ZScaleMapping¶

class lsst.afw.display.ZScaleMapping(image, nSamples=1000, contrast=0.25)¶

A mapping for a linear stretch chosen by the zscale algorithm (preserving colours independent of brightness)

x = (I - minimum)/range

Parameters:	image Image whose parameters are desired nSamples : `int` The number of samples to use to estimate the zscale parameters contrast : `float`

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)