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Verify Image File Integrity

Source: R/general_check_image.R
check_image.Rd

This function checks the integrity of image files (JPEG, PNG, TIFF, and PDF) by validating their existence, size, extension, and type using the file bash command. It confirms that the file has a recognized image or PDF format and non-zero dimensions (or page count for PDFs).

Usage

check_image(file, warning = TRUE)

Arguments

file

A character string specifying the path to the image file.

warning

A logical value indicating whether to issue warnings for invalid files (e.g., empty files, unrecognized extensions). Defaults to TRUE.

Value

A logical value: TRUE if the file is a valid image or PDF, FALSE otherwise.

Details

The function performs the following checks:

  • Validates that file is a single character string.

  • Ensures the file exists and is not a directory.

  • Checks that the file size is non-zero, issuing a warning if empty (when warning = TRUE).

  • Verifies the file extension is one of jpg, jpeg, png, tif, tiff, or pdf, issuing a warning if not (when warning = TRUE).

  • Uses the file bash command to confirm the file type and extract metadata (e.g., dimensions for images, page count for PDFs). The file is considered valid if it matches the expected type and has positive dimensions (or page count). The file command must be available on the system.

Author

Ahmed El-Gabbas

Examples

# Load required packages
ecokit::load_packages(fs)

# Create a temporary directory for test files
temp_dir <- fs::dir_create(fs::path_temp("image_test"))

# --------------------------------------------

# Valid image files

# jpeg
jpeg_path <- fs::path(temp_dir, "valid_image.jpg")
grDevices::jpeg(
  filename = jpeg_path, width = 6, height = 6, units = "cm", res = 200)
plot(1:10, 1:10, main = "Valid Image")
invisible(grDevices::dev.off())
check_image(jpeg_path)
#> [1] TRUE

# png
png_path <- fs::path(temp_dir, "valid_image.png")
png(
  filename = png_path, width = 6, height = 6, units = "cm", res = 200)
plot(1:10, 1:10, main = "Valid Image")
invisible(grDevices::dev.off())
check_image(png_path)
#> [1] TRUE


# tiff
tiff_path <- fs::path(temp_dir, "valid_image.tiff")
tiff(
  filename = tiff_path, width = 6, height = 6, units = "cm", res = 200)
plot(1:10, 1:10, main = "Valid Image")
invisible(grDevices::dev.off())
check_image(tiff_path)
#> [1] TRUE

# pdf
pdf_path <- fs::path(temp_dir, "valid_document.pdf")
grDevices::pdf(file = pdf_path, width = 6, height = 6)
plot(1:10, 1:10, main = "Valid Document")
invisible(grDevices::dev.off())
check_image(pdf_path)
#> [1] TRUE

# --------------------------------------------

# Corrupted image file

corrupt_path <- fs::path(temp_dir, "corrupt_image.jpg")
fs::file_create(corrupt_path)
writeBin(charToRaw("This is not an image"), corrupt_path)
check_image(corrupt_path)
#> [1] FALSE

corrupt_pdf_path <- fs::path(temp_dir, "valid_document.pdf")
grDevices::pdf(file = corrupt_pdf_path, width = 6, height = 6)
invisible(grDevices::dev.off())
check_image(corrupt_pdf_path)
#> [1] FALSE

# --------------------------------------------

# Non-image file

text_path <- fs::path(temp_dir, "not_an_image.txt")
fs::file_create(text_path)
writeLines("This is a text file", text_path)

check_image(text_path)
#> Warning: The file extension 'txt' is not a supported image format (JPEG, PNG, TIFF, PDF).
#> File: /tmp/RtmpCMUlEq/image_test/not_an_image.txt
#> [1] FALSE
check_image(text_path, warning = FALSE)
#> [1] FALSE

# --------------------------------------------

# Nonexistent file

nonexistent_path <- fs::path(temp_dir, "nonexistent_image.jpg")
check_image(nonexistent_path)
#> Warning: The file '/tmp/RtmpCMUlEq/image_test/nonexistent_image.jpg' does not exist.
#> [1] FALSE

check_image(temp_dir)
#> Warning: Input `file` '/tmp/RtmpCMUlEq/image_test' is a directory.
#> [1] FALSE

# --------------------------------------------

# Clean up
fs::dir_delete(temp_dir)