An example embodiment may involve obtaining (i) an a×b attribute macro-cell, and (ii) a×b pixel macro-cells for each of a luminance plane, a first color plane, and a second color plane of an input image. The a×b pixel macro-cells may each contain 4 non-overlapping m×n pixel cells. The example embodiment may also involve determining 4 attribute-plane output values that represent the 4 non-overlapping m×n attribute cells, 1 to 4 luminance-plane output values that represent the a×b pixel macro-cell of the luminance plane, a first color-plane output value to represent the a×b pixel macro-cell of the first color plane, and a second color-plane output value to represent the a×b pixel macro-cell of the second color plane. The example embodiment may further involve writing an interleaved representation of the output values to a computer-readable output medium.