Tutorial on making video puzzles with HTML5_html5 tutorial tips

A few days ago, my colleague showed me a special effect, which is a jigsaw puzzle. The difference is that the puzzle is animation. He asked me to make a DEMO, so I worked on it myself for a while, and it was indeed not difficult. It's easy to do with canvas. So this blog post is not suitable for experts. . . . I just wrote it casually for fun.
Rendering:

At least when I first saw this, I thought it was quite novel, so I thought of making it for fun. If you think the poster is out, please give me a thumbs up

Without further ado, let’s start with DEMO: Video Puzzle (You may have to wait a while to see the effect. I made a video link directly from w3school. You can drag and drop it. It's very simple, and may still have some bugs. After all, it's just a DEMO for fun. Just explain the principles.) Another point is that directly drawing the current frame of the video into the canvas does not seem to be supported on mobile devices. . . At least I looked at it on my iPad and found that I couldn’t draw. If anyone knows how to solve this problem, please answer it for me. I’d be very grateful

Principle: Each puzzle piece is a canvas, and an off-screen canvas is also required. First create a video tag

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The code is as follows:

And hide the video, and then draw each frame into the off-screen canvas when playing the video (off-screen canvas is the hidden canvas, used to save data). The writing method is very simple:

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The code is as follows:

ctx.drawImage(video, 0, 0, vw, vh);

, just use the drawImage method to draw it directly. Why use an off-screen canvas first? Because if you directly draw each frame of data into the canvas of all puzzle pieces at the same time, the browser will crash instantly. So use an off-screen canvas as a buffer. First save the data of the current frame to the canvas, and then draw the canvas into the canvas as the puzzle piece. Drawing canvas into canvas is also very simple, you can also use drawImage:

ctx2.drawImage(cs , -this.cols*this.w , -this.rows*this.h , vw , vh);

Then. . . . The principle is as simple as that. I would like to remind you later that when using requestAnimationFrame to loop through frames, you need to limit the speed. For example, as written below, I fetch every 30 milliseconds. It is recommended to take 30~50 milliseconds. If it is too low, the browser will crash easily. If it is too high, it will cause the browser to crash. If the video is stuck, the video will freeze:

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The code is as follows:

function animate(){
var newTime = new Date();
if(newTime - lastTime > 30){
lastTime = newTime;
ctx.drawImage(video , 0 , 0 , vw , vh);
canvases. forEach(function(){
var ctx2 = this.cas.getContext('2d');
ctx2.drawImage(cs , -this.cols*this.w , -this.rows*this.h , vw , vh);
});
}
if("requestAnimationFrame" in window){
requestAnimationFrame(animate);
}
else if("webkitRequestAnimationFrame" in window ){
webkitRequestAnimationFrame(animate);
}
else if("msRequestAnimationFrame" in window){
msRequestAnimationFrame(animate);
}
else if("mozRequestAnimationFrame" in window ){
mozRequestAnimationFrame(animate);
}
}

Finally post all the code:

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The code is as follows:

<script><br> var video = document.getElementById("video");<br> var cs = document.getElementById("liping");<br> var ctx = cs.getContext('2d')<br> var rows = 3,<br> cols = 3,<br> cb = document.querySelector(".allCanvas"),<br> vw = 600,<br> vh = 400,<br> canvases = [];</p> <p> function createCanvas(){<br> var num = rows*cols;<br> for(var i=0;i<cols;i ){<br> for(var j=0;j<rows;j ){<br> var canvas = new vCanvas(Math.random()*600, Math.random()*600 , vw/rows , vh/cols , j , i);<br> canvases.push(canvas);<br> }<br> }<br> }</p> <p> var vCanvas = function(x,y,w,h,cols,rows){<br> this.x = x;<br> this.y = y;<br> this.w = w;<br> this.h = h;<br> this.cols = cols;<br> this.rows = rows;<br> this.creat();<br> this.behavior();<br> }<br> vCanvas.prototype = {<br> creat:function(){<br> this.cas = document.createElement("canvas");<br> cb.appendChild(this.cas);<br> this.cas.className = "vcanvas";<br> this.cas.id = "vc_" (this.cols 1)*(this.rows 1);<br> this.cas.style.left = this.x "px";<br> this.cas.style.top = this.y "px";<br> this.cas.width = this.w;<br> this.cas.height = this.h;<br> },<br> behavior:function(){<br> this.cas.onmousedown = function(e){<br> e = e || window.event;<br> var that = this;<br> var om = {<br> x:e.clientX,<br> y:e.clientY<br> }<br> window.onmousemove = function(e){<br> e = e || window.event;<br> var nm = {<br> x:e.clientX,<br> y:e.clientY<br> }<br> that.style.left = parseInt(that.style.left.replace("px","")) (nm.x-om.x) "px";<br> that.style.top = parseInt(that.style.top.replace("px","")) (nm.y-om.y) "px";<br> om = nm;<br> }<br> window.onmouseup = function(){<br> this.onmousemove = null;<br> }<br> }<br> }<br> }</p> <p> Array.prototype.forEach = function(callback){<br> for(var i=0;i<this.length;i ){<br> callback.call(this[i]);<br> }<br> }</p> <p> var lastTime = 0;<br> function initAnimate(){<br> lastTime = new Date();<br> createCanvas();<br> animate();<br> }</p> <p> function animate(){<br> var newTime = new Date();<br> if(newTime - lastTime > 30){<br> lastTime = newTime;<br> ctx.drawImage(video , 0 , 0 , vw , vh);<br> canvases.forEach(function(){<br> var ctx2 = this.cas.getContext('2d');<br> ctx2.drawImage(cs , -this.cols*this.w , -this.rows*this.h , vw , vh);<br> });<br> }<br> if("requestAnimationFrame" in window){<br> requestAnimationFrame(animate);<br> }<br> else if("webkitRequestAnimationFrame" in window){<br> webkitRequestAnimationFrame(animate);<br> }<br> else if("msRequestAnimationFrame" in window){<br> msRequestAnimationFrame(animate);<br> }<br> else if("mozRequestAnimationFrame" in window){<br> mozRequestAnimationFrame(animate);<br> }<br> }</p> <p> video.play();<br> initAnimate();<br> </script>