Camera preview quality in Android is poor

Question

I am making a Camera app in Android and have used the following function to get the preview size:

private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
    final double ASPECT_TOLERANCE = 0.1;
    double targetRatio = (double) w / h;
    if (sizes == null) return null;

    Size optimalSize = null;
    double minDiff = Double.MAX_VALUE;

    int targetHeight = h;

    // Try to find an size match aspect ratio and size
    for (Size size : sizes) {
        double ratio = (double) size.width / size.height;
        if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
        if (Math.abs(size.height - targetHeight) < minDiff) {
            optimalSize = size;
            minDiff = Math.abs(size.height - targetHeight);
        }
    }

    // Cannot find the one match the aspect ratio, ignore the requirement
    if (optimalSize == null) {
        minDiff = Double.MAX_VALUE;
        for (Size size : sizes) {
            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }
    }
    return optimalSize;
}

And I set the size like this:

Size s = getOptimalPreviewSize(parameters.getSupportedPreviewSizes(), w, h);
parameters.setPreviewSize(s.width, s.height);

But the problem is that when I run my app, the camera preview quality is really poor. How do i get the same preview quality as I get when I run my default camera app on my phone, in other words, I want a high resolution Camera preview in my app.

I am even not sure whether the preview size is the cause of this problem.

NOTE: The function to get the preview size is taken from sample programs from Android Docs.

Answer 1

That algorithm is not the greatest.

The default algorithm in my CWAC-Camera library is now:

  public static Camera.Size getBestAspectPreviewSize(int displayOrientation,
                                                     int width,
                                                     int height,
                                                     Camera.Parameters parameters,
                                                     double closeEnough) {
    double targetRatio=(double)width / height;
    Camera.Size optimalSize=null;
    double minDiff=Double.MAX_VALUE;

    if (displayOrientation == 90 || displayOrientation == 270) {
      targetRatio=(double)height / width;
    }

    List<Size> sizes=parameters.getSupportedPreviewSizes();

    Collections.sort(sizes,
                     Collections.reverseOrder(new SizeComparator()));

    for (Size size : sizes) {
      double ratio=(double)size.width / size.height;

      if (Math.abs(ratio - targetRatio) < minDiff) {
        optimalSize=size;
        minDiff=Math.abs(ratio - targetRatio);
      }

      if (minDiff < closeEnough) {
        break;
      }
    }

    return(optimalSize);
  }

This:

• Takes into account portrait versus landscape

• Starts with the highest resolution previews and works its way down

• Can be tailored via closeEnough to opt for higher resolution as opposed to best matching the aspect ratio of the preview area