image_ffi 1.1.0

image_ffi: ^1.1.0 copied to clipboard

• Turn phone photos upright. A camera writes the sensor's pixels unrotated and records how the phone was held in the EXIF orientation tag; every viewer applies it silently. stb does not parse EXIF, so a portrait photo decoded to a landscape buffer and thumbnailJpeg produced a sideways thumbnail with nothing to indicate anything was wrong — on the most common thumbnail input there is.

  exifOrientation reads the tag and applyExifOrientation applies any of the eight values, including the four that swap the axes and the four that mirror. thumbnailJpeg and thumbnailPng now use them by default; pass applyOrientation: false for the raw sensor framing. A file with no EXIF, a malformed tag, or a value outside 1 to 8 reads as upright, so a broken tag can never fail a decode that would otherwise have worked.

• Declare the SDK this package can actually resolve on. The constraint read ^3.9.0, but the hooks dependency that runs the native build requires >=3.10.0. On Dart 3.9 the package looked supported and then failed to resolve, with an error naming hooks rather than anything the reader had asked for. The pubspec and the README now both say 3.10.

• Link libm on Android, where the decoder would otherwise fail at dlopen. stb_image calls pow for gamma conversion and stb_image_write calls frexp when writing HDR. Android keeps both in a separate libm, and its linker will not resolve a symbol from a library that is absent from DT_NEEDED, so the shim compiled cleanly and then failed to load on the device. On the 1.0.0 library llvm-nm -u --dynamic reported U pow and U frexp carrying no version tag while every other import carried one, and DT_NEEDED listed only libdl and libc. Rebuilt, the same commands report pow@LIBC, frexp@LIBC and ldexp@LIBC, with libm.so in DT_NEEDED. Every other target hid the omission: macOS and iOS take math from libSystem, and glibc 2.34 folded libm into libc. Linux is linked against libm too, because musl and older glibc still need it and on modern glibc it costs nothing.

The API is stable. No behaviour changes; this freezes the surface after an adversarial pass over the FFI boundary, and pins what it found as tests.

Verified by execution and now covered by test/native_safety_test.dart:

• Undecodable data (garbage, a truncated file, a bare header) raises ImageFfiException, and an empty buffer raises ArgumentError — the split the README describes, checked rather than assumed.
• Decoding, resizing and JPEG-encoding 2,000 times grows RSS by about four megabytes. Each cycle allocates and frees several native buffers, so leaking any of them would cost hundreds.
• thumbnailJpeg bounds the longer side and never enlarges an image already within the limit.
• A non-positive resize target is rejected instead of reaching the native call.

One honest caveat: the build hooks depend on native_toolchain_c, which is pre-1.0, so a breaking release there may need a new build of this package. It is a build-time dependency and does not reach the public API frozen here.

• Seal DecodedImage and ImageFfiException. Both carried no class modifier, so a 1.0.0 freeze would have made every field added to either one a breaking change for anyone who had subclassed it. Neither is meant to be subtyped, and nothing in the package, its tests or its example does. ResizeColorSpace is an enum and was already closed. No behaviour change.

• Fix a native buffer leak: decodeImage, resizePixels, encodeJpeg, and encodePng freed the native output buffer only after copying it into a Dart Uint8List. If that copy threw (out of memory on a large image), the native buffer was never freed. Each free now runs in a finally around the copy, so it happens whether the copy succeeds or throws.
• Fix a silent truncation risk: resizePixels takes srcWidth, srcHeight, dstWidth, and dstHeight as Dart int, but crosses the FFI boundary as a 32-bit native Int. A caller passing a dimension above 2^31-1 got it silently wrapped at the boundary instead of an error. These now throw ArgumentError before the call.

• Add thumbnailJpegBatch and thumbnailPngBatch for processing a folder. Running Future.wait over thumbnailJpegAsync spawned one isolate per image at once, each holding a full decoded buffer, which ran a real directory out of memory. The batch calls run the same per-image work off the main isolate but cap how many isolates are live at once to concurrency, defaulting to Platform.numberOfProcessors, using a semaphore over the existing async calls. Each thumbnail is emitted from the returned stream as it finishes, so results arrive in completion order rather than input order. maxDimension and quality match the async variants. The README now points at these for a folder and example/no_jank.dart shows the batch path.

• Install instructions now say pub add instead of pinning a version. The pinned number was stale by several releases and would have been stale again after the next one: the README ships frozen in the archive, so a hand-edited version line is wrong the moment anything is published. This one cannot go out of date.

• Widen the native-toolchain constraints so the package can be installed in a Flutter app at all. hooks 2.1.0 and native_toolchain_c 0.19.3 raised their meta floor to ^1.19.0, and Flutter's SDK pins meta to 1.17.0, so flutter pub add failed at version solving with "flutter from sdk is incompatible". Allowing hooks >=2.0.2 and native_toolchain_c >=0.19.2 lets the solver pick a version that works with the pinned meta, while a pure-Dart project still resolves to the newest. No API or behaviour change.

• example/no_jank.dart measures what the async variants are for. It builds a 4000x3000 JPEG so no file is needed, makes eight thumbnails on the main isolate and eight with thumbnailJpegAsync, and runs a 16 ms timer alongside to report the longest gap between two ticks. On this machine: 413 ms of silence, about 25 frames, against 18 ms and one. The work takes the same time either way, which is the point; what moves is where it happens.
• example/README.md says which call to reach for and why the thumbnail functions exist at all, given the three-step version crosses the FFI boundary three times and holds the full-size pixel buffer in Dart in between.

• Declare the benchmark chart in pubspec.yaml so pub.dev renders it on the package page. The chart was already in the repository and the README, but pub.dev shows only what the screenshots: field points at, so the page a reader lands on from search opened with text where the measurement should have been.

• Add thumbnailJpegAsync and thumbnailPngAsync. They take the same arguments as the synchronous versions and return a Future, running the whole decode, resize and encode on a background isolate with Isolate.run so a large image doesn't block the calling isolate. In a Flutter app this keeps the UI responsive while a picked photo is turned into a thumbnail, which neither the pure-Dart image package nor a synchronous FFI call can do on the main isolate. An ImageFfiException raised in the worker surfaces from the future.

• Add thumbnailPng, a one-call decode, resize, and PNG encode that keeps the alpha channel. Reach for it on logos, icons, screenshots, and anything with transparency, where thumbnailJpeg would flatten the transparent areas onto a background.

• Docs: sharpen the pub.dev description to lead with the value and the terms people search.

• resizePixels now takes a colorSpace (ResizeColorSpace.srgb by default, or .linear). sRGB is right for photographic and UI images; linear is for masks and data pixels where an sRGB curve would distort the values.
• Fix: 2-channel input is now resampled as grayscale + alpha (STBIR_RA) instead of two colour channels, so edges against transparency stay clean for gray+alpha images. Previously a 2-channel resize let transparent pixels bleed into the colour.

• Initial release.
• Decode PNG, JPEG, BMP, GIF, PSD, TGA, HDR and PIC from memory (decodeImage), with an optional forced channel count.
• Read dimensions and channel count without decoding pixels (imageInfo).
• High-quality, sRGB-correct resize (resizePixels).
• JPEG and PNG encoding to memory (encodeJpeg, encodePng).
• One-call thumbnail generation (thumbnailJpeg): decode, aspect-preserving downscale and JPEG encode.
• Native stb sources compiled from source by a Dart build hook; no prebuilt binaries.