KltTracker (feature 0.23 API)

java.lang.Object
- boofcv.alg.tracker.klt.KltTracker<InputImage,DerivativeImage>

```
public class KltTracker<InputImage extends boofcv.struct.image.ImageGray,DerivativeImage extends boofcv.struct.image.ImageGray>
extends java.lang.Object
```
A Kanade-Lucas-Tomasi (KLT) [1,2,3,4] point feature tracker for a single layer gray scale image. It tracks point features across a sequence of images by having each feature individually follow the image's gradient. Feature locations are estimated to within sub-pixel accuracy.

For this particular implementation of KLT, image derivatives is only needed when setDescription() is called. Tracker quality will degrade if features change orientation, but this technique is significantly faster.

Citations:

[1] Bruce D. Lucas and Takeo Kanade. An Iterative Image Registration Technique with an Application to Stereo Vision. International Joint Conference on Artificial Intelligence, pages 674-679, 1981.
[2] Carlo Tomasi and Takeo Kanade. Detection and Tracking of Point Features. Carnegie Mellon University Technical Report CMU-CS-91-132, April 1991.
[3] Jianbo Shi and Carlo Tomasi. Good Features to Track. IEEE Conference on Computer Vision and Pattern Recognition, pages 593-600, 1994.
[4] Stan Birchfield, http://www.ces.clemson.edu/~stb/klt/

Field Summary

Fields
Modifier and Type	Field and Description
`protected KltConfig`	`config`
`protected boofcv.struct.image.GrayF32`	`currDesc`
`protected DerivativeImage`	`derivX`
`protected DerivativeImage`	`derivY`
`protected float`	`Ex`
`protected float`	`Ey`
`protected float`	`Gxx`
`protected float`	`Gxy`
`protected float`	`Gyy`
`protected InputImage`	`image`
`protected boofcv.alg.interpolate.InterpolateRectangle<DerivativeImage>`	`interpDeriv`
`protected boofcv.alg.interpolate.InterpolateRectangle<InputImage>`	`interpInput`
`protected int`	`lengthFeature`
`protected boofcv.struct.image.GrayF32`	`subimage`
`protected int`	`widthFeature`

Constructor Summary

Constructors
Constructor and Description
`KltTracker(boofcv.alg.interpolate.InterpolateRectangle<InputImage> interpInput, boofcv.alg.interpolate.InterpolateRectangle<DerivativeImage> interpDeriv, KltConfig config)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected void`	`computeE(KltFeature feature, float x, float y)`
`protected int`	`computeGandE_border(KltFeature feature, float cx, float cy)` When part of the region is outside the image G and E need to be recomputed
`KltConfig`	`getConfig()`
`float`	`getError()` Average absolute value of the difference between each pixel in the image and the template
`protected boolean`	`internalSetDescription(KltFeature feature)`
`protected boolean`	`internalSetDescriptionBorder(KltFeature feature)` Computes the descriptor for border features.
`boolean`	`isDescriptionComplete(KltFeature feature)` Checks to see if the feature description is complete or if it was created by a feature partially outside the image
`boolean`	`isFullyInside(float x, float y)` Returns true if the features is entirely enclosed inside of the image.
`boolean`	`isFullyOutside(float x, float y)` Returns true if the features is entirely outside of the image.
`protected void`	`setAllowedBounds(KltFeature feature)` Precompute image bounds that the feature is allowed inside of
`boolean`	`setDescription(KltFeature feature)` Sets the features description using the current image and the location of the feature stored in the feature.
`void`	`setImage(InputImage image, DerivativeImage derivX, DerivativeImage derivY)` Sets the current image it should be tracking with.
`KltTrackFault`	`track(KltFeature feature)` Updates the feature's location inside the image.
`void`	`unsafe_setImage(InputImage image, DerivativeImage derivX, DerivativeImage derivY)` Same as `setImage(InputImage, DerivativeImage, DerivativeImage)`, but it doesn't check to see if the images are the same size each time

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

image

protected InputImage extends boofcv.struct.image.ImageGray image

derivX

protected DerivativeImage extends boofcv.struct.image.ImageGray derivX

derivY

protected DerivativeImage extends boofcv.struct.image.ImageGray derivY

interpInput

protected boofcv.alg.interpolate.InterpolateRectangle<InputImage extends boofcv.struct.image.ImageGray> interpInput

interpDeriv

protected boofcv.alg.interpolate.InterpolateRectangle<DerivativeImage extends boofcv.struct.image.ImageGray> interpDeriv

config
```
protected KltConfig config
```

Gxx
```
protected float Gxx
```

Gyy
```
protected float Gyy
```

Gxy
```
protected float Gxy
```

Ex
```
protected float Ex
```

Ey
```
protected float Ey
```

widthFeature
```
protected int widthFeature
```

lengthFeature
```
protected int lengthFeature
```

currDesc

protected boofcv.struct.image.GrayF32 currDesc

subimage

protected boofcv.struct.image.GrayF32 subimage

Constructor Detail

KltTracker

public KltTracker(boofcv.alg.interpolate.InterpolateRectangle<InputImage> interpInput,
                  boofcv.alg.interpolate.InterpolateRectangle<DerivativeImage> interpDeriv,
                  KltConfig config)

Method Detail
- setImage
```
public void setImage(InputImage image,
                     DerivativeImage derivX,
                     DerivativeImage derivY)
```
  Sets the current image it should be tracking with.
  
  Parameters:
  
  image - Original input image.
  
  derivX - Image derivative along the x-axis
  
  derivY - Image derivative along the y-axis
- unsafe_setImage
```
public void unsafe_setImage(InputImage image,
                            DerivativeImage derivX,
                            DerivativeImage derivY)
```
  Same as setImage(InputImage, DerivativeImage, DerivativeImage), but it doesn't check to see if the images are the same size each time
- setDescription
```
public boolean setDescription(KltFeature feature)
```
  Sets the features description using the current image and the location of the feature stored in the feature. If the feature is an illegal location and cannot be set then false is returned.
  
  Parameters:
  
  feature - Feature description which is to be set. Location must be specified.
  
  Returns:
  
  true if the feature's description was modified.
- internalSetDescription
```
protected boolean internalSetDescription(KltFeature feature)
```
- internalSetDescriptionBorder
```
protected boolean internalSetDescriptionBorder(KltFeature feature)
```
  Computes the descriptor for border features. All it needs to do is save the pixel value, but derivative information is also computed so that it can reject bad features immediately.
- track
```
public KltTrackFault track(KltFeature feature)
```
  Updates the feature's location inside the image. The feature's position can be modified even if tracking fails.
  
  Parameters:
  
  feature - Feature being tracked.
  
  Returns:
  
  If the tracking was successful or not.
- setAllowedBounds
```
protected void setAllowedBounds(KltFeature feature)
```
  Precompute image bounds that the feature is allowed inside of
- computeE
```
protected void computeE(KltFeature feature,
                        float x,
                        float y)
```
- computeGandE_border
```
protected int computeGandE_border(KltFeature feature,
                                  float cx,
                                  float cy)
```
  When part of the region is outside the image G and E need to be recomputed
- isDescriptionComplete
```
public boolean isDescriptionComplete(KltFeature feature)
```
  Checks to see if the feature description is complete or if it was created by a feature partially outside the image
- isFullyInside
```
public boolean isFullyInside(float x,
                             float y)
```
  Returns true if the features is entirely enclosed inside of the image.
- isFullyOutside
```
public boolean isFullyOutside(float x,
                              float y)
```
  Returns true if the features is entirely outside of the image. A region is entirely outside if not an entire pixel is contained inside the image. So if only 0.999 of a pixel is inside then the whole region is considered to be outside. Can't interpolate nothing...
- getError
```
public float getError()
```
  Average absolute value of the difference between each pixel in the image and the template
  
  Returns:
  
  Average error
- getConfig
```
public KltConfig getConfig()
```

Class KltTracker<InputImage extends boofcv.struct.image.ImageGray,DerivativeImage extends boofcv.struct.image.ImageGray>

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

image

derivX

derivY

interpInput

interpDeriv

config

Gxx

Gyy

Gxy

Ex

Ey

widthFeature

lengthFeature

currDesc

subimage

Constructor Detail

KltTracker

Method Detail

setImage

unsafe_setImage

setDescription

internalSetDescription

internalSetDescriptionBorder

track

setAllowedBounds

computeE

computeGandE_border

isDescriptionComplete

isFullyInside

isFullyOutside

getError

getConfig