Logluv TIFF is an encoding used for storing high-dynamic-range imaging data inside a TIFF image. It was originally developed by Greg Ward for storing HDR-output of his Radiance-photonmapper at a time where storage space was a crucial factor. Its implementation in TIFF also allowed the combination with image-compression algorithms without great programming effort. As such it has to be considered a smart compromise between the imposed limitations. It is slightly related to RGBE, the most successful HDRI storage format, an earlier invention of Greg Ward.
Logluv TIFF's design solves two specific problems: storing high-dynamic image data and doing so within a reasonable amount of space. Traditional image format generally stores pixel data in RGB-space occupying 24 bits, with 8 bits for each color component. This limits the representable colors to a subset of all visible and distinguishable colors, introducing quantization and clamping artifacts clearly visible to human observers. Using a triplet of floats to represent RGB would be a viable solution, but it would quadruple the size of the file (occupying 32 bits for each color-component, as opposed to 8 bits).
Instead of using RGB, LogLuv uses the logarithm of the luminance and the CIELUV (u’, v’) chromaticity coordinates in order to provide a perceptually uniform color space. LogLuv allocates 8 bits for each of the u’ and v’ coordinates, which allows encoding the full visible gamut with imperceptible step sizes. In order to provide the required high dynamic range with imperceptible luminance steps, LogLuv uses 16 bits to encode a fixed-point base 2 logarithm of the luminance, which allows an EV range of nearly 128 stops. The space occupied by one pixel is thus 32 bits (L16 + U8 + V8), marginally bigger than a standard 8 bit RGB-image.
Extensionedit
In an attempt to prevent the expansion of data-size, Logluv comes in a 24-bit flavour, which in a rather complicated way quantizes lightness to 10 bit and merges U/V into a 14-bit look-up based value.
Reading and writing of Logluv TIFF images can be handled via LibTIFF.[1] LibTIFF is freely available in both source and various binary packages for different platforms.
Resourcesedit
HDRI, by Reinhard et al. has a discussion regarding Logluv Tiff in the 3rd chapter.[2]
For those looking for Logluv images, there are numerous example on Greg Ward Larson's page.[3][4][5]
^(Amazon Link) High Dynamic Range Imaging by Erik Reinhard, Greg Ward, Sumanta Pattanaik, Paul Debevec
^Greg Ward Larson on LogLuv Encoding for TIFF Images
^LogLuv encoding for full-gamut, high-dynamic range images Appears to be the same paper as: Ward Larson, Gregory (1998). "LogLuv Encoding for Full-Gamut, High-Dynamic Range Images". Journal of Graphics Tools. 3 (1): 15–31. doi:10.1080/10867651.1998.10487485.
^A comparison of different HDR image encoding formats
March 15, 2024
logluv, tiff, encoding, used, storing, high, dynamic, range, imaging, data, inside, tiff, image, originally, developed, greg, ward, storing, output, radiance, photonmapper, time, where, storage, space, crucial, factor, implementation, tiff, also, allowed, comb. Logluv TIFF is an encoding used for storing high dynamic range imaging data inside a TIFF image It was originally developed by Greg Ward for storing HDR output of his Radiance photonmapper at a time where storage space was a crucial factor Its implementation in TIFF also allowed the combination with image compression algorithms without great programming effort As such it has to be considered a smart compromise between the imposed limitations It is slightly related to RGBE the most successful HDRI storage format an earlier invention of Greg Ward Contents 1 Details 1 1 Extension 2 Usage 3 Resources 4 See also 5 ReferencesDetails editLogluv TIFF s design solves two specific problems storing high dynamic image data and doing so within a reasonable amount of space Traditional image format generally stores pixel data in RGB space occupying 24 bits with 8 bits for each color component This limits the representable colors to a subset of all visible and distinguishable colors introducing quantization and clamping artifacts clearly visible to human observers Using a triplet of floats to represent RGB would be a viable solution but it would quadruple the size of the file occupying 32 bits for each color component as opposed to 8 bits Instead of using RGB LogLuv uses the logarithm of the luminance and the CIELUV u v chromaticity coordinates in order to provide a perceptually uniform color space LogLuv allocates 8 bits for each of the u and v coordinates which allows encoding the full visible gamut with imperceptible step sizes In order to provide the required high dynamic range with imperceptible luminance steps LogLuv uses 16 bits to encode a fixed point base 2 logarithm of the luminance which allows an EV range of nearly 128 stops The space occupied by one pixel is thus 32 bits L16 U8 V8 marginally bigger than a standard 8 bit RGB image Extension edit In an attempt to prevent the expansion of data size Logluv comes in a 24 bit flavour which in a rather complicated way quantizes lightness to 10 bit and merges U V into a 14 bit look up based value Usage editLogluv TIFF has widespread use in HDRI applications such as IBL image based lighting Reading and writing of Logluv TIFF images can be handled via LibTIFF 1 LibTIFF is freely available in both source and various binary packages for different platforms Resources editHDRI by Reinhard et al has a discussion regarding Logluv Tiff in the 3rd chapter 2 For those looking for Logluv images there are numerous example on Greg Ward Larson s page 3 4 5 See also editTag Image File Format RGBE image format JPEG HDR CIELUVReferences edit LibTIFF Homepage Archived 2004 09 16 at the Wayback Machine Amazon Link High Dynamic Range Imaging by Erik Reinhard Greg Ward Sumanta Pattanaik Paul Debevec Greg Ward Larson on LogLuv Encoding for TIFF Images LogLuv encoding for full gamut high dynamic range images Appears to be the same paper as Ward Larson Gregory 1998 LogLuv Encoding for Full Gamut High Dynamic Range Images Journal of Graphics Tools 3 1 15 31 doi 10 1080 10867651 1998 10487485 A comparison of different HDR image encoding formats Retrieved from https en wikipedia org w index php title Logluv TIFF amp oldid 1183319446, wikipedia, wiki, book, books, library,
