Class Resampler

java.lang.Object

com.codename1.backend.image.Resampler

public final class Resampler
extends Object

Resampling of interleaved 8-bit band data, the two-pass fixed-point convolution of Pillow's Resample.c.

The results match Pillow byte for byte, which is why the Python runtime's PIL.Image.resize delegates here. Pixels are bands consecutive bytes (L, LA, RGB, RGBA, ...), rows packed with no padding. Images with alpha should be premultiplied first ([#premultiply(byte[], int)]) and unpremultiplied afterwards, as Pillow does, so transparent pixels do not bleed their color into their neighbours.

RasterImage.scale(int, int, int) wraps this for ARGB images.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	BICUBIC	Cubic interpolation, Pillow's a = -0.5 kernel.
static final int	BILINEAR	Linear interpolation (a triangle filter).
static final int	BOX	Box filter: every input pixel under an output pixel weighs the same.
static final int	HAMMING	Hamming-windowed sinc with a support of one pixel.
static final int	LANCZOS	Lanczos, a windowed sinc with a support of three pixels.
static final int	NEAREST	Nearest neighbour: each output pixel takes the input pixel under its center.

Method Summary

Modifier and Type	Method	Description
static byte[]	premultiply(byte[] d, int bands)	Premultiplies the color bands by the last (alpha) band, Pillow's rounding (RGBA to RGBa).
static byte[]	resample(byte[] src, int w, int h, int bands, int nw, int nh, double[] box, int filter)	Resamples the region box (x0, y0, x1, y1, in source pixels, may be fractional) of a w x h image to nw x nh.
static byte[]	unpremultiply(byte[] d, int bands)	Reverses [#premultiply(byte[], int)] in place, as Pillow's rgbA2rgba.

Methods inherited from class Object

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

Field Details

NEAREST

public static final int NEAREST

Nearest neighbour: each output pixel takes the input pixel under its center.

See Also:

• Constant Field Values

LANCZOS

public static final int LANCZOS

Lanczos, a windowed sinc with a support of three pixels.

See Also:

• Constant Field Values

BILINEAR

public static final int BILINEAR

Linear interpolation (a triangle filter).

See Also:

• Constant Field Values

BICUBIC

public static final int BICUBIC

Cubic interpolation, Pillow's a = -0.5 kernel.

See Also:

• Constant Field Values

BOX

public static final int BOX

Box filter: every input pixel under an output pixel weighs the same.

See Also:

• Constant Field Values

HAMMING

public static final int HAMMING

Hamming-windowed sinc with a support of one pixel.

See Also:

• Constant Field Values

Method Details

resample

public static byte[] resample(byte[] src,
 int w,
 int h,
 int bands,
 int nw,
 int nh,
 double[] box,
 int filter)

Resamples the region box (x0, y0, x1, y1, in source pixels, may be fractional) of a w x h image to nw x nh.

Parameters

• src: the source pixels, w * h * bands bytes
• w: source width
• h: source height
• bands: bytes per pixel
• nw: output width
• nh: output height
• box: the source region, four values
• filter: one of the filter constants of this class

Returns

a new array of nw * nh * bands bytes

premultiply

public static byte[] premultiply(byte[] d,
 int bands)

Premultiplies the color bands by the last (alpha) band, Pillow's rounding (RGBA to RGBa).

Parameters

• d: interleaved pixels whose last band is alpha
• bands: bytes per pixel

Returns

a new premultiplied array

unpremultiply

public static byte[] unpremultiply(byte[] d,
 int bands)

Reverses [#premultiply(byte[], int)] in place, as Pillow's rgbA2rgba.

Parameters

• d: interleaved premultiplied pixels whose last band is alpha
• bands: bytes per pixel

Returns

d