_gradient1.addColorStop(1, 'rgba(0,0,0,1)');
ctx.fillStyle = my_gradient1;
ctx.fillRect(30, 0, width, width);
}
function init() {
colorBar();
colorBox(curColor);
bind();
}
function bind() {
can.addEventListener('click', function(e) {
var ePos = {
x: e.offsetX || e.layerX,
y: e.offsetY || e.layerY
}
var rgbaStr = '#000';
if(ePos.x >= 0 && ePos.x < 20 && ePos.y >= 0 && ePos.y < width) {
// in
rgbaStr = getRgbaAtPoint(ePos, 'bar');
colorBox('rgba(' + rgbaStr + ')');
} else if(ePos.x >= 30 && ePos.x < 30 + width && ePos.y >= 0 && ePos.y < width) {
rgbaStr = getRgbaAtPoint(ePos, 'box');
} else {
return;
}
outColor(rgbaStr.slice(0, 3).join());
cur.style.left = ePos.x + 'px';
cur.style.top = ePos.y + 'px';
cur.style.outlineColor = (rgbaStr[0] > 256 / 2 || rgbaStr[1] > 256 / 2 || rgbaStr[2] > 256 / 2) ? '#000' : '#fff';
});
can.addEventListener('mousedown', function(e) {
var ePos = {
x: e.layerX || e.offsetX,
y: e.layerY || e.offsetY
}
if(ePos.x >= 30 && ePos.x < 30 + width && ePos.y >= 0 && ePos.y < width) {
document.onmousemove = function(e) {
var pos = {
x: e.clientX,
y: e.clientY
}
pos.x = pos.x < 30 ? 30 : pos.x && (pos.x > (30 + width - 1) ? (30 + width - 1) : pos.x);
pos.y = pos.y < 0 ? 0 : pos.y && (pos.y > (width - 1) ? (width - 1) : pos.y);
rgbaStr = getRgbaAtPoint(pos, 'box');
cur.style.left = pos.x + 'px';
cur.style.top = pos.y + 'px';
cur.style.outlineColor = (rgbaStr[0] > 256 / 2 || rgbaStr[1] > 256 / 2 || rgbaStr[2] > 256 / 2) ? '#000' : '#fff';
outColor(rgbaStr.slice(0, 3).join());
};
document.onmouseup = function() {
// outColor(rgbaStr.slice(0, 3).join());
document.onmouseup = document.onmousemove = null;
}
}
});
}
function outColor(rgb) {
rgbValue.value = rgb;
hexValue.value = rgb2hex(rgb);
colorShow.style.backgroundColor = 'rgb(' + rgb + ')';
}
function getRgbaAtPoint(pos, area) {
if(area == 'bar') {
var imgData = ctx.getImageData(0, 0, 20, width);
} else {
var imgData = ctx.getImageData(0, 0, can.width, can.height);
}
var data = imgData.data;
var dataIndex = (pos.y * imgData.width + pos.x) * 4;
return [
data[dataIndex],
data[dataIndex + 1],
data[dataIndex + 2],
(data[dataIndex + 3] / 255).toFixed(2),
];
}
init();
})()
</script>
</body>
</html>
