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Html5 simply implements the sample code of graffiti board

黄舟Original: 2017-03-16 13:17:323728browse

This article mainly teaches you how to use Html5 to write your own drawing board, perform painting, color adjustment and other operations. Interested friends can refer to it

Recently learned about the powerful drawing function of html5 It surprised me, so I wrote a gadget---a graffiti pad, which can perform functions such as: drawing, changing colors, and adjusting the brush size.

html5 drawing can be divided into points, lines, surfaces, circles, Pictures, etc., points and lines, these are the basic points of all plane effects. With these two things, there is nothing that cannot be drawn, only unexpected algorithms.

First upload the code:

html

<body style="cursor:pointer">  
 <canvas id="mycavas" width="1024" height="400" style="border:solid 4px #000000"></canvas><!--画布-->  
        <input type="color" id="color1" name="color1"/><!--设色器-->  
        <output name="a" for="color1" onforminput="innerHTML=color1.value"></output>  
         <input type="range" name="points" id="size" min="5" max="20" /><!--拖动条-->  
</body>

Effect:

Html5 simply implements the sample code of graffiti board

Okay , a simple drawing interface is ready. Let’s start writing some line drawing code

$.Draw = {};   
$.extend($.Draw, {   
    D2: "",   
    CX:"",   
    Box: "mycavas",//画布id   
    BoxObj:function(){//画布对象   
        this.CX=document.getElementById(this.Box);   
    },   
    D2:function(){//2d绘图对象   
       this.D2 = this.CX.getContext("2d");   
    },   
    Cricle: function (x, y, r, color) {//画圆   
        if (this.D2) {   
            this.D2.beginPath();   
            this.D2.arc(x, y, r, 0, Math.PI * 2, true);   
            this.D2.closePath();   
            if (color) {   
                this.D2.fillStyle = color;   
            }   
            this.D2.fill();   
        }   
    },   
    init: function () {//初始化   
        this.BoxObj();   
        this.D2();   
    }   
  
})

I believe everyone can understand the simple code here. It mainly creates an object, including creating a canvas and creating 2d. Object, circle drawing method, and object initialization method.

Next, go to the front html page to call this object/p>

Look at the code:

var color = "#000000";//初始化颜色   
        var size = 5;//初始化尺寸   
        document.getElementById(&#39;color1&#39;).onchange = function () {   
            color = this.value;   
        };   
        document.getElementById(&#39;size&#39;).onchange = function () {   
            size = this.value;   
        };   
        $.Draw.init();//初始化   
        var tag = false;//控制鼠标当前状态并起到开启油墨开关的作用   
        var current = {};//存储鼠标按下时候的点   
        document.onmousedown = function (option) {//鼠标按下事件   
            current.x = option.x;   
            current.y = option.y;   
            $.Draw.Cricle(option.x, option.y, size, color);   
            tag = true;   
        }   
        document.onmouseup = function () {//鼠标抬起事件   
            tag = false;   
        }   
        document.onmousemove = function (option) {//鼠标移动事件   
            if (tag) {   
                if (size >= 0) {   
                    $.Draw.Cricle(option.x, option.y, size, color);   
                }    
            }   
        }

This code mainly has the following meanings

1. Capture the change event of the color space and drag bar control to obtain the corresponding color and size values, and store them for the following line drawing

2. Initialize the drawing object

3. Capture the mouse press, lift and move events. The key is that a switch can control the ink

Okay, a simple graffiti pad will be enough, with my calligraphy on it:

Html5 simply implements the sample code of graffiti board

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