Radiance HDR images are listed on the formats page as RAD. The IANA accepted image-vnd.radiance as an official mime type a few months ago. The default extension is .hdr. Depending on the primaries used for the image (RGB, XYZ), the extensions .rgbe and .xyze may also be used, but .hdr is by far the more common one: http://www.iana.org/assignments/media-types/image/vnd.radiance
The .rad extension is actually used for models/objects within Radiance.
The various Radiance file formats, including HDR are documented on filefmts.pdf on this page:
Just like in IM, GM only supports HDR via ra_ppm from the Radiance package. I know you guys are extremely busy with OpenMP support and other things (which is coming along superbly: I measured speed improvements of 500% on a dual-core machine), but would you consider native HDR support at some point in the future?
Many thanks for this excellent software of yours.
Thanks for the info.
Native HDR support would be nice but it should be implemented properly so that it does not penalize other uses of GraphicsMagick. For example, loading a FAX image as HDR would be obscene.
Not sure what you mean. ra_ppm converts the HDR to LDR, applying simple linear tone-mapping. It's a one-way street.
From the ra_ppm man page:
"Ra_ppm converts between RADIANCE and Poskanzer Portable Pixmap formats. The -g option specifies the exponent used in gamma correction; the default value is 2.2. An exponent of 1 turns gamma correction off. The -e option specifies an exposure compensation in f-stops (powers of two). Only integer stops are allowed, for efficiency."
By "native HDR" I thought that you were suggesting HDR support in GraphicsMagick similar to ImageMagick's build option for HDR.