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koriweb 9609c04755 docs(10_Wiki): W3Schools 위키화 — HTML/CSS/JavaScript(core)

W3Schools 튜토리얼을 P-Reinforce v3.1 포맷으로 위키화(영어 본문, 한/영 섹션 헤더).
- Topic_HTML: 59문서 (튜토리얼+예제, 레퍼런스/메타 제외)
- Topic_CSS: 190문서 (메인 + Advanced/Flexbox/Grid/RWD 전체)
- Topic_JavaScript: 120문서 (코어 언어; Temporal/DOM상세/BOM/WebAPI/AJAX/jQuery/Graphics 등은 후속)
각 폴더 00_INDEX.md(MOC) 포함. 코드 verbatim, 미확인분은 "Not found in source" 표기.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-06-23 19:21:18 +09:00

6.3 KiB

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title

CSS Image Sprites

🎯 한 줄 통찰 (One-line insight)

An image sprite packs many small images into one file, then uses background-image plus background-position offsets to display just the needed slice — cutting server requests and eliminating hover-load delay. [S1]

🧠 핵심 개념 (Core concepts)

Image sprite — a collection of various small images put into one larger image file, called a "sprite image." [S1]
Why sprites — using a single sprite reduces the number of server requests and saves bandwidth versus loading many separate images. [S1]
Two key properties — sprites are implemented with background-image (the sprite file) and background-position (which slice to show). [S1]
Transparent placeholder — a tiny transparent image (img_trans.gif, 1×1) can act as the element while CSS controls which part of the sprite is visible. [S1]
Hover without extra loads — hover effects shift background-position (e.g. 45px down) to a different region of the sprite, so no additional image needs to load. [S1]

🧩 추출된 패턴 (Extracted patterns)

Slice selection — fix an element's width/height to one icon's size and use a negative background-position to scroll the sprite so only that icon shows. [S1]
Shorthand background — combine file and position in one background: url('sprite.gif') -47px 0; declaration. [S1]
Hover row swap — keep horizontal offset, change the vertical offset on :hover to reveal a second row of the sprite for interactive feedback. [S1]

📖 세부 내용 (Details)

What is an image sprite? An image sprite is a collection of various small images put into one larger image file, called a "sprite image." This approach reduces the number of server requests and saves bandwidth. Sprites are implemented with the background-image and background-position properties. [S1]

Example 1 — Basic Image Sprites Three elements (#home, #prev, #next) each set their own width/height and reference the same img_navsprites.gif, differing only by background-position so each shows a different icon. Transparent 1×1 images serve as the element bodies: [S1]

<html>
<head>
<style>
#home {
  width: 46px;
  height: 44px;
  background-image: url(img_navsprites.gif);
  background-position: 0 0;
}

#prev {
  width: 43px;
  height: 44px;
  background-image: url('img_navsprites.gif');
  background-position: -47px 0;
}

#next {
  width: 43px;
  height: 44px;
  background-image: url('img_navsprites.gif');
  background-position: -91px 0;
}
</style>
</head>
<body>

<img id="home" src="img_trans.gif" width="1" height="1">
<img id="prev" src="img_trans.gif" width="1" height="1">
<img id="next" src="img_trans.gif" width="1" height="1">

</body>
</html>

Example 2 — Navigation List The sprite is applied to a navigation list (<ul>/<li>). The list uses relative/absolute positioning to lay items out horizontally, with each item's left offset and background shorthand isolating its icon from the sprite: [S1]

#navlist {
  position: relative;
}

#navlist li {
  margin: 0;
  padding: 0;
  list-style: none;
  position: absolute;
  top: 0;
}

#navlist li, #navlist a {
  height: 44px;
  display: block;
}

#home {
  left: 0px;
  width: 46px;
  background: url('img_navsprites.gif') 0 0;
}

#prev {
  left: 60px;
  width: 43px;
  background: url('img_navsprites.gif') -47px 0;
}

#next {
  left: 120px;
  width: 43px;
  background: url('img_navsprites.gif') -91px 0;
}

Example 3 — Hover Effect Adds interactivity by shifting background-position 45px down (to a hover row of img_navsprites_hover.gif) on :hover. Because all images preload in one file, there is no loading delay on hover: [S1]

#home a:hover {
  background: url('img_navsprites_hover.gif') 0 -45px;
}

#prev a:hover {
  background: url('img_navsprites_hover.gif') -47px -45px;
}

#next a:hover {
  background: url('img_navsprites_hover.gif') -91px -45px;
}

Advantages highlighted: a single server request instead of multiple image downloads; reduced bandwidth consumption; and no loading delay on hover effects since all images preload in one file. [S1]

🛠️ 적용 사례 (Applied in summary)

The page's three examples — basic sprite slices, a positioned navigation list, and a hover row swap — are the applied demonstrations. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Display one slice of a sprite (language: CSS):

#prev {
  width: 43px;
  height: 44px;
  background-image: url('img_navsprites.gif');
  background-position: -47px 0;
}

Hover row swap with the background shorthand (language: CSS):

#prev a:hover {
  background: url('img_navsprites_hover.gif') -47px -45px;
}

⚖️ 모순 및 업데이트 (Contradictions & updates)

No contradictions found in the source.

✅ 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: 0.89
중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

상위/루트: CSS Tutorial
관련 개념: CSS Backgrounds, CSS Position, CSS Image Gallery
참조 맥락: Referenced when optimizing icon/asset delivery by consolidating many images into one file with positioned background slices.

📚 출처 (Sources)

[S1] W3Schools — CSS Image Sprites — https://www.w3schools.com/css/css_image_sprites.asp

📝 변경 이력 (Change history)

2026-06-23: Initial draft synthesized from the W3Schools "CSS Image Sprites" page (Astra wiki-curation, P-Reinforce v3.1 format).

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