/**
* Selects the most suitable preview and picture size, given the desired width and height.
*
* <p>Even though we may only need the preview size, it's necessary to find both the preview size
* and the picture size of the camera together, because these need to have the same aspect ratio.
* On some hardware, if you would only set the preview size, you will get a distorted image.
*
* @param camera the camera to select a preview size from
* @param desiredWidth the desired width of the camera preview frames
* @param desiredHeight the desired height of the camera preview frames
* @return the selected preview and picture size pair
*/
private static SizePair selectSizePair(Camera camera, int desiredWidth, int desiredHeight) {
List<SizePair> validPreviewSizes = generateValidPreviewSizeList(camera);
// The method for selecting the best size is to minimize the sum of the differences between
// the desired values and the actual values for width and height. This is certainly not the
// only way to select the best size, but it provides a decent tradeoff between using the
// closest aspect ratio vs. using the closest pixel area.
SizePair selectedPair = null;
int minDiff = Integer.MAX_VALUE;
for (SizePair sizePair : validPreviewSizes) {
Size size = sizePair.previewSize();
int diff =
Math.abs(size.getWidth() - desiredWidth) + Math.abs(size.getHeight() - desiredHeight);
if (diff < minDiff) {
selectedPair = sizePair;
minDiff = diff;
}
}
return selectedPair;
}
/**
* Opens the camera and applies the user settings.
*
* @throws RuntimeException if the method fails
*/
@SuppressLint("InlinedApi")
private Camera createCamera() {
int requestedCameraId = getIdForRequestedCamera(mFacing);
if (requestedCameraId == -1) {
throw new RuntimeException(mContext.getString(R.string.no_requested_camera));
}
Camera camera = Camera.open(requestedCameraId);
SizePair sizePair =
selectSizePair(camera, mRequestedPreviewWidth, mRequestedPreviewHeight, mContext);
if (sizePair == null) {
throw new RuntimeException(mContext.getString(R.string.no_suitable_preview_size));
}
Size pictureSize = sizePair.pictureSize();
mPreviewSize = sizePair.previewSize();
int[] previewFpsRange = selectPreviewFpsRange(camera, mRequestedFps);
if (previewFpsRange == null) {
throw new RuntimeException(mContext.getString(R.string.no_suitable_frames_per_second));
}
Camera.Parameters parameters = camera.getParameters();
parameters.setPictureSize(pictureSize.getWidth(), pictureSize.getHeight());
parameters.setPreviewSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
parameters.setPreviewFpsRange(
previewFpsRange[Camera.Parameters.PREVIEW_FPS_MIN_INDEX],
previewFpsRange[Camera.Parameters.PREVIEW_FPS_MAX_INDEX]);
parameters.setPreviewFormat(ImageFormat.NV21);
setRotation(camera, parameters, requestedCameraId);
if (mFocusMode != null) {
if (parameters.getSupportedFocusModes().contains(mFocusMode)) {
parameters.setFocusMode(mFocusMode);
} else {
Log.i(
TAG,
mContext.getString(R.string.camera_focus_mode)
+ mFocusMode
+ mContext.getString(R.string.not_supported));
}
}
// setting mFocusMode to the one set in the params
mFocusMode = parameters.getFocusMode();
if (mFlashMode != null) {
if (parameters.getSupportedFlashModes().contains(mFlashMode)) {
parameters.setFlashMode(mFlashMode);
} else {
Log.i(
TAG,
mContext.getString(R.string.flash_mode)
+ mFlashMode
+ mContext.getString(R.string.not_supported));
}
}
// setting mFlashMode to the one set in the params
mFlashMode = parameters.getFlashMode();
camera.setParameters(parameters);
// Four frame buffers are needed for working with the camera:
//
// one for the frame that is currently being executed upon in doing detection
// one for the next pending frame to process immediately upon completing detection
// two for the frames that the camera uses to populate future preview images
camera.setPreviewCallbackWithBuffer(new CameraPreviewCallback());
camera.addCallbackBuffer(createPreviewBuffer(mPreviewSize));
camera.addCallbackBuffer(createPreviewBuffer(mPreviewSize));
camera.addCallbackBuffer(createPreviewBuffer(mPreviewSize));
camera.addCallbackBuffer(createPreviewBuffer(mPreviewSize));
return camera;
}