  A low-light image enhancement is a highly demanded image processing
technique, especially for consumer digital cameras and cameras on mobile
phones. In this paper, a gradient-based low-light image enhancement algorithm
is proposed. The key is to enhance the gradients of dark region, because the
gradients are more sensitive for human visual system than absolute values. In
addition, we involve the intensity-range constraints for the image integration.
By using the intensity-range constraints, we can integrate the output image
with enhanced gradients preserving the given gradient information while
enforcing the intensity range of the output image within a certain intensity
range. Experiments demonstrate that the proposed gradient-based low-light image
enhancement can effectively enhance the low-light images.
