image_compress_plus_android #

Android implementation of image_compress_plus.

This package is endorsed and is used by image_compress_plus automatically on Android. Most users should depend on image_compress_plus instead of this package directly.

Usage #

Add to your pubspec.yaml only if you need to depend on the Android implementation directly:

dependencies:
  image_compress_plus_android: ^3.0.0

For app-level usage APIs, see:

• https://pub.flutter-io.cn/packages/image_compress_plus
• https://github.com/WuTangNaiLao/image_compress_plus/tree/main/packages/image_compress_plus

Android Support #

• Methods: compressWithList, compressAssetImage, compressWithFile, compressAndGetFile
• Output formats: jpeg, png, webp, heic
• Params: quality, rotate, keepExif, numberOfRetries

Architecture #

The Android implementation now follows the same high-level shape as the iOS package:

• pigeon for the Dart/native contract
• a single CompressionRequest model
• a unified compression pipeline
• a system-decoder-first input strategy
• four fixed output encoders: jpeg, png, webp, heic

Input Format Support Matrix #

Android does not have a single ImageIO-equivalent framework, so input support is best understood as a system stack with fallbacks.

In practice, the plugin is optimized for:

• common raster inputs that decode to a Bitmap
• EXIF-aware rotation correction when metadata is available
• consistent conversion into one of the four supported output formats

Fallback Strategy #

The current Android pipeline uses this order:

1. Try ImageDecoder on Android 9+ for the broadest modern system support.
2. Fall back to BitmapFactory for older Android versions.
3. Read orientation metadata with ExifInterface when autoCorrectionAngle is enabled.
4. Normalize into a single in-memory bitmap path.
5. Encode only to jpeg, png, webp, or heic.
6. On memory pressure, retry with a larger decode sample size until numberOfRetries is exhausted.

This keeps Android aligned with the iOS package's design goal:

• accept as many practical system-supported inputs as possible
• constrain outputs to a small, predictable set
• keep metadata handling explicit and stable

The Android host side also reports structured native failures for:

• unsupported_input_format
• decode_failed
• unsupported_output_format
• encode_failed
• file_read_failed / transient_file_read_failed
• file_write_failed / transient_file_write_failed

keepExif Semantics #

keepExif now follows a metadata strategy closer to the iOS implementation:

• preserve metadata on a best-effort basis instead of failing the whole compression request
• normalize output orientation to normal when auto-rotation or manual rotation changes the rendered image
• preserve the original orientation only when no transform is applied
• attempt metadata preservation for all four output formats through ExifInterface on a best-effort basis
• avoid writing stale thumbnail- and maker-note-style metadata back onto transformed outputs

As with iOS, metadata preservation depends on what the destination format and runtime can actually store. png, webp, and heic should be treated as best-effort rather than guaranteed metadata-preserving outputs. If Android cannot safely re-attach metadata for a given output, the compression result is still returned.

Unsupported / Version-Dependent Cases #

• heic output uses AndroidX HeifWriter and requires Android API 28+.
• Some input formats are device- and OS-version-dependent even when Android documents platform support at a high level.
• Animated formats are decoded as still images by the current pipeline.
• Formats that do not decode into a Bitmap through the Android system stack are not yet supported by this package.

Android Requirements #

• Flutter 3.10.0+
• Dart 3.0.0+
• Kotlin 2.2.20+
• Java 17 target
• Android min SDK 24
• Android compile SDK 36
• heic output requires Android API 28+ and compatible encoder support

Reference:

• https://developer.android.com/reference/androidx/heifwriter/HeifWriter
• https://developer.android.com/reference/android/graphics/ImageDecoder
• https://developer.android.com/reference/android/graphics/BitmapFactory.Options#inSampleSize
• https://developer.android.com/reference/androidx/exifinterface/media/ExifInterface