<!DOCTYPE html>
<
html
>
<
head
>
<
title
>canvas图像处理</
title
>
</
head
>
<
body
>
<
h1
>canvas</
h1
>
<
canvas
id
=
"canvas1"
width
=
"200"
height
=
"150"
>是时候更换浏览器了<
a
href
=
"http://firefox.com.cn/download/"
>点击下载firefox</
a
></
canvas
>
<
script
>
var canvas1=document.getElementById('canvas1');
var context1=canvas1.getContext('2d');
image=new Image();
image.src="z.JPG";
image.onload=function(){
context1.drawImage(image,0,0);//绘制原始图像,(0,0)表示图像的左上角位与canvas画布的位置
}
</
script
>
<
br
/>
<
button
onclick
=
"draw()"
>图像的反转</
button
>
<
br
/>
<
canvas
id
=
"canvas2"
width
=
"200"
height
=
"150"
></
canvas
>
<
script
>
function draw(){
var canvas2=document.getElementById('canvas2');
var context2=canvas2.getContext('2d');
var imagedata=context1.getImageData(0,0,image.width,image.height);
var imagedata1=context2.createImageData(image.width,image.height);
for(var j=0;j<
image.height
;j+=1)
for(var
i
=
0
;i<image.width;i+=1){
k
=
4
*(image.width*j+i);
imagedata1.data[k+0]=255-imagedata.data[k+0];
imagedata1.data[k+1]=255-imagedata.data[k+1];
imagedata1.data[k+2]=255-imagedata.data[k+2];
imagedata1.data[k+3]=255;
}
context2.putImageData(imagedata1,0,0);
}
</script>
</
body
>
</
html
>