v0.15.0 — PNM and PFM input, metadata for animations, four conversions brought to parity

Skidbladnir 0.15.0 adds new input formats, keeps metadata for animations, and fixes four conversions so their output matches the official encoder byte for byte. It is a prerelease, like every release since the move to Tauri.

New

• PNM input: binary PGM, PPM and PAM, 8 or 16 bits, with or without alpha.
  • Converted to WebP exactly as cwebp reads them.
  • Converted to JPEG XL exactly as cjxl reads them, at the file's own bit depth.
• PFM input: floating-point images.
  • Converted to JPEG XL exactly as cjxl does, floats and all.
  • Other formats get the image clamped to its nominal range.
• Metadata in animations.
  • GIF → animated WebP: a GIF's colour profile and XMP are kept when you ask, as gif2webp -metadata keeps them.
  • Animated WebP re-encoded: its colour profile, Exif and XMP are kept when you ask. Before, they were always dropped.

Fixed (output now matches the official tool)

• TIFF with premultiplied alpha → WebP came out darker than cwebp's conversion wherever the image was semi-transparent. It now matches cwebp exactly.
• Still GIF → JPEG XL:
  • now converts as cjxl does;
  • lossless when no quality is set, as cjxl defaults for GIF.
• Lossy WebP → HEIC now converts as heif-enc does: straight from the WebP's own YCbCr planes, with no RGB round trip.
• HEIC → HEIC:
  • now converts as heif-enc does;
  • keeps the source's Exif and XMP, which were dropped before.

Under the hood

• Tauri 2.12.1, plus current dependencies.
• The Windows build now links a single C runtime (the static one) instead of a mix of static and dynamic. CI builds and drives it; it has not been run on a machine outside CI.
• Byte-for-byte parity tests against the official encoders now number 3,387 cases, up from 2,861.

Known gaps (unchanged unless noted)

• macOS: the .dmgs are built by CI but have never been launched.
• No code signing on any platform.
• TIFF alpha, two deliberate differences from the official tools:
  • A TIFF with straight alpha keeps its true colours, where cwebp darkens it.
  • A TIFF with premultiplied alpha converted to HEIC keeps its true colours, where heif-enc would not un-multiply it. This one is pending a decision.
• Animations: AVIF, JPEG XL and HEIC output take still images only.
• Inputs not yet read: Y4M, raw pixels, PGX and EXR.