Skip to content
VIPS HandbookVIPS Handbook

Default parameter differences across the four bindings

Copy page

Many assume “same input + same intent = same output”, but the four bindings expose different defaults for the same intent. Assume there is no byte-for-byte identity; check defaults before comparing.

govips reference defaults (v2.19.0)

Section titled “govips reference defaults (v2.19.0)”

WebP

Section titled “WebP”

NewWebpExportParams() returns:

Field Default
Quality 75
Lossless false
NearLossless false
ReductionEffort 4
StripMetadata false
TargetSize 0 (disabled)

JPEG

Section titled “JPEG”

NewJpegExportParams() returns Quality 80, Interlace true.

GIF

Section titled “GIF”

NewGifExportParams() returns Quality 75, Effort 7, Bitdepth 8. Note that Quality has no effect under native gifsave (see gif-quality); Effort / Bitdepth are what affect output.

Relation to this handbook’s recipes

Section titled “Relation to this handbook’s recipes”

The recipe reference baseline explicitly sets WebP output quality to 82 (see each recipe’s reference metadata). That is explicit, not a default. A default of 75 differing from the recipe-shown 82 is normal.

Key differences

Section titled “Key differences”
  • Codec quality semantics: the sharpness/size trade-off differs per format; quality is not “sharpness”.
  • Resize semantics: govips Resize is a relative multiplier (and requires a kernel), unlike sharp.resize(w,h) size semantics.
  • Metadata default: StripMetadata defaults to false, i.e. metadata is kept and may be processed (see colour-shift).
  • Animation pages: only the first page is loaded by default; you must set NumPages=-1 explicitly (see animation-multi-page).

Why identity cannot be assumed

Section titled “Why identity cannot be assumed”
  • sharp bundles libvips 8.18.7, different from the reference 8.17.3.
  • pyvips / CLI share the reference system libvips 8.17.3, so defaults are closer but still need per-item confirmation.
  • The current comparison strategy is metadata-only; pixel comparison remains comparison-pending.

When not applicable

Section titled “When not applicable”
  • If you explicitly override all relevant parameters, default differences do not affect the outcome.
  • Defaults may also change between libvips versions; do not rely only on this page’s snapshot.

Sources

Section titled “Sources”
  • govips v2.19.0 source (NewWebpExportParams, NewJpegExportParams, NewGifExportParams defaults).
  • This handbook’s toolchain baseline (libvips 8.17.3, sharp bundled 8.18.7).
  • Reference output quality 82 from recipe metadata.

This page only records the reference binding’s defaults; the sharp / pyvips / CLI default rows are comparison-pending and not run-verified by the shared runner.