[Gabrielle]

On PC I use paint.net to reduce the resolution of the photo, save it as jpg and if necessary degrade the quality to be below 500kb.

With a Smartphone you have to find an app that does the same thing.

John (Jean)

The easiest way to it, is to upload the image to a site which you can alter the dimensions, bit rate and type of file. I recommend using jpeg. Bmp files can be large, as they arent compress very well