magick: edges – R documentation

Become an expert in R — Interactive courses, Cheat Sheets, certificates and more!

edges

Edge / Line Detection

Description

Best results are obtained by finding edges with image_canny() and then performing Hough-line detection on the edge image.

Usage

image_edge(image, radius = 1)

image_canny(image, geometry = "0x1+10%+30%")

image_hough_draw(
  image,
  geometry = NULL,
  color = "red",
  bg = "transparent",
  size = 3,
  overlay = FALSE
)

image_hough_txt(image, geometry = NULL, format = c("mvg", "svg"))

Arguments

`image`	magick image object returned by `image_read()` or `image_graph()`
`radius`	edge size in pixels
`geometry`	geometry string, see details.
`color`	a valid color string such as `"navyblue"` or `"#000080"`. Use `"none"` for transparency.
`bg`	background color
`size`	size in points to draw the line
`overlay`	composite the drawing atop the input image. Only for `bg = 'transparent'`.
`format`	output format of the text, either `svg` or `mvg`

Details

For Hough-line detection, the geometry format is {W}x{H}+{threshold} defining the size and threshold of the filter used to find 'peaks' in the intermediate search image. For canny edge detection the format is {radius}x{sigma}+{lower%}+{upper%}. More details and examples are available at the imagemagick website.

Examples

if(magick_config()$version > "6.8.9"){
shape <- demo_image("shape_rectangle.gif")
rectangle <- image_canny(shape)
rectangle %>% image_hough_draw('5x5+20')
rectangle %>% image_hough_txt(format = 'svg') %>% cat()
}

magick

Advanced Graphics and Image-Processing in R

v2.7.2

MIT + file LICENSE

Authors

Jeroen Ooms [aut, cre] (<https://orcid.org/0000-0002-4035-0289>)

Initial release