如何从 canvas 示例中的椭圆三角形中识别值？
How to identify values from oval triangle on canvas example?
我试图从椭圆三角形的示例中识别以下参数，但是当我修改该行时：
drawCircle(canvas.width / 3,canvas.height / 2,2.5,'red');
//want to replace with specific values but its not working
drawCircle(32 / 3,33 / 2,2.5,'red');
我想识别正确的参数，以便演示可以将红色点更改为三角形内的其他 space
CH4= 20
C2H4= 70
C2H2= 20
演示：
https://codepen.io/Barak/pen/WwdPxQ
我从 Whosebug 社区阅读了 post，但看不到值
在您提到的 post 中，markE 很好地复制了 Duval 三角形的外观。唯一的问题是包含 drawCircle() 函数的 codepen 只是一个虚拟对象，只不过是在任意位置放置一个点，由它的 x 和 y 参数给出。
要使此函数显示三角形上实际数据的正确位置 - 例如CH4=20 | C2H4=70 | C2H2=20 - 涉及的内容更多。
让我们更深入地了解一下，如果我们要在纸上以图形方式解决这个问题。
（以下内容基于this论文）
杜瓦尔三角形基本上是这样的等边三角形，边b=%CH4，
边 a=%C2H4 边 c=%C2H2.
如果我们考虑以下示例数据%CH4=25 | %C2H4=35 | %C2H2=40
我们必须从 A 点到 C 点，b 边长度的 25% 并画一条平行于 c 边的线：
然后从C点到B点，a边长度的35%画一条平行于b边的直线：
最后从B点到A点，c边长的40%画一条平行于a边的直线：
因此，在这三条线相交的地方——如论文所述——我们有指示状态的目标位置。这可以使用普通三角函数以编程方式完成。好吧，我不太清楚为什么我们需要这三行。由于 CH4 的百分比总是平行于三角形的底边，而 C2H4 总是平行于边 b，我们还有一个交点，C2H2 的线是自动给出的。
基本上我们只需要一个函数来计算 CH4 和 C2H4 线之间的交点。
我采用了 markE 的现有代码并通过函数 plotResult() 对其进行了增强，该函数采用三个参数来表示 CH4、C2H2 和 C2H4 ppm 值：
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
// https://www.researchgate.net/publication/4345236_A_Software_Implementation_of_the_Duval_Triangle_Method
class Point {
constructor(x, y) {
this.x = x;
this.y = y;
}
}
var v0 = {
x: 114,
y: 366
};
var v1 = {
x: 306,
y: 30
};
var v2 = {
x: 498,
y: 366
};
var triangle = [v0, v1, v2];
// Define all your segments here
var segments = [{
points: [{
x: 114,
y: 366
}, {
x: 281,
y: 76
}, {
x: 324,
y: 150
}, {
x: 201,
y: 366
}],
fill: 'rgb(172,236,222)',
label: {
text: 'D1',
cx: 200,
cy: 290,
withLine: false,
endX: null,
endY: null
},
},
{
points: [{
x: 385,
y: 366
}, {
x: 201,
y: 366
}, {
x: 324,
y: 150
}, {
x: 356,
y: 204
}, {
x: 321,
y: 256
}],
fill: 'deepskyblue',
label: {
text: 'D2',
cx: 290,
cy: 290,
withLine: false,
endX: null,
endY: null
},
},
{
points: [{
x: 297,
y: 46
}, {
x: 392,
y: 214
}, {
x: 372,
y: 248
}, {
x: 441,
y: 366
}, {
x: 385,
y: 366
}, {
x: 321,
y: 256
}, {
x: 356,
y: 204
}, {
x: 281,
y: 76
}],
fill: 'lightCyan',
label: {
text: 'DT',
cx: 370,
cy: 290,
withLine: false,
endX: 366,
endY: 120
},
},
{
points: [{
x: 306,
y: 30
}, {
x: 312,
y: 40
}, {
x: 300,
y: 40
}],
fill: 'black',
label: {
text: 'PD',
cx: 356,
cy: 40,
withLine: true,
endX: 321,
endY: 40
},
},
{
points: [{
x: 312,
y: 40
}, {
x: 348,
y: 103
}, {
x: 337,
y: 115
}, {
x: 297,
y: 46
}, {
x: 300,
y: 40
}],
fill: 'navajoWhite',
label: {
text: 'T1',
cx: 375,
cy: 70,
withLine: true,
endX: 340,
endY: 75
},
},
{
points: [{
x: 348,
y: 103
}, {
x: 402,
y: 199
}, {
x: 392,
y: 214
}, {
x: 337,
y: 115
}],
fill: 'tan',
label: {
text: 'T2',
cx: 400,
cy: 125,
withLine: true,
endX: 366,
endY: 120
},
},
{
points: [{
x: 402,
y: 199
}, {
x: 498,
y: 366
}, {
x: 441,
y: 366
}, {
x: 372,
y: 248
}],
fill: 'peru',
label: {
text: 'T3',
cx: 425,
cy: 290,
withLine: false,
endX: null,
endY: null
},
},
];
// label styles
var labelfontsize = 12;
var labelfontface = 'verdana';
var labelpadding = 3;
// pre-create a canvas-image of the arrowhead
var arrowheadLength = 10;
var arrowheadWidth = 8;
var arrowhead = document.createElement('canvas');
premakeArrowhead();
var legendTexts = ['PD = Partial Discharge', 'T1 = Thermal fault < 300 celcius', '...'];
// start drawing
/////////////////////
// draw colored segments inside triangle
for (var i = 0; i < segments.length; i++) {
drawSegment(segments[i]);
}
// draw ticklines
ticklines(v0, v1, 9, 0, 20);
ticklines(v1, v2, 9, Math.PI * 3 / 4, 20);
ticklines(v2, v0, 9, Math.PI * 5 / 4, 20);
// molecules
moleculeLabel(v0, v1, 100, Math.PI, '% CH4');
moleculeLabel(v1, v2, 100, 0, '% C2H4');
moleculeLabel(v2, v0, 75, Math.PI / 2, '% C2H2');
// draw outer triangle
drawTriangle(triangle);
// draw legend
drawLegend(legendTexts, 10, 10, 12.86);
plotResult(25, 40, 35);
// end drawing
/////////////////////
function drawSegment(s) {
// draw and fill the segment path
ctx.beginPath();
ctx.moveTo(s.points[0].x, s.points[0].y);
for (var i = 1; i < s.points.length; i++) {
ctx.lineTo(s.points[i].x, s.points[i].y);
}
ctx.closePath();
ctx.fillStyle = s.fill;
ctx.fill();
ctx.lineWidth = 2;
ctx.strokeStyle = 'black';
ctx.stroke();
// draw segment's box label
if (s.label.withLine) {
lineBoxedLabel(s, labelfontsize, labelfontface, labelpadding);
} else {
boxedLabel(s, labelfontsize, labelfontface, labelpadding);
}
}
function moleculeLabel(start, end, offsetLength, angle, text) {
ctx.textAlign = 'center';
ctx.textBaseline = 'middle'
ctx.font = '14px verdana';
var dx = end.x - start.x;
var dy = end.y - start.y;
var x0 = parseInt(start.x + dx * 0.50);
var y0 = parseInt(start.y + dy * 0.50);
var x1 = parseInt(x0 + offsetLength * Math.cos(angle));
var y1 = parseInt(y0 + offsetLength * Math.sin(angle));
ctx.fillStyle = 'black';
ctx.fillText(text, x1, y1);
// arrow
var x0 = parseInt(start.x + dx * 0.35);
var y0 = parseInt(start.y + dy * 0.35);
var x1 = parseInt(x0 + 50 * Math.cos(angle));
var y1 = parseInt(y0 + 50 * Math.sin(angle));
var x2 = parseInt(start.x + dx * 0.65);
var y2 = parseInt(start.y + dy * 0.65);
var x3 = parseInt(x2 + 50 * Math.cos(angle));
var y3 = parseInt(y2 + 50 * Math.sin(angle));
ctx.beginPath();
ctx.moveTo(x1, y1);
ctx.lineTo(x3, y3);
ctx.strokeStyle = 'black';
ctx.lineWidth = 1;
ctx.stroke();
var angle = Math.atan2(dy, dx);
ctx.translate(x3, y3);
ctx.rotate(angle);
ctx.drawImage(arrowhead, -arrowheadLength, -arrowheadWidth / 2);
ctx.setTransform(1, 0, 0, 1, 0, 0);
}
function boxedLabel(s, fontsize, fontface, padding) {
var centerX = s.label.cx;
var centerY = s.label.cy;
var text = s.label.text;
ctx.textAlign = 'center';
ctx.textBaseline = 'middle'
ctx.font = fontsize + 'px ' + fontface
var textwidth = ctx.measureText(text).width;
var textheight = fontsize * 1.286;
var leftX = centerX - textwidth / 2 - padding;
var topY = centerY - textheight / 2 - padding;
ctx.fillStyle = 'white';
ctx.fillRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.lineWidth = 1;
ctx.strokeRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.fillStyle = 'black';
ctx.fillText(text, centerX, centerY);
}
function lineBoxedLabel(s, fontsize, fontface, padding) {
var centerX = s.label.cx;
var centerY = s.label.cy;
var text = s.label.text;
var lineToX = s.label.endX;
var lineToY = s.label.endY;
ctx.textAlign = 'center';
ctx.textBaseline = 'middle'
ctx.font = fontsize + 'px ' + fontface
var textwidth = ctx.measureText(text).width;
var textheight = fontsize * 1.286;
var leftX = centerX - textwidth / 2 - padding;
var topY = centerY - textheight / 2 - padding;
// the line
ctx.beginPath();
ctx.moveTo(leftX, topY + textheight / 2);
ctx.lineTo(lineToX, topY + textheight / 2);
ctx.strokeStyle = 'black';
ctx.lineWidth = 1;
ctx.stroke();
// the boxed text
ctx.fillStyle = 'white';
ctx.fillRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.strokeRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.fillStyle = 'black';
ctx.fillText(text, centerX, centerY);
}
function ticklines(start, end, count, angle, length) {
var dx = end.x - start.x;
var dy = end.y - start.y;
ctx.lineWidth = 1;
for (var i = 1; i < count; i++) {
var x0 = parseInt(start.x + dx * i / count);
var y0 = parseInt(start.y + dy * i / count);
var x1 = parseInt(x0 + length * Math.cos(angle));
var y1 = parseInt(y0 + length * Math.sin(angle));
ctx.beginPath();
ctx.moveTo(x0, y0);
ctx.lineTo(x1, y1);
ctx.stroke();
if (i == 2 || i == 4 || i == 6 || i == 8) {
var labelOffset = length * 3 / 4;
var x1 = parseInt(x0 - labelOffset * Math.cos(angle));
var y1 = parseInt(y0 - labelOffset * Math.sin(angle));
ctx.fillStyle = 'black';
ctx.fillText(parseInt(i * 10), x1, y1);
}
}
}
function premakeArrowhead() {
var actx = arrowhead.getContext('2d');
arrowhead.width = arrowheadLength;
arrowhead.height = arrowheadWidth;
actx.beginPath();
actx.moveTo(0, 0);
actx.lineTo(arrowheadLength, arrowheadWidth / 2);
actx.lineTo(0, arrowheadWidth);
actx.closePath();
actx.fillStyle = 'black';
actx.fill();
}
function drawTriangle(t) {
ctx.beginPath();
ctx.moveTo(t[0].x, t[0].y);
ctx.lineTo(t[1].x, t[1].y);
ctx.lineTo(t[2].x, t[2].y);
ctx.closePath();
ctx.strokeStyle = 'black';
ctx.lineWidth = 2;
ctx.stroke();
}
function drawLegend(texts, x, y, lineheight) {
ctx.textAlign = 'left';
ctx.textBaseline = 'top';
ctx.fillStyle = 'black';
ctx.font = '12px arial';
for (var i = 0; i < texts.length; i++) {
ctx.fillText(texts[i], x, y + i * lineheight);
}
}
function plotResult(val1, val2, val3) {
let deltaX, length;
let sum = val1 + val2 + val3;
const cos60 = Math.cos(Math.PI / 3);
const sin60 = Math.sin(Math.PI / 3);
let ch4 = val1 / sum;
let c2h2 = val2 / sum;
let c2h4 = val3 / sum;
length = Math.sqrt(Math.pow((v1.x - v0.x), 2) + Math.pow((v1.y - v0.y), 2));
let ch4PointA = new Point(v0.x + (length * ch4) * cos60, v0.y - (length * ch4) * sin60);
length = Math.sqrt(Math.pow((v2.x - v1.x), 2) + Math.pow((v2.y - v1.y), 2));
let ch4PointB = new Point(v2.x - (length * ch4) * cos60, v2.y - (length * ch4) * sin60);
length = Math.sqrt(Math.pow((v1.x - v2.x), 2) + Math.pow((v1.y - v2.y), 2));
let c2h4PointA = new Point(v1.x + (length * c2h4) * cos60, v1.y + (length * c2h4) * sin60);
deltaX = (v2.x - v0.x) * c2h4;
let c2h4PointB = new Point(v0.x + deltaX, v0.y);
let point = getIntersection(ch4PointA, ch4PointB, c2h4PointA, c2h4PointB);
ctx.beginPath();
ctx.arc(point.x, point.y, 5, 0, 2 * Math.PI, false);
ctx.fillStyle = "red";
ctx.fill();
}
function getIntersection(pointA, pointB, pointC, pointD) {
let denominator, a, b, numeratorA, numeratorB;
denominator = ((pointD.y - pointC.y) * (pointB.x - pointA.x)) - ((pointD.x - pointC.x) * (pointB.y - pointA.y));
a = pointA.y - pointC.y;
b = pointA.x - pointC.x;
numeratorA = ((pointD.x - pointC.x) * a) - ((pointD.y - pointC.y) * b);
numeratorB = ((pointB.x - pointA.x) * a) - ((pointB.y - pointA.y) * b);
a = numeratorA / denominator;
b = numeratorB / denominator;
return new Point(pointA.x + (a * (pointB.x - pointA.x)), pointA.y + (a * (pointB.y - pointA.y)));
}
body {
background-color: ivory;
padding: 10px;
}
#canvas {
border: 1px solid red;
margin: 0 auto;
}
<canvas id="canvas" width=650 height=500></canvas>
我试图从椭圆三角形的示例中识别以下参数，但是当我修改该行时：
drawCircle(canvas.width / 3,canvas.height / 2,2.5,'red');
//want to replace with specific values but its not working
drawCircle(32 / 3,33 / 2,2.5,'red');
我想识别正确的参数，以便演示可以将红色点更改为三角形内的其他 space
CH4= 20
C2H4= 70
C2H2= 20
演示： https://codepen.io/Barak/pen/WwdPxQ
我从 Whosebug 社区阅读了 post，但看不到值
在您提到的 post 中，markE 很好地复制了 Duval 三角形的外观。唯一的问题是包含 drawCircle() 函数的 codepen 只是一个虚拟对象，只不过是在任意位置放置一个点，由它的 x 和 y 参数给出。
要使此函数显示三角形上实际数据的正确位置 - 例如CH4=20 | C2H4=70 | C2H2=20 - 涉及的内容更多。
让我们更深入地了解一下，如果我们要在纸上以图形方式解决这个问题。 （以下内容基于this论文）
杜瓦尔三角形基本上是这样的等边三角形，边b=%CH4， 边 a=%C2H4 边 c=%C2H2.
如果我们考虑以下示例数据%CH4=25 | %C2H4=35 | %C2H2=40
我们必须从 A 点到 C 点，b 边长度的 25% 并画一条平行于 c 边的线：
然后从C点到B点，a边长度的35%画一条平行于b边的直线：
最后从B点到A点，c边长的40%画一条平行于a边的直线：
因此，在这三条线相交的地方——如论文所述——我们有指示状态的目标位置。这可以使用普通三角函数以编程方式完成。好吧，我不太清楚为什么我们需要这三行。由于 CH4 的百分比总是平行于三角形的底边，而 C2H4 总是平行于边 b，我们还有一个交点，C2H2 的线是自动给出的。
基本上我们只需要一个函数来计算 CH4 和 C2H4 线之间的交点。
我采用了 markE 的现有代码并通过函数 plotResult() 对其进行了增强，该函数采用三个参数来表示 CH4、C2H2 和 C2H4 ppm 值：
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
// https://www.researchgate.net/publication/4345236_A_Software_Implementation_of_the_Duval_Triangle_Method
class Point {
constructor(x, y) {
this.x = x;
this.y = y;
}
}
var v0 = {
x: 114,
y: 366
};
var v1 = {
x: 306,
y: 30
};
var v2 = {
x: 498,
y: 366
};
var triangle = [v0, v1, v2];
// Define all your segments here
var segments = [{
points: [{
x: 114,
y: 366
}, {
x: 281,
y: 76
}, {
x: 324,
y: 150
}, {
x: 201,
y: 366
}],
fill: 'rgb(172,236,222)',
label: {
text: 'D1',
cx: 200,
cy: 290,
withLine: false,
endX: null,
endY: null
},
},
{
points: [{
x: 385,
y: 366
}, {
x: 201,
y: 366
}, {
x: 324,
y: 150
}, {
x: 356,
y: 204
}, {
x: 321,
y: 256
}],
fill: 'deepskyblue',
label: {
text: 'D2',
cx: 290,
cy: 290,
withLine: false,
endX: null,
endY: null
},
},
{
points: [{
x: 297,
y: 46
}, {
x: 392,
y: 214
}, {
x: 372,
y: 248
}, {
x: 441,
y: 366
}, {
x: 385,
y: 366
}, {
x: 321,
y: 256
}, {
x: 356,
y: 204
}, {
x: 281,
y: 76
}],
fill: 'lightCyan',
label: {
text: 'DT',
cx: 370,
cy: 290,
withLine: false,
endX: 366,
endY: 120
},
},
{
points: [{
x: 306,
y: 30
}, {
x: 312,
y: 40
}, {
x: 300,
y: 40
}],
fill: 'black',
label: {
text: 'PD',
cx: 356,
cy: 40,
withLine: true,
endX: 321,
endY: 40
},
},
{
points: [{
x: 312,
y: 40
}, {
x: 348,
y: 103
}, {
x: 337,
y: 115
}, {
x: 297,
y: 46
}, {
x: 300,
y: 40
}],
fill: 'navajoWhite',
label: {
text: 'T1',
cx: 375,
cy: 70,
withLine: true,
endX: 340,
endY: 75
},
},
{
points: [{
x: 348,
y: 103
}, {
x: 402,
y: 199
}, {
x: 392,
y: 214
}, {
x: 337,
y: 115
}],
fill: 'tan',
label: {
text: 'T2',
cx: 400,
cy: 125,
withLine: true,
endX: 366,
endY: 120
},
},
{
points: [{
x: 402,
y: 199
}, {
x: 498,
y: 366
}, {
x: 441,
y: 366
}, {
x: 372,
y: 248
}],
fill: 'peru',
label: {
text: 'T3',
cx: 425,
cy: 290,
withLine: false,
endX: null,
endY: null
},
},
];
// label styles
var labelfontsize = 12;
var labelfontface = 'verdana';
var labelpadding = 3;
// pre-create a canvas-image of the arrowhead
var arrowheadLength = 10;
var arrowheadWidth = 8;
var arrowhead = document.createElement('canvas');
premakeArrowhead();
var legendTexts = ['PD = Partial Discharge', 'T1 = Thermal fault < 300 celcius', '...'];
// start drawing
/////////////////////
// draw colored segments inside triangle
for (var i = 0; i < segments.length; i++) {
drawSegment(segments[i]);
}
// draw ticklines
ticklines(v0, v1, 9, 0, 20);
ticklines(v1, v2, 9, Math.PI * 3 / 4, 20);
ticklines(v2, v0, 9, Math.PI * 5 / 4, 20);
// molecules
moleculeLabel(v0, v1, 100, Math.PI, '% CH4');
moleculeLabel(v1, v2, 100, 0, '% C2H4');
moleculeLabel(v2, v0, 75, Math.PI / 2, '% C2H2');
// draw outer triangle
drawTriangle(triangle);
// draw legend
drawLegend(legendTexts, 10, 10, 12.86);
plotResult(25, 40, 35);
// end drawing
/////////////////////
function drawSegment(s) {
// draw and fill the segment path
ctx.beginPath();
ctx.moveTo(s.points[0].x, s.points[0].y);
for (var i = 1; i < s.points.length; i++) {
ctx.lineTo(s.points[i].x, s.points[i].y);
}
ctx.closePath();
ctx.fillStyle = s.fill;
ctx.fill();
ctx.lineWidth = 2;
ctx.strokeStyle = 'black';
ctx.stroke();
// draw segment's box label
if (s.label.withLine) {
lineBoxedLabel(s, labelfontsize, labelfontface, labelpadding);
} else {
boxedLabel(s, labelfontsize, labelfontface, labelpadding);
}
}
function moleculeLabel(start, end, offsetLength, angle, text) {
ctx.textAlign = 'center';
ctx.textBaseline = 'middle'
ctx.font = '14px verdana';
var dx = end.x - start.x;
var dy = end.y - start.y;
var x0 = parseInt(start.x + dx * 0.50);
var y0 = parseInt(start.y + dy * 0.50);
var x1 = parseInt(x0 + offsetLength * Math.cos(angle));
var y1 = parseInt(y0 + offsetLength * Math.sin(angle));
ctx.fillStyle = 'black';
ctx.fillText(text, x1, y1);
// arrow
var x0 = parseInt(start.x + dx * 0.35);
var y0 = parseInt(start.y + dy * 0.35);
var x1 = parseInt(x0 + 50 * Math.cos(angle));
var y1 = parseInt(y0 + 50 * Math.sin(angle));
var x2 = parseInt(start.x + dx * 0.65);
var y2 = parseInt(start.y + dy * 0.65);
var x3 = parseInt(x2 + 50 * Math.cos(angle));
var y3 = parseInt(y2 + 50 * Math.sin(angle));
ctx.beginPath();
ctx.moveTo(x1, y1);
ctx.lineTo(x3, y3);
ctx.strokeStyle = 'black';
ctx.lineWidth = 1;
ctx.stroke();
var angle = Math.atan2(dy, dx);
ctx.translate(x3, y3);
ctx.rotate(angle);
ctx.drawImage(arrowhead, -arrowheadLength, -arrowheadWidth / 2);
ctx.setTransform(1, 0, 0, 1, 0, 0);
}
function boxedLabel(s, fontsize, fontface, padding) {
var centerX = s.label.cx;
var centerY = s.label.cy;
var text = s.label.text;
ctx.textAlign = 'center';
ctx.textBaseline = 'middle'
ctx.font = fontsize + 'px ' + fontface
var textwidth = ctx.measureText(text).width;
var textheight = fontsize * 1.286;
var leftX = centerX - textwidth / 2 - padding;
var topY = centerY - textheight / 2 - padding;
ctx.fillStyle = 'white';
ctx.fillRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.lineWidth = 1;
ctx.strokeRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.fillStyle = 'black';
ctx.fillText(text, centerX, centerY);
}
function lineBoxedLabel(s, fontsize, fontface, padding) {
var centerX = s.label.cx;
var centerY = s.label.cy;
var text = s.label.text;
var lineToX = s.label.endX;
var lineToY = s.label.endY;
ctx.textAlign = 'center';
ctx.textBaseline = 'middle'
ctx.font = fontsize + 'px ' + fontface
var textwidth = ctx.measureText(text).width;
var textheight = fontsize * 1.286;
var leftX = centerX - textwidth / 2 - padding;
var topY = centerY - textheight / 2 - padding;
// the line
ctx.beginPath();
ctx.moveTo(leftX, topY + textheight / 2);
ctx.lineTo(lineToX, topY + textheight / 2);
ctx.strokeStyle = 'black';
ctx.lineWidth = 1;
ctx.stroke();
// the boxed text
ctx.fillStyle = 'white';
ctx.fillRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.strokeRect(leftX, topY, textwidth + padding * 2, textheight + padding * 2);
ctx.fillStyle = 'black';
ctx.fillText(text, centerX, centerY);
}
function ticklines(start, end, count, angle, length) {
var dx = end.x - start.x;
var dy = end.y - start.y;
ctx.lineWidth = 1;
for (var i = 1; i < count; i++) {
var x0 = parseInt(start.x + dx * i / count);
var y0 = parseInt(start.y + dy * i / count);
var x1 = parseInt(x0 + length * Math.cos(angle));
var y1 = parseInt(y0 + length * Math.sin(angle));
ctx.beginPath();
ctx.moveTo(x0, y0);
ctx.lineTo(x1, y1);
ctx.stroke();
if (i == 2 || i == 4 || i == 6 || i == 8) {
var labelOffset = length * 3 / 4;
var x1 = parseInt(x0 - labelOffset * Math.cos(angle));
var y1 = parseInt(y0 - labelOffset * Math.sin(angle));
ctx.fillStyle = 'black';
ctx.fillText(parseInt(i * 10), x1, y1);
}
}
}
function premakeArrowhead() {
var actx = arrowhead.getContext('2d');
arrowhead.width = arrowheadLength;
arrowhead.height = arrowheadWidth;
actx.beginPath();
actx.moveTo(0, 0);
actx.lineTo(arrowheadLength, arrowheadWidth / 2);
actx.lineTo(0, arrowheadWidth);
actx.closePath();
actx.fillStyle = 'black';
actx.fill();
}
function drawTriangle(t) {
ctx.beginPath();
ctx.moveTo(t[0].x, t[0].y);
ctx.lineTo(t[1].x, t[1].y);
ctx.lineTo(t[2].x, t[2].y);
ctx.closePath();
ctx.strokeStyle = 'black';
ctx.lineWidth = 2;
ctx.stroke();
}
function drawLegend(texts, x, y, lineheight) {
ctx.textAlign = 'left';
ctx.textBaseline = 'top';
ctx.fillStyle = 'black';
ctx.font = '12px arial';
for (var i = 0; i < texts.length; i++) {
ctx.fillText(texts[i], x, y + i * lineheight);
}
}
function plotResult(val1, val2, val3) {
let deltaX, length;
let sum = val1 + val2 + val3;
const cos60 = Math.cos(Math.PI / 3);
const sin60 = Math.sin(Math.PI / 3);
let ch4 = val1 / sum;
let c2h2 = val2 / sum;
let c2h4 = val3 / sum;
length = Math.sqrt(Math.pow((v1.x - v0.x), 2) + Math.pow((v1.y - v0.y), 2));
let ch4PointA = new Point(v0.x + (length * ch4) * cos60, v0.y - (length * ch4) * sin60);
length = Math.sqrt(Math.pow((v2.x - v1.x), 2) + Math.pow((v2.y - v1.y), 2));
let ch4PointB = new Point(v2.x - (length * ch4) * cos60, v2.y - (length * ch4) * sin60);
length = Math.sqrt(Math.pow((v1.x - v2.x), 2) + Math.pow((v1.y - v2.y), 2));
let c2h4PointA = new Point(v1.x + (length * c2h4) * cos60, v1.y + (length * c2h4) * sin60);
deltaX = (v2.x - v0.x) * c2h4;
let c2h4PointB = new Point(v0.x + deltaX, v0.y);
let point = getIntersection(ch4PointA, ch4PointB, c2h4PointA, c2h4PointB);
ctx.beginPath();
ctx.arc(point.x, point.y, 5, 0, 2 * Math.PI, false);
ctx.fillStyle = "red";
ctx.fill();
}
function getIntersection(pointA, pointB, pointC, pointD) {
let denominator, a, b, numeratorA, numeratorB;
denominator = ((pointD.y - pointC.y) * (pointB.x - pointA.x)) - ((pointD.x - pointC.x) * (pointB.y - pointA.y));
a = pointA.y - pointC.y;
b = pointA.x - pointC.x;
numeratorA = ((pointD.x - pointC.x) * a) - ((pointD.y - pointC.y) * b);
numeratorB = ((pointB.x - pointA.x) * a) - ((pointB.y - pointA.y) * b);
a = numeratorA / denominator;
b = numeratorB / denominator;
return new Point(pointA.x + (a * (pointB.x - pointA.x)), pointA.y + (a * (pointB.y - pointA.y)));
}
body {
background-color: ivory;
padding: 10px;
}
#canvas {
border: 1px solid red;
margin: 0 auto;
}
<canvas id="canvas" width=650 height=500></canvas>