BMP图按位提取工具。可以打开任意一幅位图，只保留其图像区中的某几位，其余用0或1填充，得到新的图像并保存。-BMP map extract tool by bit. Any one can open a bitmap, only retain the image area of a few, the rest filled with 0 or 1, get new image and save.

对图像进行行列变换的图像加密算法 容易看懂 适合初学者-The ranks of the image transform image encryption algorithm easier to understand for beginners