[image_picker_android] ImageResizer never downsamples: calculateSampleSize reads an Options object that was never decoded #193036

Steps to reproduce

1. Use image_picker on Android and pick a large photo (e.g. a 12 MP, 4000x3000 camera image) with a size limit, e.g. ImagePicker().pickImage(source: ImageSource.gallery, maxWidth: 1280, maxHeight: 1280).
2. Look at how ImageResizer.resizeImageIfNeeded decodes the image (package image_picker_android, file android/src/main/java/io/flutter/plugins/imagepicker/ImageResizer.java; checked against the latest release, 0.8.13+23).

Expected results

calculateSampleSize picks a power-of-two inSampleSize from the original image size, so the 4000x3000 photo is decoded at 2000x1500 (about 12 MB as ARGB_8888) before createScaledBitmap scales it to 1280x960. This is what flutter/packages#3423 ("Improved Bitmap resize on Android", for #118383) set out to do.

Actual results

inSampleSize is always 1, so the photo is always decoded at full resolution (4000x3000, about 48 MB) before being scaled.

In resizeImageIfNeeded, a fresh BitmapFactory.Options is created and passed straight to calculateSampleSize:

BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize =
    calculateSampleSize(options, (int) targetSize.getWidth(), (int) targetSize.getHeight());
Bitmap bmp = decodeFile(imagePath, options);

calculateSampleSize reads options.outWidth / options.outHeight, but this options object has never been used for a decode, so those fields still hold their defaults. The condition height > targetHeight || width > targetWidth is therefore never true and the method returns 1. The original dimensions were already read by readFileDimensions(), but into a different Options instance, and only the resulting SizeFCompat is kept.

A side effect is that passing maxWidth / maxHeight makes memory use worse than not passing them: without them the plugin returns the original file untouched, with them it always does a full-resolution decode plus a re-encode. Google Play Console's Android vitals flags this pattern as "Use bitmap downsampling to improve app performance".

A possible fix is to compute the sample size from originalSize (the SizeFCompat returned by readFileDimensions) instead of from the undecoded options.

Code sample

final image = await ImagePicker().pickImage(
  source: ImageSource.gallery,
  maxWidth: 1280,
  maxHeight: 1280,
);

Screenshots or Video

N/A

Logs

N/A. The behavior follows directly from the code above; we confirmed it by reproducing calculateTargetSize + calculateSampleSize for 4000x3000, 4032x3024, 4080x3072 and 8160x6120 sources, all of which end up with inSampleSize = 1.

Flutter Doctor output

Flutter 3.47.4 (stable), macOS, Android emulator API 37.
image_picker_android 0.8.13+19 in the app; code inspected in 0.8.13+23 (latest).