网页绘图(适配移动端)
网页绘图(适配移动端)
杨润康Bla 发表于2年前
网页绘图(适配移动端)
  • 发表于 2年前
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首先创建一个Web应用,并新建相关的文件,好了之后的目录结构如下图所示

这里写图片描述

index.jsp中的代码

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>写个字呗</title>
 <script type="text/javascript" src="js/jquery-1.8.3.js"></script>
<link href="css/handwriting.css" rel="stylesheet" type="text/css"/>
<!-- 移动端 -->
<meta name="viewport" content="height = device-height, width = device-width, initial-scale = 1.0, minimum-scale = 1.0, maximum-scale = 1.0, user-scalable = no" />
</head>
<body>
    <canvas id="canvas">
        您的浏览器不支持canvas
    </canvas>
    <div id="controller">

        <div id="black_btn" class="color_btn color_btn_selected"></div>
        <div id="blue_btn" class="color_btn"></div>
        <div id="green_btn" class="color_btn"></div>
        <div id="red_btn" class="color_btn"></div>
        <div id="orange_btn" class="color_btn"></div>
        <div id="yellow_btn" class="color_btn"></div>

        <div id="clear_btn" class="op_btn">清 除</div>
        <div class="clearfix"></div>
    </div>
 <script src="js/handwriting.js"></script>
</body>
</html>

handwriting.js中的代码

//定义宽和高
var canvasWidth = Math.min(800,$(window).width()-20); //适配移动端
var canvasHeight = canvasWidth;

//定义鼠标是否按下
var isMouseDown = false;
//定义上一次鼠标的位置
var lastLoc = {x:0,y:0}; //初始化为0
//定义时间戳
var lastTimestamp = 0;
//定义上一次线条的宽度
var lastLineWidth = -1;
//当前笔的颜色
var strokeColor = "black";

//拿到canvas
var canvas = document.getElementById("canvas");
//拿到相应的上下文绘图环境
var context = canvas.getContext("2d");

//设定画布的宽和高
canvas.width = canvasWidth;
canvas.height = canvasHeight;

//适配移动端
$("#controller").css("width",canvasWidth+"px");

//绘制米字格
drawGrid();
//清除按钮操作
$("#clear_btn").click(
        function(e){
            context.clearRect(0,0,canvasWidth,canvasHeight);
            //重新绘制米字格
            drawGrid();
        }
);
$(".color_btn").click(
        function(e) {
            $(".color_btn").removeClass("color_btn_selected");
            $(this).addClass("color_btn_selected");
            strokeColor = $(this).css("background-color");
        }
);

//逻辑整合

/** * 开始 */
function beginStroke(point){
    isMouseDown = true;
    lastLoc = windowToCanvas(point.x, point.y);
    lastTimestamp = new Date().getTime();
}
/** * 结束 */
function endStroke(){
    isMouseDown = false;
}
/** * 绘图 */
function moveStroke(point){
    //核心代码
    var curLoc = windowToCanvas(point.x,point.y);
    var curTimestamp = new Date().getTime();
    /****Draw Start****/
    context.beginPath();
    context.moveTo(lastLoc.x,lastLoc.y);
    context.lineTo(curLoc.x ,curLoc.y);

    //计算速度
    var s = calcDistance(curLoc, lastLoc);
    var t = curTimestamp - lastTimestamp;
    var lineWidth = calcLineWidth(t,s);
    context.strokeStyle = strokeColor;
    context.lineWidth = lineWidth;
    context.lineCap = "round"; //矩形的帽子 可以绘制出平滑的线条
    context.lineJoin = "round";
    context.stroke();
    /****Draw End****/
    lastLoc = curLoc;
    lastTimestamp = curTimestamp;
    lastLineWidth = lineWidth;
}
//鼠标事件
canvas.onmousedown=function(e){
    e.preventDefault();
    beginStroke({x:e.clientX,y:e.clientY});
};

canvas.onmouseup=function(e){
    e.preventDefault();
    endStroke();
};

canvas.onmouseout=function(e){
    e.preventDefault();
    endStroke();
};

canvas.onmousemove=function(e){
    e.preventDefault();
    if(isMouseDown){
        //可以绘图了
        moveStroke({x:e.clientX,y:e.clientY});
    }
};
//触控事件
canvas.addEventListener('touchstart',function(e){
    e.preventDefault();
    touch = e.touches[0];
    beginStroke({x:touch.pageX,y:touch.pageY});
});
canvas.addEventListener('touchmove',function(e){
    e.preventDefault();
    if(isMouseDown){
        //可以绘图了
        touch = e.touches[0];
        moveStroke({x:touch.pageX,y:touch.pageY});
    }
});
canvas.addEventListener('touchend',function(e){
    e.preventDefault();
    endStroke();
});


/** * 绘制米字格 */
function drawGrid(){

    context.save();

    //绘制红色的正方形边框
    context.strokeStyle = "rgb(230,11,9)";

    context.beginPath();
    context.moveTo(3,3);
    context.lineTo(canvas.width - 3 ,3);
    context.lineTo(canvas.width - 3 ,canvas.height - 3);
    context.lineTo(3 ,canvas.height - 3);
    context.closePath();

    context.lineWidth = 6;
    context.stroke();

    //绘制米字格
    context.beginPath();
    context.moveTo(0,0);
    context.lineTo(canvasWidth,canvasHeight);

    context.moveTo(canvasWidth,0);
    context.lineTo(0,canvasHeight);

    context.moveTo(canvasWidth/2,0);
    context.lineTo(canvasWidth/2,canvasHeight);

    context.moveTo(0,canvasHeight/2);
    context.lineTo(canvasWidth,canvasHeight/2);

    context.lineWidth = 1;
    context.stroke();

    context.restore();
}
/** * 窗口到画布的位置 */
function windowToCanvas(x,y){
    var bbox = canvas.getBoundingClientRect();
    return {x:Math.round(x-bbox.left),y:Math.round(y-bbox.top)};
}

/** * 计算距离 */
function calcDistance(loc1,loc2){
    return Math.sqrt((loc1.x-loc2.x)*(loc1.x-loc2.x)+(loc1.y-loc2.y)*(loc1.y-loc2.y));
}

/** * 计算笔的宽度 */
var maxLineWidth = 20;
var minLineWidth = 1;
var maxStrokeV = 10;
var minStrokeV = 0.1;
function calcLineWidth(t,s){
    var v = s/t;
    var resultLineWidth;
    if(v<=minStrokeV){
        resultLineWidth = maxLineWidth;
    }else if(v>=maxStrokeV){
        resultLineWidth = minLineWidth;
    }else{
        //使用差值的方式
        resultLineWidth = maxLineWidth-(v-minStrokeV)/(maxStrokeV-minStrokeV)*(maxLineWidth-minLineWidth);
    }
    if(lastLineWidth == -1){
        return resultLineWidth;
    }
    return lastLineWidth*(2/3)+resultLineWidth*(1/3);
}



handwriting.css中的代码

#canvas{ display: block; margin: 0 auto; }
#controller{ margin: 0 auto; }
.op_btn{ float:right; margin: 10px 0 0 10px; border:2px solid #aaa; width:80px; height: 40px; line-height: 40px; font-size: 20px; text-align: center; border-radius:5px 5px; cursor:pointer; background-color: white; font-weight: bold; font-family: Microsoft Yahei,Arial; }
.op_btn:hover{ background-color: #def; }
.clearfix{ clear:both; }

.color_btn{ float:left; margin: 10px 10px 0 0; border: 5px solid white; width:40px; height: 40px; border-radius:5px 5px; cursor:pointer; }
.color_btn:hover{ border: 5px solid violet; }
.color_btn_selected{ border: 5px solid blueviolet; }

#black_btn{ background-color: black; }
#blue_btn{ background-color: blue; }
#green_btn{ background-color: green; }
#red_btn{ background-color: red; }
#orange_btn{ background-color: orange; }
#yellow_btn{ background-color: yellow; }

运行之后的效果图

PC端
这里写图片描述

移动端
这里写图片描述

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