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[android_camera_camerax] Fix incorrect camera mirroring for front cameras on devices using ImageReader Impeller backend #9233

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Merged
auto-submit merged 15 commits into from
Jun 12, 2025
Merged

[android_camera_camerax] Fix incorrect camera mirroring for front cameras on devices using ImageReader Impeller backend #9233

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7b3809a
mirror camera
camsim99 May 8, 2025
1351c20
fix tests + bump version
camsim99 May 9, 2025
ceb9865
added mirroring tests
jesswrd Jun 2, 2025
50897b2
resolved conflicts
jesswrd Jun 2, 2025
fe4ffb3
updated changelog
jesswrd Jun 2, 2025
bdf32a7
formatted files
jesswrd Jun 2, 2025
e2fba01
added helper function. has to check entire matrix
jesswrd Jun 11, 2025
c4b1fd6
Revert "added helper function. has to check entire matrix"
jesswrd Jun 11, 2025
0139263
added helper function. has to check entire matrix (take 2)
jesswrd Jun 11, 2025
a0c9bc9
Merge branch 'main' into camx_mirror_2
jesswrd Jun 11, 2025
ad702cc
formatted tests
jesswrd Jun 11, 2025
de19674
updated changelog
jesswrd Jun 11, 2025
0061ab0
Update packages/camera/camera_android_camerax/CHANGELOG.md
reidbaker Jun 12, 2025
541f537
add comment
camsim99 Jun 12, 2025
5fe7d84
Merge remote-tracking branch 'refs/remotes/origin/camx_mirror_2' into…
camsim99 Jun 12, 2025
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4 changes: 4 additions & 0 deletions packages/camera/camera_android_camerax/CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,3 +1,7 @@
## 0.6.18+3

* Fixes incorrect camera preview mirroring for front cameras of devices using the Impeller backend.

## 0.6.18+2

* Fixes premature garbage collection of native objects when app is under memory pressure.
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14 changes: 13 additions & 1 deletion packages/camera/camera_android_camerax/lib/src/image_reader_rotated_preview.dart
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Expand Up @@ -157,9 +157,21 @@ final class _ImageReaderRotatedPreviewState
sign: widget.facingSign,
);

// If the camera is front facing, mirror the camera preview
// according to the current device orientation.
Widget cameraPreview = widget.child;
if (widget.facingSign == 1) {
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@reidbaker reidbaker Jun 12, 2025

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Why is == 1 the correct comparison here?

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@camsim99 camsim99 Jun 12, 2025

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Ah because facingSign maps to the sign in https://developer.android.com/media/camera/camera2/camera-preview#orientation_calculation, which is 1 for front cameras, -1 for back facing cameras. I'll add a comment to the code!

if (deviceOrientation == DeviceOrientation.portraitDown ||
deviceOrientation == DeviceOrientation.portraitUp) {
cameraPreview = Transform.scale(scaleY: -1, child: cameraPreview);
} else {
cameraPreview = Transform.scale(scaleX: -1, child: cameraPreview);
}
}

return RotatedBox(
quarterTurns: rotationDegrees ~/ 90,
child: widget.child,
child: cameraPreview,
);
} else {
return const SizedBox.shrink();
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2 changes: 1 addition & 1 deletion packages/camera/camera_android_camerax/pubspec.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ name: camera_android_camerax
description: Android implementation of the camera plugin using the CameraX library.
repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_android_camerax
issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
version: 0.6.18+2
version: 0.6.18+3

environment:
sdk: ^3.7.0
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250 changes: 227 additions & 23 deletions packages/camera/camera_android_camerax/test/preview_rotation_test.dart
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Expand Up @@ -7,7 +7,8 @@ import 'package:camera_android_camerax/src/camerax_library.dart';
import 'package:camera_android_camerax/src/camerax_proxy.dart';
import 'package:camera_platform_interface/camera_platform_interface.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart' show RotatedBox, Texture;
import 'package:flutter/widgets.dart'
show MatrixUtils, RotatedBox, Texture, Transform;
import 'package:flutter_test/flutter_test.dart';
import 'package:mockito/mockito.dart';

Expand Down Expand Up @@ -380,6 +381,70 @@ void main() {
) =>
'Expected the preview to be rotated by $expectedQuarterTurns quarter turns (which is ${expectedQuarterTurns * 90} degrees clockwise) but instead was rotated $actualQuarterTurns quarter turns.';

/// Checks that the transform matrix (Matrix4) mirrors across the x-axis by
/// confirming the following to be the transformation matrix:
/// [[-1.0, 0.0, 0.0, 0.0],
/// [ 0.0, 1.0, 0.0, 0.0],
/// [ 0.0, 0.0, 1.0, 0.0],
/// [ 0.0, 0.0, 0.0, 1.0]]
void checkXAxisIsMirrored(Matrix4 transformationMatrix) {
final Matrix4 mirrorAcrossXMatrix = Matrix4(
-1.0,
0.0,
0.0,
0.0,
0.0,
1.0,
0.0,
0.0,
0.0,
0.0,
1.0,
0.0,
0.0,
0.0,
0.0,
1.0,
);

expect(
MatrixUtils.matrixEquals(mirrorAcrossXMatrix, transformationMatrix),
isTrue,
);
}

/// Checks that the transform matrix (Matrix4) mirrors across the y-axis by
/// confirming the following to be the transformation matrix:
/// [[1.0, 0.0, 0.0, 0.0],
/// [ 0.0, -1.0, 0.0, 0.0],
/// [ 0.0, 0.0, 1.0, 0.0],
/// [ 0.0, 0.0, 0.0, 1.0]]
void checkYAxisIsMirrored(Matrix4 transformationMatrix) {
final Matrix4 mirrorAcrossYMatrix = Matrix4(
1.0,
0.0,
0.0,
0.0,
0.0,
-1.0,
0.0,
0.0,
0.0,
0.0,
1.0,
0.0,
0.0,
0.0,
0.0,
1.0,
);

expect(
MatrixUtils.matrixEquals(mirrorAcrossYMatrix, transformationMatrix),
isTrue,
);
}

group('when handlesCropAndRotation is true', () {
// Test that preview rotation responds to initial default display rotation:
group('initial device orientation is landscapeRight,', () {
Expand Down Expand Up @@ -1167,8 +1232,19 @@ void main() {
find.byType(RotatedBox),
);

expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);
// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in portrait mode, we expect the camera
// preview to be mirrored across the y-axis.
checkYAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);
expect(
rotatedBox.quarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1216,8 +1292,20 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);
expect(
rotatedBox.quarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1265,8 +1353,20 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in portrait mode, we expect the camera
// preview to be mirrored across the y-axis.
checkYAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);
expect(
rotatedBox.quarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1314,8 +1414,20 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);
expect(
rotatedBox.quarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1406,8 +1518,19 @@ void main() {
find.byType(RotatedBox),
);

expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);
// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);
expect(
rotatedBox.quarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1455,9 +1578,22 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);

final int clockwiseQuarterTurns = rotatedBox.quarterTurns + 4;
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);
expect(
clockwiseQuarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1503,9 +1639,22 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);

final int clockwiseQuarterTurns = rotatedBox.quarterTurns + 4;
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);
expect(
clockwiseQuarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1553,9 +1702,22 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);

final int clockwiseQuarterTurns = rotatedBox.quarterTurns + 4;
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);
expect(
clockwiseQuarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1662,12 +1824,24 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix = transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);

final int clockwiseQuarterTurns =
rotatedBox.quarterTurns < 0
? rotatedBox.quarterTurns + 4
: rotatedBox.quarterTurns;
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);
expect(
clockwiseQuarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -1760,12 +1934,30 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix = transformedPreview.transform;

// When the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis. When the front camera
// is in portrait mode, we expect the camera preview to be mirrored
// across the y-axis.
if (currentDeviceOrientation == DeviceOrientation.landscapeLeft ||
currentDeviceOrientation == DeviceOrientation.landscapeRight) {
checkXAxisIsMirrored(transformedPreviewMatrix);
} else {
checkYAxisIsMirrored(transformedPreviewMatrix);
}
expect((transformedPreview.child! as Texture).textureId, cameraId);
final int clockwiseQuarterTurns =
rotatedBox.quarterTurns < 0
? rotatedBox.quarterTurns + 4
: rotatedBox.quarterTurns;
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);
expect(
clockwiseQuarterTurns,
expectedQuarterTurns,
Expand Down Expand Up @@ -2013,8 +2205,20 @@ void main() {
final RotatedBox rotatedBox = tester.widget<RotatedBox>(
find.byType(RotatedBox),
);
expect(rotatedBox.child, isA<Texture>());
expect((rotatedBox.child! as Texture).textureId, cameraId);

// We expect a Transform widget to wrap the RotatedBox with the camera
// preview to mirror the preview, since the front camera is being
// used.
expect(rotatedBox.child, isA<Transform>());

final Transform transformedPreview = rotatedBox.child! as Transform;
final Matrix4 transformedPreviewMatrix =
transformedPreview.transform;

// Since the front camera is in landscape mode, we expect the camera
// preview to be mirrored across the x-axis.
checkXAxisIsMirrored(transformedPreviewMatrix);
expect((transformedPreview.child! as Texture).textureId, cameraId);
expect(
rotatedBox.quarterTurns,
expectedQuarterTurns,
Expand Down