image_type: Identify the type of an image using the magic value at the start of the file

Description

Currently works for png, jpeg and BMP images. Will seek to start of file if passed a connection. For details of magic values for files, see e.g. http://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files

Usage

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image_type(source, Verbose = FALSE)

Arguments

source

Path to file or connection

Verbose

Whether to write a message to console on failure (Default F)

Value

character value corresponding to standard file extension of image format (i.e. jpg, png, bmp) or NA_character_ on failure.

Examples

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jpegfile=system.file("img", "Rlogo.jpg", package="jpeg")
image_type(jpegfile)
jpeg_pretending_to_be_png=tempfile(fileext = '.png')
file.copy(jpegfile, jpeg_pretending_to_be_png)
image_type(jpeg_pretending_to_be_png)
unlink(jpeg_pretending_to_be_png)

Questions? Problems? Suggestions? or email at ian@mutexlabs.com.

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