canvas

千次阅读 多人点赞 2018-04-17 15:29:27

以canvas画布的左上角为笛卡尔坐标系的原点，且y轴的正方向向下，x轴的正方向向右二、准备工作：布置画布、获取画布、获取画笔 <canvas id=“canvas”></canvas> var canvas = document....

一、规则

以canvas画布的左上角为笛卡尔坐标系的原点，且y轴的正方向向下，x轴的正方向向右

二、准备工作：布置画布、获取画布、获取画笔

<canvas id=“canvas”></canvas>
var canvas = document.getElementById("canvas")
var context = canvas.getContext("2d")

三、分类

3、1：线条

移动画笔：context.moveTo(100,100),画笔起点

画笔停点：context.linrTo(600,600),画笔终点

画笔粗细的配置：context.lineWidth='5'

画笔颜色的配置：context.strokeStyle="#353537"

绘制类型：fill()填充  、stroke()描边

beginpath（）开始绘制，可以使后面的线段的颜色等不覆盖前面的，结束绘制为fill（）、stroke（）、closePath（）

	var canvas = document.getElementById('canvas');
        var context = canvas.getContext('2d');
        context.beginPath();
        context.moveTo(20,20);
        context.lineTo(30,30);
        context.lineTo(20,40);
        context.lineTo(20,20);
        context.closePath();//不使用closePath结束绘制，左上角的会有缺口，用closePath的时候可以不用进行结尾，即最后一笔可以不画
        context.lineWidth = '2'; //线条粗细
        context.strokeStyle = '	#228B22';//线条颜色
        context.fillStyle = "yellow";//内容填充色
        context.stroke();//描边结束
        context.fill(); //绘制结束
3、2：矩形，结合上面的知识点，矩形直接上例子就可以了

     window.onload = function(){
            var canvas = document.getElementById("canvas");
            var context = canvas.getContext("2d");

            rectfun(context,80,80,100,100,2,'black','white');
            rectfun(context,85,85,90,90,2,'black','white');
            rectfun(context,87,87,85,85,1,'black','white');
            rectfun(context,90,90,80,80,2,'black','white');
            rectfun(context,100,100,60,60,2,'black','white');
            rectfun(context,110,110,40,40,2,'black','white');
            rectfun(context,120,120,20,20,2,'black','white');
            rectfun(context,130,130,1,1,2,'black','white');
     }

   function rectfun(cxt,x,y,width,height,borderwidth,bordercolor,fillcolor){
            cxt.beginPath();
            cxt.rect(x,y,width,height);//生成矩形
            // cxt.closePath() 使用rect的时候，closePath可以不用
            cxt.lineWidth = borderwidth;//宽度
            cxt.strokeStyle = bordercolor;//颜色
            cxt.fillStyle = fillcolor;//填充色
            cxt.stroke();
            cxt.fill();
     }矩形效果图如下：




 

3、3：线条属性，共有4个属性

      3.3.1、lineCap属性（线条的帽子）：定义线的终点属性，有3个属性值（这些属性只会在终点起作用，折线处不会起作用）

* butt：默认值，端点是垂直于线段边缘的平直边缘。
* round：端点是在线段边缘处以线宽为直径的半圆。
* square：端点是在选段边缘处以线宽为长、以一半线宽为宽的矩形。

    例子：

    window.onload = function(){
        var canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 600;
        var context = canvas.getContext("2d");

        context.lineWidth = 50;
        context.strokeStyle = "#1BAAAA";

        context.beginPath();
        context.moveTo(100,100);
        context.lineTo(700,100);
        context.lineCap = "butt";
        context.stroke();

        context.beginPath();
        context.moveTo(100,300);
        context.lineTo(700,300);
        context.lineCap = "round";
        context.stroke();

        context.beginPath();
        context.moveTo(100,500);
        context.lineTo(700,500);
        context.lineCap = "square";
        context.stroke();

        //下面画两个基准线方便观察
        context.lineWidth = 3;
        context.strokeStyle = "black";

        context.beginPath();
        context.moveTo(100,0);
        context.lineTo(100,600);
        context.moveTo(700,0);
        context.lineTo(700,600);
        context.stroke();
    }

    效果：



    3.3.2、lineJoin（线条的连接），定义折线处的属性，直接看代码和效果就可以明白

    代码：

window.onload = function(){
        var canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 600;
        var context = canvas.getContext("2d");

        context.beginPath();
        context.moveTo(100,100);
        context.lineTo(300,300);
        context.lineTo(100,500);
        context.lineJoin = "miter";
        context.lineWidth = 20;
        context.strokeStyle = "red";
        context.stroke();

        context.beginPath();
        context.moveTo(300,100);
        context.lineTo(500,300);
        context.lineTo(300,500);
        context.lineJoin = "bevel";
        context.lineWidth = 20;
        context.strokeStyle = "blue";
        context.stroke();

        context.beginPath();
        context.moveTo(500,100);
        context.lineTo(700,300);
        context.lineTo(500,500);
        context.lineJoin = "round";
        context.lineWidth = 20;
        context.strokeStyle = "black";
        context.stroke();
    }

    效果：

    

        3.3.3、当lineJoin设置为miter时（默认），此时可以使用miterLimit属性（不常用）

        例子：

        

window.onload = function(){
        var canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 600;
        var context = canvas.getContext("2d");

        context.beginPath();
        context.moveTo(100,100);
        context.lineTo(300,300);
        context.lineTo(100,500);
        context.lineJoin = "miter";
        context.miterLimit = 10;
        context.lineWidth = 5;
        context.strokeStyle = "red";
        context.stroke();

        context.beginPath();
        context.moveTo(300,200);
        context.lineTo(500,300);
        context.lineTo(300,400);
        context.lineJoin = "miter";
        context.miterLimit = 10;
        context.lineWidth = 5;
        context.strokeStyle = "blue";
        context.stroke();

        context.beginPath();
        context.moveTo(500,290);
        context.lineTo(700,300);
        context.lineTo(500,310);
        context.lineJoin = "miter";
        context.miterLimit = 10;
        context.lineWidth = 5;
        context.strokeStyle = "black";
        context.stroke();
    }

效果：原理链接：http://7xkcl8.com1.z0.glb.clouddn.com/edu6-4.png



3、4填充颜色

    3.4.1填充基本颜色

    （1）颜色字符串填充

context.fillStyle = "red";

    （2）十六进制字符串

context.fillStyle = "#FF0000";

    （3）rgb

context.fillStyle = "rgba(255,0,0,1)";

    （4）hsl（）

context.fillStyle = "hsl(0,100%,50%)";

    （5）hsla（）

context.fillStyle = "hsla(0,100%,50%,1)";

3、5填充渐变形状，线性和径向

    3.5.1线性渐变

        例子：

var canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 600;
        var context = canvas.getContext("2d");

        context.rect(200,100,400,400);//x起始坐标  y起始坐标  宽  高 

        //添加渐变线
        var grd = context.createLinearGradient(200,300,600,300);  //xstart,ystart,xend,yend 从（200，300）到（600，300）的径向

        //添加颜色断点
        grd.addColorStop(0,"black");
        grd.addColorStop(0.5,"white");  
        grd.addColorStop(1,"black");

        //应用渐变
        context.fillStyle = grd;

        context.fill();

        效果：

        

        3.5.2绘制矩形的快捷方式

`fillRect(x,y,width,height)`、`stroke(x,y,width,height)`。这两个函数可以分别看做`rect()`与`fill()`以及`rect()`与`stroke()`的组合。因为`rect()`仅仅只是规划路径而已，而这两个方法确实实实在在的绘制。

    例子，直接看例子就可以直接看明白：

window.onload = function(){
        var canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 600;
        var context = canvas.getContext("2d");
        //添加渐变线
        var grd = context.createLinearGradient(100,300,700,300);xstart,ystart,xend,yend 从（100，300）到（700，300）的径向
        //添加颜色断点
        grd.addColorStop(0,"olive");
        grd.addColorStop(0.5,"aqua");
        grd.addColorStop(0.75,"fuchsia");
        grd.addColorStop(0.25,"teal");
        //应用渐变
        context.fillStyle = grd;
        context.strokeStyle = grd;

        context.strokeRect(200,150,450,50);

        context.fillRect(200,300,300,50);
    }

    效果：



    3、6：填充样式，createPattern（）填充图案，需要传递两个参数createPattern（img，repeat-style），第一个对象是img实例，第二个对象是string类型，有4种填充类型，repeat，repeat-x，repeat-y，no-repeat，第一种参数还可以传入一个canvas或者是video对象，这里只说img对象，其余的自己尝试

window.onload = function(){
        var canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 600;
        var context = canvas.getContext("2d");

        var img = new Image();//创建img对象
        img.src = "1.jpg";//为img对象指定图片源
        img.onload = function(){
            var pattern = context.createPattern(img, "repeat");//指定类型
            context.fillStyle = pattern;//纹理填充
            context.fillRect(0,0,800,600);//快速制作矩形的方法，xstart，ystrart，width，height
   }

    效果图：（代码里面img使用onload，是对图片进行预加载，）



    3、7：绘制标准圆弧arc()函数

        arc（x,y,r,startAngle,endAngle,anticlockwise）

        x,y圆心坐标，r半径，   

        startAngle：开始的弧度值，endAngle：结束的弧度值

        anticlockwise：表示绘制的方法（用布尔值进行表示），是（false）顺时针还是（true）逆时针，当此值不填写的时候，默认为false，顺时针，弧度值得规则如图：

        

    例子：（我画的准备图的是随便在浏览器的页面上画的，请自动忽略无用的背景）

        var canvas = document.getElementById("canvas");
        var context = canvas.getContext("2d");
        context.fillStyle = "#FFF";
        context.fillRect(0,0,800,600);

        context.beginPath();
        context.arc(150,250,50,Math.PI, Math.PI * 3 / 2);
        context.lineTo(250,200);
        context.arc(250,250,50,Math.PI* 3 / 2, Math.PI *2);
        context.lineTo(300,400);
        context.arc(250,400,50,0, Math.PI*1/2);
        context.lineTo(150,450);
        context.arc(150,400,50,Math.PI*1/2, Math.PI);
        // context.lineTo(100,250);
        context.closePath();
        context.strokeStyle = "#0078AA";
        context.stroke();

    （准备图）



（效果图）



3、8：切点绘制圆弧arcTo（）

。。。

收起

展开全文

Canvas

千次阅读 2017-06-22 15:45:04

canvas.drawLine(0, 0, 100, 100, paint);画多条线： float []pts = {0,0,100,100,200,200,300,300}; canvas.drawLines(pts, paint);// 画虚线–也通过多条线的方式画点画一个点： canvas.drawPoint(500, 500, ...

画线

画一条直线： 

canvas.drawLine(0, 0, 100, 100, paint);

画多条线： 

float []pts = {0,0,100,100,200,200,300,300}; 

canvas.drawLines(pts, paint);// 画虚线–也通过多条线的方式 




画点

画一个点： 

canvas.drawPoint(500, 500, paint);

画多个点： 

float []pts = {0,0,100,100,200,200,300,300}; 

canvas.drawPoints(pts, paint); 




画矩形

RectF r = new RectF(100, 100, 400, 500); 

canvas.drawRect(r, paint);

canvas.drawRect(left, top, right, bottom, paint);



画圆角矩形

RectF r = new RectF(100, 100, 200, 200); 

//x-radius ,y-radius圆角的半径 

canvas.drawRoundRect(r, 10, 10, paint);



画圆

canvas.drawCircle(300, 300, 200, paint);



画椭圆

RectF r = new RectF(100, 100, 300, 200); 

canvas.drawOval(r, paint);



画圆弧

canvas.drawArc( 

            rect, 

            startAngle, //其实角度，相对X轴正方向 

            sweepAngle, //画多少角度的弧度 

            useCenter, //boolean, false：只有一个纯弧线；true：闭合的边 

            paint);

RectF r = new RectF(100, 100, 400, 400); 

canvas.drawArc(r, 0, 90, true, paint);//顺时针旋转90度

true: 


false: 




Path




  rLineTo，rMoveTo 带r开头基于前一个点的相对位置 

  LineTo，MovoTo 不带r开头的，传的是我们的绝对位置


Path path = new Path(); 

//移动 

path.moveTo(100, 300);//画笔落笔的位置 

//连线(100, 300)—(200, 100) 

path.lineTo(200, 100); 


//连线(200, 100) — (200, 200) 

path.lineTo(200, 200); 


//拼接 

path.cubicTo(250, 200, 350, 300, 450, 400);//连接(200, 200) 


//首尾相接 

path.close(); 

canvas.drawPath(path, paint); 


圆角矩形路径

RectF r = new RectF(100, 100, 200, 200);
Path path = new Path();
float radii[] = {10,10,50,50,0,0,10,10};
path.addRoundRect(r, radii, Path.Direction.CW);
canvas.drawPath(path, paint);





RectF r = new RectF(100, 100, 200, 200);
Path path = new Path();
path.addArc(r, 0, 90);
canvas.drawPath(path, paint);





贝塞尔曲线

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setStrokeWidth(4);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(Color.BLACK);
        mStartX = 60;
        mStartY = 350;
        mEndX = 450;
        mEndY = 350;
        mPath = new Path();
        mPath.reset();
        mPath.moveTo(mStartX, mStartY);
        mPath.quadTo(mContorlX, mContorlY, mEndX, mEndY);
        //mPath.addCircle(); 里面有一个方向值 --顺时针和逆时针
        // canvas.drawTextOnPath();---可以去看一下文字的绘制方向
        canvas.drawPath(mPath, mPaint);
        canvas.drawPoint(mContorlX,mContorlY,mPaint);





setFillType



        mPaint = new Paint();
        mPaint.setColor(Color.RED);
        mPaint.setStrokeWidth(2);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setAntiAlias(true);



Path.FillType.WINDING

WINDING 模式 — 取Path所有所在的区域 – 默认的模式

    private void drawWindingType(Canvas canvas) {
        mPath = new Path();
        mPath.offset(100,100);
        mPath.addCircle(200, 200, 100, Path.Direction.CW);
        mPath.addCircle(300, 300, 100, Path.Direction.CW);
        mPath.setFillType(Path.FillType.WINDING);
        mPaint.setColor(Color.RED);
        canvas.drawPath(mPath,mPaint);
    }





Path.FillType.EVEN_ODD

EVEN_ODD 模式 — 取Path所在不相交的区域

    private void drawEvenOddType(Canvas canvas) {
        mPath = new Path();
        mPath.offset(100,100);
        mPath.addCircle(200, 200, 100, Path.Direction.CW);
        mPath.addCircle(300, 300, 100, Path.Direction.CW);
        mPath.setFillType(Path.FillType.EVEN_ODD);
        mPaint.setColor(Color.RED);
        canvas.drawPath(mPath,mPaint);
    }



Path.FillType.INVERSE_WINDING

INVERSE_WINDING 模式 – 取path所有未占的区域

    private void drawInverseWinding(Canvas canvas) {
        mPath = new Path();
        mPath.offset(100,100);
        mPath.addCircle(200, 200, 100, Path.Direction.CW);
        mPath.addCircle(300, 300, 100, Path.Direction.CW);
        mPath.setFillType(Path.FillType.INVERSE_WINDING);
        mPaint.setColor(Color.RED);
        canvas.drawPath(mPath,mPaint);
    }



Path.FillType.INVERSE_EVEN_ODD

INVERSE_EVEN_ODD 模式 — 取path所有未占和相交的区域



    private void drawInverseEvenOdd(Canvas canvas) {
        mPath = new Path();
        mPath.offset(100,100);
        mPath.addCircle(200, 200, 100, Path.Direction.CW);
        mPath.addCircle(300, 300, 100, Path.Direction.CW);
        mPath.setFillType(Path.FillType.INVERSE_EVEN_ODD);
        mPaint.setColor(Color.RED);
        canvas.drawPath(mPath,mPaint);
    }





op(Path path, Op op)



        mPaint = new Paint();
        mPaint.setColor(Color.RED);
        mPaint.setStrokeWidth(8);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setAntiAlias(true);



Path.Op.DIFFERENCE

DIFFERENCE – 减去Path2后Path1区域剩下的部分

    private void drawDifferenceOp(Canvas canvas) {
        Path path1 = new Path();
        path1.addCircle(150, 150, 100, Path.Direction.CW);
        Path path2 = new Path();
        path2.addCircle(200, 200, 100, Path.Direction.CW);
        path1.op(path2, Path.Op.DIFFERENCE);
        canvas.drawPath(path1, mPaint);
        mPaint.setColor(Color.DKGRAY);
        mPaint.setStrokeWidth(2);
        canvas.drawCircle(150, 150, 100,mPaint);
        canvas.drawCircle(200, 200, 100,mPaint);
    }



Path.Op.INTERSECT

INTERSECT — 保留Path2 和 Path1 共同的部分



    private void drawIntersectOp(Canvas canvas) {
        Path path1 = new Path();
        path1.addCircle(150, 150, 100, Path.Direction.CW);
        Path path2 = new Path();
        path2.addCircle(200, 200, 100, Path.Direction.CW);
        path1.op(path2, Path.Op.INTERSECT);
        canvas.drawPath(path1, mPaint);
        mPaint.setColor(Color.DKGRAY);
        mPaint.setStrokeWidth(2);
        canvas.drawCircle(150, 150, 100,mPaint);
        canvas.drawCircle(200, 200, 100,mPaint);
    }



Path.Op.UNION

UNION – 保留Path1 和 Path 2



    private void drawUnionOp(Canvas canvas) {
        Path path1 = new Path();
        path1.addCircle(150, 150, 100, Path.Direction.CW);
        Path path2 = new Path();
        path2.addCircle(200, 200, 100, Path.Direction.CW);
        path1.op(path2, Path.Op.UNION);
        canvas.drawPath(path1, mPaint);
        mPaint.setColor(Color.DKGRAY);
        mPaint.setStrokeWidth(2);
        canvas.drawCircle(150, 150, 100,mPaint);
        canvas.drawCircle(200, 200, 100,mPaint);
    }



Path.Op.XOR

XOR — 保留Path1 和 Path2 还有共同的部分

    private void drawXorOp(Canvas canvas) {
        Path path1 = new Path();
        path1.addCircle(150, 150, 100, Path.Direction.CW);
        Path path2 = new Path();
        path2.addCircle(200, 200, 100, Path.Direction.CW);
        path1.op(path2, Path.Op.XOR);
        canvas.drawPath(path1, mPaint);
        mPaint.setColor(Color.DKGRAY);
        mPaint.setStrokeWidth(2);
        canvas.drawCircle(150, 150, 100,mPaint);
        canvas.drawCircle(200, 200, 100,mPaint);
    }



Path.Op.REVERSE_DIFFERENCE

REVERSE_DIFFERENCE — 减去Path1后Path2区域剩下的部分



    private void drawReverseDifferenceOp(Canvas canvas) {
        Path path1 = new Path();
        path1.addCircle(150, 150, 100, Path.Direction.CW);
        Path path2 = new Path();
        path2.addCircle(200, 200, 100, Path.Direction.CW);
        path1.op(path2, Path.Op.REVERSE_DIFFERENCE);
        canvas.drawPath(path1, mPaint);
        mPaint.setColor(Color.DKGRAY);
        mPaint.setStrokeWidth(2);
        canvas.drawCircle(150, 150, 100,mPaint);
        canvas.drawCircle(200, 200, 100,mPaint);
    }



Region

        RectF r = new RectF(100, 100, 200, 300);
        Path path = new Path();
        path.addOval(r, Path.Direction.CCW);

        //创建一块矩形的区域
        Region region = new Region(100, 100, 200, 250);
        Region region1 = new Region();
        region1.setPath(path, region);//path的椭圆区域和矩形区域进行交集

        //结合区域迭代器使用（得到图形里面的所有的矩形区域）
        RegionIterator iterator = new RegionIterator(region1);

        Rect rect = new Rect();
        while (iterator.next(rect)) {
            canvas.drawRect(rect, paint);
        }



合并union：



        //合并
        Region region = new Region(50, 50, 100, 250);
        Rect r = new Rect(30, 30, 200, 100);
//        canvas.drawRect(r, paint);
//        paint.setColor(Color.BLUE);
        region.union(r);
//        region.op(r, Region.Op.INTERSECT);//交集部分 region是调用者A，r是求交集的B
        RegionIterator iterator = new RegionIterator(region);

        Rect rect = new Rect();
        while (iterator.next(rect)) {
            canvas.drawRect(rect, paint);
        }



求交集：



        Region region = new Region(50, 50, 100, 250);
        Rect r = new Rect(30, 30, 200, 100);
//        canvas.drawRect(r, paint);
//        paint.setColor(Color.BLUE);
//        region.union(r);
        region.op(r, Region.Op.INTERSECT);//交集部分 region是调用者A，r是求交集的B
        RegionIterator iterator = new RegionIterator(region);

        Rect rect = new Rect();
        while (iterator.next(rect)) {
            canvas.drawRect(rect, paint);
        }





Canvas变换



平移

canvas.translate(150, 50);



        // 绘制坐标系
        // 第一次绘制坐标轴
        paint.setColor(Color.GREEN);
        canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
        paint.setColor(Color.BLUE);
        canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴

        //平移--即改变坐标原点
        canvas.translate(150, 50);
        // 第二次绘制坐标轴
        paint.setColor(Color.GREEN);
        canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
        paint.setColor(Color.BLUE);
        canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴





缩放

//sx,sy：分别对x/y方向的一个缩放系数,画布的缩放会导致里面所有的绘制的东西都会有一个缩放效果 

canvas.scale(1.5f, 0.5f);



        RectF r = new RectF(0, 0, 400, 500);
        canvas.drawRect(r, paint);
        paint.setColor(Color.BLUE);
        //sx,sy：分别对x/y方向的一个缩放系数,画布的缩放会导致里面所有的绘制的东西都会有一个缩放效果
        canvas.scale(1.5f, 0.5f);
        canvas.drawRect(r, paint);





旋转

canvas.rotate(30);



        // 绘制坐标系
        // 第一次绘制坐标轴
        paint.setColor(Color.GREEN);
        canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
        paint.setColor(Color.BLUE);
        canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴

        //旋转
        canvas.rotate(30);
        // 第二次绘制坐标轴
        paint.setColor(Color.GREEN);
        canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
        paint.setColor(Color.BLUE);
        canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴





斜拉

//sx,sy倾斜度：X轴方向上倾斜60度，tan60=根号3 

canvas.skew(1.73f, 0);



        RectF r = new RectF(100, 100, 200, 200);
        canvas.drawRect(r, paint);
        paint.setColor(Color.BLUE);
        //sx,sy倾斜度：X轴方向上倾斜60度，tan60=根号3
        canvas.skew(1.73f, 0);
        canvas.drawRect(r, paint);





裁剪

canvas.clipRect(new Rect(250, 250, 300, 400));



        RectF r = new RectF(200, 200, 400, 500);
        canvas.drawRect(r, paint);
        paint.setColor(Color.BLUE);
        canvas.clipRect(new Rect(250, 250, 300, 400));
        canvas.drawBitmap(mBitmap, 250, 250, paint);
        paint.setColor(Color.GREEN);





save和restore、restoreToCount



    private void saveRestore(Canvas canvas, Paint paint) {
        canvas.translate(50, 50);
        RectF r = new RectF(0, 0, 200, 100);
        paint.setColor(Color.GREEN);
        canvas.drawRect(r, paint);
        canvas.save();
        //平移
        canvas.translate(50, 50);


        paint.setColor(Color.BLUE);
        canvas.drawRect(r, paint);

        canvas.restore();
        //canvas.rotate(45);

        paint.setColor(Color.YELLOW);
        r = new RectF(0, 0, 100, 200);

        canvas.drawRect(r, paint);
    }





        Paint paint = new Paint();
        RectF r = new RectF(50, 50, 150, 150);
        //当canvas执行saveLayer的时候就会新建一个新的透明画布图层
        int layer = canvas.saveLayer(0,0,canvas.getWidth(),canvas.getHeight(),null,Canvas.ALL_SAVE_FLAG);

        canvas.drawColor(Color.YELLOW);
        canvas.translate(50, 50);
        paint.setColor(Color.BLUE);
        canvas.drawRect(r, paint);

        canvas.restoreToCount(layer);


        RectF rectF = new RectF(0,0,100,100);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(10);
        paint.setColor(Color.GREEN);

        canvas.drawRect(rectF, paint);
        canvas.translate(50,50);





        Paint paint = new Paint();
        RectF rectF = new RectF(0,0,100,100);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(10);
        paint.setColor(Color.GREEN);

        canvas.drawRect(rectF, paint);
        canvas.translate(50,50);

        int layerid = canvas.saveLayer(0,0,canvas.getWidth(),canvas.getHeight(),null,Canvas.ALL_SAVE_FLAG);
        //canvas.save();
        canvas.drawColor(Color.BLUE);// 通过drawColor可以发现saveLayer是新建了一个图层，
        // 同时结合Lsn5的16种Xfermode叠加形式Demo可以验证是新建的透明图层
        paint.setColor(Color.YELLOW);
        canvas.drawRect(rectF,paint);
//        canvas.restore();
        canvas.restoreToCount(layerid);

        RectF rectF1 = new RectF(10,10,300,400);
        paint.setColor(Color.RED);
        canvas.drawRect(rectF1,paint);





        //save restoreToCount
        mBitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
        Paint mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setStrokeWidth(10);
        canvas.save();//1

        canvas.translate(200, 200);
        mPaint.setColor(Color.RED);
        RectF rectF = new RectF(0,0,200,200);

        canvas.drawRect(rectF,mPaint);

        canvas.save();//2

        canvas.rotate(45);
        mPaint.setColor(Color.BLUE);
        canvas.drawRect(rectF,mPaint);

        canvas.save();//3

        canvas.rotate(45);
        mPaint.setColor(Color.YELLOW);
        canvas.drawRect(rectF,mPaint);

        canvas.save();//4

        canvas.restoreToCount(1);

        canvas.translate(20, 100);
        mPaint.setColor(Color.GREEN);
        canvas.drawRect(rectF,mPaint);

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(精华)2020年6月28日 Canvas 元素拖动
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javascript

炫酷渐变色背景粒子线条折线连接canvas动画

万次阅读 2019-11-28 17:09:39

1.新建canvas.js // 炫酷渐变色背景粒子线条折线连接canvas动画 export const canvas = (val) => { var requestAnimationFrame = window.requestAnimationFrame || function (callback) { window....

博客地址：http://www.globm.top/blog/1/detail/34

效果图：



1.新建canvas.js

// 炫酷渐变色背景粒子线条折线连接canvas动画
export const canvas = (val) => {
  var requestAnimationFrame = window.requestAnimationFrame || function (callback) {
    window.setTimeout(callback, 1000 / 60)
  }

  // var canvas = document.getElementsByTagName("canvas")[0];
  let canvas = val
  let ctx = canvas.getContext('2d')
  let maximumPossibleDistance
  let mousePositionX
  let mousePositionY
  let mouseElement
  let lines = 0
  let objects = []
  var initAnimation = function () {
    canvas.width = window.innerWidth
    canvas.height = window.innerHeight
    maximumPossibleDistance = Math.round(Math.sqrt((canvas.width * canvas.width) + (canvas.height * canvas.height)))
    Math.floor(canvas.width / 2)
    Math.floor(canvas.height / 2)
    objects.length = 0
    clearCanvas()
    createParticles()
  }
  window.addEventListener('resize', function () { initAnimation() }, false)
  // 线条参数配置
  var options = {
    // 初始线条数量
    particlesNumber: 80,
    // 圆点大小
    initialSize: 3,
    moveLimit: 50,
    durationMin: 50,
    durationMax: 300,
    drawConnections: true,
    mouseInteractionDistance: 150,
    mouseGravity: true,
    drawMouseConnections: true,
    // 图标色彩
    red: 25,
    green: 200,
    blue: 255,
    opacity: 1,
    // 已连接线条
    connectionRed: 255,
    connectionGreen: 255,
    connectionBlue: 255,
    connectionOpacity: 0.2,
    // 鼠标移动线条
    mouseConnectionRed: 255,
    mouseConnectionGreen: 255,
    mouseConnectionBlue: 255,
    mouseConnectionOpacity: 0.2

  }
  var getRandomBetween = function (a, b) {
    return Math.floor(Math.random() * b) + a
  }
  var getDistance = function (element1, element2) {
    var difX = Math.round(Math.abs(element1.positionX - element2.positionX))
    var difY = Math.round(Math.abs(element1.positionY - element2.positionY))

    return Math.round(Math.sqrt((difX * difX) + (difY * difY)))
  }
  function Particle (positionX, positionY, size, red, green, blue, opacity) {
    this.positionX = positionX
    this.positionY = positionY
    this.size = size

    this.duration = getRandomBetween(options.durationMin, options.durationMax)
    this.limit = options.moveLimit
    this.timer = 0

    this.red = red
    this.green = green
    this.blue = blue
    this.opacity = opacity

    this.color = 'rgba(' + this.red + ',' + this.green + ',' + this.blue + ',+' + this.opacity + ')'
  }
  function MouseParticle (positionX, positionY, size, red, green, blue, opacity) {
    this.positionX = mousePositionX
    this.positionY = mousePositionY
    this.size = size

    this.red = red
    this.green = green
    this.blue = blue
    this.opacity = opacity

    this.color = 'rgba(' + this.red + ',' + this.green + ',' + this.blue + ',+' + this.opacity + ')'
  }
  Particle.prototype.animateTo = function (newX, newY) {
    var duration = this.duration

    var animatePosition = function (newPosition, currentPosition) {
      if (newPosition > currentPosition) {
        var step = (newPosition - currentPosition) / duration
        newPosition = currentPosition + step
      } else {
        step = (currentPosition - newPosition) / duration
        newPosition = currentPosition - step
      }

      return newPosition
    }

    this.positionX = animatePosition(newX, this.positionX)
    this.positionY = animatePosition(newY, this.positionY)

    // generate new vector

    if (this.timer === this.duration) {
      this.calculateVector()
      this.timer = 0
    } else {
      this.timer++
    }
  }
  Particle.prototype.updateColor = function () {
    this.color = 'rgba(' + this.red + ',' + this.green + ',' + this.blue + ',+' + this.opacity + ')'
  }
  Particle.prototype.calculateVector = function () {
    var distance
    var newPosition = {}
    var particle = this

    var getCoordinates = function () {
      newPosition.positionX = getRandomBetween(0, window.innerWidth)
      newPosition.positionY = getRandomBetween(0, window.innerHeight)

      distance = getDistance(particle, newPosition)
    }

    // eslint-disable-next-line no-unmodified-loop-condition
    while ((typeof distance === 'undefined') || (distance > this.limit)) {
      getCoordinates()
    }

    this.vectorX = newPosition.positionX
    this.vectorY = newPosition.positionY
  }
  Particle.prototype.testInteraction = function () {
    if (!options.drawConnections) return
    var closestElement
    var distanceToClosestElement = maximumPossibleDistance
    for (var x = 0; x < objects.length; x++) {
      var testedObject = objects[x]
      var distance = getDistance(this, testedObject)
      if ((distance < distanceToClosestElement) && (testedObject !== this)) {
        distanceToClosestElement = distance
        closestElement = testedObject
      }
    }
    if (closestElement) {
      ctx.beginPath()
      ctx.moveTo(this.positionX + this.size / 2, this.positionY + this.size / 2)
      ctx.lineTo(closestElement.positionX + closestElement.size * 0.5, closestElement.positionY + closestElement.size * 0.5)
      ctx.strokeStyle = 'rgba(' + options.connectionRed + ',' + options.connectionGreen + ',' + options.connectionBlue + ',' + options.connectionOpacity + ')'
      ctx.stroke()
      lines++
    }
  }
  MouseParticle.prototype.testInteraction = function () {
    if (options.mouseInteractionDistance === 0) return

    var closestElements = []
    // var distanceToClosestElement = maximumPossibleDistance;

    for (var x = 0; x < objects.length; x++) {
      var testedObject = objects[x]
      var distance = getDistance(this, testedObject)

      if ((distance < options.mouseInteractionDistance) && (testedObject !== this)) {
        closestElements.push(objects[x])
      }
    }

    for (var i = 0; i < closestElements.length; i++) {
      if (options.drawMouseConnections) {
        var element = closestElements[i]
        ctx.beginPath()
        ctx.moveTo(this.positionX, this.positionY)
        ctx.lineTo(element.positionX + element.size * 0.5, element.positionY + element.size * 0.5)
        ctx.strokeStyle = 'rgba(' + options.mouseConnectionRed + ',' + options.mouseConnectionGreen + ',' + options.mouseConnectionBlue + ',' + options.mouseConnectionOpacity + ')'
        ctx.stroke()
        lines++
      }
      if (options.mouseGravity) {
        closestElements[i].vectorX = this.positionX
        closestElements[i].vectorY = this.positionY
      }
    }
  }
  Particle.prototype.updateAnimation = function () {
    this.animateTo(this.vectorX, this.vectorY)
    this.testInteraction()
    ctx.fillStyle = this.color
    ctx.fillRect(this.positionX, this.positionY, this.size, this.size)
  }
  MouseParticle.prototype.updateAnimation = function () {
    this.positionX = mousePositionX
    this.positionY = mousePositionY
    this.testInteraction()
  }
  var createParticles = function () {
    // create mouse particle
    mouseElement = new MouseParticle(0, 0, options.initialSize, 255, 255, 255)
    for (var x = 0; x < options.particlesNumber; x++) {
      var randomX = Math.floor((Math.random() * window.innerWidth) + 1)
      var randomY = Math.floor((Math.random() * window.innerHeight) + 1)
      var particle = new Particle(randomX, randomY, options.initialSize, options.red, options.green, options.blue, options.opacity)
      particle.calculateVector()
      objects.push(particle)
    }
  }
  var updatePosition = function () {
    for (var x = 0; x < objects.length; x++) {
      objects[x].updateAnimation()
    }
    // handle mouse
    mouseElement.updateAnimation()
  }
  window.onmousemove = function (e) {
    mousePositionX = e.clientX
    mousePositionY = e.clientY
  }
  var clearCanvas = function () {
    ctx.clearRect(0, 0, window.innerWidth, window.innerHeight)
  }
  var lastCalledTime
  var fps
  var averageFps
  var averageFpsTemp = 0
  var averageFpsCounter = 0

  function requestFps () {
    if (!lastCalledTime) {
      lastCalledTime = Date.now()
      fps = 0
      return
    }
    var delta = (new Date().getTime() - lastCalledTime) / 1000
    lastCalledTime = Date.now()
    fps = Math.floor(1 / delta)

    averageFpsTemp = averageFpsTemp + fps
    averageFpsCounter++
    if (averageFpsCounter === 5) {
      averageFps = Math.floor(averageFpsTemp / 5)
      averageFpsCounter = 0
      averageFpsTemp = 0
    }
    if (!averageFps) {

    } else if (averageFps < 10) {

    }
  }
  var loop = function () {
    clearCanvas()
    updatePosition()
    ctx.fillStyle = '#fff'
    // ctx.fillText("FPS: " + fps + " lines: " + lines + " Average FPS: " + averageFps , 10, 20);
    lines = 0
    requestAnimationFrame(loop)
    requestFps()
  }
  initAnimation()
  loop()
  return lines
}


2.引入canvas.js,实现效果
<template>
  <div class="canvas-page">
    <canvas></canvas>
  </div>
</template>
<script>
import { canvas } from '../plugins/canvas'
export default {
  name: 'CanvasPage',
  mounted () {
    canvas(document.getElementsByTagName('canvas')[0])
  }
}
</script>
<style lang="less" scoped>
.canvas-page {
  height: 100vh;
  width: 100vw;
  background-size: cover;
  position: relative;
  background-color: #474747;
  background-image: radial-gradient(circle at 2% 60%, #27278f, transparent 100%),
    radial-gradient(circle at 98% 70%, #000c91, transparent 100%),
    radial-gradient(circle at 50% 50%, #ed68ed, transparent 100%);
  canvas {
    position: absolute;
    left: 0;
    top: 0;
    background: transparent;
    z-index: 15;
  }
}
</style>


附：canvas速查表 http://canvas.migong.org/html5-canvas

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动画

js实现截图并保存图片（html转canvas、canvas转image）

万次阅读 热门讨论 2018-07-23 15:16:43

js实现截图并保存图片在本地（html转canvas、canvas转image）一、html转canvas 需要的库html2canvas.js和canvas2image.js 话不多说，直接上代码！ html &amp;amp;amp;lt;h2&amp;amp;amp...

js实现截图并保存图片在本地（html转canvas、canvas转image）

简介

JavaScript实现网页截图，使用的库有两个：

Html2Canvas.js
Canvas2Image.js

我主要是做了两个demo和一个npm包：

1. 如何使用简单版

直接打开index.html即可

2. 如何使用Webpack+Vue+Element版

# 安装依赖
npm install

# 在localhost：8080进行热重新加载
npm run dev

# 压缩构建为生产环境代码
npm run build

# 构建为生产环境代码并查看捆绑分析器报告
npm run build --report

使用示例

原始html是这样的：

在这里插入图片描述

这是元素节点：

在这里插入图片描述

这是转成canvas之后：

在这里插入图片描述

这是元素节点：

在这里插入图片描述

这是转成img之后：

在这里插入图片描述

这是元素节点：

在这里插入图片描述

这是最终截图结果：

在这里插入图片描述

3. 使用npm安装js_screen_shots

npm install --save js_screen_shots

详情见README.md

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canvas
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canvas

一、规则

二、准备工作：布置画布、获取画布、获取画笔

三、分类

Canvas

画线

画点

画矩形

画圆角矩形

画圆

画椭圆

画圆弧

Path

圆角矩形路径

贝塞尔曲线

setFillType

Path.FillType.WINDING

Path.FillType.EVEN_ODD

Path.FillType.INVERSE_WINDING

Path.FillType.INVERSE_EVEN_ODD

op(Path path, Op op)

Path.Op.DIFFERENCE

Path.Op.INTERSECT

Path.Op.UNION

Path.Op.XOR

Path.Op.REVERSE_DIFFERENCE

Region

Canvas变换

平移

缩放

旋转

斜拉

裁剪

save和restore、restoreToCount

(精华)2020年6月28日 Canvas 元素拖动

炫酷渐变色背景粒子线条折线连接canvas动画

js实现截图并保存图片（html转canvas、canvas转image）

js实现截图并保存图片在本地（html转canvas、canvas转image）

简介

1. 如何使用简单版

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