Question

我试图在包含图像的弯曲矩形的边框后面绘制阴影。但是，下面的代码将阴影置于图像后面而不是边框上。如何更改此代码以使阴影位于边框后面？

为了澄清，边框当前被图像阴影遮挡，但我不希望图像具有任何阴影。这是图像周围的白色边框，我想要一个阴影。我不希望画布周围有阴影，但画布中的弯曲的矩形边框

。

var c=document.getElementById('game'), canvasX=c.offsetLeft, canvasY=c.offsetTop, ctx=c.getContext('2d') elements = []; var x=25, y=25, w=150, h=150; var img=new Image(); img.src='https://i.stack.imgur.com/ddSWa.jpg'; ctx.beginPath(); ctx.lineWidth='8'; ctx.strokeStyle='white'; ctx.moveTo(x+10, y); ctx.lineTo(x+w-10, y); ctx.quadraticCurveTo(x+w, y, x+w, y+10); ctx.lineTo(x+w, y+h-10); ctx.quadraticCurveTo(x+w, y+h, x+w-10, y+h); ctx.lineTo(x+10, y+h); ctx.quadraticCurveTo(x, y+h, x, y+h-10); ctx.lineTo(x, y+10); ctx.quadraticCurveTo(x, y, x+10, y); ctx.shadowColor = '#000000'; ctx.shadowBlur = 20; ctx.shadowOffsetX = 5; ctx.shadowOffsetY = 5; ctx.stroke(); ctx.drawImage(img, x+2.5, y+2.5, w-5, h-5);

canvas { display: block; margin: 1em auto; border: 1px solid black; background: #FF9900; }

<!doctype html> <html lang="en"> <head> <meta charset="UTF-8"> <title>uTalk Demo</title> <link rel='stylesheet' type='text/css' href='game.css' media='screen'></style> </head> <body> <canvas id="game" width = "200" height = "200"></canvas> </body> </html>

Answer 1

在绘制图像之前，只需删除shadowOffset即可。设置此属性时，所有后续图形都将具有阴影。

var c=document.getElementById('game'),
		canvasX=c.offsetLeft,
		canvasY=c.offsetTop,
		ctx=c.getContext('2d')
		elements = [];
    
var x=25, y=25, w=150, h=150;

var img=new Image(); 
img.src='https://i.stack.imgur.com/ddSWa.jpg';
ctx.beginPath();
ctx.lineWidth='8';
ctx.strokeStyle='white';
ctx.moveTo(x+10, y);
ctx.lineTo(x+w-10, y);
ctx.quadraticCurveTo(x+w, y, x+w, y+10);
ctx.lineTo(x+w, y+h-10);
ctx.quadraticCurveTo(x+w, y+h, x+w-10, y+h);
ctx.lineTo(x+10, y+h);
ctx.quadraticCurveTo(x, y+h, x, y+h-10);
ctx.lineTo(x, y+10);
ctx.quadraticCurveTo(x, y, x+10, y);
ctx.shadowColor = '#000000';
ctx.shadowBlur = 20;
ctx.shadowOffsetX = 5;
ctx.shadowOffsetY = 5;
ctx.stroke();
// now reset the shadow
ctx.shadowBlur = 0;
ctx.shadowOffsetX = 0;
ctx.shadowOffsetY = 0;

ctx.drawImage(img, x+2.5, y+2.5, w-5, h-5);

canvas {
  display: block;
  margin: 1em auto;
  border: 1px solid black;
  background: #FF9900;
}

<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>uTalk Demo</title>
	<link rel='stylesheet' type='text/css' href='game.css' media='screen'></style>
</head>
<body>
	<canvas id="game" width = "200" height = "200"></canvas>
</body>
</html>

Answer 2

您正在绘制的形状只是一个图像，而不是border。它只会留在画布内。但是如果你做这样的事情，你只需要玩x,y coordinates。否则，您可以使用border和box-shadow属性

＆＃13;

var c=document.getElementById('game'),
		canvasX=c.offsetLeft,
		canvasY=c.offsetTop,
		ctx=c.getContext('2d')
		elements = [];
    
var x= 20, y=20, w=160, h=160;

var img=new Image(); 
img.src='https://i.stack.imgur.com/ddSWa.jpg';
ctx.beginPath();
ctx.lineWidth='8';
ctx.strokeStyle='white';
ctx.moveTo(x+10, y);
ctx.lineTo(x+w-10, y);
ctx.quadraticCurveTo(x+w, y, x+w, y+10);
ctx.lineTo(x+w, y+h-10);
ctx.quadraticCurveTo(x+w, y+h, x+w-10, y+h);
ctx.lineTo(x+10, y+h);
ctx.quadraticCurveTo(x, y+h, x, y+h-10);
ctx.lineTo(x, y+10);
ctx.quadraticCurveTo(x, y, x+10, y);
ctx.shadowColor = '#000000';
ctx.shadowBlur = 20;
ctx.shadowOffsetX = 5;
ctx.shadowOffsetY = 5;
ctx.stroke();
ctx.drawImage(img, x+27.5, y+27.5, w-55, h-55);

＆＃13;

canvas {
  display: block;
  margin: 1em auto;
  background: transparent;
}

＆＃13;

<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>uTalk Demo</title>
	<link rel='stylesheet' type='text/css' href='game.css' media='screen'></style>
</head>
<body>
	<canvas id="game" width = "200" height = "200"></canvas>
</body>
</html>

＆＃13;

Answer 3

不确定你需要什么。我发现您的代码没有任何问题。你试过用过：

ctx.strokeStyle = 'grey'; //or the color you want.
ctx.lineWidth = 5; //For thickness

HTML Canvas＆amp; Javascript - 阴影而不是边框

3 个答案: