Starting from the definition for a set of ordered elements, the area histogram has been extended to analysis gray -level image through the notions of image thresholding decomposition and level sets.

从为有序元素集定义面积直方图出发，通过图像的阀值分解及层集等概念，面积直方图被扩展到了灰度图像。

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Therefore, when applying a thresholding algorithm to an image, we generally assume that the background and target in that image occupy different gray level zone.

传统的阈值化算法仅仅使用像素点的灰度级信息，因而要求图像中的目标和背景在灰度级上是可分的。

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It solves the difficulty in binarization due to gray level confusion between local background and image by automatic thresholding with local image enhancement.

通过局部图像增强的自动阈值选择等手段，解决视网膜血管图像与局部背景之间因灰度混同所造成的二值化困难；

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