如何在画布中填充图案并沿形状弯曲?-前端问题

How to fill pattern in canvas and curving along the shape?(如何在画布中填充图案并沿形状弯曲?)

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问题描述

我有一张这样的图像我想用这样的图案填充得到这样的结果 .

I have one image like this and I want to fill with pattern like this to make result like this .

我可以使用以下代码填充图案，但我不知道如何沿着衣领形状正确弯曲图案，因为它应该看起来像真的，但我的结果变成了这样..

I can fill the pattern using following code but I don't know how to curve pattern properly along the collar shape because it should look like real but my result become like this. .

这是我的示例脚本

$(function(){
drawCanvas("body","collar","images/collar.png", 180);

function drawCanvas(overlayType, canvasID, imageSource, degreeRotate){
    var canvas=document.getElementById(canvasID);
    var ctx=canvas.getContext("2d");

    var imgBody=new Image();
    var imgPattern=new Image();
    imgPattern.onload=function(){

        imgBody.onload=function(){
            start();
        }

        imgBody.src=imageSource;
    }
    imgPattern.src="images/pattern.png";

    function start(){
        ctx.drawImage(imgBody,0,0);
        if(overlayType=="body"){
            ctx.globalCompositeOperation="source-atop";
            ctx.globalAlpha=.85;

            var pattern = ctx.createPattern(imgPattern, 'repeat');
            ctx.fillStyle = pattern;
            ctx.rect(0, 0, canvas.width, canvas.height);
            ctx.rotate(degreeRotate * Math.PI/180);

            ctx.fill();
            ctx.translate(150,0);

            ctx.globalAlpha=.1;     
            ctx.drawImage(imgBody,150,0);   
        }
    }
}});

有人可以指导我如何管理图案以沿着侧领形状弯曲以看起来像真的吗?

Can someone guide me to how to manage pattern to curve along side collar shape to look like real?

推荐答案

你可以通过简单地垂直切割和偏移你的图案来实现这一点

原领"图:

用弯曲的格子纹理填充的衣领

Collar filled with curved checkered texture

**方法:*

使用您的方格纹理创建平铺图像.
将该纹理图像绘制到临时画布上.
获取临时画布的图像数据.
对于每一列像素，将整列偏移你领子的曲线.
二次曲线非常适合您的衣领曲线，因此我在示例中使用它来确定 Y 偏移量.
将图像数据放回临时画布上.
(您现在可以将曲线方格图案应用于您的衣领图像).
在主画布上绘制衣领图像.
设置 context.globalCompositeOperation="source-atop"
将纹理从临时画布绘制到主画布上.
(合成模式只会在衣领上绘制纹理，而不是背景)

这是代码和小提琴:http://jsfiddle.net/m1erickson/hdXyk/

<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>

<style>
    body{ background-color: ivory; padding:20px; }
    canvas{border:1px solid red;}
</style>

<script>
$(function(){

    // get canvas references (canvas=collar, canvas1=texture)
    var canvas=document.getElementById("canvas");
    var ctx=canvas.getContext("2d");
    var canvas1=document.getElementById("canvas1");
    var ctx1=canvas1.getContext("2d");

    // preload the texture and collar images before starting

    var textureImg,collarImg;
    var imageURLs=[];
    var imagesOK=0;
    var imgs=[];
    imageURLs.push("https://dl.dropboxusercontent.com/u/139992952/stackoverflow/checkered.png");
    imageURLs.push("https://dl.dropboxusercontent.com/u/139992952/stackoverflow/collar.png");
    loadAllImages();

    function loadAllImages(callback){
        for (var i = 0; i < imageURLs.length; i++) {
            var img = new Image();
            img.crossOrigin="anonymous";
            imgs.push(img);
            img.onload = function(){ 
                imagesOK++; 
                if (imagesOK==imageURLs.length ) {
                      textureImg=imgs[0];
                      collarImg=imgs[1];
                      start();
                }
            }; 
            img.src = imageURLs[i];
        }      
    }


    function start(){

        // set both canvas dimensions
        canvas.width=collarImg.width;
        canvas.height=collarImg.height+5;
        canvas1.width=textureImg.width;
        canvas1.height=textureImg.height;

        // draw the textureImg on canvas1
        ctx1.drawImage(textureImg,0,0,canvas1.width,canvas1.height);

        // curve the texture into a collar shaped curved 
        curveTexture(collarImg.width,collarImg.height);

        // draw the collarImg on canvas
        ctx.drawImage(collarImg,0,0);

        // set compositing to source-atop
        // any new drawing will ONLY fill existing non-transparent pixels
        ctx.globalCompositeOperation="source-atop";

        // draw the curved texture from canvas1 onto the collar of canvas
        // (the existing pixels are the collar, so only the collar is filled)
        ctx.drawImage(canvas1,0,0);



    }

    function curveTexture(w,h){

        // define a quadratic curve that fits the collar bottom
        // These values change if the collar image changes (+5,-32)
        var x0=0;
        var y0=h+5;
        var cx=w/2;
        var cy=h-32;
        var x1=w;
        var y1=h+5;

        // get a,b,c for quadratic equation
        // equation is used to offset columns of texture pixels
        // in the same shape as the collar
        var Q=getQuadraticEquation(x0,y0,cx,cy,x1,y1);

        // get the texture canvas pixel data
        // 2 copies to avoid self-referencing
        var imageData0 = ctx1.getImageData(0,0,w,h);
        var data0 = imageData0.data;
        var imageData1 = ctx1.getImageData(0,0,w,h);
        var data1 = imageData1.data;

        // loop thru each vertical column of pixels
        // Offset the pixel column into the shape of the quad-curve
        for(var y=0; y<h; y++) {
          for(var x=0; x<w; x++) {

              // the pixel to write
              var n=((w*y)+x)*4;
              // the vertical offset amount
              var yy=parseInt(y+h-(Q.a * x*x + Q.b*x + Q.c));
              // the offset pixel to read
              var nn=((w*yy)+x)*4;

              // offset this pixel by the quadCurve Y value (yy)
              data0[n+0]=data1[nn+0];
              data0[n+1]=data1[nn+1];
              data0[n+2]=data1[nn+2];
              data0[n+3]=data1[nn+3];
          }
        }
        ctx1.putImageData(imageData0,0,0);
    }


    // Quadratic Curve: given x coordinate, find y coordinate
    function getQuadraticY(x,Q){
        return(Q.a * x*x + Q.b*x + Q.c);
    }

    // Quadratic Curve: 
    // Given: start,control,end points
    // Find: a,b,c in quadratic equation ( y=a*x*x+b*x+c )
    function getQuadraticEquation(x0,y0,cx,cy,x2,y2){
        // need 1 more point on q-curve, so calc its midpoint XY
        // Note: since T=0.5 therefore TT=(1-T)=0.5 also [so could simplify]
        var T=0.50;
        var TT=1-T;
        var x1=TT*TT*x0+2*TT*T*cx+T*T*x2;
        var y1=TT*TT*y0+2*TT*T*cy+T*T*y2;
        var A = ((y1-y0)*(x0-x2) 
              + (y2-y0)*(x1-x0))/((x0-x2)*(x1*x1-x0*x0) 
              + (x1-x0)*(x2*x2-x0*x0));
        var B = ((y1-y0)-A*(x1*x1-x0*x0))/(x1-x0);
        var C = y0-A*x0*x0-B*x0;
        return({a:A,b:B,c:C});
    }


}); // end $(function(){});
</script>

</head>

<body>
    <p>"Curve" a texture by offsetting Y pixels based on Q-curve</p>
    <canvas id="canvas" width=300 height=300></canvas>
    <p>The temporary texture canvas</p>
    <canvas id="canvas1" width=300 height=300></canvas>
</body>
</html>

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