Package com.jhlabs.image

Class ImageMath

java.lang.Object

com.jhlabs.image.ImageMath

public class ImageMath
extends java.lang.Object

A class containing static math methods useful for image processing.

Field Summary

Fields

Modifier and Type	Field	Description
static float	HALF_PI	The value of half pi as a float.
static float	PI	The value of pi as a float.
static float	QUARTER_PI	The value of quarter pi as a float.
static float	TWO_PI	The value of two pi as a float.

Constructor Summary

Constructors

Constructor	Description
ImageMath()

Method Summary

Modifier and Type	Method	Description
static float	bias(float a, float b)	Apply a bias to a number in the unit interval, moving numbers towards 0 or 1 according to the bias parameter.
static int	bilinearInterpolate(float x, float y, int nw, int ne, int sw, int se)	Bilinear interpolation of ARGB values.
static int	brightnessNTSC(int rgb)	Return the NTSC gray level of an RGB value.
static float	circleDown(float x)	A "circle down" function.
static float	circleUp(float x)	A "circle up" function.
static float	clamp(float x, float a, float b)	Clamp a value to an interval.
static int	clamp(int x, int a, int b)	Clamp a value to an interval.
static int	colorSpline(float x, int numKnots, int[] knots)	Compute a Catmull-Rom spline for RGB values.
static int	colorSpline(int x, int numKnots, int[] xknots, int[] yknots)	Compute a Catmull-Rom spline for RGB values, but with variable knot spacing.
static float	gain(float a, float b)	A variant of the gamma function.
static float	lerp(float t, float a, float b)	Linear interpolation.
static int	lerp(float t, int a, int b)	Linear interpolation.
static int	mixColors(float t, int rgb1, int rgb2)	Linear interpolation of ARGB values.
static double	mod(double a, double b)	Return a mod b.
static float	mod(float a, float b)	Return a mod b.
static int	mod(int a, int b)	Return a mod b.
static void	premultiply(int[] p, int offset, int length)	Premultiply a block of pixels.
static float	pulse(float a, float b, float x)	The pulse function.
static void	resample(int[] source, int[] dest, int length, int offset, int stride, float[] out)	An implementation of Fant's resampling algorithm.
static float	smoothPulse(float a1, float a2, float b1, float b2, float x)	A smoothed pulse function.
static float	smoothStep(float a, float b, float x)	A smoothed step function.
static float	spline(float x, int numKnots, float[] knots)	Compute a Catmull-Rom spline.
static float	spline(float x, int numKnots, int[] xknots, int[] yknots)	Compute a Catmull-Rom spline, but with variable knot spacing.
static float	step(float a, float x)	The step function.
static float	triangle(float x)	The triangle function.
static void	unpremultiply(int[] p, int offset, int length)	Unpremultiply a block of pixels

Methods inherited from class java.lang.Object

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

Field Detail

PI

public static final float PI

The value of pi as a float.

See Also:

Constant Field Values

HALF_PI

public static final float HALF_PI

The value of half pi as a float.

See Also:

Constant Field Values

QUARTER_PI

public static final float QUARTER_PI

The value of quarter pi as a float.

See Also:

Constant Field Values

TWO_PI

public static final float TWO_PI

The value of two pi as a float.

See Also:

Constant Field Values

Constructor Detail

ImageMath

public ImageMath()

Method Detail

bias

public static float bias(float a,
                         float b)

Apply a bias to a number in the unit interval, moving numbers towards 0 or 1 according to the bias parameter.

Parameters:

a - the number to bias

b - the bias parameter. 0.5 means no change, smaller values bias towards 0, larger towards 1.

Returns:

the output value

gain

public static float gain(float a,
                         float b)

A variant of the gamma function.

Parameters:

a - the number to apply gain to

b - the gain parameter. 0.5 means no change, smaller values reduce gain, larger values increase gain.

Returns:

the output value

step

public static float step(float a,
                         float x)

The step function. Returns 0 below a threshold, 1 above.

Parameters:

a - the threshold position

x - the input parameter

Returns:

the output value - 0 or 1

pulse

public static float pulse(float a,
                          float b,
                          float x)

The pulse function. Returns 1 between two thresholds, 0 outside.

Parameters:

a - the lower threshold position

b - the upper threshold position

x - the input parameter

Returns:

the output value - 0 or 1

smoothPulse

public static float smoothPulse(float a1,
                                float a2,
                                float b1,
                                float b2,
                                float x)

A smoothed pulse function. A cubic function is used to smooth the step between two thresholds.

Parameters:

a1 - the lower threshold position for the start of the pulse

a2 - the upper threshold position for the start of the pulse

b1 - the lower threshold position for the end of the pulse

b2 - the upper threshold position for the end of the pulse

x - the input parameter

Returns:

the output value

smoothStep

public static float smoothStep(float a,
                               float b,
                               float x)

A smoothed step function. A cubic function is used to smooth the step between two thresholds.

Parameters:

a - the lower threshold position

b - the upper threshold position

x - the input parameter

Returns:

the output value

circleUp

public static float circleUp(float x)

A "circle up" function. Returns y on a unit circle given 1-x. Useful for forming bevels.

Parameters:

x - the input parameter in the range 0..1

Returns:

the output value

circleDown

public static float circleDown(float x)

A "circle down" function. Returns 1-y on a unit circle given x. Useful for forming bevels.

Parameters:

x - the input parameter in the range 0..1

Returns:

the output value

clamp

public static float clamp(float x,
                          float a,
                          float b)

Clamp a value to an interval.

Parameters:

a - the lower clamp threshold

b - the upper clamp threshold

x - the input parameter

Returns:

the clamped value

clamp

public static int clamp(int x,
                        int a,
                        int b)

Clamp a value to an interval.

Parameters:

a - the lower clamp threshold

b - the upper clamp threshold

x - the input parameter

Returns:

the clamped value

mod

public static double mod(double a,
                         double b)

Return a mod b. This differs from the % operator with respect to negative numbers.

Parameters:

a - the dividend

b - the divisor

Returns:

a mod b

mod

public static float mod(float a,
                        float b)

Return a mod b. This differs from the % operator with respect to negative numbers.

Parameters:

a - the dividend

b - the divisor

Returns:

a mod b

mod

public static int mod(int a,
                      int b)

Return a mod b. This differs from the % operator with respect to negative numbers.

Parameters:

a - the dividend

b - the divisor

Returns:

a mod b

triangle

public static float triangle(float x)

The triangle function. Returns a repeating triangle shape in the range 0..1 with wavelength 1.0

Parameters:

x - the input parameter

Returns:

the output value

lerp

public static float lerp(float t,
                         float a,
                         float b)

Linear interpolation.

Parameters:

t - the interpolation parameter

a - the lower interpolation range

b - the upper interpolation range

Returns:

the interpolated value

lerp

public static int lerp(float t,
                       int a,
                       int b)

Linear interpolation.

Parameters:

t - the interpolation parameter

a - the lower interpolation range

b - the upper interpolation range

Returns:

the interpolated value

mixColors

public static int mixColors(float t,
                            int rgb1,
                            int rgb2)

Linear interpolation of ARGB values.

Parameters:

t - the interpolation parameter

rgb1 - the lower interpolation range

rgb2 - the upper interpolation range

Returns:

the interpolated value

bilinearInterpolate

public static int bilinearInterpolate(float x,
                                      float y,
                                      int nw,
                                      int ne,
                                      int sw,
                                      int se)

Bilinear interpolation of ARGB values.

Parameters:

x - the X interpolation parameter 0..1

y - the y interpolation parameter 0..1

nw - The ARGB northwest value

ne - The ARGB northeast value

sw - The ARGB southwest value

se - The ARGB southeast value

Returns:

the interpolated value

brightnessNTSC

public static int brightnessNTSC(int rgb)

Return the NTSC gray level of an RGB value.

Parameters:

rgb - the input pixel

Returns:

the gray level (0-255)

spline

public static float spline(float x,
                           int numKnots,
                           float[] knots)

Compute a Catmull-Rom spline.

Parameters:

x - the input parameter

numKnots - the number of knots in the spline

knots - the array of knots

Returns:

the spline value

spline

public static float spline(float x,
                           int numKnots,
                           int[] xknots,
                           int[] yknots)

Compute a Catmull-Rom spline, but with variable knot spacing.

Parameters:

x - the input parameter

numKnots - the number of knots in the spline

xknots - the array of knot x values

yknots - the array of knot y values

Returns:

the spline value

colorSpline

public static int colorSpline(float x,
                              int numKnots,
                              int[] knots)

Compute a Catmull-Rom spline for RGB values.

Parameters:

x - the input parameter

numKnots - the number of knots in the spline

knots - the array of knots

Returns:

the spline value

colorSpline

public static int colorSpline(int x,
                              int numKnots,
                              int[] xknots,
                              int[] yknots)

Compute a Catmull-Rom spline for RGB values, but with variable knot spacing.

Parameters:

x - the input parameter

numKnots - the number of knots in the spline

xknots - the array of knot x values

yknots - the array of knot y values

Returns:

the spline value

resample

public static void resample(int[] source,
                            int[] dest,
                            int length,
                            int offset,
                            int stride,
                            float[] out)

An implementation of Fant's resampling algorithm.

Parameters:

source - the source pixels

dest - the destination pixels

length - the length of the scanline to resample

offset - the start offset into the arrays

stride - the offset between pixels in consecutive rows

out - an array of output positions for each pixel

premultiply

public static void premultiply(int[] p,
                               int offset,
                               int length)

Premultiply a block of pixels.

Parameters:

p - The block of pixels.

offset - The starting pixel.

length - The number of pixels to premultiply.

unpremultiply

public static void unpremultiply(int[] p,
                                 int offset,
                                 int length)

Unpremultiply a block of pixels

Parameters:

p - The block of pixels.

offset - The starting pixel.

length - The number of pixels to premultiply.