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Криницын Игорь #5

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Криницын Игорь #5

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iok144 Mar 2, 2017
9a569b1
Snowflake can be drawn with any canvas size
iok144 Mar 6, 2017
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110 changes: 0 additions & 110 deletions index.html
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9 changes: 9 additions & 0 deletions snowflake.html
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<!doctype html>
<html>
<script src="snowflake.js"></script>
<body>
<canvas height="500" width="500" id="snowflake"></canvas>
<input size="10" id="input"></input>
<button style="width:75px;height:20px" name="Start" onclick="run()">Draw</button>
</body>
</html>
81 changes: 81 additions & 0 deletions snowflake.js
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function drawSnowflake(iteration) {
var canvas = document.getElementById("snowflake");
var canvasHeight = parseInt(canvas.getAttribute("height"));
var canvasWidth = parseInt(canvas.getAttribute("width"));

var len;
if(canvasHeight / canvasWidth <= (Math.sin(Math.PI / 3) * 4 / 3)) {
len = canvasHeight * 3 / (4 * Math.sin(Math.PI / 3));
} else {
len = canvasWidth;
}
var x = 0;
var y = len * Math.sin(Math.PI / 3);
var angle = -60 * Math.PI / 180;

var context = canvas.getContext("2d");

canvas.width = canvas.width;//Очистка канваса
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Делаешь хак - не пиши комментарий, а выдели метод/функцию. Удачная функция: function clearCanvas(canvas);

Кстати, на StackOverflow по поводу этого хака.
Заметь, что context.clearRect понятен без комментария и отдельного метода.

Use: context.clearRect(0, 0, canvas.width, canvas.height);

This is the fastest and most descriptive way to clear the entire canvas.

Do not use: canvas.width = canvas.width;

Resetting canvas.width resets all canvas state (e.g. transformations, lineWidth, strokeStyle, etc.), it is very slow (compared to clearRect), it doesn't work in all browsers, and it doesn't describe what you are actually trying to do.


context.lineWidth = "1";
context.strokeStyle = "#0000FF";

drawSide(iteration, x, y, angle, len, context);

x = x + len * Math.cos(angle);
y = y + len * Math.sin(angle);
angle += 120 * Math.PI / 180;
drawSide(iteration, x, y, angle, len, context);

x = x + len * Math.cos(angle);
y = y + len * Math.sin(angle);
angle += 120 * Math.PI / 180;
drawSide(iteration, x, y, angle, len, context);
}
/**
* Рисует сторону снежинки Коха
*
* @param {Number} iteration Количество итераций
* @param {Number} x Абсцисса
* @param {Number} y Ордината
* @param {Number} angle Угол поворота
* @param {Number} len Длина линии
* @param {object} context HTML context
*/
function drawSide(iteration, x, y, angle, len, context) {
if(iteration > 0) {
drawSide(iteration - 1, x, y, angle, len/3, context);

x = x + len / 3 * Math.cos(angle);
y = y + len / 3 * Math.sin(angle);
angle -= 60 * Math.PI / 180;
drawSide(iteration - 1, x, y, angle, len/3, context);

x = x + len / 3 * Math.cos(angle);
y = y + len / 3 * Math.sin(angle);
angle += 120 * Math.PI / 180;
drawSide(iteration - 1, x, y, angle, len/3, context);

x = x + len / 3 * Math.cos(angle);
y = y + len / 3 * Math.sin(angle);
angle -= 60 * Math.PI / 180;
drawSide(iteration - 1, x, y, angle, len/3, context);
}
else {
var finishX = x + len * Math.cos(angle);
var finishY = y + len * Math.sin(angle);
drawLine(x, y, finishX, finishY, context);
}
}

function drawLine(x, y, finishX, finishY, context) {
context.beginPath();
context.moveTo(x, y);
context.lineTo(finishX, finishY);
context.stroke();
}

function run() {
var iteration = document.getElementById("input").value;
drawSnowflake(iteration);
}