Android Camera 2 preview size and devices aspect ratio

Question

I'm implementing Camera 2 API in my project. I'm using TextureView and these line of codes to set the camera fullscreen preview size:

StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
                mPreviewSize = map.getOutputSizes(SurfaceTexture.class)[0];

This seems to be the largest preview size that device support. I'm not sure if this size works with all devices and fit its device's aspect ratio without being stretched. Does anyone know?

Answer 1

There might be edge cases where that approach would fail, but I don't have a perfect answer to your question why.

In contrast, I have a proper approach on how to implement a version that will most certainly work:

Looking at the Google API demos for the Camera 2, I found some sample code that should be helpful to you to make sure it will fit all screen sized correctly:

/**
 * Given {@code choices} of {@code Size}s supported by a camera, choose the smallest one that
 * is at least as large as the respective texture view size, and that is at most as large as the
 * respective max size, and whose aspect ratio matches with the specified value. If such size
 * doesn't exist, choose the largest one that is at most as large as the respective max size,
 * and whose aspect ratio matches with the specified value.
 *
 * @param choices           The list of sizes that the camera supports for the intended output
 *                          class
 * @param textureViewWidth  The width of the texture view relative to sensor coordinate
 * @param textureViewHeight The height of the texture view relative to sensor coordinate
 * @param maxWidth          The maximum width that can be chosen
 * @param maxHeight         The maximum height that can be chosen
 * @param aspectRatio       The aspect ratio
 * @return The optimal {@code Size}, or an arbitrary one if none were big enough
 */
private static Size chooseOptimalSize(Size[] choices, int textureViewWidth,
        int textureViewHeight, int maxWidth, int maxHeight, Size aspectRatio) {

    // Collect the supported resolutions that are at least as big as the preview Surface
    List<Size> bigEnough = new ArrayList<>();
    // Collect the supported resolutions that are smaller than the preview Surface
    List<Size> notBigEnough = new ArrayList<>();
    int w = aspectRatio.getWidth();
    int h = aspectRatio.getHeight();
    for (Size option : choices) {
        if (option.getWidth() <= maxWidth && option.getHeight() <= maxHeight &&
                option.getHeight() == option.getWidth() * h / w) {
            if (option.getWidth() >= textureViewWidth &&
                option.getHeight() >= textureViewHeight) {
                bigEnough.add(option);
            } else {
                notBigEnough.add(option);
            }
        }
    }

    // Pick the smallest of those big enough. If there is no one big enough, pick the
    // largest of those not big enough.
    if (bigEnough.size() > 0) {
        return Collections.min(bigEnough, new CompareSizesByArea());
    } else if (notBigEnough.size() > 0) {
        return Collections.max(notBigEnough, new CompareSizesByArea());
    } else {
        Log.e(TAG, "Couldn't find any suitable preview size");
        return choices[0];
    }
}

Source

Also you should take a look at the whole Camera2BasicFragment.java and AutoFitTextureView.java classes for proper implementation.