我有一个功能,当单击按钮时,可以清除 Canvas 中背景图像中的所有绘图,但是当您再次绘图时,旧的(之前清除的绘图)会重新出现。如何进行硬删除,以便无需重新加载页面即可再次绘制
'use strict';
function initCanvas() {
let bMouseIsDown = false;
let canvas = document.getElementById('cvs');
let ctx = canvas.getContext('2d');
let convert = document.getElementById('convert');
let sel = 'png';
let imgs = document.getElementById('imgs');
let imgW = 300;
let imgH = 200;
let background = new Image();
background.crossOrigin = '';
background.src = "http://i.imgur.com/yf6d9SX.jpg";
background.onload = function(){
ctx.drawImage(background,0,0,600,400);
}
bind(canvas,ctx,convert,sel,imgs,imgW,imgH,bMouseIsDown);
};
initCanvas()
function bind (canvas,ctx,convert,sel,imgs,imgW,imgH,bMouseIsDown) {
let iLastX = 0;
let iLastY = 0;
let iX;
let iY;
canvas.onmousedown = function(e) {
bMouseIsDown = true;
iLastX = e.clientX - canvas.offsetLeft + (window.pageXOffset||document.body.scrollLeft||document.documentElement.scrollLeft);
iLastY = e.clientY - canvas.offsetTop + (window.pageYOffset||document.body.scrollTop||document.documentElement.scrollTop);
}
canvas.onmouseup = function() {
bMouseIsDown = false;
iLastX = -1;
iLastY = -1;
}
canvas.onmousemove = function(e) {
if (bMouseIsDown) {
iX = e.clientX - canvas.offsetLeft + (window.pageXOffset||document.body.scrollLeft||document.documentElement.scrollLeft);
iY = e.clientY - canvas.offsetTop + (window.pageYOffset||document.body.scrollTop||document.documentElement.scrollTop);
ctx.moveTo(iLastX, iLastY);
ctx.lineTo(iX, iY);
ctx.stroke();
ctx.strokeStyle = "blue";
ctx.lineJoin = "round";
ctx.lineWidth = 5;
iLastX = iX;
iLastY = iY;
}
};
document.getElementById('clear').addEventListener('click', function() {
rerenderImg();
});
function rerenderImg() {
iY = [];
iX=[];
initCanvas()
}
};
最佳答案
您需要调用ctx.beginPath();
然后再次在 Canvas 上绘制。
合理的放置位置是在调用 ctx.moveTo 之前。
here 给出了为什么需要这样做的解释。 .
关于javascript - 永久清除 Canvas 中的绘图,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40746724/