我用
CSS3看过一些很酷的图像遮罩和其他效果.只使用CSS3我们可以在下面的代码中看到这种效果,或者看到工作小提琴.
HTML
<canvas id="canvas1" width="400" height="400"></canvas>
使用Javascript
var can = document.getElementById('canvas1');
var ctx = can.getContext('2d');
can.addEventListener('mousemove',function(e) {
var mouse = getMouse(e,can);
redraw(mouse);
},false);
function redraw(mouse) {
console.log('a');
can.width = can.width;
ctx.drawImage(img,0);
ctx.beginPath();
ctx.rect(0,500,500);
ctx.arc(mouse.x,mouse.y,70,Math.PI*2,true)
ctx.clip();
ctx.drawImage(img2,0);
}
var img = new Image();
img.onload = function() {
redraw({x: -450,y: -500})
}
img.src = 'http://placekitten.com/400/400';
var img2 = new Image();
img2.onload = function() {
redraw({x: -450,y: -500})
}
img2.src = 'http://placekitten.com/400/395';
function getMouse(e,canvas) {
var element = canvas,offsetX = 0,offsetY = 0,mx,my;
if (element.offsetParent !== undefined) {
do {
offsetX += element.offsetLeft;
offsetY += element.offsetTop;
} while ((element = element.offsetParent));
}
mx = e.pageX - offsetX;
my = e.pageY - offsetY;
return {
x: mx,y: my
};
}
解决方法
这是使用背景图像的替代方法.它更灵活,你得到一个圆形(或任意形状)视口：
http://jsfiddle.net/maackle/66uCs/
HTML
<div class="masker">
<img class="base" src="http://lorempixel.com/400/400/cats/1" />
<div class="overlay"></div>
</div>
CSS
.masker {
position: relative;
}
.overlay {
position: absolute;
display: none;
width: 100px;
height: 100px;
border-radius: 50%;
background: url(http://lorempixel.com/400/400/cats/2) no-repeat;
}
jQuery 1.10.1
$('.masker').on('mousemove',function (e) {
var r,x,y,top,left,bottom,right,attr,$base,$overlay;
r = 100;
$base = $(this).find('.base');
$overlay = $(this).find('.overlay');
x = e.pageX - $base.offset().left;
y = e.pageY - $base.offset().top;
top = y - r / 2;
left = x - r / 2;
if (x < 0 || y < 0 || x > $base.width() || y > $base.height()) {
$overlay.hide();
} else {
$overlay.show().css({
'background-position': '' + (-left) + 'px ' + (-top) + 'px','left': left,'top': top
});
}
});
//just for good measure
$('.masker').on('mouSEOut',function (e) {
$(this).find('.overlay').hide();
});