我正在尝试创建一个连续的颜色转换，就像在Windows 8安装中那样We're getting your PC ready。
我无法弄清楚如何编写shift函数。检查所有R，G，B值并将当前颜色与下一种颜色匹配。
任何人都可以帮我这个吗？或者让我知道是否有更好的方法呢？
function switchColor(id) {
var elm = document.getElementById(id);
// getting elm's current rgb values
var elmColor = window.getComputedStyle(elm).getPropertyValue("background");
var startIndex = elmColor.indexOf("(");
var finishIndex = elmColor.indexOf(")");
var elmRGB = elmColor.substring(startIndex + 1, finishIndex);
var currentColor = elmRGB.split(",");
for (var i = 0; i<3; i++) { currentColor[i] = currentColor[i].trim(); }
// generating a random color => [r, g, ,b]
var nextColor = [];
for (var i = 0; i < 3; i++) {
nextColor[i] = Math.floor(Math.random()*250);
}
// function to convert rgb array to hex color => [r, g, b] = #rgb
function rgbToHex(clr) {
var rgb = clr;
var hex;
var hex1 = rgb[0].toString(16);
var hex2 = rgb[1].toString(16);
var hex3 = rgb[2].toString(16);
if (hex1.length < 2) { hex1 = "0" + hex1; }
if (hex2.length < 2) { hex2 = "0" + hex2; }
if (hex3.length < 2) { hex3 = "0" + hex3; }
return hex = "#" + hex1 + hex2 + hex3;
}
// checking if nextColor rgb values are greater than current rgb's
// so we can increase or decrease for smooth transition
var status = [];
for (var i = 0; i < 3; i++) {
if (nextColor[i] > currentColor[i]) { status.push(1); }
else { status.push(0); }
}
// this isn't part of the code, just testing
elm.style.background = rgbToHex(nextColor);
function shift() {
// shift between colors
// modify currentColor's rgb values and apply it to the elm
// elm.style.background = rgbToHex(currentColor);
}
var handler = setInterval(shift, 100);
}
setInterval(function() { switchColor("sandbox"); }, 2000);
答案 0 :(得分：13)
检查此JSFiddle以获得带有花式图的转换。
/* ==================== Required Functions ==================== */
// This is required to get the initial background-color of an element.
// The element might have it's bg-color already set before the transition.
// Transition should continue/start from this color.
// This will be used only once.
function getElementBG(elm) {
var bg = getComputedStyle(elm).backgroundColor;
bg = bg.match(/\((.*)\)/)[1];
bg = bg.split(",");
for (var i = 0; i < bg.length; i++) {
bg[i] = parseInt(bg[i], 10);
}
if (bg.length > 3) { bg.pop(); }
return bg;
}
// A function to generate random numbers.
// Will be needed to generate random RGB value between 0-255.
function random() {
if (arguments.length > 2) {
return 0;
}
switch (arguments.length) {
case 0:
return Math.random();
case 1:
return Math.round(Math.random() * arguments[0]);
case 2:
var min = arguments[0];
var max = arguments[1];
return Math.round(Math.random() * (max - min) + min);
}
}
// Generates a random RGB value.
function generateRGB(min, max) {
var min = min || 0;
var max = min || 255;
var color = [];
for (var i = 0; i < 3; i++) {
var num = random(min, max);
color.push(num);
}
return color;
}
// Calculates the distance between the RGB values.
// We need to know the distance between two colors
// so that we can calculate the increment values for R, G, and B.
function calculateDistance(colorArray1, colorArray2) {
var distance = [];
for (var i = 0; i < colorArray1.length; i++) {
distance.push(Math.abs(colorArray1[i] - colorArray2[i]));
}
return distance;
}
// Calculates the increment values for R, G, and B using distance, fps, and duration.
// This calculation can be made in many different ways.
function calculateIncrement(distanceArray, fps, duration) {
var fps = fps || 30;
var duration = duration || 1;
var increment = [];
for (var i = 0; i < distanceArray.length; i++) {
var incr = Math.abs(Math.floor(distanceArray[i] / (fps * duration)));
if (incr == 0) {
incr = 1;
}
increment.push(incr);
}
return increment;
}
// Converts RGB array [32,64,128] to HEX string #204080
// It's easier to apply HEX color than RGB color.
function rgb2hex(colorArray) {
var color = [];
for (var i = 0; i < colorArray.length; i++) {
var hex = colorArray[i].toString(16);
if (hex.length < 2) { hex = "0" + hex; }
color.push(hex);
}
return "#" + color.join("");
}
/* ==================== Setup ==================== */
// Duration is not what it says. It's a multiplier in the calculateIncrement() function.
// duration = 1-4, fast-to-slow
var fps = 30;
var duration = 3;
var transElement = document.body;
var currentColor = getElementBG(transElement);
var transHandler = null;
startTransition();
/* ==================== Transition Initiator ==================== */
function startTransition() {
clearInterval(transHandler);
targetColor = generateRGB();
distance = calculateDistance(currentColor, targetColor);
increment = calculateIncrement(distance, fps, duration);
transHandler = setInterval(function() {
transition();
}, 1000/fps);
}
/* ==================== Transition Calculator ==================== */
function transition() {
// checking R
if (currentColor[0] > targetColor[0]) {
currentColor[0] -= increment[0];
if (currentColor[0] <= targetColor[0]) {
increment[0] = 0;
}
} else {
currentColor[0] += increment[0];
if (currentColor[0] >= targetColor[0]) {
increment[0] = 0;
}
}
// checking G
if (currentColor[1] > targetColor[1]) {
currentColor[1] -= increment[1];
if (currentColor[1] <= targetColor[1]) {
increment[1] = 0;
}
} else {
currentColor[1] += increment[1];
if (currentColor[1] >= targetColor[1]) {
increment[1] = 0;
}
}
// checking B
if (currentColor[2] > targetColor[2]) {
currentColor[2] -= increment[2];
if (currentColor[2] <= targetColor[2]) {
increment[2] = 0;
}
} else {
currentColor[2] += increment[2];
if (currentColor[2] >= targetColor[2]) {
increment[2] = 0;
}
}
// applying the new modified color
transElement.style.backgroundColor = rgb2hex(currentColor);
// transition ended. start a new one
if (increment[0] == 0 && increment[1] == 0 && increment[2] == 0) {
startTransition();
}
}body {
background: white;
}
答案 1 :(得分：1)
这是使用纯JavaScript和CSS的另一种颜色过渡/动画实现
const randomColor = () => '#' + Math.random().toString(16).substr(-6)
const changeColor = () => document.body.style.backgroundColor = randomColor()
setInterval(() => {
changeColor()
}, 5000)
// start color animation as soon as document is ready
document.onreadystatechange = () => {
if (document.readyState === 'complete') {
changeColor()
}
}body {
transition: background 5s;
}
答案 2 :(得分：0)
变量太多了？ 这个怎么样？
var el = document.getElementById("sandbox"),
interval = 2000;
function getNewColor(){
//generate color
}
function getOldColor(el){
//get current color
}
function switchColor(el, oldColor, newColor){
//change color
}
setInterval(function(){
swithColors(el, getOldColor(el), getNewColor());
},interval);
答案 3 :(得分：0)
感谢akinuri，我设法让他的答案适应在requestanimationframe上运行的动态函数。再次感谢akinuri，很好的代码。 ps：currentColor和targetColor请求一个rgb值的字符串（'rgb（0,0,0）'）
function startColorFade(fps, duration, element, currentColor, targetColor) {
var stop = false;
var fpsInterval = 1000 / fps;
var now;
var then = Date.now();
var elapsed;
var startTime = then;
var currentColorArray = getElementBG(currentColor);
var targetColorArray = getElementBG(targetColor);
var distance = calculateDistance(currentColorArray, targetColorArray);
var increment = calculateIncrement(distance, fps, duration);
animateColor(duration, element, currentColorArray, targetColorArray, increment, stop, fpsInterval, now, then, elapsed, startTime);
}
function animateColor( duration, element, currentColorArray, targetColorArray, increment, stop, fpsInterval, now, then, elapsed, startTime ) {
var step = function() {
if (stop) {
return;
}
// request another frame
requestAnimationFrame(function() //arguments can passed on the callback by an anonymous funtion
{
animateColor(duration, element, currentColorArray, targetColorArray, increment, stop, fpsInterval, now, then, elapsed, startTime);
colorTransition(element, currentColorArray, targetColorArray, increment);
});
// calc elapsed time since last loop
now = Date.now();
elapsed = now - then;
// if enough time has elapsed, draw the next frame
if (elapsed > fpsInterval) {
// Get ready for next frame by setting then=now, but...
// Also, adjust for fpsInterval not being multiple of 16.67
then = now - (elapsed % fpsInterval);
// draw stuff here
var sinceStart = now - startTime;
}
if (sinceStart / 1000 * 100 >= duration * 100)
{
stop = true;
}
}
step();
}
function colorTransition(element, currentColorArray, targetColorArray, increment) {
// checking R
if (currentColorArray[0] > targetColorArray[0]) {
currentColorArray[0] -= increment[0];
if (currentColorArray[0] <= targetColorArray[0]) {
increment[0] = 0;
}
} else {
currentColorArray[0] += increment[0];
if (currentColorArray[0] >= targetColorArray[0]) {
increment[0] = 0;
}
}
// checking G
if (currentColorArray[1] > targetColorArray[1]) {
currentColorArray[1] -= increment[1];
if (currentColorArray[1] <= targetColorArray[1]) {
increment[1] = 0;
}
} else {
currentColorArray[1] += increment[1];
if (currentColorArray[1] >= targetColorArray[1]) {
increment[1] = 0;
}
}
// checking B
if (currentColorArray[2] > targetColorArray[2]) {
currentColorArray[2] -= increment[2];
if (currentColorArray[2] <= targetColorArray[2]) {
increment[2] = 0;
}
} else {
currentColorArray[2] += increment[2];
if (currentColorArray[2] >= targetColorArray[2]) {
increment[2] = 0;
}
}
// apply the new modified color
element.style.backgroundColor = rgb2hex(currentColorArray);
}
function getElementBG(elmBGColor) {
var bg = elmBGColor; // i.e: RGB(255, 0, 0)
bg = bg.match(/\((.*)\)/)[1];
bg = bg.split(",");
for (var i = 0; i < bg.length; i++) {
bg[i] = parseInt(bg[i], 10);
}
if (bg.length > 3) { bg.pop(); }
return bg; // return array
}
function calculateDistance(colorArray1, colorArray2) {
var distance = [];
for (var i = 0; i < colorArray1.length; i++) {
distance.push(Math.abs(colorArray1[i] - colorArray2[i]));
}
return distance;
}
function calculateIncrement(distanceArray, fps, duration) {
var increment = [];
for (var i = 0; i < distanceArray.length; i++) {
increment.push(Math.abs(Math.floor(distanceArray[i] / (fps * duration))));
if (increment[i] == 0) {
increment[i]++;
}
}
return increment;
}
function rgb2hex(colorArray) {
var hex = [];
for (var i = 0; i < colorArray.length; i++) {
hex.push(colorArray[i].toString(16));
if (hex[i].length < 2) { hex[i] = "0" + hex[i]; }
}
return "#" + hex.join("");
}
//random rgb values in array, very nice
function generateRGB(min, max) {
var min = min || 0;
var max = max || 255;
var color = [];
for (var i = 0; i < 3; i++) {
var num = Math.floor(Math.random() * max);
while (num < min) {
num = Math.floor(Math.random() * max);
}
color.push(num);
}
return color;
}
答案 4 :(得分：0)
使用hsl()
例如在ReactJS（此处使用CoffeeScript）中作用于SVG文本元素，虽然相同的技术可以使用HTML p / span / h1等（颜色而不是填充属性）：
render: ->
#[... svg setup]
text
x: 50
y: 50
fontSize: 20
fill: "hsl(#{@state.el_hue}, #{@state.el_sat}%, @state.el_lum)%"
"Hello from randomly changing color text."
getInitialState: ->
el_hue: 0
el_sat: 0
el_lum: 0
componentDidMount: ->
setInterval =>
@setState
el_hue: Math.random() * 360
el_sat: Math.random() * 100
el_lum: Math.random() * 100
, 30
# should do crazy things, change color etc
在这里，我每隔一段时间用hsl vals做随机事情，但你可以这样做。因此，您可以通过恰当地更改色调值来设置红色到蓝色的过渡。