Android Open Source - nightvision Night Vision View

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License

The source code is released under:

Copyright (c) 2012 Ford Motor Company All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are me...

Java Source Code

package com.ford.openxc.nightvision;
//  www .j a v a2  s  .co  m
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.media.MediaPlayer;
import android.util.AttributeSet;
import android.util.Log;

import com.ford.openxc.webcam.WebcamPreview;

public class NightVisionView extends WebcamPreview {
    private final static String TAG = "NightVisionView";
    private final int DETECT_FRAME_FREQUENCY = 4;

    private static Paint sOverlayPaint = new Paint();
    private Bitmap mBitmapEdges;
    private Bitmap mBitmapObjectOverlay;
    private boolean mObjectInPreviousFrame = false;
    private MediaPlayer mMediaPlayer;
    private int mFrameCount;

    /** Detect edges in the image using the Sobel operator and store the result
     * in a new alpha bitmap.
     *
     * The Sobel operator calculates the gradient of the image intensity at each
     * point. The result therefore shows how "abruptly" or "smoothly" the image
     * changes at that point, and therefore how likely it is that that part of
     * the image represents an edge, as well as how that edge is likely to be
     * oriented. The operator uses two 3x3 matrices which are convolved with the
     * original image to calculate approximations of the derivatives - one for
     * horizontal changes, and one for vertical.
     *
     * @param imageBitmap Source image for edge detection, assumed to be ARGB.
     * @param edgeBitmap Target for edge detection output, will be modified.
     */
    public native void detectEdges(final Bitmap imageBitmap, Bitmap edgeBitmap);

    /** Detect clusters of edges in a bitmap and highlight the output in a
     * separate bitmap to show objects.
     *
     * This function performs rudimentary object detection using a bitmap
     * of edges identified in some unseen source image. The detection is bounded
     * within an area in the middle of the image (see DETECTION_WINDOW_SIZE in
     * the JNI part) for performance and to minimize false positives, since the
     * area of interest for app is the road ahead at the horizon.
     *
     * Blocks of a reasonable size within these bounds that contain more than
     * 40% edges are considered to be "objects". The block is shaded in the
     * output bitmap, which can then be used as an overlay for the source image.
     *
     * @param edgeBitmap Input bitmap that highlights edges in pure white, and
     *      everything else black.
     * @param overlayBitmap Bitmap to store object highlight output.
     * @return true if at least one object is detected
     */
    public native boolean detectObjects(final Bitmap edgeBitmap,
            Bitmap overlayBitmap);

    static {
        System.loadLibrary("nightvision");
        sOverlayPaint.setAlpha(130);
        sOverlayPaint.setColor(Color.RED);
    }

    public NightVisionView(Context context) {
        super(context);
        init();
    }

    public NightVisionView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    protected void drawOnCanvas(Canvas canvas, Bitmap videoBitmap) {
        initializeBitmaps(videoBitmap);
        canvas.drawColor(Color.BLACK);

        if(mFrameCount == DETECT_FRAME_FREQUENCY) {
            detectEdges(videoBitmap, mBitmapEdges);

            mBitmapObjectOverlay.eraseColor(Color.TRANSPARENT);
            boolean objectDetected = detectObjects(mBitmapEdges,
                    mBitmapObjectOverlay);
            if (!mObjectInPreviousFrame && objectDetected) {
                mMediaPlayer.start();
                mObjectInPreviousFrame = true;
                Log.d(TAG, "Object detected");
            } else if(mObjectInPreviousFrame && !objectDetected) {
                mObjectInPreviousFrame = false;
                Log.d(TAG, "Object left frame");
            }

            mFrameCount = 0;
        } else {
            mFrameCount++;
        }

        canvas.drawBitmap(videoBitmap, null, getViewingWindow(), null);
        canvas.drawBitmap(mBitmapObjectOverlay, null, getViewingWindow(),
                sOverlayPaint);
    }

    private void init() {
        mMediaPlayer = MediaPlayer.create(getContext(), R.raw.alert);
    }

    private void initializeBitmaps(Bitmap videoBitmap) {
        if(mBitmapEdges == null ||
                mBitmapEdges.getWidth() != videoBitmap.getWidth() ||
                mBitmapEdges.getHeight() != videoBitmap.getHeight()) {
            mBitmapEdges = Bitmap.createBitmap(videoBitmap.getWidth(),
                    videoBitmap.getHeight(), Bitmap.Config.ALPHA_8);
        }

        if(mBitmapObjectOverlay == null ||
                mBitmapObjectOverlay.getWidth() != videoBitmap.getWidth() ||
                mBitmapObjectOverlay.getHeight() != videoBitmap.getHeight()) {
            mBitmapObjectOverlay = Bitmap.createBitmap(videoBitmap.getWidth(),
                    videoBitmap.getHeight(), Bitmap.Config.ALPHA_8);
        }
    }
}

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