THotPDF.OptimizeLoadedStreams Method

Rewrites selected loaded stream families as Flate only when the replacement is smaller by the requested threshold

Declaration

function OptimizeLoadedStreams(
  FilterFamilies: THPDFLoadedStreamFilterFamilies;
  MinimumSavingsBytes: Int64;
  out AInfo: THPDFLoadedStreamOptimizationInfo): Integer; overload;

function OptimizeLoadedStreams(
  FilterFamilies: THPDFLoadedStreamFilterFamilies;
  MinimumSavingsBytes: Int64;
  RecompressionMode: THPDFFlateRecompressionMode;
  out AInfo: THPDFLoadedStreamOptimizationInfo): Integer; overload;

Unit

HPDFDoc

Parameters

Name	Purpose
`FilterFamilies`	Selects unfiltered, Flate, LZW, ASCII85, ASCIIHex, and RunLength candidates
`MinimumSavingsBytes`	Positive minimum byte reduction required before a candidate replaces its source stream
`RecompressionMode`	Selects the standard single-pass path or deterministic four-strategy high-ratio Flate selection
`AInfo`	Receives scanned, candidate, rewritten, unsupported, failed, before, after, and saved-byte totals

Return value

Returns the number of stream payloads replaced in the loaded object graph

Usage notes

CompressionLevel selects the zlib speed and ratio, while clNone makes the pass a no-op
frmHighRatio tries default, filtered, run-length, and Huffman-only maximum-compression strategies and retains the smallest standards-compatible stream
Decoded and compressed candidates spill to owned temporary files after LoadedStreamMemoryThreshold, keeping large-document memory bounded
The original payload and dictionary remain unchanged after decode failure or insufficient savings
Streams with /DecodeParms are skipped so predictor and non-default LZW semantics cannot be changed accidentally
Multi-filter chains are eligible only when every family is selected and supported
Call SaveLoadedDocument after the pass to persist adopted payloads

Types and diagnostics

THPDFLoadedStreamFilterFamily = (lsffUnfiltered, lsffFlate, lsffLZW,
  lsffASCII85, lsffASCIIHex, lsffRunLength);
THPDFLoadedStreamFilterFamilies = set of THPDFLoadedStreamFilterFamily;

THPDFLoadedStreamOptimizationInfo = record
  ScannedStreamCount: Integer;
  CandidateStreamCount: Integer;
  RewrittenStreamCount: Integer;
  UnsupportedStreamCount: Integer;
  DecodeFailureCount: Integer;
  BytesBefore: Int64;
  BytesAfter: Int64;
  BytesSaved: Int64;
  FilterStatistics: THPDFLoadedStreamFilterStatistics;
  RecompressionMode: THPDFFlateRecompressionMode;
  CompressionTrialCount: Integer;
end;

FilterStatistics records the pre-optimisation stream count, encoded bytes, and per-family stage attribution without forcing an additional decode pass

Example

Families := [lsffUnfiltered, lsffFlate, lsffLZW];
Count := PDF.OptimizeLoadedStreams(Families, 16, frmHighRatio, Info);
if Count > 0 then
  PDF.SaveLoadedDocument('optimized.pdf');