Backend API. Server-side code: this runs in a Codename One backend, not in the app on the device.

public final class Resampler

Object
Resampler

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.

Fields

`public static final int NEAREST = 0`	Nearest neighbour: each output pixel takes the input pixel under its center.
`public static final int LANCZOS = 1`	Lanczos, a windowed sinc with a support of three pixels.
`public static final int BILINEAR = 2`	Linear interpolation (a triangle filter).
`public static final int BICUBIC = 3`	Cubic interpolation, Pillow’s `a = -0.5` kernel.
`public static final int BOX = 4`	Box filter: every input pixel under an output pixel weighs the same.
`public static final int HAMMING = 5`	Hamming-windowed sinc with a support of one pixel.

Methods

`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`.
`public static byte[] premultiply(byte[] d, int bands)`	Premultiplies the color bands by the last (alpha) band, Pillow’s rounding (`RGBA` to `RGBa`).
`public static byte[] unpremultiply(byte[] d, int bands)`	Reverses [#premultiply(byte[], int)] in place, as Pillow’s `rgbA2rgba`.

Inherited methods

From Object

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

Field details

NEAREST

public static final int NEAREST = 0

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

LANCZOS

public static final int LANCZOS = 1

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

BILINEAR

public static final int BILINEAR = 2

Linear interpolation (a triangle filter).

BICUBIC

public static final int BICUBIC = 3

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

BOX

public static final int BOX = 4

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

HAMMING

public static final int HAMMING = 5

Hamming-windowed sinc with a support of one pixel.

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 byte[]: the source pixels, w * h * bands bytes
w int: source width
h int: source height
bands int: bytes per pixel
nw int: output width
nh int: output height
box double[]: the source region, four values
filter int: 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 byte[]: interleaved pixels whose last band is alpha
bands int: 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 byte[]: interleaved premultiplied pixels whose last band is alpha
bands int: bytes per pixel

Returns

d