Data Compression

Exr-IO supports all default OpenEXR compression methods. This page provides an overview over the compression methods.


This compression method is a very good general purpose choice and is especially well suited for texture maps because it allows for fast file reading.


This compression method is similar to ZIP but compresses only one image row at a time.


PIZ compression works especially well for images with a lot of noise or film grain. Opening files is a bit slower than with ZIP but saving files is faster.


A very fast compression format that provides good results for large areas with identical colors. Results are worse for images with a lot of detail.


This compression method causes loss of data!

This format only stores 24 bits of the 32 bit data and has subsequently a significant loss of precision. This method is only applied when saving in FLOAT color depth. HALF and UINT remain unchanged.


This compression method causes loss of data!

This compression method only applies to images stored in HALF color depth. Blocks of 4×4 pixels are stored with using only 14 byte each (instead of the 32 byte they would normally need). Each block is compressed to the exact same size. Different images with the same dimensions require the same storage space regardless of image content.


This compression method causes loss of data!

A modified version of B44. If all pixels in a 4*4 block have the same color it will use only 3 instead of 14 byte.


This compression method causes loss of data!

This is a very efficient compression with an adjustable compression strength (The DWA compression level option). Higher levels reduce file size while introducing increasingly more loss of quality. The default value of 45 creates images that have no visible (but measurable) loss of color accuracy. Values of around 250 introduce slightly visible color distortion. High values over 1000 are not recommended because they introduce clearly visible compression artifacts into the image.


This compression method causes loss of data!

A variation of DWAA that compresses blocks of 256 rows at a time instead of 32 like DWAA.