expand_noncircular: Expand non-circular

In GastonMauroDiaz/rcaiman: CAnopy IMage ANalysis

Expand non-circular

Description

Expand a non-circular hemispherical photograph.

Usage

expand_noncircular(caim, z, zenith_colrow)

Arguments

caim	SpatRaster. The output of read_caim() or read_caim_raw().
z	SpatRaster built with zenith_image().
zenith_colrow	Numeric vector of length two. Raster coordinates of the zenith. See calc_zenith_colrow().

Value

An object of class SpatRaster that is the result of adding margins (NA pixels) to the argument caim. The zenith point depicted in the picture should be in the center of the image or very close to it.

See Also

Other Lens Functions: azimuth_image(), calc_diameter(), calc_relative_radius(), calc_zenith_colrow(), calibrate_lens(), crosscalibrate_lens(), extract_radiometry(), fisheye_to_equidistant(), fisheye_to_pano(), lens(), test_lens_coef(), zenith_image()

Examples

## Not run: 

# ====================================================================
# Non-circular fisheye images from a smartphone with an auxiliary Lens
# (also applicable to non-circular fisheye images from DSLR cameras)
# ====================================================================

path <- system.file("external/APC_0581.jpg", package = "rcaiman")
caim <- read_caim(path)
z <- zenith_image(2132/2,  c(0.7836, 0.1512, -0.1558))
a <- azimuth_image(z)
zenith_colrow <- c(1063, 771)/2
caim <- expand_noncircular(caim, z, zenith_colrow)
plot(caim$Blue, col = seq(0,1,1/255) %>% grey())
m <- !is.na(caim$Red) & !is.na(z)
plot(m, add = TRUE, alpha = 0.3, legend = FALSE)


# ============================
# Restricted view canopy photo
# ============================

path <- system.file("external/APC_0020.jpg", package = "rcaiman")
caim <- read_caim(path)
plot(caim)
caim <- normalize_minmax(caim)
diameter <- calc_diameter(lens(), sqrt(nrow(caim)^2 + ncol(caim)^2)/2, 90)
z <- zenith_image(diameter, lens())
caim <- expand_noncircular(caim, z, c(ncol(caim)/2, nrow(caim)/2))
m <- !is.na(caim$Red)
a <- azimuth_image(z)
caim[!m] <- 0

# Knowing from metadata that the diagonal FOV is 60.3 degrees and assuming
# central perspective projection, it is possible to build a lens function with
# radius relative to 30.15 degrees but declaring it as 90 degrees, but after
# generating the zenith image rescaling it accordingly. This is a workaround
# since central perspective cannot include the horizon.

theta <- seq(0, 30.15, 0.15) * pi/180
px <- tan(theta)/tan(30.15 * pi/180)
theta <- normalize_minmax(theta) * pi/2

fit <- lm(px ~ poly(theta, 3, raw = TRUE) - 1)
coef(fit) %>% round(3)
test_lens_coef(c(0.579, -0.009, 0.03))

z <- zenith_image(diameter, c(0.579, -0.009, 0.03))
rings_segmentation(z, 10) %>% plot()
z <- normalize_minmax(z, 0, 90) * 30.15

plot(caim$Blue, col = seq(0,1,1/255) %>% grey())
m <- !is.na(caim$Red) & !is.na(z)
plot(m, add = TRUE, alpha = 0.3, legend = FALSE)

## End(Not run)

GastonMauroDiaz/rcaiman documentation built on April 14, 2025, 9:39 a.m.