
Load in Photo Scissors on the Mac. Mark in green the part wanted. Mark in red what has to be removed. Check and make any adjustments where the program makes a mistake. Crop and save the rose as a PNG with a transparent background:

Pop that in Serif Affinity Designer. Flood fill the background with a dark colour. Tidy up any remaining small errors around the edges of the rose. Save the end result:

Total time taken about fifteen minutes.
The new title piccy was produced in Serif Affinity Designer while I was learning how to use layers and how to cut bits from photos and paste them in a new picture.