Frequently Asked Questions




Q: What is a Lossless Date Stamp?

A: JPEG is a lossy image compression format. So if a software de-compresses the entire jpeg file to pixels to put the date stamp and re-compresses it to back to the jpeg format there will be minor differences at the pixel level in the entire image though you have added a date stamp only in a corner. Jambula is a specialized software that uses Jpegtran to extract and add the date stamp only in the small rectangular area required and then drops back the stamped section onto the original image. So the pixels outside the stamped area are exactly the same thus preserving the original image quality.

Q: Where does Jambula get the Date/Time info from?

A: It gets it from Meta Data stored in the jpeg files by digital cameras called EXIF. In case the EXIF header is missing Jambula stamps the Last Modified Time of the File

Q: Since the picture date and time is already there in the header is it required to add a Date Stamp to my photos?

A: It is good to have the original image without any water mark. However it is useful to create a Date Stamped copy of all or selected pictures for uses like taking prints and showing in a digital photo frame.


Q: Sometimes all files do not get stamped. How can I find out the omitted files.

A: Sometimes some files do not get date stamped because of errors. It is not possible to find out the missing files and the error from the UI. However you can run jambula with the -cmd option from a command prompt to see the console logs in Windows. The console logs are shown on the terminal in Linux and Mac.

Q: Can I stamp other info like File Name, Focal Length, Exposure, Flash etc.

A: No currently only Title and Comment are supported. However it might be possible to hack the config/commentTags.json in the distribution and fake some of these fields as title or comment.

Copyright © 2016, Suresh Mahalingam