js，canvas获取图片色值
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>获取图片的周边的色值</title> </head> <body> <style type="text/css"> canvas{ /* position:absolute; opacity:0; */ } </style> <!-- <div style="width:0;overflow:hidden"> --> <canvas id="canvas">对不你，你的浏览器不支持Canvas</canvas> <!-- </div> --> <div id="upside">up</div> <div id="rightside">right</div> <div id="downside">down</div> <div id="leftside">left</div> <script> function getImgColor(url){ function add(side,data,i){ side[0]+=data[i]; side[1]+=data[i+1]; side[2]+=data[i+2]; side[3]+=1; } function getColor(side){ var r = side[0]/side[3]; var g = side[1]/side[3]; var b = side[2]/side[3]; var color='rgb('+r+','+g+','+b+')'; return color; } var img = new Image; img.src = url; img.onload = function(){ canvas.setAttribute('width',img.width+'px'); canvas.setAttribute('height',img.height+'px'); var ctxt = canvas.getContext('2d'); ctxt.drawImage(img, 0, 0); var data = ctxt.getImageData(0, 0, img.width, img.height).data;//读取整张图片的像素。 var w=img.width; var h=img.height; var gap=3; var up=[0,0,0,0]; var down=[0,0,0,0]; var left=[0,0,0,0]; var right=[0,0,0,0]; for(var i =0,len = data.length; i<len;i+=4){ if(i/4<w*gap){ add(up,data,i) }else if(i/4%w<gap){ add(left,data,i) }else if(i/4%w>w-gap){ add(right,data,i) }else if(i/4>w*h-w*gap && i/4<w*h){ add(down,data,i) } } var upcolor=getColor(up); var rightcolor=getColor(right); var leftcolor=getColor(left); var downcolor=getColor(down); upside.setAttribute('style',"background:"+upcolor); rightside.setAttribute('style',"background:"+rightcolor); leftside.setAttribute('style',"background:"+leftcolor); downside.setAttribute('style',"background:"+downcolor); console.log([upcolor,rightcolor,downcolor,leftcolor].toString()); }; }; getImgColor('../img/banner/qq_01.jpg');//只需要把这个图片路径改成你自己的图片路径就行了 </script> </body> </html>
这是为了拿到图片四周各自的颜色，方便在设置背景色的时候使用，只是遍历所有像素可能效率比较低吧，不知道有什么更好的方法，计算的更快，更准
注意：直接在浏览器里打开会报错
Uncaught DOMException: Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The canvas has been tainted by cross-origin data.
需要在服务器环境下打开！
