---
id: html-canvas
title: "HTML Canvas"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["canvas element", "HTML5 Canvas", "<canvas>", "2d context", "getContext"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.90
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["html", "web", "frontend", "canvas", "graphics", "html5", "w3schools"]
raw_sources: ["https://www.w3schools.com/html/html5_canvas.asp"]
applied_in: []
github_commit: ""
---

# [[HTML Canvas]]

## 🎯 한 줄 통찰 (One-line insight)
The HTML `<canvas>` element is an empty container for graphics; all actual drawing — lines, shapes, text, gradients, images — is done at runtime with JavaScript via a 2D drawing context. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`<canvas>` is just a container** — it has no drawing ability of its own; JavaScript draws into it. [S1]
- **It can draw** paths, boxes, circles, text, and images, and is supported by all major browsers. [S1]
- **Always set `id`, `width`, and `height`** — the `id` lets scripts reference it; `width`/`height` set its drawable size. A border style makes the otherwise invisible canvas visible. [S1]
- **The 2D context is the drawing surface** — obtain it with `canvas.getContext("2d")`; all drawing methods (`moveTo`, `lineTo`, `arc`, `fillText`, etc.) are called on that context object. [S1]
- **Gradients** — created with `createLinearGradient(...)` or `createRadialGradient(...)`, then color stops are added and the gradient is assigned to `fillStyle`. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Setup pattern** — `getElementById` → `getContext("2d")` → draw. [S1]
- **Path/line pattern** — `moveTo(x,y)` then `lineTo(x,y)` then `stroke()`. [S1]
- **Circle pattern** — `beginPath()` → `arc(x,y,r,0,2*Math.PI)` → `stroke()`. [S1]
- **Text pattern** — set `font`, then `fillText(...)` (filled) or `strokeText(...)` (outline). [S1]
- **Gradient fill pattern** — create gradient → `addColorStop()` → assign to `fillStyle` → `fillRect(...)`. [S1]
- **Image pattern** — `drawImage(img, x, y)` paints an existing image element. [S1]

## 📖 세부 내용 (Details)
**What is HTML Canvas?** The HTML `<canvas>` element is used to draw graphics, on the fly, via JavaScript. The `<canvas>` element is only a container for graphics — you must use JavaScript to actually draw. Canvas can draw paths, boxes, circles, text, and add images, and it works in all major browsers. [S1]

**The Canvas element** — a canvas is a rectangular area on an HTML page, specified with the `<canvas>` element. Always specify an `id` (to refer to it in a script) and a `width` and `height` (to define its size). To add a border, use the `style` attribute: [S1]
```html
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #000000;">
</canvas>
```

**Draw a Line** — [S1]
```html
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.moveTo(0, 0);
ctx.lineTo(200, 100);
ctx.stroke();
</script>
```

**Draw a Circle** — [S1]
```html
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(95, 50, 40, 0, 2 * Math.PI);
ctx.stroke();
</script>
```

**Draw Text** — set the font and use `fillText(text, x, y)`: [S1]
```html
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.font = "30px Arial";
ctx.fillText("Hello World", 10, 50);
</script>
```

**Stroke Text** — set the font and use `strokeText(text, x, y)` for outlined text: [S1]
```html
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.font = "30px Arial";
ctx.strokeText("Hello World", 10, 50);
</script>
```

**Draw Linear Gradient** — gradients can fill rectangles, circles, lines, text, etc. Create a linear gradient, add color stops, set it as the fill style, and fill a rectangle: [S1]
```html
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");

// Create gradient
var grd = ctx.createLinearGradient(0, 0, 200, 0);
grd.addColorStop(0, "red");
grd.addColorStop(1, "white");

// Fill with gradient
ctx.fillStyle = grd;
ctx.fillRect(10, 10, 150, 80);
</script>
```

**Draw Radial Gradient** — [S1]
```html
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");

// Create gradient
var grd = ctx.createRadialGradient(75, 50, 5, 90, 60, 100);
grd.addColorStop(0, "red");
grd.addColorStop(1, "white");

// Fill with gradient
ctx.fillStyle = grd;
ctx.fillRect(10, 10, 150, 80);
</script>
```

**Draw Image** — use `drawImage(image, x, y)` to paint an existing image element onto the canvas: [S1]
```html
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var img = document.getElementById("scream");
ctx.drawImage(img, 10, 10);
</script>
```

## 🛠️ 적용 사례 (Applied in summary)
The examples above are the canonical applied uses: drawing a diagonal line, a circle, filled and outlined text, linear and radial gradient-filled rectangles, and painting an existing image into the canvas. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Canvas setup + draw a line (HTML + JavaScript):
```html
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #000000;"></canvas>
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.moveTo(0, 0);
ctx.lineTo(200, 100);
ctx.stroke();
</script>
```
Circle (JavaScript):
```javascript
ctx.beginPath();
ctx.arc(95, 50, 40, 0, 2 * Math.PI);
ctx.stroke();
```
Linear gradient fill (JavaScript):
```javascript
var grd = ctx.createLinearGradient(0, 0, 200, 0);
grd.addColorStop(0, "red");
grd.addColorStop(1, "white");
ctx.fillStyle = grd;
ctx.fillRect(10, 10, 150, 80);
```

## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
The source frames Canvas in contrast to SVG: SVG describes 2D graphics in XML, while Canvas draws 2D graphics on the fly with JavaScript. In Canvas, once a graphic is drawn it is "forgotten" by the browser (immediate-mode, pixel/bitmap output), whereas in SVG each drawn shape is remembered as an object and re-rendered on change (retained-mode). Canvas is resolution dependent, has no built-in event handlers, has poor text rendering, but can save the result as a .png/.jpg image and is well suited to graphic-intensive games. See [[HTML SVG]] for the complementary trade-offs. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
No contradictions found in the source. Note the immediate-mode nature: Canvas does not retain a scene graph, so anything that must be interactive or re-rendered on data change has to be redrawn manually by your script. [S1]

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.90
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[HTML Tutorial]]
- **관련 개념:** [[HTML SVG]], [[HTML Graphics]], [[HTML Media]], [[HTML5]]
- **참조 맥락:** Referenced when rendering dynamic, script-driven, pixel-based graphics such as charts, visualizations, or games.

## 📚 출처 (Sources)
- [S1] W3Schools — HTML Canvas — https://www.w3schools.com/html/html5_canvas.asp

## 📝 변경 이력 (Change history)
- 2026-06-23: Initial draft synthesized from the W3Schools "HTML Canvas" page (Astra wiki-curation, P-Reinforce v3.1 format).