Icon settings for CHROME extended notes (switch between color and gray)

Icon settings for CHROME extended notes (switch between color and gray)

// 返回灰色画布
function grey_img(src,callback){
　　/*创建一个canvas*/
	var canvas=document.createElement('canvas');
	var ctx=canvas.getContext('2d');
	var img=new Image();
	img.src=src;
	img.onload = function(){
		// 因为图片加载时异步的，所以需要采用回调的方式，不然图片宽高读取会变成0导致 Failed to execute 'getImageData' on 'CanvasRenderingContext2D' 报错
		canvas.height=img.height;
		canvas.width=img.width;
		ctx.drawImage(img,0,0);
		var imgdata=ctx.getImageData(0,0,canvas.width,canvas.height);var data=imgdata.data;
		/*灰度处理：求r，g，b的均值，并赋回给r，g，b*/
		for(var i=0,n=data.length;i<n;i+=4){
			var average=(data[i]+data[i+1]+data[i+2])/3;
			data[i]=average;
			data[i+1]=average;
			data[i+2]=average;
		}
		ctx.putImageData(imgdata,0,0);
		if(typeof callback === 'function'){
			/*将处理后的回调给调用者*/
			callback({canvas,ctx});
		}
	}
}
// 灰图变量
var grey_img_icon = null;
var Cicon_state = null;
// 设置图标函数
function switch_icon(_on_off){
	_on_off = !zsl.empty(_on_off);
	if(Cicon_state !== _on_off){
		let path = 'img/icon_128.png';
		Cicon_state = _on_off;
		if(_on_off){
			// 恢复正常图标
			chrome.browserAction.setIcon({
				path
			});
			// 启动程序
			// start code……
		}else{
			if(zsl.empty(grey_img_icon)){
				grey_img(path,function(imgObj){
					// 设置灰色图标
					chrome.browserAction.setIcon({
						imageData: imgObj.ctx.getImageData(0,0,128,128)
					});
				})
			}
			
			// 关闭程序
			// close code……
		}
	}
}