我发现只有填充矩形，但没有圆角，我该怎么做？
答案 0 :(得分：291)
我需要做同样的事情并创建一个方法来做到这一点。
// Now you can just call
var ctx = document.getElementById("rounded-rect").getContext("2d");
// Draw using default border radius,
// stroke it but no fill (function's default values)
roundRect(ctx, 5, 5, 50, 50);
// To change the color on the rectangle, just manipulate the context
ctx.strokeStyle = "rgb(255, 0, 0)";
ctx.fillStyle = "rgba(255, 255, 0, .5)";
roundRect(ctx, 100, 5, 100, 100, 20, true);
// Manipulate it again
ctx.strokeStyle = "#0f0";
ctx.fillStyle = "#ddd";
// Different radii for each corner, others default to 0
roundRect(ctx, 300, 5, 200, 100, {
tl: 50,
br: 25
}, true);
/**
* Draws a rounded rectangle using the current state of the canvas.
* If you omit the last three params, it will draw a rectangle
* outline with a 5 pixel border radius
* @param {CanvasRenderingContext2D} ctx
* @param {Number} x The top left x coordinate
* @param {Number} y The top left y coordinate
* @param {Number} width The width of the rectangle
* @param {Number} height The height of the rectangle
* @param {Number} [radius = 5] The corner radius; It can also be an object
* to specify different radii for corners
* @param {Number} [radius.tl = 0] Top left
* @param {Number} [radius.tr = 0] Top right
* @param {Number} [radius.br = 0] Bottom right
* @param {Number} [radius.bl = 0] Bottom left
* @param {Boolean} [fill = false] Whether to fill the rectangle.
* @param {Boolean} [stroke = true] Whether to stroke the rectangle.
*/
function roundRect(ctx, x, y, width, height, radius, fill, stroke) {
if (typeof stroke == 'undefined') {
stroke = true;
}
if (typeof radius === 'undefined') {
radius = 5;
}
if (typeof radius === 'number') {
radius = {tl: radius, tr: radius, br: radius, bl: radius};
} else {
var defaultRadius = {tl: 0, tr: 0, br: 0, bl: 0};
for (var side in defaultRadius) {
radius[side] = radius[side] || defaultRadius[side];
}
}
ctx.beginPath();
ctx.moveTo(x + radius.tl, y);
ctx.lineTo(x + width - radius.tr, y);
ctx.quadraticCurveTo(x + width, y, x + width, y + radius.tr);
ctx.lineTo(x + width, y + height - radius.br);
ctx.quadraticCurveTo(x + width, y + height, x + width - radius.br, y + height);
ctx.lineTo(x + radius.bl, y + height);
ctx.quadraticCurveTo(x, y + height, x, y + height - radius.bl);
ctx.lineTo(x, y + radius.tl);
ctx.quadraticCurveTo(x, y, x + radius.tl, y);
ctx.closePath();
if (fill) {
ctx.fill();
}
if (stroke) {
ctx.stroke();
}
}<canvas id="rounded-rect" width="500" height="200">
<!-- Insert fallback content here -->
</canvas>
答案 1 :(得分：91)
我从@jhoff的解决方案开始，但重新编写它以使用宽度/高度参数，使用arcTo使它更加简洁：
CanvasRenderingContext2D.prototype.roundRect = function (x, y, w, h, r) {
if (w < 2 * r) r = w / 2;
if (h < 2 * r) r = h / 2;
this.beginPath();
this.moveTo(x+r, y);
this.arcTo(x+w, y, x+w, y+h, r);
this.arcTo(x+w, y+h, x, y+h, r);
this.arcTo(x, y+h, x, y, r);
this.arcTo(x, y, x+w, y, r);
this.closePath();
return this;
}
同样返回上下文，以便您可以链接一点。 E.g：
ctx.roundRect(35, 10, 225, 110, 20).stroke(); //or .fill() for a filled rect
答案 2 :(得分：41)
答案 3 :(得分：15)
Juan，我对你的方法做了一些改进，允许分别改变每个矩形角半径：
/**
* Draws a rounded rectangle using the current state of the canvas.
* If you omit the last three params, it will draw a rectangle
* outline with a 5 pixel border radius
* @param {Number} x The top left x coordinate
* @param {Number} y The top left y coordinate
* @param {Number} width The width of the rectangle
* @param {Number} height The height of the rectangle
* @param {Object} radius All corner radii. Defaults to 0,0,0,0;
* @param {Boolean} fill Whether to fill the rectangle. Defaults to false.
* @param {Boolean} stroke Whether to stroke the rectangle. Defaults to true.
*/
CanvasRenderingContext2D.prototype.roundRect = function (x, y, width, height, radius, fill, stroke) {
var cornerRadius = { upperLeft: 0, upperRight: 0, lowerLeft: 0, lowerRight: 0 };
if (typeof stroke == "undefined") {
stroke = true;
}
if (typeof radius === "object") {
for (var side in radius) {
cornerRadius[side] = radius[side];
}
}
this.beginPath();
this.moveTo(x + cornerRadius.upperLeft, y);
this.lineTo(x + width - cornerRadius.upperRight, y);
this.quadraticCurveTo(x + width, y, x + width, y + cornerRadius.upperRight);
this.lineTo(x + width, y + height - cornerRadius.lowerRight);
this.quadraticCurveTo(x + width, y + height, x + width - cornerRadius.lowerRight, y + height);
this.lineTo(x + cornerRadius.lowerLeft, y + height);
this.quadraticCurveTo(x, y + height, x, y + height - cornerRadius.lowerLeft);
this.lineTo(x, y + cornerRadius.upperLeft);
this.quadraticCurveTo(x, y, x + cornerRadius.upperLeft, y);
this.closePath();
if (stroke) {
this.stroke();
}
if (fill) {
this.fill();
}
}
像这样使用：
var canvas = document.getElementById("canvas");
var c = canvas.getContext("2d");
c.fillStyle = "blue";
c.roundRect(50, 100, 50, 100, {upperLeft:10,upperRight:10}, true, true);
答案 4 :(得分：9)
下面的drawPolygon函数可用于绘制带圆角的任何多边形。
function drawPolygon(ctx, pts, radius) {
if (radius > 0) {
pts = getRoundedPoints(pts, radius);
}
var i, pt, len = pts.length;
ctx.beginPath();
for (i = 0; i < len; i++) {
pt = pts[i];
if (i == 0) {
ctx.moveTo(pt[0], pt[1]);
} else {
ctx.lineTo(pt[0], pt[1]);
}
if (radius > 0) {
ctx.quadraticCurveTo(pt[2], pt[3], pt[4], pt[5]);
}
}
ctx.closePath();
}
function getRoundedPoints(pts, radius) {
var i1, i2, i3, p1, p2, p3, prevPt, nextPt,
len = pts.length,
res = new Array(len);
for (i2 = 0; i2 < len; i2++) {
i1 = i2-1;
i3 = i2+1;
if (i1 < 0) {
i1 = len - 1;
}
if (i3 == len) {
i3 = 0;
}
p1 = pts[i1];
p2 = pts[i2];
p3 = pts[i3];
prevPt = getRoundedPoint(p1[0], p1[1], p2[0], p2[1], radius, false);
nextPt = getRoundedPoint(p2[0], p2[1], p3[0], p3[1], radius, true);
res[i2] = [prevPt[0], prevPt[1], p2[0], p2[1], nextPt[0], nextPt[1]];
}
return res;
};
function getRoundedPoint(x1, y1, x2, y2, radius, first) {
var total = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2)),
idx = first ? radius / total : (total - radius) / total;
return [x1 + (idx * (x2 - x1)), y1 + (idx * (y2 - y1))];
};
该函数接收带有多边形点的数组，如下所示：
var canvas = document.getElementById("cv");
var ctx = canvas.getContext("2d");
ctx.strokeStyle = "#000000";
ctx.lineWidth = 5;
drawPolygon(ctx, [[20, 20],
[120, 20],
[120, 120],
[ 20, 120]], 10);
ctx.stroke();
这是一个端口，是发布here的解决方案的更通用版本。
答案 5 :(得分：7)
这是我写的一个...使用弧而不是二次曲线来更好地控制半径。此外，它留下了抚摸和填补你
/* Canvas 2d context - roundRect
*
* Accepts 5 parameters, the start_x and start_y points, the end_x and end_y points, and the radius of the corners
*
* No return value
*/
CanvasRenderingContext2D.prototype.roundRect = function(sx,sy,ex,ey,r) {
var r2d = Math.PI/180;
if( ( ex - sx ) - ( 2 * r ) < 0 ) { r = ( ( ex - sx ) / 2 ); } //ensure that the radius isn't too large for x
if( ( ey - sy ) - ( 2 * r ) < 0 ) { r = ( ( ey - sy ) / 2 ); } //ensure that the radius isn't too large for y
this.beginPath();
this.moveTo(sx+r,sy);
this.lineTo(ex-r,sy);
this.arc(ex-r,sy+r,r,r2d*270,r2d*360,false);
this.lineTo(ex,ey-r);
this.arc(ex-r,ey-r,r,r2d*0,r2d*90,false);
this.lineTo(sx+r,ey);
this.arc(sx+r,ey-r,r,r2d*90,r2d*180,false);
this.lineTo(sx,sy+r);
this.arc(sx+r,sy+r,r,r2d*180,r2d*270,false);
this.closePath();
}
以下是一个例子：
var _e = document.getElementById('#my_canvas');
var _cxt = _e.getContext("2d");
_cxt.roundRect(35,10,260,120,20);
_cxt.strokeStyle = "#000";
_cxt.stroke();
答案 6 :(得分：6)
因此，这是基于使用lineJoin =“ round”并以适当的比例，数学和逻辑进行的，我已经能够实现此功能，虽然它并不完美，但希望能有所帮助。如果要使每个角具有不同的半径，请查看：https://p5js.org/reference/#/p5/rect
在这里：
CanvasRenderingContext2D.prototype.roundRect = function (x,y,width,height,radius) {
radius = Math.min(Math.max(width-1,1),Math.max(height-1,1),radius);
var rectX = x;
var rectY = y;
var rectWidth = width;
var rectHeight = height;
var cornerRadius = radius;
this.lineJoin = "round";
this.lineWidth = cornerRadius;
this.strokeRect(rectX+(cornerRadius/2), rectY+(cornerRadius/2), rectWidth-cornerRadius, rectHeight-cornerRadius);
this.fillRect(rectX+(cornerRadius/2), rectY+(cornerRadius/2), rectWidth-cornerRadius, rectHeight-cornerRadius);
this.stroke();
this.fill();
}
CanvasRenderingContext2D.prototype.roundRect = function (x,y,width,height,radius) {
radius = Math.min(Math.max(width-1,1),Math.max(height-1,1),radius);
var rectX = x;
var rectY = y;
var rectWidth = width;
var rectHeight = height;
var cornerRadius = radius;
this.lineJoin = "round";
this.lineWidth = cornerRadius;
this.strokeRect(rectX+(cornerRadius/2), rectY+(cornerRadius/2), rectWidth-cornerRadius, rectHeight-cornerRadius);
this.fillRect(rectX+(cornerRadius/2), rectY+(cornerRadius/2), rectWidth-cornerRadius, rectHeight-cornerRadius);
this.stroke();
this.fill();
}
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext('2d');
function yop() {
ctx.clearRect(0,0,1000,1000)
ctx.fillStyle = "#ff0000";
ctx.strokeStyle = "#ff0000"; ctx.roundRect(Number(document.getElementById("myRange1").value),Number(document.getElementById("myRange2").value),Number(document.getElementById("myRange3").value),Number(document.getElementById("myRange4").value),Number(document.getElementById("myRange5").value));
requestAnimationFrame(yop);
}
requestAnimationFrame(yop);<input type="range" min="0" max="1000" value="10" class="slider" id="myRange1"><input type="range" min="0" max="1000" value="10" class="slider" id="myRange2"><input type="range" min="0" max="1000" value="200" class="slider" id="myRange3"><input type="range" min="0" max="1000" value="100" class="slider" id="myRange4"><input type="range" min="1" max="1000" value="50" class="slider" id="myRange5">
<canvas id="myCanvas" width="1000" height="1000">
</canvas>
答案 7 :(得分：5)
var canvas = document.createElement("canvas");
document.body.appendChild(canvas);
var ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.moveTo(100,100);
ctx.arcTo(0,100,0,0,30);
ctx.arcTo(0,0,100,0,30);
ctx.arcTo(100,0,100,100,30);
ctx.arcTo(100,100,0,100,30);
ctx.fill();
答案 8 :(得分：3)
为了使函数与使用画布上下文的常规方法更加一致，可以将画布上下文类扩展为包含“fillRoundedRect”方法 - 可以以相同的方式调用{{1被称为：
fillRect代码检查画布上下文对象的构造函数的原型是否包含“var canv = document.createElement("canvas");
var cctx = canv.getContext("2d");
// If thie canvasContext class doesn't have a fillRoundedRect, extend it now
if (!cctx.constructor.prototype.fillRoundedRect) {
// Extend the canvaseContext class with a fillRoundedRect method
cctx.constructor.prototype.fillRoundedRect =
function (xx,yy, ww,hh, rad, fill, stroke) {
if (typeof(rad) == "undefined") rad = 5;
this.beginPath();
this.moveTo(xx+rad, yy);
this.arcTo(xx+ww, yy, xx+ww, yy+hh, rad);
this.arcTo(xx+ww, yy+hh, xx, yy+hh, rad);
this.arcTo(xx, yy+hh, xx, yy, rad);
this.arcTo(xx, yy, xx+ww, yy, rad);
if (stroke) this.stroke(); // Default to no stroke
if (fill || typeof(fill)=="undefined") this.fill(); // Default to fill
}; // end of fillRoundedRect method
}
”属性并添加一个 - 第一次。它的调用方式与fillRoundedRect方法相同：
fillRect该方法使用Grumdring所做的 ctx.fillStyle = "#eef"; ctx.strokeStyle = "#ddf";
// ctx.fillRect(10,10, 200,100);
ctx.fillRoundedRect(10,10, 200,100, 5);
方法。在该方法中，arcTo是对this对象的引用。如果未定义，则stroke参数默认为false。如果未定义，fill参数默认填充矩形。
（在Firefox上测试过，我不知道所有实现是否都允许以这种方式进行扩展。）
答案 9 :(得分：3)
Opera，ffs。
if (window["CanvasRenderingContext2D"]) {
/** @expose */
CanvasRenderingContext2D.prototype.roundRect = function(x, y, w, h, r) {
if (w < 2*r) r = w/2;
if (h < 2*r) r = h/2;
this.beginPath();
if (r < 1) {
this.rect(x, y, w, h);
} else {
if (window["opera"]) {
this.moveTo(x+r, y);
this.arcTo(x+r, y, x, y+r, r);
this.lineTo(x, y+h-r);
this.arcTo(x, y+h-r, x+r, y+h, r);
this.lineTo(x+w-r, y+h);
this.arcTo(x+w-r, y+h, x+w, y+h-r, r);
this.lineTo(x+w, y+r);
this.arcTo(x+w, y+r, x+w-r, y, r);
} else {
this.moveTo(x+r, y);
this.arcTo(x+w, y, x+w, y+h, r);
this.arcTo(x+w, y+h, x, y+h, r);
this.arcTo(x, y+h, x, y, r);
this.arcTo(x, y, x+w, y, r);
}
}
this.closePath();
};
/** @expose */
CanvasRenderingContext2D.prototype.fillRoundRect = function(x, y, w, h, r) {
this.roundRect(x, y, w, h, r);
this.fill();
};
/** @expose */
CanvasRenderingContext2D.prototype.strokeRoundRect = function(x, y, w, h, r) {
this.roundRect(x, y, w, h, r);
this.stroke();
};
}
由于Opera正在使用WebKit，因此在旧版本中也应该保持有效。
答案 10 :(得分：1)
大家好消息！
roundRect(x, y, width, height, radii); 现在正式成为 Canvas 2D API 的一部分.它暴露在 CanvasRenderingContext2D、Path2D 和 OffscreenCanvasRenderingContext2D 对象上。
它的 radii 参数是一个数组，其中包含任何一个
目前，只有 Chrome 有可用的实现（稳定版本仍然不支持 DOMPointInit 对象，但只支持真正的 DOMPoints），您可以在 this repo 中找到我制作的 polyfill。
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
ctx.roundRect(20,20,80,80,[new DOMPoint(60,80), new DOMPoint(110,100)]);
ctx.strokeStyle = "green";
ctx.stroke();
const path = new Path2D();
path.roundRect(120,30,60,90,[0,25,new DOMPoint(60,80), new DOMPoint(110,100)]);
ctx.fillStyle = "purple";
ctx.fill(path);
// and a simple one
ctx.beginPath();
ctx.roundRect(200,20,80,80,[10]);
ctx.fillStyle = "orange";
ctx.fill();<script src="https://cdn.jsdelivr.net/gh/Kaiido/roundRect/roundRect.js"></script>
<canvas></canvas>答案 11 :(得分：0)
这是使用lineJoin来解决问题的解决方案。如果您只需要实心形状，则可以使用，但如果您需要的细边框小于边框半径，则不需要那么多。
function _roundedRect(ctx, options) {
ctx.strokeStyle = options.color;
ctx.fillStyle = options.color;
ctx.lineJoin = "round";
ctx.lineWidth = options.radius;
ctx.strokeRect(
options.x+(options.radius*.5),
options.y+(options.radius*.5),
options.width-options.radius,
options.height-options.radius
);
ctx.fillRect(
options.x+(options.radius*.5),
options.y+(options.radius*.5),
options.width-options.radius,
options.height-options.radius
);
ctx.stroke();
ctx.fill();
}
const canvas = document.getElementsByTagName("CANVAS")[0];
let ctx = canvas.getContext('2d');
roundedRect(ctx, {
x: 10,
y: 10,
width: 200,
height: 100,
radius: 10,
color: "red"
});
答案 12 :(得分：0)
当您想获得圆角时，尝试添加此行：ctx.lineCap =“ round”;