This paper introduces a unified coding algorithm for dithered image and text data. When a gray scale image is represented by binary pseudo‐half‐tone, various binary patterns representing the same gray scale are generated based on the degree of freedom in the dither matrix. Then one of the binary patterns is selected to represent the corresponding text data. The proposed algorithm permits approximately 70k bytes of text data to be embedded into a 256 × 256‐pixel image. It enables the transmission and handling of the mixture of image and text data without processing the two types of data separately.