<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<script>
window.onload = function ()
{
var oc = document.getElementById('c1');
var ogc = oc.getContext('2d');
var yimg = new Image();
yimg.onload = function ()
{
draw(this);
}
yimg.src = 'img/5-5.jpg';
function draw(obj)
{
oc.width = obj.width;
oc.height = obj.height*2;
ogc.drawImage(obj,0,0);
var oimg = ogc.getImageData(0,0,obj.width,obj.height);
var w = oimg.width;
var h = oimg.height;
var newimg = ogc.createImageData(obj.width,obj.height);
for(var i = 0; i < h; i++)
{
for(var j = 0; j < w; j++)
{
var color = getXY(oimg,j,i)
var result = [];
result[0] = 255 - color[0];
result[1] = 255 - color[1];
result[2] = 255 - color[2];
result[3] = 255*i/h;
setXY(newimg,j,h-i,result);
}
}
ogc.putImageData(newimg,0,obj.height);
}
function getXY(obj,x,y)
{
var w = obj.width;
var h = obj.height;
var d = obj.data;
var color = [];
color[0] = d[ 4*(y*w+x)];
color[1] = d[ 4*(y*w+x) +1];
color[2] = d[ 4*(y*w+x) +2];
color[3] = d[ 4*(y*w+x) +3];
return color;
}
function setXY(obj,x,y,color)
{
var w = obj.width;
var h = obj.height;
var d = obj.data;
d[ 4*(y*w+x)] = color[0];
d[ 4*(y*w+x) +1] = color[1];
d[ 4*(y*w+x) +2] = color[2];
d[ 4*(y*w+x) +3] = color[3];
}
}
</script>
<style>
body{
background:pink;
}
#c1{
background:white;
}
</style>
</head>
<body>
<canvas id="c1" width="400" height="800"></canvas>
</body>
</html>
