device function

Magick Graphics Device

Graphics device that produces a Magick image. Can either be used like a regular device for making plots, or alternatively via image_draw to open a device which draws onto an existing image using pixel coordinates. The latter is vectorized, i.e. drawing operations are applied to each frame in the image.

image_graph(
  width = 800,
  height = 600,
  bg = "white",
  pointsize = 12,
  res = 72,
  clip = TRUE,
  antialias = TRUE
)

image_draw(image, pointsize = 12, res = 72, antialias = TRUE, ...)

image_capture()

Arguments

• width: in pixels
• height: in pixels
• bg: background color
• pointsize: size of fonts
• res: resolution in pixels
• clip: enable clipping in the device. Because clipping can slow things down a lot, you can disable it if you don't need it.
• antialias: TRUE/FALSE: enables anti-aliasing for text and strokes
• image: an existing image on which to start drawing
• ...: additional device parameters passed to plot.window such as xlim, ylim, or mar.

Details

The device is a relatively recent feature of the package. It should support all operations but there might still be small inaccuracies. Also it is a bit slower than some of the other devices, in particular for rendering text and clipping. Hopefully this can be optimized in the next version.

By default image_draw sets all margins to 0 and uses graphics coordinates to match image size in pixels (width x height) where (0,0) is the top left corner. Note that this means the y axis increases from top to bottom which is the opposite of typical graphics coordinates. You can override all this by passing custom xlim, ylim or mar values to image_draw.

The image_capture function returns the current device as an image. This only works if the current device is a magick device or supports dev.capture .

Examples

# Regular image
frink <- image_read("https://jeroen.github.io/images/frink.png")

# Produce image using graphics device
fig <- image_graph(res = 96)
ggplot2::qplot(mpg, wt, data = mtcars, colour = cyl)
dev.off()

# Combine
out <- image_composite(fig, frink, offset = "+70+30")
print(out)

# Or paint over an existing image
img <- image_draw(frink)
rect(20, 20, 200, 100, border = "red", lty = "dashed", lwd = 5)
abline(h = 300, col = 'blue', lwd = '10', lty = "dotted")
text(10, 250, "Hoiven-Glaven", family = "monospace", cex = 4, srt = 90)
palette(rainbow(11, end = 0.9))
symbols(rep(200, 11), seq(0, 400, 40), circles = runif(11, 5, 35),
  bg = 1:11, inches = FALSE, add = TRUE)
dev.off()
print(img)

# Vectorized example with custom coordinates
earth <- image_read("https://jeroen.github.io/images/earth.gif")
img <- image_draw(earth, xlim = c(0,1), ylim = c(0,1))
rect(.1, .1, .9, .9, border = "red", lty = "dashed", lwd = 5)
text(.5, .9, "Our planet", cex = 3, col = "white")
dev.off()
print(img)

See Also

Other image: _index_, analysis, animation, attributes(), color, composite, defines, edges, editing, effects(), fx, geometry, morphology, ocr, options(), painting, segmentation, transform(), video