Below is the original photograph with elementary adjustments involving contrast, sharpening, and white and black point adjustments and a more extremely manipulated version using Photoshop's paint daub component of the filter gallery. It still retains primarily its representational character, but bears comparison to an oil painting. In more extreme form, it could be made more abstract, or its colors exaggerated in the extreme. The question is at what point does it cease to be a photograph or even whether it does. There have been legal cases where manipulated photographs have been challenged on evidentiary grounds and may well be admitted where the proper foundation explaining the methodology of manipulation and its purpose has been satisfactorily explained.
In some ways, such manipulated photography may be returning to its pictorial branch, where photographs were posed to replicate classical notions of what constituted a good painting. Regardless, computers and the programs that run on them may be viewed as just another medium, just as paintings moved from tempera to oil and to a far broader mix of materials in use today.