com.googlecode.leptonica.android

Class Skew

java.lang.Object

com.googlecode.leptonica.android.Skew

public class Skew
extends Object

Image rotation and skew detection methods.

Author:

alanv@google.com (Alan Viverette)

Field Summary

Fields

Modifier and Type	Field and Description
static float	SEARCH_MIN_DELTA Default search minimum delta, reasonably accurate within 0.05 degrees.
static int	SEARCH_REDUCTION Default sweep reduction, one-fourth the size of the original image.
static float	SWEEP_DELTA Default sweep delta, reasonably accurate within 0.05 degrees.
static float	SWEEP_RANGE Default range for sweep, will detect rotation of + or - 30 degrees.
static int	SWEEP_REDUCTION Default sweep reduction, one-eighth the size of the original image.

Constructor Summary

Constructors

Constructor and Description
Skew()

Method Summary

Methods

Modifier and Type	Method and Description
static float	findSkew(Pix pixs) Finds and returns the skew angle using default parameters.
static float	findSkew(Pix pixs, float sweepRange, float sweepDelta, int sweepReduction, int searchReduction, float searchMinDelta) Finds and returns the skew angle, doing first a sweep through a set of equal angles, and then doing a binary search until convergence.

Methods inherited from class java.lang.Object

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

Field Detail

SWEEP_RANGE

public static final float SWEEP_RANGE

Default range for sweep, will detect rotation of + or - 30 degrees.

See Also:

Constant Field Values

SWEEP_DELTA

public static final float SWEEP_DELTA

Default sweep delta, reasonably accurate within 0.05 degrees.

See Also:

Constant Field Values

SWEEP_REDUCTION

public static final int SWEEP_REDUCTION

Default sweep reduction, one-eighth the size of the original image.

See Also:

Constant Field Values

SEARCH_REDUCTION

public static final int SEARCH_REDUCTION

Default sweep reduction, one-fourth the size of the original image.

See Also:

Constant Field Values

SEARCH_MIN_DELTA

public static final float SEARCH_MIN_DELTA

Default search minimum delta, reasonably accurate within 0.05 degrees.

See Also:

Constant Field Values

Constructor Detail

Skew

public Skew()

Method Detail

findSkew

public static float findSkew(Pix pixs)

Finds and returns the skew angle using default parameters.

Parameters:

pixs - Input pix (1 bpp).

Returns:

the detected skew angle, or 0.0 on failure

findSkew

public static float findSkew(Pix pixs,
             float sweepRange,
             float sweepDelta,
             int sweepReduction,
             int searchReduction,
             float searchMinDelta)

Finds and returns the skew angle, doing first a sweep through a set of equal angles, and then doing a binary search until convergence.

Notes:

1. In computing the differential line sum variance score, we sum the result over scanlines, but we always skip:
   • at least one scanline
   • not more than 10% of the image height
   • not more than 5% of the image width

Parameters:

pixs - Input pix (1 bpp).

sweepRange - Half the full search range, assumed about 0; in degrees.

sweepDelta - Angle increment of sweep; in degrees.

sweepReduction - Sweep reduction factor = 1, 2, 4 or 8.

searchReduction - Binary search reduction factor = 1, 2, 4 or 8; and must not exceed redsweep.

searchMinDelta - Minimum binary search increment angle; in degrees.

Returns:

the detected skew angle, or 0.0 on failure