All Symbols - @binstruct/png documentation

default

PNG (Portable Network Graphics) file format support for binary structure encoding and decoding.

Examples

Basic PNG file encoding and decoding

import { assertEquals } from "@std/assert";
import { pngFile, type PngChunkUnknown } from "@binstruct/png";

const pngCoder = pngFile();
const testPng = {
  signature: {
    highBitByte: 137,
    signature: "PNG",
    dosEOF: "\u001a",
    dosLineEnding: "\r\n",
    unixLineEnding: "\n"
  },
  chunks: [
    {
      length: 13,
      type: new Uint8Array([73, 72, 68, 82]), // "IHDR"
      data: new Uint8Array([0, 0, 0, 1, 0, 0, 0, 1, 8, 2, 0, 0, 0]),
      crc: 0x12345678,
    } as PngChunkUnknown,
  ],
};

const buffer = new Uint8Array(100);
const bytesWritten = pngCoder.encode(testPng, buffer);
const [decodedPng, bytesRead] = pngCoder.decode(buffer);

assertEquals(bytesRead, 93);
assertEquals(decodedPng.signature, testPng.signature);
assertEquals(decodedPng.chunks.length, 6);

Functions

f

bkgdChunkRefiner(): Refiner<PngChunkUnknown, BkgdChunk, []>

Creates a refiner for bKGD (background color) chunks.

f

chunkCrc(bytesOrChunk: Uint8Array | { type: Uint8Array; data: Uint8Array; }): number

Calculates the CRC32 checksum for PNG chunk data.

f

idatChunkRefiner(): Refiner<PngChunkUnknown, IdatChunk, []>

Creates a refiner for IDAT (Image Data) chunks.

f

iendChunkRefiner(): Refiner<PngChunkUnknown, IendChunk, []>

Creates a refiner for IEND (Image End) chunks.

f

ihdrChunkRefiner(): Refiner<PngChunkUnknown, IhdrChunk, []>

Creates a refiner for IHDR (Image Header) chunks.

f

plteChunkRefiner(): Refiner<PngChunkUnknown, PlteChunk, []>

Creates a refiner for PLTE (Palette) chunks.

f

pngChunkRefined(): Coder<

PngChunkUnknown
| IhdrChunk
| PlteChunk
| TrnsChunk
| BkgdChunk
| IdatChunk
| IendChunk

Creates a coder for PNG chunks with type-specific refinement.

f

pngChunkUnknown(): Coder<PngChunkUnknown>

Creates a coder for unknown/generic PNG chunks.

f

pngFile(): Coder<

PngChunkUnknown
| IhdrChunk
| PlteChunk
| TrnsChunk
| BkgdChunk
| IdatChunk
| IendChunk

Creates a coder for complete PNG files with automatic chunk refinement.

f

TChunk = ReturnType<pngChunkRefined> extends Coder<infer T> ? T : never

>(chunkCoder?: Coder<TChunk>): Coder<PngFile<TChunk>>

Creates a coder for PNG files with a custom chunk coder.

f

trnsChunkRefiner(): Refiner<PngChunkUnknown, TrnsChunk, []>

Creates a refiner for tRNS (transparency) chunks.

Interfaces

I

PNG bKGD (background color) chunk structure.

data: { values: number[]; }
Background color data
type: "bKGD"
Chunk type identifier, always "bKGD"

I

Refined IDAT (Image Data) chunk structure.

data: ZlibUncompressedData
Decompressed zlib data structure
type: "IDAT"
Chunk type identifier, always "IDAT"

I

Refined IEND (Image End) chunk structure.

crc: number
CRC checksum (always the same for IEND since data is empty)
type: "IEND"
Chunk type identifier, always "IEND"

I

Refined IHDR (Image Header) chunk structure.

data: { width: number; height: number; bitDepth: number; colorType: number; compressionMethod: number; filterMethod: number; interlaceMethod: number; }
Parsed image header data
type: "IHDR"
Chunk type identifier, always "IHDR"

I

Refined PLTE (Palette) chunk structure.

data: { colors: [number, number, number][]; }
Parsed palette data
type: "PLTE"
Chunk type identifier, always "PLTE"

I

PngChunkUnknown

Generic PNG chunk structure.

crc: number
CRC (4 bytes)
data: Uint8Array
Data (variable length)
length: number
Length of the data field in bytes (4-byte big-endian)
type: Uint8Array
Type (4 bytes)

I

PNG file structure containing signature and chunks.

chunks: TChunk[]
Array of PNG chunks in the file
signature: { highBitByte: number; signature: string; dosLineEnding: string; dosEOF: string; unixLineEnding: string; }
The 8-byte PNG signature: [137, 80, 78, 71, 13, 10, 26, 10]

I

PNG tRNS (transparency) chunk structure.

data: { values: number[]; }
Transparency data
type: "tRNS"
Chunk type identifier, always "tRNS"