看起来,如果没有额外的代码,使用pixi.js无法实现您所需的内容,但我们可以进行一些魔法使其发生。这是我得到的结果:
https://jsfiddle.net/exkf3zfo/21/
底部颜色是纯红色,透明度为0.2。
我将整个过程分解为以下步骤:
- 绘制渐变
- 用圆形遮罩遮盖渐变
以下是代码本身:
var app = new PIXI.Application(800, 600, {
antialias: true
});
document.body.appendChild(app.view);
var prepareRGBChannelColor = function(channelColor) {
var colorText = channelColor.toString(16);
if (colorText.length < 2) {
while (colorText.length < 2) {
colorText = "0" + colorText;
}
}
return colorText;
}
var getRGBChannels = function(color) {
var colorText = color.toString(16);
if (colorText.length < 6) {
while (colorText.length < 6) {
colorText = "0" + colorText;
}
}
var result = {
red: parseInt(colorText.slice(0, 2), 16),
green: parseInt(colorText.slice(2, 4), 16),
blue: parseInt(colorText.slice(4, 6), 16)
};
return result;
}
var prepareColorData = function(color, alpha) {
return {
color: color,
alpha: alpha,
channels: getRGBChannels(color)
}
}
var getColorOfGradient = function(from, to, coef) {
if (!from.alpha && from.alpha !== 0) {
from.alpha = 1;
}
if (!from.alpha && from.alpha !== 0) {
to.alpha = 1;
}
var colorRed = Math.floor(from.channels.red + coef * (to.channels.red - from.channels.red));
colorRed = Math.min(colorRed, 255);
var colorGreen = Math.floor(from.channels.green + coef * (to.channels.green - from.channels.green));
colorGreen = Math.min(colorGreen, 255);
var colorBlue = Math.floor(from.channels.blue + coef * (to.channels.blue - from.channels.blue));
colorBlue = Math.min(colorBlue, 255);
var rgb = prepareRGBChannelColor(colorRed) + prepareRGBChannelColor(colorGreen) + prepareRGBChannelColor(colorBlue);
return {
color: parseInt(rgb, 16),
alpha: from.alpha + coef * (to.alpha - from.alpha)
};
}
var startTime = Date.now();
console.log("start: " + startTime);
var gradient = new PIXI.Graphics();
app.stage.addChild(gradient);
var rect = {
width: 200,
height: 200
};
var round = 20;
var colorFromData = prepareColorData(0xFF00FF, 1);
var colorToData = prepareColorData(0xFF0000, 0.2);
var stepCoef;
var stepColor;
var stepAlpha;
var stepsCount = 100;
var stepHeight = rect.height / stepsCount;
for (var stepIndex = 0; stepIndex < stepsCount; stepIndex++) {
stepCoef = stepIndex / stepsCount;
stepColor = getColorOfGradient(colorFromData, colorToData, stepCoef);
gradient.beginFill(stepColor.color, stepColor.alpha);
gradient.drawRect(
0,
rect.height * stepCoef,
rect.width,
stepHeight
);
}
var roundMask = new PIXI.Graphics();
roundMask.beginFill(0x000000);
roundMask.drawRoundedRect(0, 0, rect.width, rect.height, round);
app.stage.addChild(roundMask);
gradient.mask = roundMask;
var endTime = Date.now();
console.log("end: " + endTime);
console.log("total: " + (endTime - startTime));
有趣的是,整个过程只需要大约2-5毫秒!
如果你想将渐变颜色更改为白色>黑色(如问题所述),只需更改下一个参数:
var colorFromData = prepareColorData(0xFF00FF, 1);
var colorToData = prepareColorData(0xFF0000, 0.2);
致:
var colorFromData = prepareColorData(0xFFFFFF, 1);
var colorToData = prepareColorData(0x000000, 0.2);