# X-ray Image Enhancement Based on Adaptive Gradient Domain Guided Image Filtering
## 4 Experimental Results
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **AG** & **H** & **ALC** & **SF** & **MG** \\ \hline McCann & 6.3692 & 7.6512 & 0.4712 & 10.9025 & 5.3625 \\ \hline RLBHE & 3.8103 & 6.9851 & 0.1225 & 6.2601 & 3.2202 \\ \hline RESIHE & 6.5199 & 7.6378 & 0.5963 & 10.9708 & 5.5011 \\ \hline TBCCSR & 7.7360 & 6.4739 & 0.9298 & 13.2405 & 6.5689 \\ \hline GDGIF & 8.0281 & 7.6542 & 0.9125 & 12.7309 & 6.7635 \\ \hline SMIPC & 6.2976 & 7.7175 & 0.6225 & 10.8886 & 5.3096 \\ \hline FuzzyII & 6.8285 & 7.4938 & 0.7476 & 11.8243 & 5.7914 \\ \hline Proposed & 10.3812 & 7.7013 & 1.4911 & 17.6055 & 8.8347 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The metric data of eight methods on X-ray image 1. Figure 2 shows the enhancement images of eight approaches experimented on X-ray image 2. Figure 2a shows the original X-ray image 2; Figure 2b is the result obtained by McCann--the contrast is low; Figure 2c presents the image enhanced by RLBHE--it does not achieve the effect of image enhancement, the image is too dark, and we can hardly get effective information from it; Figure 2d shows the result achieved by RESIRE--the effect of enhancement is not obvious; the images obtained by TBCSSR and FuzzyII are shown in Figures 2e and 2h, respectively. The contrast and the definition are low; Figures 2f and 2g show the results enhanced by GDGIF and SMIPC, respectively. The two images appear to have noise amplification. The result enhanced by the proposed algorithm is shown in Figure 2i--it reveals more image details and suppresses the noise. Bone information can be clearly obtained, which is helpful for doctors to diagnose. Table 2 is the evaluation index values of various methods in Figure 2. Except for H, our method is the best for other indicators. Figure 1: Comparison on X-ray image 1. (**a**) Original image; (**b**) McCann; (**c**) RLBHE; (**d**) RESIRE; (**e**) TBCSSR; (**f**) GDGIF; (**g**) SMIPC; (**h**) FuzzyII; (**i**) Proposed method. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **AG** & **H** & **ALC** & **SF** & **MG** \\ \hline McCann & 5.1281 & 7.4184 & 0.4665 & 12.5124 & 4.3633 \\ \hline RLBHE & 2.3495 & 6.0856 & 0.4310 & 6.7396 & 1.9789 \\ \hline RESIHE & 5.3859 & 7.1987 & 0.8933 & 13.3430 & 4.6023 \\ \hline TBCSSR & 5.3069 & 5.8050 & 1.2322 & 15.4840 & 4.5424 \\ \hline GDGIF & 6.9491 & 7.3688 & 1.3773 & 15.1471 & 5.8878 \\ \hline SMIPC & 5.2131 & 7.2701 & 0.8633 & 13.1491 & 4.4709 \\ \hline FuzzyII & 5.1984 & 7.0568 & 0.9300 & 14.1044 & 4.4660 \\ \hline Proposed & 7.5621 & 7.1856 & 1.8069 & 20.1044 & 6.5175 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The metric data of eight methods on X-ray image 2. Figure 2: Comparison on X-ray image 2. (**a**) Original image; (**b**) McCann; (**c**) RLBHE; (**d**) RESIHE; (**e**) TBCSSR; (**f**) GDGIF; (**g**) SMIPC; (**h**) FuzzyII; (**i**) Proposed method. Figure 3 shows the enhancement images of eight approaches experimented on X-ray image 3. Figure 3a shows the original X-ray image 3; Figure 3b shows the enhancement result computed by McCann--the image is too bright, resulting in the loss of image details; Figure 3c shows the image achieved by RLBHE--the image is too dark, the useful information is lost; Figure 3d depicts the result achieved by RESIHE--the effect of enhancement is not obvious; Figure 3e shows the image obtained by TBCSSR--the image becomes gray and it is difficult to observe the details; the results enhanced by GDGIF, SMIPC, and FuzzyII are shown in Figure 3f-h, respectively. They are very similar and the enhancement effect is not prominent. Our method is depicted in Figure 3i--it performs well, and more details are retained. Table 3 shows the evaluation index values of the methods in Figure 3. Our method obtains the best values for all the metrics. Figure 3: Comparison on X-ray image 3. (**a**) Original image; (**b**) McCann; (**c**) RLBHE; (**d**) RESIHE; (**e**) TBCSSR; (**f**) GDGIF; (**g**) SMIPC; (**h**) FuzzyII; (i) Proposed method. Figure 4 shows the enhancement images of eight approaches experimented on X-ray image 4.