【发布时间】：2021-02-09 17:51:37
【问题描述】：
当它以离子连接时，我试图在线条之间填充颜色。当四线相互接触时，我想在线之间填充颜色。为此，我使用触摸事件创建了一个画布演示。请帮助解决我的问题。
我们在画布框中有 4 条线，我们将拖动它们并连接每条线并给出一个形状线框。这意味着我们的线已连接，现在在线之间填充颜色，因此框被颜色填充。
html 文件：
<canvas #canvasDraw width="300" height="300" (touchstart)="handleTouchStart($event)"
(touchmove)="handleTouchmove($event)"
(touchend)="handleTouchEnd($event)">
You need a browser that supports HTML5!
</canvas>
ts 文件：
import { Component, ElementRef, ViewChild } from '@angular/core';
@Component({
selector: 'app-home',
templateUrl: 'home.page.html',
styleUrls: ['home.page.scss'],
})
export class HomePage {
@ViewChild('canvasDraw', { static: false }) canvas: ElementRef;
canvasElement: any;
lines: any[];
isDown: boolean = false;
startX: number;
startY: number;
nearest: any;
offsetX: any;
offsetY: any;
constructor() {
}
ngAfterViewInit() {
this.canvasElement = this.canvas.nativeElement;
this.lines = [];
this.lines.push({ x0: 75, y0: 25, x1: 125, y1: 25 });
this.lines.push({ x0: 75, y0: 100, x1: 125, y1: 100 });
this.lines.push({ x0: 50, y0: 35, x1: 50, y1: 85 });
this.lines.push({ x0: 150, y0: 35, x1: 150, y1: 85 });
this.draw();
//this.reOffset();
requestAnimationFrame(() => {
this.reOffset()
})
}
reOffset() {
let BB = this.canvasElement.getBoundingClientRect();
this.offsetX = BB.left;
this.offsetY = BB.top;
}
// select the this.nearest line to the mouse
closestLine(mx, my) {
let dist = 100000000;
let index, pt;
for (let i = 0; i < this.lines.length; i++) {
//
let xy = this.closestXY(this.lines[i], mx, my);
//
let dx = mx - xy.x;
let dy = my - xy.y;
let thisDist = dx * dx + dy * dy;
if (thisDist < dist) {
dist = thisDist;
pt = xy;
index = i;
}
}
let line = this.lines[index];
return ({ pt: pt, line: line, originalLine: { x0: line.x0, y0: line.y0, x1: line.x1, y1: line.y1 } });
}
// linear interpolation -- needed in setClosestLine()
lerp(a, b, x) {
return (a + x * (b - a));
}
// find closest XY on line to mouse XY
closestXY(line, mx, my) {
let x0 = line.x0;
let y0 = line.y0;
let x1 = line.x1;
let y1 = line.y1;
let dx = x1 - x0;
let dy = y1 - y0;
let t = ((mx - x0) * dx + (my - y0) * dy) / (dx * dx + dy * dy);
t = Math.max(0, Math.min(1, t));
let x = this.lerp(x0, x1, t);
let y = this.lerp(y0, y1, t);
return ({ x: x, y: y });
}
// draw the scene
draw() {
let ctx = this.canvasElement.getContext('2d');
let cw = this.canvasElement.width;
let ch = this.canvasElement.height;
ctx.clearRect(0, 0, cw, ch);
// draw all lines at their current positions
for (let i = 0; i < this.lines.length; i++) {
this.drawLine(this.lines[i], 'black');
}
// draw markers if a line is being dragged
if (this.nearest) {
// point on line this.nearest to mouse
ctx.beginPath();
ctx.arc(this.nearest.pt.x, this.nearest.pt.y, 5, 0, Math.PI * 2);
ctx.strokeStyle = 'red';
ctx.stroke();
// marker for original line before dragging
this.drawLine(this.nearest.originalLine, 'red');
// hightlight the line as its dragged
this.drawLine(this.nearest.line, 'red');
}
}
drawLine(line, color) {
let ctx = this.canvasElement.getContext('2d');
ctx.beginPath();
ctx.moveTo(line.x0, line.y0);
ctx.lineTo(line.x1, line.y1);
ctx.strokeStyle = color;
ctx.stroke();
}
handleTouchStart(e) {
// tell the browser we're handling this event
let tch = e.touches[0];
// tch.preventDefault();
// tch.stopPropagation();
// mouse position
this.startX = tch.clientX - this.offsetX;
this.startY = tch.clientY - this.offsetY;
// find this.nearest line to mouse
this.nearest = this.closestLine(this.startX, this.startY);
this.draw();
// set dragging flag
this.isDown = true;
}
handleTouchEnd(e) {
// tell the browser we're handling this event
let tch = e.touches[0];
// tch.preventDefault();
// tch.stopPropagation();
// clear dragging flag
this.isDown = false;
this.nearest = null;
this.draw();
}
handleTouchmove(e) {
if (!this.isDown) { return; }
// tell the browser we're handling this event
let tch = e.touches[0];
// tch.preventDefault();
// tch.stopPropagation();
// mouse position
const mouseX = tch.clientX - this.offsetX;
const mouseY = tch.clientY - this.offsetY;
// calc how far mouse has moved since last mousemove event
let dx = mouseX - this.startX;
let dy = mouseY - this.startY;
this.startX = mouseX;
this.startY = mouseY;
// change this.nearest line vertices by distance moved
let line = this.nearest.line;
line.x0 += dx;
line.y0 += dy;
line.x1 += dx;
line.y1 += dy;
// redraw
this.draw();
let ctx = this.canvasElement.getContext('2d');
ctx.beginPath();
ctx.rect(line.x0, line.y0, line.x1, line.y1);
ctx.fillStyle = "red";
ctx.fill();
}
}
四线接触或连接时如何填充颜色？
【问题讨论】：
-
如何使用 HTML 矩形函数：w3schools.com/tags/canvas_rect.asp 和/或 JavaScript fillRect() 函数：javascripttutorial.net/web-apis/javascript-fillrect
-
你想要像颜色填充功能这样的实际“填充”吗？
-
我想像我连接四线框时那样做，而不是用颜色填充。我将添加更多有问题的细节。
标签： javascript angularjs ionic-framework