extent for rasterImage angle

[mdsumner]

angle_extent <- function(dimension, extent = NULL, angle = 0){

  ## Adapted from rasterImageAdj in Ecfun by Spencer Graves
  ## https://CRAN.R-project.org/package=Ecfun
  imagePixels <- dimension
  if (is.null(extent)) extent <- c(0, dimension[1], 0, dimension[2])
  xleft <- extent[1]
  xright <- extent[2]
  ybottom <- extent[3]
  ytop <- extent[4]

  ##
  ## 2.  x, y pixels per inch
  ##
  imageUnits.x <- (xright-xleft)
  imageUnits.y <- (ytop-ybottom)
  #  2.2.   plot units per inch (we should just use the scale of extent/dimension)
  u <- par("usr")
  xyinches <-  c(u[2L] - u[1L], u[4L] - u[3L])/par("pin")
  #print(xyinches)
  #print(dimension / diff(extent)[c(1, 3)])

  #  2.3.  x, y pixels per inch in image region
  pixelsPerInch.x <- (imagePixels[1]*xyinches[1] /
                        as.numeric(imageUnits.x))
  pixelsPerInch.y <- (imagePixels[2]*xyinches[2] /
                        imageUnits.y)
  ##
  ## 3.  Shrink imageUnits to max(PixelsPerInch)
  ##
  maxPPI <- max(pixelsPerInch.x, pixelsPerInch.y)
  imageUAdj.x <- (imagePixels[1] * xyinches[1] / maxPPI)
  imageUAdj.y <- (imagePixels[2] * xyinches[2] / maxPPI)
  ##
  ## 4.  (dX, dY) = imageUnitsAdj/2
  ##              = half of the (width, height) in plotting units.
  ##
  dX <- imageUAdj.x/2
  dY <- imageUAdj.y/2
  # lower left = 45 degrees from center
  # Therefore, max deviation of a corner from the center:  at 45 degrees
  dX. <- dX*sqrt(2)
  dY. <- dY*sqrt(2)
  ##
  ## 5.  cntr = (xleft, ybottom) + imageUnits/2
  ##
  cntr.x <- (xleft+(imageUnits.x/2))
  cntr.y <- (ybottom+(imageUnits.y/2))
  ##
  ## 6.  (x, y) location of the nominal lower left corner
  ##     after rotation
  ##
  adj.x <- sin((angle-45)*pi/180)*dX.
  adj.y <- cos((angle-45)*pi/180)*dY.
  xleft0 <- (cntr.x + adj.x)
  xright0 <- (xleft0 + imageUAdj.x)
  ybottom0 <- (cntr.y - adj.y)
  ytop0 <- (ybottom0 + imageUAdj.y)

  c(xleft0, xright0, ybottom0, ytop0)
}


library(png)
img <- readPNG(system.file("img", "Rlogo.png", package="png"), T)

imrot <- function(x, extent = c(0, ncol(x), 0, nrow(x)), interpolate = FALSE, add = FALSE, angle = 0, ...) {

  if (!add) {
    plot.new()
    plot.window(xlim = extent[1:2], ylim = extent[3:4], asp = 1)
  }
  ## use of par in here means plot must already be set up
   extent <- angle_extent(dim(x), extent, angle = angle)

  rasterImage(x, extent[1], extent[3], extent[2], extent[4], interpolate = interpolate, angle = angle, ...)
  invisible(extent)
}


library(png)
img <- readPNG(system.file("img", "Rlogo.png", package="png"), T)
imrot(img)
imrot(img, angle = -90, add = TRUE)

should be able to unpick all the silly graphics device stuff and just use dimension and extent (and this possibly belongs in vaster not here)

[mdsumner]

good fun stuff

library(whatarelief)
ex <- c(-1, 1, -1, 1) * 1e6
img <- imagery(extent = ex, projection = "+proj=laea +lon_0=147 +lat_0=-42")
imrot(img, extent = ex, angle = -90 - 45)
imrot(img, extent = ex, add = T)

(couldn't figure out alpha for a good example ...)

[mdsumner]

alpha() drops dim

par(mfrow = c(1, 2), xpd = NA, mar = rep(0, 4))
library(whatarelief)
ex <- c(-1, 1, -1, 1) * 2e5
crs <- "+proj=laea +lon_0=147 +lat_0=-42 +type=crs"
cst <- coastline(extent = ex, projection = crs)
img <- imagery(extent = ex, projection = crs)

img2 <- img; img2[] <- scales::alpha(img2, 0.5)
imrot(img2, extent = ex, angle = -90 - 45)
lines(cst, col = "hotpink")
imrot(img, extent = ex, add = F)