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PNG File Format/File Structure

ํŒŒ ตฌกฐ

PNG ํŒŒ€ PNG ‹œทธ„ˆฒ˜™€ —ฌŸฌฐœ˜ chunkกœ ดฃจ–ดง.

1. PNG file ‹œทธ„ˆฒ˜

  • PNGํŒŒ˜ ฒ˜Œ 8ฐ”ดํŠธŠ” ‹คŒ˜ ‹ญ„ ฐ’“คกœ ‹œž‘.

    137 80 78 71 13 10 26 10
      

2. Chunk Layout

  • ฐ chunkŠ” „€„œกœ ‚˜‰˜–ด„‹ค.
    • Length : 4ฐ”ดํŠธ. Length, Chunk Type, CRC ธธดŠ” ํฌํ•จ˜€ •Š€ ฐ’ด‹ค.
    • Chunk Type : 4ฐ”ดํŠธ. ฐ˜“œ‹œ •ŒํŒŒฒณด–ด• ํ•จ(ํŽธฆฌํ•จ. €…„„ œ„ํ•ด). —”ฝ””, ””ฝ””Š” ด ฐ’„ ด„ ฐ’œกœ ธ€.
    • Chunk Data : Type — ”ฐฅธ ฐดํ„ฐ. ธธด€ 0ˆ˜ žˆŒ.
    • CRC : Chunk Type + Chunk Data — Œ€ํ•œ 4 ฐ”ดํŠธ CRC ฐ’.

3. Chunk ด„ง“ธฐ ทœ™

4. CRC •Œณ ฆฌฆ˜

5. Chunk Spec.

  •  œ ฒ˜Œ—Š” IHDR chunk€ ˜คŠ”ฐ, ‹คŒ˜ š”†Œกœ ดฃจ–ด ธ žˆ‹ค.
    • Width : ํ”ฝ…€‹จœ„˜ ด€ „ˆ„
    • Height : ํ”ฝ…€‹จœ„˜ ด€ †’ด
    • Bit depth : ํ•˜‚˜˜ ƒ˜ํ”Œ(ํ”ฝ…€Š” ‹คฅธฐœ…)‹ ˜Š” ํŒŒ ˆํŠธ ธŠค‹ “ฐดŠ” „ํŠธ˜ ˆ˜
    • Compression method : ด€ ฐดํ„ ••ถ•ํ•˜Š”ฐ “ฐŠ” ฐฉฒ•
    • Filter method : ด€ ฐดํ„— Œ€ํ•œ  „ฒ˜ฆฌ ฐฉฒ•. Compression € จ.
    • Interlace method : ด€— Œ€ํ•œ „ํŠธ˜ค”.
      Color Type Allowed Bit Depths Interpretation
      0 1,2,4,8,16 Each pixel is a grayscale sample.
      2 8, 16 Each pixel is an R, G, B triple.
      3 1, 2, 4, 8 Each pixel is a palette index; a PLTE chunk must appear.
      4 8, 16 Each pixel is a grayscle sample, followed by an alpha sample.
      6 8, 16 Each pixel is an R, G, B triple, followed by an alpha sample.

  • PLTE chunk : 256ฐœ˜ —”ํŠธฆฌ ฐ–Œ. R, G, B ƒ‰ƒ)
  • IDAT chunk : ‹ค œ ํ”ฝ…€ฐ’. IDATŠ” —ฌŸฌฐœ€ ˜ฌ ˆ˜ žˆ‹ค. (see also PNGFileFormat/ImageData)
  • IEND chunk : ฐ˜“œ‹œ ด chunk กœ ‚˜• ํ•จ. Data ธธดŠ” 0.

Summary

Name —ฌŸฌฐœ ํ—ˆšฉ? ํŒŒƒ˜ œ„˜  œ•ฝ
IHDR x ฐ˜“œ‹œ  œ •ž— ™€•ํ•จ (ฒ˜Œ˜ 8„ํŠธ  œ™ธ)
PLTE x IDAT „— ™€•ํ•จ
IDAT o —ฌŸฌฐœ€ ‚ฌšฉœ‹คฉด ฐ˜“œ‹œ —ฐ† ด–ด• ํ•จ
IEND x ฐ˜“œ‹œ  œ — ™€• ํ•จ
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PNGFileFormat
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