There was a similar trick used for compressing game backgrounds in Commodore 64 games.
The compressor would create a special font (C64 "charsets" are 8x8 pixels), and slice the picture into 8x8 tiles where each block corresponds to an ASCII character. Although C64's hires resolution was 320x200 (160x200 in multicolor mode), because of repeating blocks it would usually end up using less than 256 characters. The actual background would then be drawn using those characters with the special font. There is no eager decompression involved.
The compressor would create a special font (C64 "charsets" are 8x8 pixels), and slice the picture into 8x8 tiles where each block corresponds to an ASCII character. Although C64's hires resolution was 320x200 (160x200 in multicolor mode), because of repeating blocks it would usually end up using less than 256 characters. The actual background would then be drawn using those characters with the special font. There is no eager decompression involved.