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<section class="canvas-demo">
<h2>Canvas绘图示例</h2>
<div class="canvas-container">
<h3>基础图形绘制</h3>
<canvas
id="basic-canvas"
width="800"
height="400"
style="border: 1px solid #ccc;"
>
您的浏览器不支持Canvas，请升级浏览器。
</canvas>
<div class="canvas-controls">
<button onclick="drawBasicShapes()">绘制基础图形</button>
<button onclick="clearCanvas('basic-canvas')">清除画布</button>
</div>
</div>
<div class="canvas-container">
<h3>交互式绘图</h3>
<canvas
id="interactive-canvas"
width="800"
height="400"
style="border: 1px solid #ccc; cursor: crosshair;"
></canvas>
<div class="drawing-controls">
<label>画笔颜色：
<input type="color" id="brush-color" value="#000000">
</label>
<label>画笔大小：
<input type="range" id="brush-size" min="1" max="50" value="5">
<span id="brush-size-display">5</span>px
</label>
<button onclick="clearCanvas('interactive-canvas')">清除画布</button>
<button onclick="saveCanvas()">保存图片</button>
</div>
</div>
<div class="canvas-container">
<h3>Canvas动画</h3>
<canvas
id="animation-canvas"
width="800"
height="400"
style="border: 1px solid #ccc;"
></canvas>
<div class="animation-controls">
<button onclick="startAnimation()">开始动画</button>
<button onclick="stopAnimation()">停止动画</button>
<button onclick="resetAnimation()">重置动画</button>
</div>
</div>
</section>
<script>
class CanvasDrawing {
constructor() {
this.isDrawing = false;
this.animationId = null;
this.balls = [];
this.initInteractiveCanvas();
this.initAnimation();
}
drawBasicShapes() {
const canvas = document.getElementById('basic-canvas');
const ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.fillStyle = '#ff6b6b';
ctx.fillRect(50, 50, 100, 80);
ctx.strokeStyle = '#4ecdc4';
ctx.lineWidth = 3;
ctx.strokeRect(200, 50, 100, 80);
ctx.beginPath();
ctx.arc(400, 90, 40, 0, 2 * Math.PI);
ctx.fillStyle = '#45b7d1';
ctx.fill();
ctx.beginPath();
ctx.moveTo(500, 50);
ctx.lineTo(550, 130);
ctx.lineTo(600, 50);
ctx.closePath();
ctx.fillStyle = '#f9ca24';
ctx.fill();
ctx.font = '24px Arial';
ctx.fillStyle = '#2d3436';
ctx.fillText('HTML5 Canvas绘图', 50, 200);
const gradient = ctx.createLinearGradient(50, 250, 200, 350);
gradient.addColorStop(0, '#ff7675');
gradient.addColorStop(1, '#fd79a8');
ctx.fillStyle = gradient;
ctx.fillRect(50, 250, 150, 100);
const img = new Image();
img.onload = function() {
ctx.drawImage(img, 250, 250, 100, 100);
};
img.src = 'data:image/svg+xml;base64,PHN2ZyB3aWR0aD0iMTAwIiBoZWlnaHQ9IjEwMCIgeG1sbnM9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc3ZnIj48cmVjdCB3aWR0aD0iMTAwIiBoZWlnaHQ9IjEwMCIgZmlsbD0iIzc0YjlmZiIvPjx0ZXh0IHg9IjUwIiB5PSI1NSIgZm9udC1mYW1pbHk9IkFyaWFsIiBmb250LXNpemU9IjE0IiBmaWxsPSJ3aGl0ZSIgdGV4dC1hbmNob3I9Im1pZGRsZSI+SVNWRzwvdGV4dD48L3N2Zz4=';
}
initInteractiveCanvas() {
const canvas = document.getElementById('interactive-canvas');
const ctx = canvas.getContext('2d');
const brushSizeSlider = document.getElementById('brush-size');
const brushSizeDisplay = document.getElementById('brush-size-display');
brushSizeSlider.addEventListener('input', (e) => {
brushSizeDisplay.textContent = e.target.value;
});
canvas.addEventListener('mousedown', (e) => {
this.isDrawing = true;
this.draw(e, ctx, canvas);
});
canvas.addEventListener('mousemove', (e) => {
if (this.isDrawing) {
this.draw(e, ctx, canvas);
}
});
canvas.addEventListener('mouseup', () => {
this.isDrawing = false;
ctx.beginPath();
});
canvas.addEventListener('mouseout', () => {
this.isDrawing = false;
ctx.beginPath();
});
canvas.addEventListener('touchstart', (e) => {
e.preventDefault();
this.isDrawing = true;
const touch = e.touches[0];
const mouseEvent = new MouseEvent('mousedown', {
clientX: touch.clientX,
clientY: touch.clientY
});
canvas.dispatchEvent(mouseEvent);
});
canvas.addEventListener('touchmove', (e) => {
e.preventDefault();
if (this.isDrawing) {
const touch = e.touches[0];
const mouseEvent = new MouseEvent('mousemove', {
clientX: touch.clientX,
clientY: touch.clientY
});
canvas.dispatchEvent(mouseEvent);
}
});
canvas.addEventListener('touchend', (e) => {
e.preventDefault();
this.isDrawing = false;
ctx.beginPath();
});
}
draw(e, ctx, canvas) {
const rect = canvas.getBoundingClientRect();
const x = e.clientX - rect.left;
const y = e.clientY - rect.top;
const color = document.getElementById('brush-color').value;
const size = document.getElementById('brush-size').value;
ctx.lineWidth = size;
ctx.lineCap = 'round';
ctx.strokeStyle = color;
ctx.lineTo(x, y);
ctx.stroke();
ctx.beginPath();
ctx.moveTo(x, y);
}
initAnimation() {
for (let i = 0; i < 10; i++) {
this.balls.push({
x: Math.random() * 800,
y: Math.random() * 400,
vx: (Math.random() - 0.5) * 4,
vy: (Math.random() - 0.5) * 4,
radius: Math.random() * 20 + 10,
color: `hsl(${Math.random() * 360}, 70%, 60%)`
});
}
}
animate() {
const canvas = document.getElementById('animation-canvas');
const ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
this.balls.forEach(ball => {
ball.x += ball.vx;
ball.y += ball.vy;
if (ball.x + ball.radius > canvas.width || ball.x - ball.radius < 0) {
ball.vx = -ball.vx;
}
if (ball.y + ball.radius > canvas.height || ball.y - ball.radius < 0) {
ball.vy = -ball.vy;
}
ctx.beginPath();
ctx.arc(ball.x, ball.y, ball.radius, 0, 2 * Math.PI);
ctx.fillStyle = ball.color;
ctx.fill();
ctx.shadowColor = ball.color;
ctx.shadowBlur = 10;
ctx.fill();
ctx.shadowBlur = 0;
});
this.animationId = requestAnimationFrame(() => this.animate());
}
startAnimation() {
if (!this.animationId) {
this.animate();
}
}
stopAnimation() {
if (this.animationId) {
cancelAnimationFrame(this.animationId);
this.animationId = null;
}
}
resetAnimation() {
this.stopAnimation();
this.initAnimation();
const canvas = document.getElementById('animation-canvas');
const ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
}
let canvasDrawing;
document.addEventListener('DOMContentLoaded', function() {
canvasDrawing = new CanvasDrawing();
});
function drawBasicShapes() {
canvasDrawing.drawBasicShapes();
}
function clearCanvas(canvasId) {
const canvas = document.getElementById(canvasId);
const ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
function saveCanvas() {
const canvas = document.getElementById('interactive-canvas');
const link = document.createElement('a');
link.download = 'canvas-drawing.png';
link.href = canvas.toDataURL();
link.click();
}
function startAnimation() {
canvasDrawing.startAnimation();
}
function stopAnimation() {
canvasDrawing.stopAnimation();
}
function resetAnimation() {
canvasDrawing.resetAnimation();
}
</script>
|
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