varc=document.querySelector('#drawing');varctx=c.getContext("2d");varimage=newImage();image.onload=function(){ctx.drawImage(image,0,0);}image.src="images/palette.jpg";varmakePixelGrayScale=function(r,g,b,a){vary=(0.3*r)+（0.59*g）+(0.11*b);return{r:y,g:y,b:y,a:y};}//灰度计算函数makeGrayScale(){varr,g,b,a;varimageData=ctx.getImageData(0,0,300,300);varnumPixels=imageData.data.length/4;对于(vari=0;i
