Visual impact enhancement via image histogram smoothing and continuous intensity relocation

Image contrast enhancement is a fundamental pre-processing stage in applications requiring image processing operations. Among revenues of available approaches, histogram equalization is a popular and attractive candidate method to produce resultant images of increased contrast. However, images obtained from canonical histogram equalization frequently suffer from the accompanying artefacts and give rises to uncomfortable viewing particularly in homogeneous regions. In this work, the problem is tackled using the histogram matching concept where the intensity histogram of the input image is matched to its smoothed version for contrast enhancement. Furthermore, homogeneous pixel intensities are randomly perturbed in order to reduce undesirable artefacts. The resultant image intensities are thus distributed over the available range and an increased image contrast is derived. Satisfactory results are obtained from a collection of benchmark images captured under different conditions to verify the effectiveness of the proposed approach.

Figure optionsDownload as PowerPoint slideHighlights
► We studied methods for image contrast enhancement and causes of artefacts.
► A histogram smoothing and continuous distribution allocation approach is proposed.
► Target intensity distribution is obtained from smoothing the input image intensity.
► Pixel values are re-assigned into the continuous intensity distribution.
► Image contrast improved with better use of available intensity range.