Logluv TIFF
Logluv
Details
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
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
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
Logluv TIFF has widespread use in
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
- 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]
See also
- Tag Image File Format
- RGBE image format
- JPEG-HDR
- CIELUV