registerBand: Single Band-to-Band Registration (Translation)

In hyperbrick: Accessory Tools for Preprocessing Hyper-Spectral Images

Single Band-to-Band Registration (Translation)

Description

Hyperspectral image acquisition normaly causes spatial misalignment between the spectral bands (layers) due to both equipment (such as band-to-band recording delay) and external factors (e.g. sensor vibrations). In this case, a geometric correction is necessary for remote sensing applications such as combining/merging spectral bands. This function uses the HOG (Histogram of Oriented Gradient) descriptor in order to find the optimal translation (xy shift) on a 'slave' band to be spatially align with a 'master' (reference) band.

Usage

registerBand(slave, master, ncells = 24, orient = 8)

Arguments

slave	An object of class RasterLayer (from package raster).
master	An object of class RasterLayer (from package raster).
ncells	An integer giving the number of cells to compute the oriented gradients of the HOG descriptor. Default is 24. See OpenImageR::HOG().
orient	An integer giving the number of orientations to compute the oriented gradients of the HOG descriptor. Default is 8. See OpenImageR::HOG().

Details

The affine parameters are estimated using a general optimization algorithm. This function only estimates translation parameters. To register bands also with rotation fixes, please check registerBand3(). But this should be used carefully, as rotation affects the spatial dimensions.

Value

An object of the same classe as the input slave, with the fixed extent. An additional attribute called 'affine_pars' is stored, containing the shift in x and y, in the same unit as the spatial extent of the image.

See Also

OpenImageR::HOG(), registerBrick(), registerBand3()

Examples

# load an image
path <- system.file('exdata', 'obory.dat', package = 'hyperbrick')
dpath <- system.file('exdata', 'obory_dark.dat', package = 'hyperbrick')
im <- buildBrick(path, hFOV = 36.8, vFOV = 36.8, height = 45,
                ref_layer = 35, spectral_feature = 'radiance',
                dark_path = dpath)
print(im)

# check bands 11 (550 nm) and 35 (670 nm)
plot(im[[35]], col = gray.colors(20), asp = 0)
plot(im[[11]], add = TRUE, legend = FALSE,
    col = adjustcolor(heat.colors(20), 0.3))

# register band 11 to band 35
new11 <- registerBand(slave = im[[11]], master = im[[35]])
plot(im[[35]], col = gray.colors(20), asp = 0)
plot(new11, add = TRUE, legend = FALSE,
    col = adjustcolor(heat.colors(20), 0.3))

# see the xy shift on band 11
attr(new11, "affine_pars")

hyperbrick documentation built on April 1, 2022, 9:07 a.m.