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Image Contrast Enhancement based Combined Techniques without Over-enhanced Noise


I.A.Humied, F.E.Z.Abou-Chadi, M.Z.Rashad


Vol. 13  No. 7  pp. 113-120


In order to enhance the contrast noisy images where the amplitudes of it histogram components are very high at one location on the gray scale and very small in the rest of the gray scale, conventional global contrast enhancement schemes over-equalize these images so that too bright or dark pixels are resulted and local contrast enhancement schemes produce unexpected discontinuities at the boundaries of the blocks or not fully automated. A new combined technique was presented for contrast enhancement these images. The new combined technique segments the original histogram into tow sub-histograms with reference to the location of the highest amplitude of the histogram components and equalizes the left sub-histogram using Histogram Equalization (HE) and the right using Fast Gray Level Grouping (FGLG). The final image is determined as the sum of the equalized images obtained by using the sub-histogram equalizations and the over-equalization effect is eliminated. Also the result image does not miss feature information in low density histogram region since it applied separating equalization. In the present paper, the effect of noise on the performance of this technique is investigated.


Contrast Enhancement, Histogram Equalization, Fast Gray-Level Grouping, Equalization Noisy Images.