第41讲 Touch AE实战 - Android Camera2 API

本讲是Android Camera专题系列的第41讲，我们介绍Android Camera2 API专题的Touch AE实战。

更多资源：

判断是否支持设置AE Regions

CameraCharacteristics.CONTROL_MAX_REGIONS_AE

private void printMaxAERegions(Context context, int cameraId) {
    try {
        String cameraIdS = mCameraManager.getCameraIdList()[cameraId];
        CameraCharacteristics characteristics = mCameraManager.getCameraCharacteristics(cameraIdS);
        Integer regionCount = characteristics.get(CameraCharacteristics.CONTROL_MAX_REGIONS_AE);
        Log.i(TAG, "[Touch AEAF]cameraId:" + cameraIdS + ", printMaxAERegions:" + regionCount);
    } catch (Exception e) {

    }
}

点击屏幕设置Touch AE(坐标系转换)

Camera坐标系转换到View坐标系

private void calculateCameraToPreviewMatrix() {
    if( MyDebug.LOG )
        Log.d(TAG, "calculateCameraToPreviewMatrix");
    if( mCameraController == null )
        return;
    camera_to_preview_matrix.reset();
    if( !using_android_l ) {
        // see http://developer.android.com/reference/android/hardware/Camera.Face.html#rect
        // Need mirror for front camera
        boolean mirror = (mCameraController.getFacing() == CameraController.Facing.FACING_FRONT);
        camera_to_preview_matrix.setScale(mirror ? -1 : 1, 1);
        int display_orientation = mCameraController.getDisplayOrientation();
        if( MyDebug.LOG ) {
            Log.d(TAG, "orientation of display relative to camera orientaton: " + display_orientation);
        }
        camera_to_preview_matrix.postRotate(display_orientation);
    }
    else {
        // Unfortunately the transformation for Android L API isn't documented, but this seems to work for Nexus 6.
        // This is the equivalent code for android.hardware.Camera.setDisplayOrientation, but we don't actually use setDisplayOrientation()
        // for CameraController2, except testing on Nexus 6 shows that we shouldn't change "result" for front facing camera.
        boolean mirror = (mCameraController.getFacing() == CameraController.Facing.FACING_FRONT);
        camera_to_preview_matrix.setScale(1, mirror ? -1 : 1);
        int degrees = getDisplayRotationDegrees();
        Log.d(TAG, "[Touch AEAF] view degrees:" + degrees);
        int result = (mCameraController.getCameraOrientation() - degrees + 360) % 360;
        if( MyDebug.LOG ) {
            Log.d(TAG, "orientation of display relative to natural orientaton: " + degrees);
            Log.d(TAG, "orientation of display relative to camera orientaton: " + result);
        }
        camera_to_preview_matrix.postRotate(result);
    }
    // Camera driver coordinates range from (-1000, -1000) to (1000, 1000).
    // UI coordinates range from (0, 0) to (width, height).
    camera_to_preview_matrix.postScale(mCameraSurface.getView().getWidth() / 2000f, mCameraSurface.getView().getHeight() / 2000f);
    camera_to_preview_matrix.postTranslate(mCameraSurface.getView().getWidth() / 2f, mCameraSurface.getView().getHeight() / 2f);
}

Camera API坐标系转换到Camera API2坐标系

private Rect convertRectToCamera2(Rect crop_rect, Rect rect) {
    // CameraController.Area is always [-1000, -1000] to [1000, 1000] for the viewable region
    // but for CameraController2, we must convert to be relative to the crop region
    double left_f = (rect.left+1000)/2000.0;
    double top_f = (rect.top+1000)/2000.0;
    double right_f = (rect.right+1000)/2000.0;
    double bottom_f = (rect.bottom+1000)/2000.0;
    int left = (int)(crop_rect.left + left_f * (crop_rect.width()-1));
    int right = (int)(crop_rect.left + right_f * (crop_rect.width()-1));
    int top = (int)(crop_rect.top + top_f * (crop_rect.height()-1));
    int bottom = (int)(crop_rect.top + bottom_f * (crop_rect.height()-1));
    left = Math.max(left, crop_rect.left);
    right = Math.max(right, crop_rect.left);
    top = Math.max(top, crop_rect.top);
    bottom = Math.max(bottom, crop_rect.top);
    left = Math.min(left, crop_rect.right);
    right = Math.min(right, crop_rect.right);
    top = Math.min(top, crop_rect.bottom);
    bottom = Math.min(bottom, crop_rect.bottom);
    Log.i(TAG, "[Touch AEAF] convertRectToCamera2 crop_rect:" + crop_rect +
            ", rect:" + rect +
            ", result:" + new Rect(left, top, right, bottom));

    return new Rect(left, top, right, bottom);
}

View坐标转换到Camera API2坐标

/**
 * Given (nx, ny) \in [0, 1]^2, in the display's portrait coordinate system,
 * returns normalized sensor coordinates \in [0, 1]^2 depending on how the
 * sensor's orientation \in {0, 90, 180, 270}.
 * <p>
 * Returns null if sensorOrientation is not one of the above.
 * </p>
 */
public static PointF normalizedSensorCoordsForNormalizedDisplayCoords(
        float nx, float ny, int sensorOrientation) {
    switch (sensorOrientation) {
        case 0:
            return new PointF(nx, ny);
        case 90:
            return new PointF(ny, 1.0f - nx);
        case 180:
            return new PointF(1.0f - nx, 1.0f - ny);
        case 270:
            return new PointF(1.0f - ny, nx);
        default:
            return null;
    }
}

/** Compute 3A regions for a sensor-referenced touch coordinate.
 * Returns a MeteringRectangle[] with length 1.
 *
 * @param nx x coordinate of the touch point, in normalized portrait coordinates.
 * @param ny y coordinate of the touch point, in normalized portrait coordinates.
 * @param fraction Fraction in [0,1]. Multiplied by min(cropRegion.width(), cropRegion.height())
 *             to determine the side length of the square MeteringRectangle.
 * @param cropRegion Crop region of the image.
 * @param sensorOrientation sensor orientation as defined by
 *             CameraCharacteristics.get(CameraCharacteristics.SENSOR_ORIENTATION).
 */
private static MeteringRectangle[] regionsForNormalizedCoord(float nx, float ny,
    float fraction, final Rect cropRegion, int sensorOrientation) {
    // Compute half side length in pixels.
    int minCropEdge = Math.min(cropRegion.width(), cropRegion.height());
    int halfSideLength = (int) (0.5f * fraction * minCropEdge);

    // Compute the output MeteringRectangle in sensor space.
    // nx, ny is normalized to the screen.
    // Crop region itself is specified in sensor coordinates.

    // Normalized coordinates, now rotated into sensor space.
    PointF nsc = CameraUtil.normalizedSensorCoordsForNormalizedDisplayCoords(
        nx, ny, sensorOrientation);

    int xCenterSensor = (int)(cropRegion.left + nsc.x * cropRegion.width());
    int yCenterSensor = (int)(cropRegion.top + nsc.y * cropRegion.height());

    Rect meteringRegion = new Rect(xCenterSensor - halfSideLength,
        yCenterSensor - halfSideLength,
        xCenterSensor + halfSideLength,
        yCenterSensor + halfSideLength);

    // Clamp meteringRegion to cropRegion.
    meteringRegion.left = CameraUtil.clamp(meteringRegion.left, cropRegion.left, cropRegion.right);
    meteringRegion.top = CameraUtil.clamp(meteringRegion.top, cropRegion.top, cropRegion.bottom);
    meteringRegion.right = CameraUtil.clamp(meteringRegion.right, cropRegion.left, cropRegion.right);
    meteringRegion.bottom = CameraUtil.clamp(meteringRegion.bottom, cropRegion.top, cropRegion.bottom);

    return new MeteringRectangle[]{new MeteringRectangle(meteringRegion, CAMERA2_REGION_WEIGHT)};
}

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