Using the exif Command (with examples)

The exif command is a powerful tool for working with the EXIF information in JPEG files. It allows users to view and modify various attributes such as camera settings, thumbnail images, and metadata. In this article, we will explore several use cases of the exif command, providing code examples and explanations for each one.

Use Case 1: Show all recognized EXIF information in an image

exif path/to/image.jpg

Motivation: Sometimes, it is necessary to view all the EXIF information stored in an image file. This can be useful for understanding camera settings, date and time of capture, and other technical details. By using the exif command, we can easily access this information in a comprehensive format.

Explanation: The exif command is followed by the path to the image file, path/to/image.jpg, for which we want to display the EXIF information. This command will show all the recognized EXIF attributes of the specified image.

Example Output: The output will display a list of EXIF tags along with their corresponding values, providing a comprehensive overview of the image’s EXIF information.

Use Case 2: Show a table listing known EXIF tags and their existence in an image

exif --list-tags --no-fixup image.jpg

Motivation: Often, we need to know which EXIF tags exist in an image file. By using the exif command with the --list-tags option, we can obtain a table that lists all the known EXIF tags and whether each one exists in the specified image.

Explanation: In this use case, the --list-tags option is used to produce a table that displays the known EXIF tags. The --no-fixup option prevents the command from attempting to fix any formatting issues in the provided image file, ensuring that the output accurately reflects the existence of each tag.

Example Output: The output will be a table with two columns: the EXIF tag names and a “yes” or “no” value indicating whether each tag exists in the image.

Use Case 3: Extract the image thumbnail into a separate file

exif --extract-thumbnail --output=thumbnail.jpg image.jpg

Motivation: Thumbnails are small preview images that can be embedded within the original image file. Extracting a thumbnail can be useful for displaying a quick preview or for creating visually appealing representations of a collection of images. By using the exif command with the --extract-thumbnail option, we can easily extract the thumbnail from an image and save it as a separate file.

Explanation: The --extract-thumbnail option tells the exif command to extract and save the thumbnail image. The --output parameter specifies the name of the file into which the thumbnail image should be saved, in this case thumbnail.jpg. Lastly, the image.jpg argument represents the path to the original image file.

Example Output: The command will save the extracted thumbnail image as thumbnail.jpg, allowing you to view it separately from the original image.

Use Case 4: Show the raw contents of a specific EXIF tag in an image

exif --ifd=0 --tag=Model --machine-readable image.jpg

Motivation: Sometimes, we only need to retrieve the value of a specific EXIF tag for further processing or analysis. By using the exif command with the --ifd and --tag options, we can retrieve the raw contents of a particular tag. This can be helpful when scripting or automating tasks that require access to specific EXIF information.

Explanation: In this use case, the --ifd=0 option specifies which Image File Directory (IFD) contains the desired tag. The --tag=Model option specifies the tag we want to access, which in this example is the “Model” tag. The --machine-readable option formats the output in a machine-readable manner. Finally, image.jpg represents the path to the image file from which we want to retrieve the tag’s value.

Example Output: The output will be the raw contents of the “Model” tag, which typically describes the camera model that was used to capture the image.

Use Case 5: Change the value of an EXIF tag and save it to a new file

exif --output=new.jpg --ifd=0 --tag="Artist" --set-value="John Smith" --no-fixup image.jpg

Motivation: There may be instances where it is necessary to modify the values of certain EXIF tags. By using the exif command with the --set-value option, we can change the value of a specific tag and save the modified image to a new file. This can be useful for adding or updating metadata, such as the artist’s name or copyright information.

Explanation: In this use case, the --output option specifies the name of the file to which the modified image should be saved, in this case new.jpg. The --ifd=0 option specifies the IFD that contains the tag to be modified. The --tag="Artist" option defines the tag we want to change, which is the “Artist” tag in this example. The --set-value="John Smith" option assigns a new value, “John Smith”, to the “Artist” tag. The --no-fixup option ensures that the command does not attempt to fix any formatting issues in the provided image file, preserving the original structure.

Example Output: The modified image, with the updated “Artist” tag value, will be saved as new.jpg. This new file can be used to distribute the image with the updated EXIF information.