photosort

There are two objectives for code found in this repository; first and formost, to facilitate my learning of Go, in addition I'm hoping to build a collection of utilities that help organise an ever growing folder of photos pulled off my phone.

Part 1 - Exif, the Exchangeable image format

Much of the data we use when sorting photos is stored as hidden meta-data within the image files, the most common format for this data is Exif. There are many existing utilities for reading and modifying this data, but in building my own I'm hoping to familiarise myself with using a couple of packages in the standard library, io and bufio.

The idea for this command line utility, exifls is to take a path to a set of images (.jpg only for now) and to list the data extracted from the images.

To build and run this utility against a sample set of images use the following commands from the root folder of the project.

go build -v ./cmd/...
./exifls ./sample_data/*

Sample output should look something similar to this.

2016/09/17 22:54:44 File: 2016-09-16 17.07.34.jpg
2016/09/17 22:54:44     Model : unknown
2016/09/17 22:54:44     Make : unknown
2016/09/17 22:54:44     XResolution : unknown
2016/09/17 22:54:44     YResolution : unknown
2016/09/17 22:54:44     ResolutionUnit : unknown
2016/09/17 22:54:44     Software : unknown
2016/09/17 22:54:44     DateTime : unknown
2016/09/17 22:54:44     YCbCrPositioning : unknown
2016/09/17 22:54:44     Exif IFD : unknown
2016/09/17 22:54:44     Orientation : unknown
2016/09/17 22:54:44     GPS IFD : unknown
2016/09/17 22:54:44 File: error_file
2016/09/17 22:54:44 Unable to parse image header: EOF
2016/09/17 22:54:44 File: random_file
2016/09/17 22:54:44 The image doesn't appear to be a JPEG. Unknown header found.

Approach

There is an article by Ben Johnson (@benbjohnson) on the Standard Package Layout that has been doing the rounds in the Go community. On first read, I didn't understand many of the things talked about. In building exifls I'm going to attempt to follow the package structure outlined in the article. Some other thoughts on my approach are:

• The file path will be passed as a command line argument
• Exif data will be listed to stdout
• Errors in parsing one file will not cause the pogram to crash
• Errors will be written to stderr

Limitations

• None of this works yet

References

• Exchangeable image file format for digital still cameras: Exif Version 2.2 (pdf)
• Exchangeable image file format for digital still cameras: Exif Version 2.3 (pdf
• Description of the Exif file format
• How is Exif info encoded