The correct answer is A. 2097152 bits.
The maximum entropy of an image is the entropy of the image with the most uniform distribution of probabilities. In this case, each of the 512 Ã 512 picture elements can take any of the 8 distinguishable intensity levels, so the probability of each intensity level is 1/8. The entropy of this image is then $H = -\sum_{i=1}^8 p_i \log p_i = -\frac{8}{8} \log \frac{8}{8} = 8 \log 8 = 2097152$ bits.
Option B is incorrect because it is the entropy of an image with a uniform distribution of probabilities, but the image in the question does not have a uniform distribution of probabilities.
Option C is incorrect because it is the entropy of an image with a non-uniform distribution of probabilities, but the image in the question does not have a non-uniform distribution of probabilities.
Option D is incorrect because it is the entropy of an image with a uniform distribution of probabilities, but the image in the question does not have a uniform distribution of probabilities.