This app allows you to re an image to whatever you like (with limitation), quickly and easily.
It is a really rer app. You can specify the output format using one of the following four units of measurement: pixels, millimeters, centimeters, inches. To preserve aspect ratio just tap on the chain icon between width and height input fields. Image Size gives you the option of saving, emailing, printing or sharing the final image.

Re your image in just four easy steps
1. Open an image or take a photo
2. Enter your desired output
3. Crop the image with your fingers using multitouch gestures
4. Save / print / send / share image
System Requirements:
Requirements: Android 8.0+

Home Page - https://play.google.com/store/apps/details?id=de.vsmedia.imagesize&hl=en