快捷方便

下面的类实现了本文中描述的快速方法，并包含了所有您需要的:readPixel, putPixel，获取宽度/高度。类在调用refresh()方法后更新画布。算例求解二维波动方程的简单情形

class Screen{ constructor(canvasSelector) { this.canvas = document.querySelector(canvasSelector); this.width = this.canvas.width; this.height = this.canvas.height; this.ctx = this.canvas.getContext('2d'); this.imageData = this.ctx.getImageData(0, 0, this.width, this.height); this.buf = new ArrayBuffer(this.imageData.data.length); this.buf8 = new Uint8ClampedArray(this.buf); this.data = new Uint32Array(this.buf); } // r,g,b,a - red, gren, blue, alpha components in range 0-255 putPixel(x,y,r,g,b,a=255) { this.data[y * this.width + x] = (a<<24) | (b<<16) | (g<<8) | r; } readPixel(x,y) { let p= this.data[y * this.width + x] return [p&0xff, p>>8&0xff, p>>16&0xff, p>>>24]; } refresh() { this.imageData.data.set(this.buf8); this.ctx.putImageData(this.imageData, 0, 0); } } // -------- // TEST // -------- let s= new Screen('#canvas'); // initialise function draw() { for (var y = 1; y < s.height-1; ++y) { for (var x = 1; x < s.width-1; ++x) { let a = [[1,0],[-1,0],[0,1],[0,-1]].reduce((a,[xp,yp])=> a+= s.readPixel(x+xp,y+yp)[0] // read pixel ,0); let v= a/1.99446-tmp[x][y]; tmp[x][y]=v<0 ? 0:v; } } for (var y = 1; y < s.height-1; ++y) { for (var x = 1; x < s.width-1; ++x) { let v=tmp[x][y]; tmp[x][y]= s.readPixel(x,y)[0]; // read pixel s.putPixel(x,y, v,0,0); // put pixel } } s.refresh(); window.requestAnimationFrame(draw) } // temporary 2d buffer ()for solving wave equation) let tmp = [...Array(s.width)].map(x => Array(s.height).fill(0)); function move(e) { s.putPixel(e.x-10, e.y-10, 255,255,255);} draw(); <canvas id="canvas" height="150" width="512" onmousemove="move(event)"></canvas> <div>Move mouse on black square</div>

我没有考虑过fillRect()，但答案促使我对putImage()进行基准测试。

在(旧的)MacBook Pro上使用Chrome 9.0.597.84在随机位置放置100,000个随机颜色的像素，使用putImage()只需不到100毫秒，但使用fillRect()需要近900毫秒。(基准代码在http://pastebin.com/4ijVKJcC)。

如果我在循环之外选择一种颜色，并在随机位置绘制该颜色，putImage()需要59ms而fillRect()需要102ms。

在rgb(…)语法中生成和解析CSS颜色规范的开销似乎是造成大部分差异的原因。

另一方面，将原始RGB值直接放入ImageData块中不需要字符串处理或解析。

function setPixel(imageData, x, y, r, g, b, a) {
    var index = 4 * (x + y * imageData.width);
    imageData.data[index+0] = r;
    imageData.data[index+1] = g;
    imageData.data[index+2] = b;
    imageData.data[index+3] = a;
}

由于不同的浏览器似乎更喜欢不同的方法，也许在加载过程中对所有这三种方法进行一个较小的测试，以找出使用哪个方法最好，然后在整个应用程序中使用该方法是有意义的。

嗯，你也可以只做一个1像素宽的线，长度为1像素，让它的方向沿着一个轴移动。

            ctx.beginPath();
            ctx.lineWidth = 1; // one pixel wide
            ctx.strokeStyle = rgba(...);
            ctx.moveTo(50,25); // positioned at 50,25
            ctx.lineTo(51,25); // one pixel long
            ctx.stroke();

快捷方便

下面的类实现了本文中描述的快速方法，并包含了所有您需要的:readPixel, putPixel，获取宽度/高度。类在调用refresh()方法后更新画布。算例求解二维波动方程的简单情形

class Screen{ constructor(canvasSelector) { this.canvas = document.querySelector(canvasSelector); this.width = this.canvas.width; this.height = this.canvas.height; this.ctx = this.canvas.getContext('2d'); this.imageData = this.ctx.getImageData(0, 0, this.width, this.height); this.buf = new ArrayBuffer(this.imageData.data.length); this.buf8 = new Uint8ClampedArray(this.buf); this.data = new Uint32Array(this.buf); } // r,g,b,a - red, gren, blue, alpha components in range 0-255 putPixel(x,y,r,g,b,a=255) { this.data[y * this.width + x] = (a<<24) | (b<<16) | (g<<8) | r; } readPixel(x,y) { let p= this.data[y * this.width + x] return [p&0xff, p>>8&0xff, p>>16&0xff, p>>>24]; } refresh() { this.imageData.data.set(this.buf8); this.ctx.putImageData(this.imageData, 0, 0); } } // -------- // TEST // -------- let s= new Screen('#canvas'); // initialise function draw() { for (var y = 1; y < s.height-1; ++y) { for (var x = 1; x < s.width-1; ++x) { let a = [[1,0],[-1,0],[0,1],[0,-1]].reduce((a,[xp,yp])=> a+= s.readPixel(x+xp,y+yp)[0] // read pixel ,0); let v= a/1.99446-tmp[x][y]; tmp[x][y]=v<0 ? 0:v; } } for (var y = 1; y < s.height-1; ++y) { for (var x = 1; x < s.width-1; ++x) { let v=tmp[x][y]; tmp[x][y]= s.readPixel(x,y)[0]; // read pixel s.putPixel(x,y, v,0,0); // put pixel } } s.refresh(); window.requestAnimationFrame(draw) } // temporary 2d buffer ()for solving wave equation) let tmp = [...Array(s.width)].map(x => Array(s.height).fill(0)); function move(e) { s.putPixel(e.x-10, e.y-10, 255,255,255);} draw(); <canvas id="canvas" height="150" width="512" onmousemove="move(event)"></canvas> <div>Move mouse on black square</div>