Image data is transposed between successively arranged first data points in a first image field and successively arranged second data points in a second image field by a method comprising: (1) successively specifying a first data point (i); (2) summing first control data indicative of a residue with second control data indicative of a constant value; (3.sub.1) if the result of the summation does not exceed a predetermined value, updating the first control data with the summation result and specifying a second data point (j) corresponding to the specified first data point, or (3.sub.2) if the result exceeds the predetermined value, subtracting it from the summation result to update the first control data with the residue, and specifying a second data point (j) which is shifted by one data point with respect to the specified first data point; (4) transferring the image data from the specified first data point to the specified second data point or from the specified second data point to the specified first data point depending on the relative size of the first and second image fields. The steps (1) to (4) are repeated until all the second data points are filled with the image data.