Well, i've selected bmp since it requires nearly no processing time (one has just to add a header and to inverse the raws order) and, hence, relatively fast (~0.15-0.17s @ K2 and K3). The bmp-size is certainly too large, but one may compress it by gzip- or bzip2-compressors available in any Linux.
My first attempts to convert 4bpp to common 8bpp for 600x800 pixels took muuuch more CPU-time (~2.5s @ K3). I suspect that png-compression would continue even longer (especially for 824x1200 KDX).
But png-output test is nevertheless "versuchswert"
