“Precompressed” tiles

See first an overview of what precompressed tiles are and which formats support them.

This feature is primarily exposed in the bfconvert command, using the -precompressed option. When the -precompressed option is used, best results are obtained by:

  • using the -noflat option

  • not using the -compression option (this can work, but may force tile recompression)

  • not using the -tilex or -tiley options (this can work, but may force tile recompression)

There are several advantages to converting using the “precompressed” feature for formats that support it:

  • faster tile read and write times, as no tile compression/decompression needs to be performed

  • no change in compression quality

  • very little change in file sizes between input and output data

There are also a few disadvantages:

  • tile sizes cannot be changed during conversion

  • compression type cannot be changed during conversion

  • input and output format must support same compression type and tile size

  • the input format must have precompressed tile reading support (see the list of supported readers)

  • the output format must have precompressed tile writing support (see the list of supported writers)

  • command-line tools other than bfconvert do not currently make use of the precompressed tile API

For additional discussion of the “precompressed” tiles feature, see: