edu.umich.eecs.april.tag

Class TagFamily

java.lang.Object

edu.umich.eecs.april.tag.TagFamily

Direct Known Subclasses:

Tag16h5, Tag25h7, Tag25h9, Tag36h10, Tag36h11, Tag36h9

public class TagFamily
extends java.lang.Object

Generic class for all tag encoding families.

Field Summary

Fields

Modifier and Type	Field and Description
int	bits number of bits in the tag.
int	blackBorder How many pixels wide is the inner black border?
long[]	codes The array of the codes.
int	d dimension of tag. e.g. for 16 bits, d=4.
int	errorRecoveryBits The error recovery value determines our position on the ROC curve.
int	minimumHammingDistance What is the minimum hamming distance between any two codes (accounting for rotational ambiguity?
(package private) static byte[]	popCountTable
(package private) static int	popCountTableShift
int	whiteBorder How many pixels wide is the outer-most white border?

Constructor Summary

Constructors

Constructor and Description
TagFamily(int bits, int minimumHammingDistance, long[] codes) The codes array is not copied internally and so must not be modified externally.

Method Summary

Modifier and Type	Method and Description
void	decode(TagDetection det, long rcode) Given an observed tag with code 'rcode', try to recover the id.
java.awt.image.BufferedImage	getAllImagesMosaic()
int	getTagRenderDimension() Return the dimension of the tag including borders when we render it.
static int	hammingDistance(long a, long b) Compute the hamming distance between two longs.
static void	main(java.lang.String[] args)
java.awt.image.BufferedImage	makeImage(int id)
static int	popCount(long w)
(package private) static int	popCountReal(long w) How many bits are set in the long?
void	printHammingDistances()
static long	rotate90(long w, int d) if the bits in w were arranged in a d*d grid and that grid was rotated, what would the new bits in w be?
void	setErrorRecoveryBits(int b) Set the error recovery bits.
void	setErrorRecoveryFraction(double v)
void	writeAllImages(java.lang.String dirpath) Generate all valid tags, writing them as PNGs in the specified directory.
void	writeAllImagesMosaic(java.lang.String filepath)
void	writeAllImagesPostScript(java.lang.String filepath)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

whiteBorder

public int whiteBorder

How many pixels wide is the outer-most white border? This is only used when rendering a tag, not for decoding a tag (since we look for the white/black edge).

blackBorder

public int blackBorder

How many pixels wide is the inner black border?

bits

public final int bits

number of bits in the tag. Must be a square (n^2).

d

public final int d

dimension of tag. e.g. for 16 bits, d=4. Must be sqrt(bits).

minimumHammingDistance

public final int minimumHammingDistance

What is the minimum hamming distance between any two codes (accounting for rotational ambiguity? The code can recover (minHammingDistance-1)/2 bit errors.

errorRecoveryBits

public int errorRecoveryBits

The error recovery value determines our position on the ROC curve. We will report codes that are within errorRecoveryBits of a valid code. Small values mean greater rejection of bogus tags (but false negatives). Large values mean aggressive reporting of bad tags (but with a corresponding increase in false positives).

codes

public final long[] codes

The array of the codes. The id for a code is its index.

popCountTableShift

static final int popCountTableShift

See Also:

Constant Field Values

popCountTable

static final byte[] popCountTable

Constructor Detail

TagFamily

public TagFamily(int bits,
                 int minimumHammingDistance,
                 long[] codes)

The codes array is not copied internally and so must not be modified externally.

Method Detail

setErrorRecoveryBits

public void setErrorRecoveryBits(int b)

Set the error recovery bits.

setErrorRecoveryFraction

public void setErrorRecoveryFraction(double v)

rotate90

public static long rotate90(long w,
                            int d)

if the bits in w were arranged in a d*d grid and that grid was rotated, what would the new bits in w be? The bits are organized like this (for d = 3): 8 7 6 2 5 8 0 1 2 5 4 3 ==> 1 4 7 ==> 3 4 5 (rotate90 applied twice) 2 1 0 0 3 6 6 7 8

hammingDistance

public static final int hammingDistance(long a,
                                        long b)

Compute the hamming distance between two longs.

popCountReal

static final int popCountReal(long w)

How many bits are set in the long?

popCount

public static final int popCount(long w)

decode

public void decode(TagDetection det,
                   long rcode)

Given an observed tag with code 'rcode', try to recover the id. The corresponding fields of TagDetection will be filled in.

getTagRenderDimension

public int getTagRenderDimension()

Return the dimension of the tag including borders when we render it.

makeImage

public java.awt.image.BufferedImage makeImage(int id)

writeAllImages

public void writeAllImages(java.lang.String dirpath)
                    throws java.io.IOException

Generate all valid tags, writing them as PNGs in the specified directory. The files will be named tag##_##_####.png, where the first block is nbits, the second block is hamming distance, and the final block is the id.

Throws:

java.io.IOException

getAllImagesMosaic

public java.awt.image.BufferedImage getAllImagesMosaic()

writeAllImagesMosaic

public void writeAllImagesMosaic(java.lang.String filepath)
                          throws java.io.IOException

Throws:

java.io.IOException

printHammingDistances

public void printHammingDistances()

writeAllImagesPostScript

public void writeAllImagesPostScript(java.lang.String filepath)
                              throws java.io.IOException

Throws:

java.io.IOException

main

public static void main(java.lang.String[] args)