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 the high-ratio zlib and Zopfli selection path
`AInfo`	Receives stream totals plus zlib trial and Zopfli attempt, completion, selection, budget, byte-saving, and elapsed-time telemetry

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 establishes the smallest of four maximum-compression zlib strategies, then uses budgeted Zopfli block splitting only when it produces a strictly smaller stream
ZopfliFlateOptions bounds input, iterations, block count, output, and elapsed time; disabled, over-budget, late, failed, or non-improving attempts retain the zlib baseline
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;
  ZopfliAttemptCount: Integer;
  ZopfliCompletedCount: Integer;
  ZopfliSelectedCount: Integer;
  ZopfliBudgetExceededCount: Integer;
  ZopfliInputBytes: Int64;
  ZopfliBytesSavedOverBaseline: Int64;
  ZopfliElapsedMilliseconds: Int64;
end;

FilterStatistics records the pre-optimization 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');