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Image layer

Source: R/mark_image.R
mark_image.Rd

Places an image at each (x, y): the isotype / photo-scatter mark (Observable Plot Image). Sources are png/jpeg file paths, http(s) URLs, or pre-read raster arrays (e.g. via magick); arrays skip decoding entirely. A single size sets the image's larger dimension as a fraction of the panel and the aspect ratio is preserved (clip = "circle" crops to a disc).

Usage

mark_image(
  plot,
  mapping = NULL,
  data = NULL,
  position = NULL,
  ...,
  size = 0.05,
  clip = "rectangle",
  interpolate = TRUE,
  rasterize = FALSE,
  rasterize_dpi = 300,
  rasterize_dev = "cairo"
)

Arguments

plot

A plotit object

mapping

Optional aesthetics: x, y, src

data

Optional data for this layer

position

Position adjustment.

...

Other arguments passed to the internal layer constructor. Rotation (Observable Plot rotate) is a recorded extension position, not implemented.

size

Larger image dimension as a fraction of the panel (default 0.05).

clip

"rectangle" (default) or "circle" (crop to a disc).

interpolate

Pass smooth interpolation to the raster (default TRUE; FALSE keeps pixel edges crisp, useful for large-scale isotype tiles).

rasterize

If TRUE, rasterize via ggrastr::rasterise().

rasterize_dpi

DPI for rasterization (default 300).

rasterize_dev

Graphics device for rasterization (default "cairo").

Value

Modified plotit object

Details

Rows with NA or empty src are dropped. Images are decoded once per source and cached for the session. Like any glyph, an image that would extend past the data range is clipped by the panel: boundary placements should widen the scale limits (e.g. scale_x(limits = c(0, 4))).

References

Observable Plot: Plot.image (src channel, round clip, imageRendering)

AntV G2: image (via G2 mark extensions)

Examples

# build a small in-memory png, then scatter it
tmp_png <- tempfile(fileext = ".png")
png::writePNG(array(c(0.2, 0.4, 0.8), dim = c(1, 1, 3)), tmp_png)
df <- data.frame(x = c(1, 2), y = c(1, 2), src = tmp_png)
plotit(df, encode(x = x, y = y, src = src)) |>
  mark_image(size = 0.2)