我有一个视频元素和画布元素。样式有以下方式:
canvas {
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
height:100%;
width:100%;
background-color: rgba(0,0,255,0.5);
z-index:10;
}
video {
position: absolute;
top: 0;
left: 0;
}
HTML如下
<video id="local-video" class="ui large image hidden" autoplay></video>
<canvas id="c1" class="ui large"></canvas>
我试图在画布上绘制视频元素。当我将画布的位置设置为固定时,我可以使用下面的代码绘制画布,但画布不会叠加在视频中。但是当我将位置设置为绝对时,画布会叠加在视频中,但我无法在视频中绘制。我检查了我的控制台的context.moveTo()和context.lineTo()的点,它们显示完美,但没有在画布中绘制。请帮忙。 // canvas var canvas = document.getElementById('c1'); var context = canvas.getContext('2d'); var localVideo = document.getElementById('local-video')localVideo.addEventListener(“loadedmetadata”,function(e){var width = this.videoWidth,height = this.videoHeight; canvas.height = height; canvas.width = width ;},false);
$('#c1').mousedown(function(e){
var mouseX = e.pageX - this.offsetLeft;
var mouseY = e.pageY - this.offsetTop;
paint = true;
addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop,false);
redraw();
});
$('#c1').mousemove(function(e){
if(paint){
addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop, true);
redraw();
}
});
$('#c1').mouseup(function(e){
paint = false;
});
$('#c1').mouseleave(function(e){
paint = false;
});
var clickX = new Array();
var clickY = new Array();
var clickDrag = new Array();
var paint;
function addClick(x, y, dragging)
{
clickX.push(x);
clickY.push(y);
clickDrag.push(dragging);
}
function redraw(){
context.clearRect(0, 0, context.canvas.width, context.canvas.height); // Clears the canvas
context.strokeStyle = "rgba(0,0,255,0)";
context.lineJoin = "round";
context.lineWidth = 5;
for(var i=0; i < clickX.length; i++) {
context.beginPath();
if(clickDrag[i] && i){
context.moveTo(clickX[i-1], clickY[i-1]);
}else{
context.moveTo(clickX[i]-1, clickY[i]);
}
context.lineTo(clickX[i], clickY[i]);
context.stroke();
context.closePath();
}
}
我不知道这是否是你要找的帽子:我正在使用视频和画布。我可以点击开始并停止视频,我可以在画布上自由绘制。
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
let cw = canvas.width = 400,
cx = cw / 2;
let ch = canvas.height = 200,
cy = ch / 2;
ctx.strokeStyle = "#fff";
let drawing = false;
// a function to detect the mouse position
function oMousePos(element, evt) {
var ClientRect = element.getBoundingClientRect();
return { //objeto
x: Math.round(evt.clientX - ClientRect.left),
y: Math.round(evt.clientY - ClientRect.top)
}
}
parentDiv.addEventListener('mousedown', function(evt) {
drawing = true; // you can draw now
let m = oMousePos(parentDiv, evt);
ctx.beginPath();
ctx.moveTo(m.x,m.y);
}, false);
parentDiv.addEventListener('mouseup', function(evt) {
drawing = false; // you can't draw anymore
}, false);
parentDiv.addEventListener('mouseleave', function(evt) {
drawing = false; // you can't draw anymore
}, false);
parentDiv.addEventListener("mousemove", function(evt) {
if (drawing) {
let m = oMousePos(parentDiv, evt);
ctx.lineTo(m.x, m.y);
ctx.stroke();
}
}, false);
body {
background-color: #222;
overflow: hidden;
}
video,canvas {
width:400px;
height:200px;
display: block;
position:absolute;
}
canvas {pointer-events:none;}
<div id="parentDiv">
<video width="400" controls>
<source src="https://www.w3schools.com/html/mov_bbb.mp4" type="video/mp4">
<source src="https://www.w3schools.com/html/mov_bbb.ogg" type="video/ogg">
Your browser does not support HTML5 video.
</video>
<canvas id="canvas"></canvas>
</div>
<p>
Video courtesy of
<a href="https://www.bigbuckbunny.org/" target="_blank">Big Buck Bunny</a>.
</p>
我不是在使用jQuery,但我希望你能得到这个想法。
我用普通的js重写了脚本,让HTML和CSS像你的一样,现在它可以工作了
var oldX, oldY;
var draw=false;
canvas.onmousedown=function(e) {
oldX = (e.pageX - this.offsetLeft)/4;
oldY = (e.pageY - this.offsetTop)/4;
draw=true;
}
canvas.onmousemove=function(e) {
var mouseX = (e.pageX - this.offsetLeft)/4; //was out of scale, this gets it almost
var mouseY = (e.pageY - this.offsetTop)/4; // where I want it to be, to fix
if(draw) {
context.beginPath();
context.moveTo(oldX, oldY);
context.lineTo(mouseX, mouseY);
// console.log(mouseX, mouseY);
context.stroke();
context.closePath();
oldX=mouseX;
oldY=mouseY;
}
}
canvas.onmouseup=function(e) {
draw=false;
}