AsinhZScaleMapping

class lsst.afw.display.AsinhZScaleMapping(image, Q=8, pedestal=None)

Bases: lsst.afw.display.AsinhMapping

A mapping for an asinh stretch, estimating the linear stretch by zscale

x = asinh(Q (I - z1)/(z2 - z1))/Q

Parameters:

image

The image to analyse, or a list of 3 images to be converted to an intensity image

Q : int

The asinh softening parameter

pedestal : float or sequence of float, optional

The value, or array of 3 values, to subtract from the images

N.b. pedestal, if not None, is removed from the images when calculating the zscale stretch, and added back into Mapping.minimum[]

See also

AsinhMapping

Methods Summary

intensity(imageR, imageG, imageB)	Return the total intensity from the red, blue, and green intensities
makeRgbImage([imageR, imageG, imageB, …])	Convert 3 arrays, imageR, imageG, and imageB into a numpy RGB image
mapIntensityToUint8(intensity)	Return an array which, when multiplied by an image, returns that image mapped to the range of a uint8, [0, 255] (but not converted to uint8)

Methods Documentation

intensity(imageR, imageG, imageB)

Return the total intensity from the red, blue, and green intensities

Notes

This is a naive computation, and may be overridden by subclasses

makeRgbImage(imageR=None, imageG=None, imageB=None, xSize=None, ySize=None, rescaleFactor=None)

Convert 3 arrays, imageR, imageG, and imageB into a numpy RGB image

imageR : lsst.afw.image.Image or numpy.ndarray, (Nx, Ny)

Image to map to red (if None, use the image passed to the ctor)

imageG : lsst.afw.image.Image or numpy.ndarray, (Nx, Ny), optional

Image to map to green (if None, use imageR)

imageB : lsst.afw.image.Image or numpy.ndarray, (Nx, Ny), optional

Image to map to blue (if None, use imageR)

xSize : int, optional

Desired width of RGB image. If ySize is None, preserve aspect ratio

ySize : int, optional

Desired height of RGB image

rescaleFactor : float, optional

Make size of output image rescaleFactor*size of the input image

mapIntensityToUint8(intensity)

Return an array which, when multiplied by an image, returns that image mapped to the range of a uint8, [0, 255] (but not converted to uint8)

The intensity is assumed to have had minimum subtracted (as that can be done per-band)