针对一般缩小算法随着缩小比例降低,图像信息丢失愈发严重的现象,提出了一种基于映射图像子块的图像缩小加权平均算法.首先,根据缩小比例,求出缩小图像中每点映射在原始图像中的子块,然后,根据各子块,加权平均算出缩小图像中每点的像素值,从而达到缩小的目的.缩小后的图像具有较好的完整性,且算法简单、快速有效.实验结果表明,该算法与其他缩小算法相比,在保持图像完整性方面具一定的特点.最后,针对缩小后图像对比度偏低这一现象,提出了一种灰度拉伸的处理方法,并进行了实验对比,取得了较好效果.

A weighted averaging algorithm of image zooming-out based on image sub-block information is presented in this paper. This algorithm overcomes the shortcoming of some common algorithms of image zooming-out that will lead to image visible distortion. First, according to the scale-down proportion the sub-block of every pixel at zoomed-out image is obtained from original image, and then the value of every pixel can be calculated based on corresponding sub-block by the method of weighted averaging. In the process of zooming-out the whole image information is reserved to the greatest degree, and the image after zoomed-out shows good integrity. The algorithm is simple, effective and rapid. The experimental results show that the advantage is evident compared with the common algorithms especially at image integrity. But the contrast of the image is reduced. To solve this problem the paper advances an extension of gray-scale method to improve the quality of zoomed-out image in the end of the paper. The experiments have verified the effectivity of the algorithm in this paper.