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<!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; 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>
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原文地址：http://www.cnblogs.com/mayufo/p/4296361.html
