Crop camera preview for TextureView

Question

I have a TextureView with a fixed width and height and I want to show a camera preview inside of it. I need to crop the camera preview so that it doesn't look stretched inside my TextureView. How to do the cropping? If I need to use OpenGL, how to tie the Surface Texture to OpenGL and how to do the cropping with OpenGL?

public class MyActivity extends Activity implements TextureView.SurfaceTextureListener  {     private Camera mCamera;    private TextureView mTextureView;    @Override   protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_options);      mTextureView = (TextureView) findViewById(R.id.camera_preview);     mTextureView.setSurfaceTextureListener(this); }  @Override public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {     mCamera = Camera.open();      try      {         mCamera.setPreviewTexture(surface);         mCamera.startPreview();     } catch (IOException ioe) {         // Something bad happened     } }  @Override public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {     mCamera.stopPreview();     mCamera.release();     return true; }  @Override public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) { }  @Override public void onSurfaceTextureUpdated(SurfaceTexture surface)  {     // Invoked every time there's a new Camera preview frame  } } 

Also, after doing the preview correctly, I need to be able to read in real-time the pixels found in the center of the cropped image.

Answer 1

Provided earlier solution by @Romanski works fine but it scales with cropping. If you need to scale to fit, then use the following solution. Call updateTextureMatrix every time when surface view is changed: i.e. in onSurfaceTextureAvailable and in onSurfaceTextureSizeChanged methods. Also note that this solution relies that activity ignores configuration changes (i.e. android:configChanges="orientation|screenSize|keyboardHidden" or something like that):

private void updateTextureMatrix(int width, int height) {     boolean isPortrait = false;      Display display = getWindowManager().getDefaultDisplay();     if (display.getRotation() == Surface.ROTATION_0 || display.getRotation() == Surface.ROTATION_180) isPortrait = true;     else if (display.getRotation() == Surface.ROTATION_90 || display.getRotation() == Surface.ROTATION_270) isPortrait = false;      int previewWidth = orgPreviewWidth;     int previewHeight = orgPreviewHeight;      if (isPortrait)     {         previewWidth = orgPreviewHeight;         previewHeight = orgPreviewWidth;     }      float ratioSurface = (float) width / height;     float ratioPreview = (float) previewWidth / previewHeight;      float scaleX;     float scaleY;      if (ratioSurface > ratioPreview)     {         scaleX = (float) height / previewHeight;         scaleY = 1;     }     else     {         scaleX = 1;         scaleY = (float) width / previewWidth;     }      Matrix matrix = new Matrix();      matrix.setScale(scaleX, scaleY);     textureView.setTransform(matrix);      float scaledWidth = width * scaleX;     float scaledHeight = height * scaleY;      float dx = (width - scaledWidth) / 2;     float dy = (height - scaledHeight) / 2;     textureView.setTranslationX(dx);     textureView.setTranslationY(dy); } 

Also you need the following fields:

private int orgPreviewWidth; private int orgPreviewHeight; 

initialize it in onSurfaceTextureAvailable mathod before calling updateTextureMatrix:

Camera.Parameters parameters = camera.getParameters(); parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);  Pair<Integer, Integer> size = getMaxSize(parameters.getSupportedPreviewSizes()); parameters.setPreviewSize(size.first, size.second);  orgPreviewWidth = size.first; orgPreviewHeight = size.second;  camera.setParameters(parameters); 

getMaxSize method:

private static Pair<Integer, Integer> getMaxSize(List<Camera.Size> list) {     int width = 0;     int height = 0;      for (Camera.Size size : list) {         if (size.width * size.height > width * height)         {             width = size.width;             height = size.height;         }     }      return new Pair<Integer, Integer>(width, height); } 

And last thing - you need to correct camera rotation. So call setCameraDisplayOrientation method in Activity onConfigurationChanged method (and also make initial call in onSurfaceTextureAvailable method):

public static void setCameraDisplayOrientation(Activity activity, int cameraId, Camera camera) {     Camera.CameraInfo info = new Camera.CameraInfo();     Camera.getCameraInfo(cameraId, info);     int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();     int degrees = 0;     switch (rotation)     {         case Surface.ROTATION_0:             degrees = 0;             break;         case Surface.ROTATION_90:             degrees = 90;             break;         case Surface.ROTATION_180:             degrees = 180;             break;         case Surface.ROTATION_270:             degrees = 270;             break;     }      int result;     if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT)     {         result = (info.orientation + degrees) % 360;         result = (360 - result) % 360;  // compensate the mirror     }     else     {  // back-facing         result = (info.orientation - degrees + 360) % 360;     }     camera.setDisplayOrientation(result);      Camera.Parameters params = camera.getParameters();     params.setRotation(result);     camera.setParameters(params); } 

Answer 2

Just calculate the aspect ratio, generate a scaling matrix and apply it to the TextureView. Based on the aspect ratio of the surface and the aspect ratio of the preview image, the preview image is cropped on the top and the bottom or left and right. Another solution I found out is that if you open the camera before the SurfaceTexture is available, the preview is already scaled automatically. Just try to move mCamera = Camera.open(); to your onCreate function after you set the SurfaceTextureListener. This worked for me on the N4. With this solution you'll probably get problems when you rotate from portrait to landscape. If you need portrait and landscape support, then take the solution with the scale matrix!

private void initPreview(SurfaceTexture surface, int width, int height) {     try {         camera.setPreviewTexture(surface);     } catch (Throwable t) {         Log.e("CameraManager", "Exception in setPreviewTexture()", t);     }      Camera.Parameters parameters = camera.getParameters();     previewSize = parameters.getSupportedPreviewSizes().get(0);      float ratioSurface = width > height ? (float) width / height : (float) height / width;     float ratioPreview = (float) previewSize.width / previewSize.height;      int scaledHeight = 0;     int scaledWidth = 0;     float scaleX = 1f;     float scaleY = 1f;      boolean isPortrait = false;      if (previewSize != null) {         parameters.setPreviewSize(previewSize.width, previewSize.height);         if (display.getRotation() == Surface.ROTATION_0 || display.getRotation() == Surface.ROTATION_180) {             camera.setDisplayOrientation(display.getRotation() == Surface.ROTATION_0 ? 90 : 270);             isPortrait = true;         } else if (display.getRotation() == Surface.ROTATION_90 || display.getRotation() == Surface.ROTATION_270) {             camera.setDisplayOrientation(display.getRotation() == Surface.ROTATION_90 ? 0 : 180);             isPortrait = false;         }         if (isPortrait && ratioPreview > ratioSurface) {             scaledWidth = width;             scaledHeight = (int) (((float) previewSize.width / previewSize.height) * width);             scaleX = 1f;             scaleY = (float) scaledHeight / height;         } else if (isPortrait && ratioPreview < ratioSurface) {             scaledWidth = (int) (height / ((float) previewSize.width / previewSize.height));             scaledHeight = height;             scaleX = (float) scaledWidth / width;             scaleY = 1f;         } else if (!isPortrait && ratioPreview < ratioSurface) {             scaledWidth = width;             scaledHeight = (int) (width / ((float) previewSize.width / previewSize.height));             scaleX = 1f;             scaleY = (float) scaledHeight / height;         } else if (!isPortrait && ratioPreview > ratioSurface) {             scaledWidth = (int) (((float) previewSize.width / previewSize.height) * width);             scaledHeight = height;             scaleX = (float) scaledWidth / width;             scaleY = 1f;         }                    camera.setParameters(parameters);     }      // calculate transformation matrix     Matrix matrix = new Matrix();      matrix.setScale(scaleX, scaleY);     textureView.setTransform(matrix); }