[HTML] canvas 태그
https://www.w3schools.com/graphics/canvas_intro.asp 
https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API 
//------------------------------------- 
예제 
<canvas id="canvas"></canvas> 
<script> 
const canvas = document.getElementById('canvas'); 
const ctx = canvas.getContext('2d'); 
ctx.fillStyle = 'green'; 
ctx.fillRect(10, 10, 150, 100); 
</script> 
//------------------------------------- 
CanvasRenderingContext2D 
https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D 
arc(),  
drawImage() 
ellipse() 
lineTo() 
rect() 
rotate() 
scale() 
transform() 
translate() 
//------------------------------------- 
Canvas vs SVG 장단점
http://tcpschool.com/html/html5_graphic_canvasVsSvg 
* svg  
화면이 크거나, 픽셀 수가 적을 경우(<10k). 
- 정지 이미지 
- 태그 
* canvas  
화면이 작거나, 픽셀 수가 많을 경우(>10k)
- 동적 이미지 
- 자바스크립트