Android Camera2 preview is stretched

Question

I'm trying to learn Camera2 API and I have built a simple camera app just for taking pictures but the problem that I'm facing is that the preview is stretched for some resolutions. I went through a number of different posts and all them suggested that my aspect ratio might be wrong but I have used google's recommended AutoFitTextureView with the correct aspect ratio still my preview is stretched. I downloaded some open source camera apps from playstore and a bunch of them also had the same issue with my front camera(EXCEPT OPEN CAMERA) but the funny part is I used my same app in another device and the preview was absolutely perfect. So finally I decided to test my app with different resolutions and observe the results but I couldn't find any pattern can anyone please help me to make some sense out of it???

my device display size is 720x1280
Front camera results: 
SurfaceTexture        AutoFitTextureView         Result
buffer size           size       
2576x1932             720x960                    Normal
2560x1440             720x1280                   Normal
2048x1536             720x960                    Normal
2048x1152             720x1280                   Normal
1920x1920             720x720                    Normal
1920x1080             720x1280                   Normal
1440x1080             720x960                    Horizontally Stretched
1280x720              720x1280                   Horizontally Stretched
1072x1072             720x720                    Normal
960x720               720x960                    Normal
720x480               720x1080                   Horizontally Stretched
640x480               720x960                    Horizontally Stretched
352x288               720x880                    Normal
320x240               720x960                    Normal
256x144               720x1280                   Horizontally Stretched
176x144               720x880                    Normal

Answer 1

They key is to set the correct transform on the TextureView on which you're rendering the preview. The TextureView's width and height are set to match its parent layout.

TextureView textureView;

void setTextureTransform(CameraCharacteristics characteristics) {
    Size previewSize = getPreviewSize(characteristics);
    int width = previewSize.getWidth();
    int height = previewSize.getHeight();
    int sensorOrientation = getCameraSensorOrientation(characteristics);
    // Indicate the size of the buffer the texture should expect
    textureView.getSurfaceTexture().setDefaultBufferSize(width, height);
    // Save the texture dimensions in a rectangle
    RectF viewRect = new RectF(0,0, textureView.getWidth(), textureView.getHeight());
    // Determine the rotation of the display
    float rotationDegrees = 0;
    try {
        rotationDegrees = (float)getDisplayRotation();
    } catch (Exception ignored) {
    }
    float w, h;
    if ((sensorOrientation - rotationDegrees) % 180 == 0) {
        w = width;
        h = height;
    } else {
        // Swap the width and height if the sensor orientation and display rotation don't match
        w = height;
        h = width;
    }
    float viewAspectRatio = viewRect.width()/viewRect.height();
    float imageAspectRatio = w/h;
    final PointF scale;
    // This will make the camera frame fill the texture view, if you'd like to fit it into the view swap the "<" sign for ">"
    if (viewAspectRatio < imageAspectRatio) {
        // If the view is "thinner" than the image constrain the height and calculate the scale for the texture width
        scale = new PointF((viewRect.height() / viewRect.width()) * ((float) height / (float) width), 1f);
    } else {
        scale = new PointF(1f, (viewRect.width() / viewRect.height()) * ((float) width / (float) height));
    }
    if (rotationDegrees % 180 != 0) {
        // If we need to rotate the texture 90º we need to adjust the scale
        float multiplier = viewAspectRatio < imageAspectRatio ? w/h : h/w;
        scale.x *= multiplier;
        scale.y *= multiplier;
    }

    Matrix matrix = new Matrix();
    // Set the scale
    matrix.setScale(scale.x, scale.y, viewRect.centerX(), viewRect.centerY());
    if (rotationDegrees != 0) {
        // Set rotation of the device isn't upright
        matrix.postRotate(0 - rotationDegrees, viewRect.centerX(), viewRect.centerY());
    }
    // Transform the texture
    textureView.setTransform(matrix);
}

int getDisplayRotation() {
    switch (textureView.getDisplay().getRotation()) {
        case Surface.ROTATION_0:
        default:
            return 0;
        case Surface.ROTATION_90:
            return  90;
        case Surface.ROTATION_180:
            return  180;
        case Surface.ROTATION_270:
            return 270;
    }
}

Size getPreviewSize(CameraCharacteristics characteristics) {
    StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
    Size[] previewSizes = map.getOutputSizes(SurfaceTexture.class);
    // TODO: decide on which size fits your view size the best
    return previewSizes[0];
}

int getCameraSensorOrientation(CameraCharacteristics characteristics) {
    Integer cameraOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
    return (360 - (cameraOrientation != null ? cameraOrientation : 0)) % 360;
}