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sinxy.html
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sinxy.html
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<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
#infoBox {
position: fixed;
bottom: 20px;
left: 0;
width: 100%;
z-index: -2;
text-align: center;
}
#info {
display: inline-block;
position: relative;
top: 0;
left: 0;
background: rgba(255, 255, 255, 0.5);
padding: 0 10px;
z-index: 50;
text-align: left;
}
#canvas {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
z-index: -5;
}
#error {
font-size: small;
color: #FF2222;
text-align: center;
}
#zoom {
font-size: small;
text-align: left;
}
#smallNote {
padding-bottom: 0.5em;
font-size: x-small;
text-align: center;
}
</style>
</head>
<body>
<div id="infoBox">
<div id="info">
<p><form action="javascript:doPlot();">
<input id="formula" type="text" size="50"
value="sin(x) + sin(y) - sin(x*y)"/>
<input id="plotBtn" type="submit" value=">"/>
<div id="error"> </div>
<div id="zoom">
Масштаб на <input id="zoomK" type="text" value="10" size="2"/>%
<a href="javascript:zoom(1);">больше</a>/
<a href="javascript:zoom(-1);">меньше</a>
</div>
</form></p>
<div id="smallNote">Мышкой можно двигать картинку, только тормозит безбожно.</div>
</div>
</div>
<canvas id="canvas"></canvas>
<script type="text/javascript">
/* TODO
- consistent wait
- disable button
*/
var canvas = document.getElementById ("canvas");
var context = canvas.getContext ("2d");
var img = context.createImageData (canvas.width, canvas.height);
var xMin = -40;
var xMax = 40;
var yMid = 5;
var fun = function (x,y) { return 1; };
function sin (x) { return Math.sin (x); }
function cos (x) { return Math.cos (x); }
function tan (x) { return Math.tan (x); }
var wait = false;
function plot () {
var error = document.getElementById ("error");
error.innerHTML = "Нужно подождать";
var height = canvas.height = canvas.clientHeight; // FIXME: переинициализация происходит?
var width = canvas.width = canvas.clientWidth;
if (img.width != width || img.height != height) {
img = context.createImageData (width, height);
}
var xSize = xMax - xMin;
var step = xSize / width;
var ySize = xSize*height/width;
var yMin = yMid - ySize/2;
var yMax = yMid + ySize/2;
for (var j = 0; j < height; ++j) {
var y = yMin + step*j;
var jx = 4*j*width;
for (var i = 0; i < width; ++i) {
var x = xMin + step*i;
var f = fun (x, y);
var ix = 4*i + jx;
if (f < 0) {
img.data[ix] = Math.floor (-f*70)+30;
img.data[ix+1] = img.data[ix+2] = 0;
} else {
img.data[ix] = img.data[ix+1] = 0;
img.data[ix+2] = Math.floor (f*70)+30;
}
img.data[ix+3] = 0xff;
}
}
context.putImageData (img, 0, 0);
error.innerHTML = "";
wait = false;
}
function zoom (s) {
var k = s * document.getElementById ("zoomK").value / 100;
var dx = k*(xMax - xMin)/2;
xMin = Math.floor (xMin + dx);
xMax = Math.floor (xMax - dx);
doPlot ();
}
var lastX = 0;
var lastY = 0;
function mousedown (e) {
if (e.button == 0) {
lastX = e.clientX;
lastY = e.clientY;
}
}
function mouseup (e) {
var dx = e.clientX - lastX;
var dy = e.clientY - lastY;
if (!wait) {
var xSize = xMax - xMin;
var step = xSize / img.width;
var dxx = Math.floor (dx*step);
xMin = xMin - dxx;
xMax = xMax - dxx
yMid = yMid - Math.floor (dy*step);
wait = true;
plot ();
}
}
function doPlot () {
var formula = document.getElementById ("formula");
formula.readonly = true;
try {
fun = eval(
"(function () { return function (x,y) { return "
+ formula.value
+ ";}})()");
fun (0,0);
plot ();
} catch (ex) {
var error = document.getElementById ("error");
error.innerHTML = ex;
}
formula.readonly = false;
}
doPlot ();
canvas.addEventListener ("mousedown", mousedown, false);
canvas.addEventListener ("mouseup", mouseup, false);
window.onresize = doPlot;
</script>
</body>
</html>