为什么Javascript会自动混合我的颜色？ [英] Why is Javascript automatically blending my colors?
问题描述
我刚刚开始使用Javascript和HTML5，所以我很可能犯了一些非常愚蠢的错误。事实上，我希望这就是一切，这是一个简单的解决方案。
I'm just starting out with Javascript and HTML5 so it's entirely likely that I'm making some really dumb mistake. In fact I hope that's all it is and that this is an easy fix.
这是我得到的输出：
（自己尝试一下！）
我想要发生的只是在灰色矩形上绘制一个蓝色矩形，其中两种颜色是他们自己的事情。我真的很困惑为什么这种混合是默认的（在我的机器上使用Chrome）。
What I want to happen is just to draw a blue rectangle over the gray rectangle, where both colors are their own thing. I'm honestly confused as to why this blending is the default (using Chrome on my machine).
这是最小的工作示例（同样，对于我的机器）：
Here is the minimal working example (again, for my machine):
（html）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Simple Canvas Game</title>
</head>
<body>
<script src="js/game.js"></script>
</body>
</html>
（javascript，这是game.js）
(javascript, this is the game.js)
//set up the canvas
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 512;
canvas.height = 480;
document.body.appendChild(canvas);
// Draw everything
var render = function () {
ctx.clearRect(50, 50, 100, 100);
ctx.fillStyle = "rgb(240, 240, 240)";
ctx.fillRect(0, 0, 100, 100);
ctx.strokeStyle="rgb(0, 0, 255)";
ctx.strokeRect(20,20,150,100);
}
setInterval(render, 10);
推荐答案
这不是混合，只是笔画是1像素宽，画布中的坐标是正方形，而线条在正方形之间。你的线在像素之间，并且是消除锯齿的。如果希望笔划与像素对齐，则需要使用（99.5,99.5），而不是（100,100）的坐标。很难描述，但有大量的文档可用。
This is not blending, it's just that the stroke is 1 pixel wide, and the coordinates in canvas are those of squares, while lines go between squares. Your lines go between pixels and are anti-aliased. If you want your strokes to align with pixels, you need to use coordinates like (99.5,99.5), not (100,100). Hard to describe, but there is plenty of documentation available.
长话短说，你必须将整个绘图代码翻译0.5,0.5。尝试类似：
To make long story short, you have to translate the whole drawing code by 0.5,0.5. Try something like:
ctx.save();
ctx.translate(0.5,0.5);
ctx.clearRect(50, 50, 100, 100);
ctx.fillStyle = "rgb(240, 240, 240)";
ctx.fillRect(0, 0, 100, 100);
ctx.strokeStyle="rgb(0, 0, 255)";
ctx.strokeRect(20,20,150,100);
ctx.restore();
这篇关于为什么Javascript会自动混合我的颜色？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
