imgrayscaling实现灰度线性变换，具有很好的兼容性，它可以处理灰度、彩色、索引不同类型，以及double、uint8等不同存储方式的图像。-imgrayscaling achieve gray-scale linear transformation, with good compatibility, it can handle grayscale, color, index of different types, as well as double, uint8 images of d