# A Color Consistency Processing Method for HY-1C Images of Antarctica
## 4 Results and Discussion
### Multi-View Color Consistency Evaluation
#### 4.2.2 Quantitative Evaluation  
In order to evaluate the consistency between images objectively, we calculated the overall standard deviation of the three images in Figure 12. With the proposed method, the standard deviation of the images was smaller; the difference in the brightness and color was smaller; and the consistency was good. We also calculated the mean and histogram similarity of the two parts on either side of the mosaic line in each image. If the contents of the two sides were similar, the mean values and the distribution of the histogram should showed small differences. The histogram similarity was calculated as follows:  
\[r(H_{1},H_{2})=\frac{\sum_{c}(H_{1}(c)-\overline{H_{1}})(H_{2}(c)-\overline{H_ {2}})}{\sqrt{\sum_{c}(H_{1}(c)-\overline{H_{1}})^{2}\sum_{c}(H_{2}(c)-\overline{ H_{2}})}}, \tag{28}\]  
\[\overline{H_{k}}=\frac{1}{N}\sum_{J}H_{k}(J), \tag{29}\]  
where \(H_{1}\) and \(H_{2}\) are the histograms of the two parts (different sides of the mosaic line); \(N\) is the bin number of the image, which was set to \(8\times 8\times 8=512\); \(c\) is the pixel value; \(H(c)\) is the number of pixels with a value \(c\). The background part did not participate in the calculation. The statistical results are shown in Figure 14.  
Figure 13: The details of the mosaic boundaries with (**a**) the original images, (**b**) the Wallis method, and (**c**) the proposed method.  
From the statistical results, it is shown in Figure 14a that the value of the standard deviation for the Wallis method was increased, while the value for the proposed method was greatly reduced. In the details of the images in Figure 14b, the standard deviation of the results of the proposed method was also lower than that of the original images, which illustrated that the proposed approach obtained results with a more concentrated color and brightness distribution. In terms of the details, the upper part and lower part of the result of the proposed method had a smaller mean difference and higher histogram similarity in Figure 14c,d. This was consistent with the subjective view that the two parts should have similar hues and brightness. Overall, the experimental results confirmed that the proposed method obtained good multi-view color consistency for the mosaic preprocessing of HY-IC images of Antarctica.  
Figure 14: Statistical results for the color consistency processing between images. (**a**) The standard deviation values of the mosaic results of the original images, the Wallis method results, and the results of the proposed method. (**b**) The standard deviation values of the mosaic results of the details of the original images and the details of the results of the proposed method. (**c**) The mean values and the difference values of the upper and lower part of the details of the original images and the details of the results of the proposed method. (**d**) The histogram similarity values between the upper part and the lower part of the mosaic result of the details of the original images and the mosaic result of the details of the proposed method.