我正在构建一个Android相机应用程序（不使用camera2 api）来拍摄室外条件下某些物体的近距离照片。图片需要以连拍模式拍摄，即一旦激活，相机将连续拍摄5张照片，并且所有照片都需要很好地聚焦。用户可能在拍摄照片时移动相机，并且用户将无法手动选择焦点。物体颜色较深，有时相机视野中的明亮物体会过度曝光相机
我知道如何将焦点区域设置为摄像机参数，但必须自动更改焦点区域的位置，以便始终将焦点集中在摄像机视图中的暗区域。在摄像机视图中，暗物体的位置不固定，因此应用程序必须在设置对焦区域之前在每个帧中查找暗像素。
我正在考虑检查onPreviewFrame()回调中的暗区域，但我不确定这是否是正确的方法。有谁做过这个，谁可以指出我正确的方向？例如，是否有一个项目将使Android摄像头始终使用面部检测器专注于脸部？我试图在互联网上查找，但找不到任何相关项目。
答案 0 :(得分：0)
你必须实现触摸焦点。像这样的东西：
@Override
public boolean onTouchEvent(MotionEvent event) {
if(event.getAction() == MotionEvent.ACTION_DOWN){
float x = event.getX();
float y = event.getY();
float touchMajor = event.getTouchMajor();
float touchMinor = event.getTouchMinor();
Rect touchRect = new Rect(
(int)(x - touchMajor/2),
(int)(y - touchMinor/2),
(int)(x + touchMajor/2),
(int)(y + touchMinor/2));
if (mTouchEventListener != null)
mTouchEventListener.touchFocus(touchRect, false);
}
其中touchFocus看起来像这样：
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public void touchFocus(Rect tfocusRect, boolean useInMid) {
if (mCamera == null) return;
try{
mCamera.cancelAutoFocus();
//Convert from View's width and height to +/- 1000
Rect targetFocusRect = (useInMid || sfv == null) ? new Rect() :
new Rect(tfocusRect.left * 2000/sfv.getWidth() - 1000,
tfocusRect.top * 2000/sfv.getHeight() - 1000,
tfocusRect.right * 2000/sfv.getWidth() - 1000,
tfocusRect.bottom * 2000/sfv.getHeight() - 1000);
final List<Camera.Area> focusList = new ArrayList<Camera.Area>();
Camera.Area focusArea = new Camera.Area(targetFocusRect, 1000);
focusList.add(focusArea);
Parameters para = mCamera.getParameters();
O.Log.d(TAG,para.getMaxNumFocusAreas() + ";" + para.getMaxNumMeteringAreas() + " >> " + tfocusRect.toString());
para.setFocusAreas(focusList);
para.setMeteringAreas(focusList);
try{
mCamera.setParameters(para);
}catch(RuntimeException e){
O.Log.e(TAG, "setParameters failed", e);
}
mCamera.autoFocus(myAutoFocusCallback);
// _.setCameraTorch(1);
}catch (Exception e){
O.Log.e(TAG, "Touch Focus Camera Error", e);
}
}
private static AutoFocusCallback myAutoFocusCallback = new AutoFocusCallback() {
@Override
public void onAutoFocus(boolean success, Camera camera) {
// TODO Auto-generated method stub
}
};
for new API阅读了这篇文章http://www.morethantechnical.com/2017/02/28/android-camera2-touch-to-focus/
//Override in your touch-enabled view (this can be differen than the view you use for displaying the cam preview)
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
final int actionMasked = motionEvent.getActionMasked();
if (actionMasked != MotionEvent.ACTION_DOWN) {
return false;
}
if (mManualFocusEngaged) {
Log.d(TAG, "Manual focus already engaged");
return true;
}
final Rect sensorArraySize = mCameraInfo.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);
//TODO: here I just flip x,y, but this needs to correspond with the sensor orientation (via SENSOR_ORIENTATION)
final int y = (int)((motionEvent.getX() / (float)view.getWidth()) * (float)sensorArraySize.height());
final int x = (int)((motionEvent.getY() / (float)view.getHeight()) * (float)sensorArraySize.width());
final int halfTouchWidth = 150; //(int)motionEvent.getTouchMajor(); //TODO: this doesn't represent actual touch size in pixel. Values range in [3, 10]...
final int halfTouchHeight = 150; //(int)motionEvent.getTouchMinor();
MeteringRectangle focusAreaTouch = new MeteringRectangle(Math.max(x - halfTouchWidth, 0),
Math.max(y - halfTouchHeight, 0),
halfTouchWidth * 2,
halfTouchHeight * 2,
MeteringRectangle.METERING_WEIGHT_MAX - 1);
CameraCaptureSession.CaptureCallback captureCallbackHandler = new CameraCaptureSession.CaptureCallback() {
@Override
public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
super.onCaptureCompleted(session, request, result);
mManualFocusEngaged = false;
if (request.getTag() == "FOCUS_TAG") {
//the focus trigger is complete -
//resume repeating (preview surface will get frames), clear AF trigger
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, null);
mCameraOps.setRepeatingRequest(mPreviewRequestBuilder.build(), null, null);
}
}
@Override
public void onCaptureFailed(CameraCaptureSession session, CaptureRequest request, CaptureFailure failure) {
super.onCaptureFailed(session, request, failure);
Log.e(TAG, "Manual AF failure: " + failure);
mManualFocusEngaged = false;
}
};
//first stop the existing repeating request
mCameraOps.stopRepeating();
//cancel any existing AF trigger (repeated touches, etc.)
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_OFF);
mCameraOps.capture(mPreviewRequestBuilder.build(), captureCallbackHandler, mBackgroundHandler);
//Now add a new AF trigger with focus region
if (isMeteringAreaAFSupported()) {
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_REGIONS, new MeteringRectangle[]{focusAreaTouch});
}
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_AUTO);
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);
mPreviewRequestBuilder.setTag("FOCUS_TAG"); //we'll capture this later for resuming the preview
//then we ask for a single request (not repeating!)
mCameraOps.capture(mPreviewRequestBuilder.build(), captureCallbackHandler, mBackgroundHandler);
mManualFocusEngaged = true;
return true;
}
private boolean isMeteringAreaAFSupported() {
return mCameraInfo.get(CameraCharacteristics.CONTROL_MAX_REGIONS_AF) >= 1;
}