## 3 Experimental Results and Evaluations  
This section presents comparative evaluations of the proposed method and three conventional methods: iCAM06 [7], [PERSON]'s method [10], and [PERSON]'s method [11]. The experiments apply several publicly available HDRIs widely used in assessing tone mapping performance and the images captured under five standard illuminations (D, SWF, TL84, A, and UV). The several widely used HDRIs and the captured images under five illuminants are tone-mapped by the proposed method and the three conventional methods respectively and their resulting images are compared with each other. Figures 4-6 are the original HDRIs and their resulting images processed by tone mapping techniques of iCAM06 [7], [PERSON]'s method [10], [PERSON]'s method [11], and the proposed method. For each Figure, (a) shows an original HDRI and (b) shows its resulting image processed by the iCAM06 tone mapping method where its MATLAB codes are implemented and parameters are fixed as suggested in [7]. The contrast in the resulting image tone-mapped by iCAM06 has improved relative to that of its original image. However, the contrast is still low with the resulting image overall much darker. The reason is that the luminance factor is a model of adaptation to the changing illumination levels and the luminance adaptation has a sigmoidal relation used to compress the dynamic range. Therefore, as color shift in a given chromaticity moves the sigmodal curve to the left, the luminance factor likely decreases. Furthermore, iCAM06, one of color appearance models, produces several unwanted artifacts such as color or hue shift and color leakage due to the surround factor. (c) is the resulting image tone-mapped by [PERSON]'s method [10] which is implementation of the MATLAB  
codes according to [10]. By taking the 90 th percentile in a given luminance max value, [PERSON]'s method computes and chooses the maximum scene luminance such that the small but extremely bright region does not bias further computation. Hence, the contrast in the original image can no longer increase especially in the low contrast region of image. The resulting image makes some progress in terms of color leakage and color or hue shift problems, but it is still overall as dark as that of iCAM06. This is why the loss of detailed information takes place in the entire resulting image. (d) shows the resulting image processed by [PERSON]'s method [11]. [PERSON]'s method is designed to overcome the limitations of the iCAM06 and [PERSON]'s methods such as color leakage, color or hue shift, and an overall darker resulting image. Yet this method, which is based on the global tone mapping to reduce time cost, causes loss of detailed information in the overall resulting image after color correction. To address this problem and represent detailed information in the tone-mapped resulting image, an ICH-based tone mapping method is proposed, which has the strengths of image without noise, tolerance to image rotation, size variation, and more as described in the introduction section. (e) is the resulting image processed by the proposed method. The resulting image overall represents more detailed information and also its contrast markedly increases without color distortion such as color leakage and color or hue shift compared to those from the conventional methods, especially iCAM06 and [PERSON]'s method. As supporting evidence, other images are processed and compared in Figure 7.  
Figure 4: “Montreal_float_o935” images with (**a**) an original HDRI and resulting images of (**b**) iCAM06, (**c**) [PERSON]’s method, (**d**) [PERSON]’s method, and (**e**) the proposed method. Table 1 is a summary of comparative evaluation results of computational cost between iCAM06, [PERSON]'s method, [PERSON]'s method and the proposed method. The used computer consists of Intel (R) Core (TM) i7-6700 CPU @ 3.40 GHz 3.41 GHz and 16.0 GB RAM. The proposed method has a higher computational cost. It is noticeable that there is trade-off between computational cost and performance.