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BoofCV is an open source Java library for real-time computer vision and robotics applications.
/*
* Copyright (c) 2011-2015, Peter Abeles. All Rights Reserved.
*
* This file is part of BoofCV (http://boofcv.org).
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package boofcv.alg.background;
import boofcv.alg.InputSanityCheck;
import boofcv.struct.distort.PointTransformModel_F32;
import boofcv.struct.image.ImageBase;
import boofcv.struct.image.ImageType;
import boofcv.struct.image.ImageUInt8;
import georegression.struct.InvertibleTransform;
import georegression.struct.point.Point2D_F32;
/**
*
* Base class for classifying pixels and background based on the apparent motion of pixels when the camera is moving.
* The camera motion is provided externally.
*
*
* There are three coordinate systems.
*
* - World is the background model's coordinate system.
* - Home is the image which all the camera motion is relative to
* - Current is the location of the current image.
*
*
*
* The background model is composed of a single fixed sized image. The background image size is specified in
* the {@link #initialize(int, int, InvertibleTransform)} function. After that the background model is updated
* by calling {@link #updateBackground(InvertibleTransform, ImageBase)}. To flag pixels as background/motion
* call {@link #segment(InvertibleTransform, ImageBase, ImageUInt8)}.
*
*
*
* If a pixel in the current frame has no corresponding pixel in the background or the background
* pixel hasn't been observed yet then it will be assigned a special value, which is user configurable.
* The default value is 0, which is a background pixel. See {@link #setUnknownValue(int)}}
*
*
* @author Peter Abeles
*/
public abstract class BackgroundModelMoving>
extends BackgroundModel
{
// Convert the motion model into a usable format
protected PointTransformModel_F32 transform;
// transforms
protected MotionModel homeToWorld;
protected MotionModel worldToHome;
protected MotionModel currentToWorld;
protected MotionModel worldToCurrent;
// width and height of background image. must be set by child
protected int backgroundWidth;
protected int backgroundHeight;
// storage for corners which are used to find bounding box
protected Point2D_F32 corners[] = new Point2D_F32[4];
// storage for transformed coordinate
protected Point2D_F32 work = new Point2D_F32();
/**
* Constructor which provides the motion model and image type
* @param transform Point transform which can be used to apply the motion model
* @param imageType Type of input image
*/
public BackgroundModelMoving(PointTransformModel_F32 transform, ImageType imageType) {
super(imageType);
this.transform = transform;
this.homeToWorld = transform.newInstanceModel();
this.worldToHome = transform.newInstanceModel();
this.currentToWorld = transform.newInstanceModel();
this.worldToCurrent = transform.newInstanceModel();
for (int i = 0; i < corners.length; i++) {
corners[i] = new Point2D_F32();
}
}
/**
* Initializes background model. Specifies the size of the background image and transform from the "home" image
* to the background "world"
*
* @param backgroundWidth Width of background
* @param backgroundHeight Height of background
* @param homeToWorld Transform from home to world.
*/
public abstract void initialize( int backgroundWidth , int backgroundHeight , MotionModel homeToWorld );
/**
* Updates the background with new image information.
*
* @param homeToCurrent Transform from home image to the current image
* @param frame The current image in the sequence
*/
public void updateBackground(MotionModel homeToCurrent, T frame) {
worldToHome.concat(homeToCurrent, worldToCurrent);
worldToCurrent.invert(currentToWorld);
// find the distorted polygon of the current image in the "home" background reference frame
transform.setModel(currentToWorld);
transform.compute(0, 0, corners[0]);
transform.compute(frame.width-1,0,corners[1]);
transform.compute(frame.width-1,frame.height-1,corners[2]);
transform.compute(0, frame.height-1, corners[3]);
// find the bounding box
int x0 = Integer.MAX_VALUE;
int y0 = Integer.MAX_VALUE;
int x1 = -Integer.MAX_VALUE;
int y1 = -Integer.MAX_VALUE;
for (int i = 0; i < 4; i++) {
Point2D_F32 p = corners[i];
int x = (int)p.x;
int y = (int)p.y;
if( x0 > x ) x0 = x;
if( y0 > y ) y0 = y;
if( x1 < x ) x1 = x;
if( y1 < y ) y1 = y;
}
x1++;y1++;
if( x0 < 0 ) x0 = 0;
if( x1 > backgroundWidth ) x1 = backgroundWidth;
if( y0 < 0 ) y0 = 0;
if( y1 > backgroundHeight ) y1 = backgroundHeight;
updateBackground(x0,y0,x1,y1,frame);
}
/**
* Call to update the background with the frame inside the bounding box. Implementing class needs to
* make sure the rectangle is inside the background.
*/
protected abstract void updateBackground( int x0 , int y0 , int x1 , int y1 , T frame );
/**
* Invoke to use the background image to segment the current frame into background and foreground pixels
*
* @param homeToCurrent Transform from home image to the current image
* @param frame current image
* @param segmented Segmented image. 0 = background, 1 = foreground/moving
*/
public void segment( MotionModel homeToCurrent , T frame , ImageUInt8 segmented ) {
InputSanityCheck.checkSameShape(frame,segmented);
worldToHome.concat(homeToCurrent, worldToCurrent);
worldToCurrent.invert(currentToWorld);
_segment(currentToWorld,frame,segmented);
}
protected abstract void _segment( MotionModel currentToWorld , T frame , ImageUInt8 segmented );
}