如何放大到画布三角 [英] how to zoom to triangle in canvas
问题描述
嘿,我已经创造了帆布一个三角形,我已经使用2种方法:
主要方法:createTriangle它叫createInterval 3倍。
三角形是由仅3个顶点。
现在我想缩放选项添加到当前画布。
放大和缩小,但不知从哪里开始知道吗?
的一点改进的是,我没有任何的中心点为当前三角形和O的不知道如何计算它的事实开始。
任何指导将是有益的。)
更新
有关可以安装在画布指令或库是什么?
$(函数(){\r
VAR帆布=的document.getElementById(画布上);\r
变种CTX = canvas.getContext(2D);\r
//定义三角形顶点:3个顶点为一个三角形。\r
VAR VER0 = {\r
X:114,\r
Y:366\r
};\r
VAR VER1 = {\r
X:306,\r
Y:30\r
};\r
VAR VER2 = {\r
X:498,\r
Y:366\r
}\r
VAR三角= [VER0,VER1,VER2]\r
\r
\r
\r
drawTriangle(三角形);\r
\r
\r
\r
\r
功能drawTriangle(三角形){\r
的console.log('drawTriangle',三角形);\r
变种V0 =三角形[0];\r
变种V1 =三角形[1];\r
变种V2 =三角形[2];\r
ctx.beginPath();\r
createInterval(V0,V1);\r
createInterval(V1,V2);\r
createInterval(V0,V2);\r
ctx.closePath();\r
}\r
\r
功能createInterval(点1,点2){\r
的console.log('createInterval,点1,点2);\r
ctx.moveTo(point1.x,point1.y);\r
ctx.lineTo(point2.x,point2.y);\r
ctx.strokeStyle =黑色;\r
ctx.stroke();\r
}\r
});
\r
&LT;脚本SRC =https://ajax.googleapis.com/ajax /libs/jquery/2.1.1/jquery.min.js\"></script>\r
&LT;帆布ID =画布WIDTH = 650 HEIGHT = 500&GT;&LT; /帆布&GT;
\r
给定一个多边形的顶点,你可以通过计算顶点X的&放的算术平均值计算的可接受放大点; ÿ的。这实际上是一种大规模的多边形的中心,但它是一个好点的使用变焦。
VAR SUMX = vert0.x + vert1.x + vert2.x;
VAR苏梅= vert0.y + vert1.y + vert2.y;
VAR zoomX = SUMX / 3; // 3个顶点
VAR zoomY =苏梅/ 3;
Hey I have created a triangle in canvas, I have used 2 methods: main method: createTriangle which called to createInterval 3 times. The triangle is composed of 3 vertices only. Now I want to add zoom option to current canvas. Zoom In and Zoom out, but I don't know from where to start? The problen start from the fact that,I don't have any center point for current triangle and O don't know how to calculate it.
Any guidance will be helpfull :).
Update
What about directives or libraries which can be installed over the canvas?
$(function() {
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
//define triangle vertices: 3 vertices for one triangle.
var ver0 = {
x: 114,
y: 366
};
var ver1 = {
x: 306,
y: 30
};
var ver2 = {
x: 498,
y: 366
}
var triangle = [ver0, ver1, ver2]
drawTriangle(triangle);
function drawTriangle(triangle) {
console.log('drawTriangle', triangle);
var v0 = triangle[0];
var v1 = triangle[1];
var v2 = triangle[2];
ctx.beginPath();
createInterval(v0, v1);
createInterval(v1, v2);
createInterval(v0, v2);
ctx.closePath();
}
function createInterval(point1, point2) {
console.log('createInterval', point1, point2);
ctx.moveTo(point1.x, point1.y);
ctx.lineTo(point2.x, point2.y);
ctx.strokeStyle = "black";
ctx.stroke();
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<canvas id="canvas" width=650 height=500></canvas>
Given the vertices of a polygon, you can calculate an acceptable zoom point by calculating the arithmetic mean of the vertices X's & Y's. This is actually the polygon's center of mass, but it's a good point to use for zooming.
var sumX=vert0.x+vert1.x+vert2.x;
var sumY=vert0.y+vert1.y+vert2.y;
var zoomX=sumX/3; // 3 vertices
var zoomY=sumY/3;
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