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Create a Gap-Free Thermal Image Montage

Source: R/visualization.r
plot_thermal_montage.Rd

Combines a list of 'BioThermR' objects into a single, high-resolution grid plot (montage). Unlike standard faceting, this function uses a custom integer-coordinate system to center each subject within a uniform grid cell, ensuring pixel-perfect alignment without the visual artifacts (white gaps) often seen in R raster plots.

Usage

plot_thermal_montage(
  img_list,
  ncol = NULL,
  padding = 10,
  palette = "inferno",
  text_color = "black",
  text_size = 4
)

Arguments

img_list

A list of 'BioThermR' objects (e.g., output from read_thermal_batch or roi_filter_interactive).

ncol

Integer. The number of columns in the grid. If NULL (default), it is automatically calculated based on the square root of the number of images to create a roughly square layout.

padding

Integer. The size of the whitespace gap (in pixels) between grid cells. Default is 10.

palette

String. The color palette to use (from 'viridis' package). Default is "inferno".

text_color

String. Color of the filename labels. Default is "black".

text_size

Integer. Font size for the filename labels. Default is 4.

Value

A ggplot object representing the combined montage.

Details

The function executes a two-pass algorithm:

  1. Scan Pass: Iterates through all objects to calculate the bounding box dimensions of the largest subject. This defines the uniform cell size for the grid.

  2. Layout Pass: Calculates the integer offsets required to center each smaller subject within the master cell. It merges all pixel data into a single master data frame.

The result is rendered using geom_tile(width=1, height=1) to guarantee continuous, gap-free visualization.

Examples

if (FALSE) { # \dontrun{
# Load a batch of images
batch <- read_thermal_batch("data/cohort_A")

# Create a montage with 4 columns
p <- plot_thermal_montage(batch, ncol = 4, padding = 20)

# Save the high-res result
ggsave("montage_cohort_A.png", p, width = 12, height = 10, dpi = 300)
} # }