awaforge

pdfLegacyDeprecatedFilters

AGPL-3.0-onlyRelease 2L4

LZWDecode (via fw) + CCITTFax (via pdfCcittFaxDecoder) + DCT/JPX passthrough — legacy.

Module pdfLegacyDeprecatedFilters | Source packages/front/office/pdf/src/extra/legacy-deprecated-filters.js | Deps pdfErrors, lzw (fw binding), pdfCcittFaxDecoder | Worker-safe yes

Read side of three legacy filters. LZWDecode = wrapper over @awacloud/fw/io/compress/lzw (TIFF profile, MSB-first, 8-bit min, CLEAR/END), supports /EarlyChange. CCITTFaxDecode validates the DecodeParms shape and then delegates the actual Group 3/Group 4 decode to the pdfCcittFaxDecoder dependency — this module is a thin, validated pass-through, not a decoder itself. DCTDecode/JPXDecode are signature-checked passthroughs (JPEG/JPX bytes returned unchanged).

Resolve

const ext = runtime.resolve('pdfLegacyDeprecatedFilters');
// Returns: { lzwDecode, lzwEncode, validateCcittParms, ccittFaxDecode,
//   dctDecode, jpxDecode, CCITT_KEYS }

API

Member Signature Returns
lzwDecode (bytes, decodeParms?) => Uint8Array TIFF-profile LZW decode.
lzwEncode (bytes) => Uint8Array TIFF-profile LZW encode.
validateCcittParms (parms) => NormalizedParms Validates and normalizes the CCITT DecodeParms shape.
ccittFaxDecode (bytes, decodeParms) => Uint8Array Validates parms then calls pdfCcittFaxDecoder.decode(bytes, parms).
dctDecode (bytes) => Uint8Array Checks the JPEG SOI marker, then passthrough.
jpxDecode (bytes) => Uint8Array Checks the JP2/codestream signature, then passthrough.
CCITT_KEYS Set Accepted CCITT DecodeParms keys (K, EndOfLine, EncodedByteAlign, Columns, Rows, EndOfBlock, BlackIs1, DamagedRowsBeforeError).

Examples

LZW decode

const ext = runtime.resolve('pdfLegacyDeprecatedFilters');
const plain = ext.lzwDecode(streamBytes, { EarlyChange: 1 });

CCITT parms validation + decode

const p = ext.validateCcittParms({ K: -1, Columns: 1728, Rows: 100 });
p.K;        // -1 (Group 4)
p.Columns;  // 1728

const image = ext.ccittFaxDecode(streamBytes, { K: -1, Columns: 1728, Rows: 100 });

Errors

Code Class When
pdf/filters/missing-lzw ParseError The lzw fw dependency has no decode/encode.
pdf/filters/missing-ccitt ParseError The pdfCcittFaxDecoder dependency has no decode.
pdf/filters/bad-input ParseError bytes is not a Uint8Array.
pdf/lzw/bad-earlychange ParseError /EarlyChange is not 0 or 1.
pdf/lzw/decode-failed ParseError The fw decode threw.
pdf/lzw/encode-failed ParseError The fw encode threw.
pdf/ccitt/bad-parms ParseError parms is not an object.
pdf/ccitt/unknown-parm ParseError A key outside CCITT_KEYS.
pdf/dct/bad-soi ParseError JPEG SOI marker absent.
pdf/jpx/bad-signature ParseError Not a recognized JPEG 2000 codestream or JP2 box stream.

Actual T.4/T.6 decode failures (truncation, unrecognized codes) surface through pdfCcittFaxDecoder's own error codes (see that page) — this module does not wrap or rename them.

See also