pixeltable.functions.image - Pixeltable Documentation

Pixeltable UDFs for ImageType. Example:

import pixeltable as pxt

t = pxt.get_table(...)
t.select(t.img_col.convert('L')).collect()

View source on GitHub

UDFs

`alpha_composite()` _udf

Alpha composite im2 over im1. Signature:

alpha_composite(
    im1: Image,
    im2: Image
)-> Image

Parameters:

im1 (Image): The first image. Must have mode RGBA or LA.
im2 (Image): The second image. Must have the same mode and size as the first image.

Returns:

Image: An ~PIL.Image.Image object.

`b64_encode()` _udf

Convert image to a base64-encoded string. Signature:

b64_encode(
    img: Image,
    image_format: String
)-> String

Parameters:

img (Image): image
image_format (String): image format supported by PIL

`blend()` _udf

Creates a new image by interpolating between two input images, using a constant alpha:: out = image1 * (1.0 - alpha) + image2 * alpha Signature:

blend(
    im1: Image,
    im2: Image,
    alpha: Float
)-> Image

Parameters:

im1 (Image): The first image.
im2 (Image): The second image. Must have the same mode and size as the first image.
alpha (Float): The interpolation alpha factor. If alpha is 0.0, a copy of the first image is returned. If alpha is 1.0, a copy of the second image is returned. There are no restrictions on the alpha value. If necessary, the result is clipped to fit into the allowed output range.

Returns:

Image: An ~PIL.Image.Image object.

`composite()` _udf

Create composite image by blending images using a transparency mask. Signature:

composite(
    image1: Image,
    image2: Image,
    mask: Image
)-> Image

Parameters:

image1 (Image): The first image.
image2 (Image): The second image. Must have the same mode and size as the first image.
mask (Image): A mask image. This image can have mode “1”, “L”, or “RGBA”, and must have the same size as the other two images.

`convert()` _udf

Convert the image to a different mode. Equivalent to PIL.Image.Image.convert(). Signature:

convert(
    self: Image,
    mode: String
)-> Image

Parameters:

mode (String): The mode to convert to. See the Pillow documentation for a list of supported modes.

`crop()` _udf

Returns a rectangular region from this image. The box is a 4-tuple defining the left, upper, right, and lower pixel coordinate. See :ref:coordinate-system. Note: Prior to Pillow 3.4.0, this was a lazy operation. Signature:

crop(
    self: Image,
    box: Json
)-> Image

Parameters:

box (Json): The crop rectangle, as a (left, upper, right, lower)-tuple.

Returns:

Image: An ~PIL.Image.Image object.

`effect_spread()` _udf

Randomly spread pixels in an image. Signature:

effect_spread(
    self: Image,
    distance: Int
)-> Image

Parameters:

distance (Int): Distance to spread pixels.

`entropy()` _udf

Calculates and returns the entropy for the image. A bilevel image (mode “1”) is treated as a grayscale (“L”) image by this method. If a mask is provided, the method employs the histogram for those parts of the image where the mask image is non-zero. The mask image must have the same size as the image, and be either a bi-level image (mode “1”) or a grayscale image (“L”). Signature:

entropy(
    self: Image,
    mask: Optional[Image],
    extrema: Optional[Json]
)-> Float

Parameters:

mask (Optional[Image]): An optional mask.
extrema (Optional[Json]): An optional tuple of manually-specified extrema.

Returns:

Float: A float value representing the image entropy

`get_metadata()` _udf

Return metadata for the image. Signature:

get_metadata(self: Image)-> Json

`getbands()` _udf

Returns a tuple containing the name of each band in this image. For example, getbands on an RGB image returns (“R”, “G”, “B”). Signature:

getbands(self: Image)-> Json

Returns:

Json: A tuple containing band names.

`getbbox()` _udf

Calculates the bounding box of the non-zero regions in the image. Signature:

getbbox(
    self: Image,
    alpha_only: Bool
)-> Json

Parameters:

alpha_only (Bool): Optional flag, defaulting to True. If True and the image has an alpha channel, trim transparent pixels. Otherwise, trim pixels when all channels are zero. Keyword-only argument.

Returns:

Json: The bounding box is returned as a 4-tuple defining the left, upper, right, and lower pixel coordinate. See :ref:coordinate-system. If the image is completely empty, this method returns None.

`getchannel()` _udf

Returns an image containing a single channel of the source image. Signature:

getchannel(
    self: Image,
    channel: Int
)-> Image

Parameters:

channel (Int): What channel to return. Could be index (0 for “R” channel of “RGB”) or channel name (“A” for alpha channel of “RGBA”).

Returns:

Image: An image in “L” mode. .. versionadded:: 4.3.0

`getcolors()` _udf

Returns a list of colors used in this image. The colors will be in the image’s mode. For example, an RGB image will return a tuple of (red, green, blue) color values, and a P image will return the index of the color in the palette. Signature:

getcolors(
    self: Image,
    maxcolors: Int
)-> Json

Parameters:

maxcolors (Int): Maximum number of colors. If this number is exceeded, this method returns None. The default limit is 256 colors.

Returns:

Json: An unsorted list of (count, pixel) values.

`getextrema()` _udf

Gets the minimum and maximum pixel values for each band in the image. Signature:

getextrema(self: Image)-> Json

Returns:

Json: For a single-band image, a 2-tuple containing the minimum and maximum pixel value. For a multi-band image, a tuple containing one 2-tuple for each band.

`getpalette()` _udf

Returns the image palette as a list. Signature:

getpalette(
    self: Image,
    mode: Optional[String]
)-> Json

Parameters:

rawmode (Any): The mode in which to return the palette. None will return the palette in its current mode. .. versionadded:: 9.1.0

Returns:

Json: A list of color values [r, g, b, …], or None if the image has no palette.

`getpixel()` _udf

Return the pixel value at the given position. The position xy is a tuple containing the x and y coordinates. Equivalent to PIL.Image.Image.getpixel() Signature:

getpixel(
    self: Image,
    xy: Json
)-> Json

Parameters:

xy (Json): The coordinates, given as (x, y).

`getprojection()` _udf

Get projection to x and y axes Signature:

getprojection(self: Image)-> Json

Returns:

Json: Two sequences, indicating where there are non-zero pixels along the X-axis and the Y-axis, respectively.

`height()` _udf

Signature:

height(self: Image)-> Int

`histogram()` _udf

Returns a histogram for the image. The histogram is returned as a list of pixel counts, one for each pixel value in the source image. Counts are grouped into 256 bins for each band, even if the image has more than 8 bits per band. If the image has more than one band, the histograms for all bands are concatenated (for example, the histogram for an “RGB” image contains 768 values). A bilevel image (mode “1”) is treated as a grayscale (“L”) image by this method. If a mask is provided, the method returns a histogram for those parts of the image where the mask image is non-zero. The mask image must have the same size as the image, and be either a bi-level image (mode “1”) or a grayscale image (“L”). Signature:

histogram(
    self: Image,
    mask: Optional[Image],
    extrema: Optional[Json]
)-> Json

Parameters:

mask (Optional[Image]): An optional mask.
extrema (Optional[Json]): An optional tuple of manually-specified extrema.

Returns:

Json: A list containing pixel counts.

`mode()` _udf

Signature:

mode(self: Image)-> String

`point()` _udf

Map image pixels through a lookup table. Equivalent to PIL.Image.Image.point() Signature:

point(
    self: Image,
    lut: Json,
    mode: Optional[String]
)-> Image

Parameters:

lut (Json): A lookup table.

`quantize()` _udf

Convert the image to ‘P’ mode with the specified number of colors. Signature:

quantize(
    self: Image,
    colors: Int,
    method: Optional[Int],
    kmeans: Int,
    palette: Optional[Int],
    dither: Int
)-> Image

Parameters:

colors (Int): The desired number of colors, <= 256
method (Optional[Int]): Quantize.MEDIANCUT (median cut), Quantize.MAXCOVERAGE (maximum coverage), Quantize.FASTOCTREE (fast octree), Quantize.LIBIMAGEQUANT (libimagequant; check support using PIL.features.check_feature with feature="libimagequant"). By default, Quantize.MEDIANCUT will be used. The exception to this is RGBA images. Quantize.MEDIANCUT and Quantize.MAXCOVERAGE do not support RGBA images, so Quantize.FASTOCTREE is used by default instead.
kmeans (Int): Integer greater than or equal to zero.
palette (Optional[Int]): Quantize to the palette of given PIL.Image.Image.
dither (Int): Dithering method, used when converting from mode “RGB” to “P” or from “RGB” or “L” to “1”. Available methods are Dither.NONE or Dither.FLOYDSTEINBERG (default).

Returns:

Image: A new image

`reduce()` _udf

Returns a copy of the image reduced factor times. If the size of the image is not dividable by factor, the resulting size will be rounded up. Signature:

reduce(
    self: Image,
    factor: Int,
    box: Optional[Json]
)-> Image

Parameters:

factor (Int): A greater than 0 integer or tuple of two integers for width and height separately.
box (Optional[Json]): An optional 4-tuple of ints providing the source image region to be reduced. The values must be within (0, 0, width, height) rectangle. If omitted or None, the entire source is used.

`resize()` _udf

Return a resized copy of the image. The size parameter is a tuple containing the width and height of the new image. Equivalent to PIL.Image.Image.resize() Signature:

resize(
    self: Image,
    size: Json
)-> Image

`rotate()` _udf

Return a copy of the image rotated by the given angle. Equivalent to PIL.Image.Image.rotate() Signature:

rotate(
    self: Image,
    angle: Int
)-> Image

Parameters:

angle (Int): The angle to rotate the image, in degrees. Positive angles are counter-clockwise.

`transpose()` _udf

Transpose image (flip or rotate in 90 degree steps) Signature:

transpose(
    self: Image,
    method: Int
)-> Image

Parameters:

method (Int): One of :pyTranspose.FLIP_LEFT_RIGHT, :pyTranspose.FLIP_TOP_BOTTOM, :pyTranspose.ROTATE_90, :pyTranspose.ROTATE_180, :pyTranspose.ROTATE_270, :pyTranspose.TRANSPOSE or :pyTranspose.TRANSVERSE.

Returns:

Image: Returns a flipped or rotated copy of this image.

`width()` _udf

Signature:

width(self: Image)-> Int

SDK Reference

​UDFs

​alpha_composite() udf

​b64_encode() udf

​blend() udf

​composite() udf

​convert() udf

​crop() udf

​effect_spread() udf

​entropy() udf

​get_metadata() udf

​getbands() udf

​getbbox() udf

​getchannel() udf

​getcolors() udf

​getextrema() udf

​getpalette() udf

​getpixel() udf

​getprojection() udf

​height() udf

​histogram() udf

​mode() udf

​point() udf

​quantize() udf

​reduce() udf

​resize() udf

​rotate() udf

​transpose() udf

​width() udf

UDFs

`alpha_composite()` _udf

`b64_encode()` _udf

`blend()` _udf

`composite()` _udf

`convert()` _udf

`crop()` _udf

`effect_spread()` _udf

`entropy()` _udf

`get_metadata()` _udf

`getbands()` _udf

`getbbox()` _udf

`getchannel()` _udf

`getcolors()` _udf

`getextrema()` _udf

`getpalette()` _udf

`getpixel()` _udf

`getprojection()` _udf

`height()` _udf

`histogram()` _udf

`mode()` _udf

`point()` _udf

`quantize()` _udf

`reduce()` _udf

`resize()` _udf

`rotate()` _udf

`transpose()` _udf

`width()` _udf