slideview (version 0.2.1)

slideView: slideView

Description

Two images are overlaid and a slider is provided to interactively compare the two images in a before-after like fashion. img1 and img2 can either be two RasterLayers, two RasterBricks/Stacks or two character strings. In the latter case it is assumed that these point to .png images on the disk.

NOTE: In case you want to include multiple slideviews in one page in a Rmd or flexdashboard we highly recommend using package widgetframe. Also, make sure to use different image names and/or labels for each of the RasterLayers/Bricks/Stacks. Otherwise things will likely not work properly.

This is a modified implementation of http://bl.ocks.org/rfriberg/8327361

Usage

# S4 method for SpatRaster,SpatRaster
slideView(
  img1,
  img2,
  label1 = deparse(substitute(img1, env = parent.frame())),
  label2 = deparse(substitute(img2, env = parent.frame())),
  r = 1,
  g = 2,
  b = 3,
  col.regions = viridisLite::inferno(256),
  legend = TRUE,
  na.color = "#BEBEBE",
  maxpixels = 1e+07,
  sliderInfoCSS = list(),
  ...
)
# S4 method for Raster,Raster
slideView(
  img1,
  img2,
  label1 = deparse(substitute(img1, env = parent.frame())),
  label2 = deparse(substitute(img2, env = parent.frame())),
  ...
)
# S4 method for RasterStackBrick,RasterStackBrick
slideView(
  img1,
  img2,
  label1 = deparse(substitute(img1, env = parent.frame())),
  label2 = deparse(substitute(img2, env = parent.frame())),
  ...
)
# S4 method for Raster,RasterStackBrick
slideView(
  img1,
  img2,
  label1 = deparse(substitute(img1, env = parent.frame())),
  label2 = deparse(substitute(img2, env = parent.frame())),
  ...
)
# S4 method for RasterStackBrick,Raster
slideView(
  img1,
  img2,
  label1 = deparse(substitute(img1, env = parent.frame())),
  label2 = deparse(substitute(img2, env = parent.frame())),
  ...
)
# S4 method for character,character
slideView(
  img1,
  img2,
  label1 = deparse(substitute(img1, env = parent.frame())),
  label2 = deparse(substitute(img2, env = parent.frame())),
  sliderInfoCSS = list()
)
# S4 method for ANY
slideview(...)

Arguments

img1

a RasterStack/Brick, RasterLayer or path to a .png file

img2

a RasterStack/Brick, RasterLayer or path to a .png file

label1

slider label for img1 (defaults to object name)

label2

slider label for img2 (defaults to object name)

r

integer. Index of the Red channel, between 1 and nlayers(x)

g

integer. Index of the Green channel, between 1 and nlayers(x)

b

integer. Index of the Blue channel, between 1 and nlayers(x)

col.regions

color (palette).See levelplot for details.

legend

whether to plot legends for the two images (ignored for RatserStacks/*Bricks).

na.color

the color to be used for NA pixels

maxpixels

integer > 0. Maximum number of cells to use for the plot. If maxpixels < ncell(x), sampleRegular is used before plotting.

sliderInfoCSS

list of valid css key-value pairs for the slider info at the top of the window.

...

additional arguments passed on to respective functions.

color

the color palette to be used for visualising RasterLayers

Methods (by class)

• slideView(img1 = Raster, img2 = Raster): for RasterLayers

• slideView(img1 = RasterStackBrick, img2 = RasterStackBrick): for RasterStackBrick, RasterStackBrick

• slideView(img1 = Raster, img2 = RasterStackBrick): for RasterLayer, RasterStackBrick

• slideView(img1 = RasterStackBrick, img2 = Raster): for RasterStackBrick, RasterLayer

• slideView(img1 = character, img2 = character): for png files

• slideview(ANY): alias for ease of typing

Author

Tim Appelhans

Stephan Woellauer

Details

Compare two images trough interactive swiping overlay

For slideView a few keyboard shortcuts are defined:

• space - toggle antialiasing

• esc - zoom to layer extent

• enter - set zoom to 1

• ctrl - increase panning speed by 10

Examples

if (interactive()) {
### example taken from
### http://www.news.com.au/technology/environment/nasa-images-reveal-
### aral-sea-is-shrinking-before-our-eyes/story-e6frflp0-1227074133835

library(jpeg)
library(terra)

web_img2000 <- "http://cdn.newsapi.com.au/image/v1/68565a36c0fccb1bc43c09d96e8fb029"

jpg2000 <- readJPEG(readBin(web_img2000, "raw", 1e6))

img2000 <- rast(jpg2000)

web_img2013 <- "http://cdn.newsapi.com.au/image/v1/5707499d769db4b8ec76e8df61933f2a"

jpg2013 <- readJPEG(readBin(web_img2013, "raw", 1e6))

img2013 <- rast(jpg2013)

slideView(img2000, img2013, label1 = "before", label2 = "after", legend = FALSE)

## adjust layout of the info slider
slideView(
  img2000
  , img2013
  , sliderInfoCSS = list(
    "background-color" = "#00ffff"
    , "color" = "#ff00ff"
    , opacity = 0.8
    , "font-size" = "30px"
    , "font-family" = "courier"
  )
  , legend = FALSE
)

}