Image formats

sceptre decodes input images through the image crate — pure-Rust decoders only, no C image libraries.

Supported

Format
PNG
JPEG
BMP
GIF
TIFF
WebP
NetPBM (PNM)

Out of scope

HEIF, AVIF, and the JPEG 2000 family (jp2/j2k/jpx/jpm/mj2/j2c) are not supported. Their only mature decoders are C libraries (libheif, dav1d, openjpeg), which would pull a C toolchain dependency into the build and break the pure-Rust tract WASM/Android path.

Note

This is a deliberate tradeoff, not an oversight: keeping every decoder pure-Rust preserves the WASM/Android backend story (see Backends) and keeps the dependency/audit surface modest. If demand warrants, HEIF/AVIF/JP2 support could be added later behind an optional, native-only feature that WASM/Android builds omit — see ADR 0022.

These formats show up as a distinct capability group in the benchmark — reported as gaps rather than silently skipped, so the coverage limit stays visible.