Topaz Photo AI

After save as Preserved input format.
That photo can not share to Facebook because it is .png format.

  1. Facebook post image size.

You can upload files in any of the following formats: JPEG, BMP, PNG, GIF, or TIFF. If you’re uploading a PNG file, it’s best to keep the file size below 1MB. PNG files larger than 1MB may appear pixelated.

Of course FB accepts PNG files. But I don’t advise doing that because FB converts them to JPG and makes them a massacre. I recommend converting the file to JPG format yourself in around 95% quality, for example with XnView, where you have full control over the compression parameters.