(This app is not related to WhatsApp or WhatsApp Inc. in any way)
WhatsApp image optimizer is a simple tool to reorganzie your images after they have been messed up WhatsApp. This means that the images are not properly sorted by the date they have been taken at.
Why does this happen?
Whenever you send an image via WhatsApp, WhatsApp removes any unnecessary metadata from the image, including the date taken. The metadate that is affected by this is called Exif-Data(see below)
The removal of this data normally does not cause any problems as the phone gallery uses the file creation date information to sort the imagesd in your gallery. So the normal use does not encounter any issues. But in case of, for example, a user restoring a WhatsApp-Backup after switching to a new device, the file creation date changes to the date the backup is restored. This will cause all WhatsApp images to be shown as taken on the same day. This is the point when this app comes to your help. Using the file name, in which WhatsApp saves the date created of the image, we will recreate the date taken and save it into the images metadata. After the optimization process is done, all your images will be sorted properly again. THIS APP WILL NOT OVERRIDE IMAGES WHICH ALREADY CONTAIN EXIF DATA.

THE CREATOR OF THIS APP DOES NOT TAKE RESPONSIBILITY FOR ANY PROBLEMS CAUSED BY THIS APP DURING THE OPTIMIZATION PROCESS.

--- What is EXIF? ---
from Wikipedia:
"Exchangeable image file format (officially Exif, according to JEIDA/JEITA/CIPA specifications) is a standard that specifies the formats for images, sound, and ancillary tags used by digital cameras
The metadata tags defined in the Exif standard cover a broad spectrum:

- Date and time information. Digital cameras will record the current date and time and save this in the metadata.
- Camera settings. This includes static information such as the camera model and make, and information that varies with each image such as orientation (rotation), aperture, shutter speed, focal length, metering mode, and ISO speed information.
- A thumbnail for previewing the picture on the camera's LCD screen, in file managers, or in photo manipulation software.
- Descriptions
- Copyright information."