Module: lib/png-chunks-extractor

Source:

Requires

Methods

(static) default(file, optionsopt) → {Promise.<{chunks: Array.<Chunk>, chunksByType: Array.<{type:number, chunks:Array.<Chunk>}>}>|null}

Parse a PNG file and return its data chunks

Parameters:
Name Type Attributes Description
file PathLike | FileHandle

PNG file
options Object <optional>

Parsing options

Properties
Name Type Attributes Default Description
validateStruct boolean <optional>
 true

If truthy, validate the general PNG structure (file starts with PNG signature and chunk stream begins with an IHDR chunk and ends with an empty IEND chunk). Return null when validation fails
validateCrc boolean <optional>
 false

If truthy, check crc signature of each chunk and ignore it if there is a mismatch, further mismatch behaviour depends on options.throwOnError and options.logOnError
throwOnError boolean <optional>
 false

If truthy, throws error when validation fails
logOnError boolean <optional>
 true

If truthy, logs if validation fails
Source:
Returns:

The raw chunks array (by order of appearance) and an object of these chunks indexed by chunk type (as a 32 bit unsigned int)

Type
Promise.<{chunks: Array.<Chunk>, chunksByType: Array.<{type:number, chunks:Array.<Chunk>}>}> | null

(inner) extractNextChunk(buffer, offset, parseCrcopt) → {Object.<{offset: number, crc: number, crcBuf: Buffer, chunk: Chunk}>}

Extract a chunk from a PNG buffer

Parameters:
Name Type Attributes Default Description
buffer Buffer

Raw PNG Buffer
offset number

Current read offset
parseCrc boolean <optional>
 false

If truthy, crc of each chunk is parsed
Source:
Returns:

Parsed chunk, chunk's CRC and new offset

Type
Object.<{offset: number, crc: number, crcBuf: Buffer, chunk: Chunk}>