Different capture output size on certain camera resolutions in Android

问题

I am developing a custom camera application using the Android Camera2 API where you can switch between the different camera and video resolutions available in the phone. It also offers the possibility to take squared 1:1 pictures. To take the square pictures, I take a normal 4:3 picture and then crop it to maintain the 1:1. (So 4032x3024 would be 3024x3024).

I noticed a problem when taking a 1:1 picture on certain resolutions, the output is slightly cropped (zoomed). This is the result of the same picture taken with two different resolutions:

The first picture was taken at 1944x1944

The second picture was taken at 3024x3024

My Nexus 5X supports 12MP, 8MP, 5MP and 2MP on 4:3. This problem happens when I use any resolution bigger than 5MP.

The method I use to crop the images is the following:

ByteBuffer buffer = mImage.getPlanes()[0].getBuffer();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
cropSquareImageByteArray(bytes);

The cropSquareImageByteArray method:

public static byte[] cropSquareImageByteArray(byte[] bytes) {
    ByteArrayOutputStream bos = new ByteArrayOutputStream();

    Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
    int w = bitmap.getWidth();
    int h = bitmap.getHeight();
    Bitmap dst = Bitmap.createBitmap(bitmap, 0, h - w, w, w);
    dst.compress(Bitmap.CompressFormat.JPEG, 98, bos);
    return bos.toByteArray();
}

I am guessing the reason for the cropping is a 4:3 image in a 16:9 container. Because I noticed that when calling

    Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);

The dimensions for the generated bitmap output are 1280x960 (4:3) in 2MP, 1600x1200 (4:3) in 5MP but for bigger resolutions are 1920x1080 (16:9), so the 4:3 image is adjusted to a 16:9 bitmap, maybe causing the crop.

I am trying to figure out how to solve this. I also checked this post Android 5.0 Wrong crop regions on preview surface and captured still image but didn't find a solution there.

*edit: My ImageReader is configured like this:

public void configureImageReader(Size pictureSizeValue, ImageReader.OnImageAvailableListener listener) {

    if (mImageReader == null) {
        mImageReader = ImageReader.newInstance(pictureSizeValue.getWidth(), pictureSizeValue.getHeight(),
                ImageFormat.JPEG, 2);
    } 
    mImageReader.setOnImageAvailableListener(listener, mBackgroundHandler);

}

The value for pictureSizeValue is the output I want. So for a squared image, it is something like 3024x3024.

回答1:

Up to a certain point,the camera device will round your requested size to a supported one, to make camera preview more flexible to set up, but only up to 1080p (to generally guarantee a reasonable frame rate for preview).

Past that, you need to actually select a supported resolution from the list provided by the device, or you'll just get rounded down to 1080p.

The camera's supported output sizes and formats can be queried with StreamConfigurationMap.getOutputSizes(). You'll need to scan the list for a size that matches your requirements and has an aspect ratio that matches the aspect ratio of the image sensor (available through activeArraySize)

I'd double-check all the sizes below 1080p as well, to make sure you're actually getting what you want. The rounding is always to a lower resolution, to minimize performance and memory requirements.

来源：https://stackoverflow.com/questions/36156837/different-capture-output-size-on-certain-camera-resolutions-in-android