A Draft.ImageInfo object is used to specify on write and retrieve on read the image’s compression, quality, tile size and Timecode, when applicable.

Implementation Details

Besides the image’s channel data type described in the section Image File Channel Map in Concepts, other image saving settings can be controlled. Unlike the file channel map, those saving settings are not associated with a Draft.Image but with a Draft.ImageInfo. An ImageInfo stores those saving settings using the four properties: compression, quality, tileSize and timecode.

To specify the saving settings, you can simply set those properties in an ImageInfo and pass that ImageInfo as an additional parameter in the function WriteToFile().

To retrieve the saving settings, you can pass an ImageInfo as an additional parameter in the function ReadFromFile() and the fields in ImageInfo will be automatically populated. Those fields can then be easily queried.

Valid Compression Values

Valid values for compression are summarized in the following table.

File Format Valid compression
EXR ‘none’, ‘rle’, ‘zip’, ‘zips’, ‘piz’, ‘pxr24’, ‘b44’, ‘b44a’, ‘dwaa’ and ‘dwab’
GIF ‘lzw’
HDR ‘rle’
JPEG/JPG ‘jpeg’
PNG ‘zip’
TGA ‘none’ and ‘rle’
TIF/TIFF ‘none’, ‘jpeg’, ‘lzw’, ‘rle’ and ‘zip’

The property compression defaults to ‘default’ which corresponds to the file format default.

Valid quality values are integer value in the range [0..100]. The property quality defaults to None and is only valid for format EXR and JPEG/JPG.

Note that the mapping between Draft and OpenEXR DWA quality is done using an exponential regression to fit the three points proposed by Karl Rasche (creator of DWA). See:

Valid tileSize values are tuples of size 2 of strictly positive integers. The property tileSize default to None which corresponds to non-tiled image and is only valid for the file format EXR.

Please, consult the section Timecode in Concepts for valid timecodes values.