Xamarin Android Camera2Api“ GetOutputSizes”始终返回最大640x480

Question

I'm very new to Android development and decided to approach it using Xamarin. I grabbed the Xamarin (C#) Camera2Api sample from Xamarin's website and got it to the point where I can load the camera preview, take a picture and persist that picture to disk. However, when I look at the picture, it's always 640x480, which is fairly square.

I notice in the Camera2Api project that this is set by grabbing the ScalerStreamConfigurationMap from the camera characteristics, and determining the largest supported size. Here's the snippet:

var map = (StreamConfigurationMap)characteristics.Get(CameraCharacteristics.ScalerStreamConfigurationMap);
if (map == null) {
    continue;
}

// For still image captures, we use the largest available size.
Size largest = (Size)Collections.Max(Arrays.AsList(map.GetOutputSizes((int)ImageFormatType.Jpeg)),
                                                     new CompareSizeByArea());

For whatever reason, the map.GetOutputSizes((int)ImageFormatType.Jpeg)) always returns a maximum of 640x480.

Can anyone shed some light as to why my emulator only supports such a square image, despite the actual camera preview taking up the full width and height of the screen?

Answer 1

When using the Camera APIs it is important to remember that the capture image size is independent of the preview size.So even though your preview may be full width/height of screen this has no bearing on your capture image size.

The reason 640x480 is being returned as your image size is because that is the largest size image that the "device" you are emulating supports, or its a limitation with the emulator itself. If you were to run this test on a real device you would most likely see a different size image than what you are seeing on the emulator. Alternatively you could print a list of supported capture sizes with map.GetOutputSizes((int)ImageFormatType.Jpeg) and select a size from that list of a 4:3 aspect ratio at 640x480 is not what you want.