Interactive seed selection for SNIC segmentation

Collect seed points interactively by clicking on the image. Each left-click adds a new seed; pressing ESC ends the session. After each click, SNIC segmentation is recomputed and plotted for visual feedback. This is intended for exploratory and fine-tuning workflows, where automatic seeding may not be ideal.

Usage

snic_grid_manual(
  x,
  seeds = NULL,
  ...,
  snic_args = list(compactness = 0.5),
  snic_plot_args = list(stretch = "lin", seeds_plot_args = list(pch = 4, col = "#FFFF00",
    cex = 1), seg_plot_args = list(border = "#FFFF00", col = NA, lwd = 0.4))
)

Arguments

x

A SpatRaster object with a valid spatial reference and extent. Mouse clicks are interpreted in map coordinates.

seeds

Optional existing seed set to display and extend. If pixel coordinates are supplied, they are internally converted. If NULL, the seed set is initialized empty and populated interactively.

...

Arguments forwarded to snic_plot for display control. These may include band, r, g, b, stretch, seeds_plot_args, or seg_plot_args.

snic_args

A list of arguments passed to snic, such as compactness.

snic_plot_args

A list of display modifiers forwarded to snic_plot when rendering the preview.

Value

A two-column data frame of seed coordinates. If x lacks a CRS the result is always pixel indices (r, c). When x has a CRS:

• If seeds were supplied, their coordinate system is preserved in the output.

• Otherwise the result is expressed as (lat, lon) in EPSG:4326.

The output can be passed directly to snic.

Details

After each new seed is placed interactively, segmentation is recomputed to provide immediate feedback on how the seed placement affects clustering.

See also

snic, snic_grid, snic_animation.

Examples

if (interactive() && requireNamespace("terra", quietly = TRUE)) {
    tiff_dir <- system.file("demo-geotiff",
        package = "snic",
        mustWork = TRUE
    )
    files <- file.path(
        tiff_dir,
        c(
            "S2_20LMR_B02_20220630.tif",
            "S2_20LMR_B04_20220630.tif",
            "S2_20LMR_B08_20220630.tif",
            "S2_20LMR_B12_20220630.tif"
        )
    )
    s2 <- terra::aggregate(terra::rast(files), fact = 8)

    seeds <- snic_grid_manual(
        s2,
        snic_args = list(compactness = 0.1),
        snic_plot_args = list(r = 4, g = 3, b = 1)
    )

    seg <- snic(s2, seeds, compactness = 0.1)

    snic_plot(
        s2,
        r = 4, g = 3, b = 1,
        stretch = "lin",
        seeds = seeds,
        seg = seg
    )
}