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lab03.html
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lab03.html
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<HTML>
<BODY>
<canvas id="lab03" width="500" height="400">
</canvas>
<script>
function Line(idata, x0, y0, x1, y1) {
var y = y0;
var eps = 0;
var k=2*(y1-y0);
var pw=1;
for (var x=x0; x<=x1; x++) {
idata.data[(x+y*idata.width)*4+3]=255*
Math.pow(Math.abs(0.5- (eps/(2*(x1-x0))) ),pw);
idata.data[(x+(y+1)*idata.width)*4+3]=255*
Math.pow(Math.abs(0.5+ (eps/(2*(x1-x0))) ), pw);
eps = eps+k;
if (eps>(x1-x0)) {
y++;
eps = eps - 2*(x1-x0);
}
}
}
</script>
<script>
var canvas = document.getElementById("lab03");
var ctx = canvas.getContext("2d");
var flag = 0;
var idata = ctx.getImageData(0, 0, canvas.width, canvas.height);
console.log(idata);
canvas.addEventListener("click", function(event){
if (!flag) {
x0 = event.offsetX;
y0 = event.offsetY;
flag = 1;
} else {
x1 = event.offsetX;
y1 = event.offsetY;
Line(idata, x0, y0, x1, y1);
ctx.putImageData(idata, 0, 0);
flag = 0;
}
});
</script>
</BODY>
</HTML>