[cairo] cairo Summer-of-code participant introduction

[Kai-Uwe Behrmann]

A C library implementing the 16-bit HALF float with a liberal license 
(BSD) would be very welcome. It could be shared or used in Oyranos as 
well.

Cairo may consider to not to rely on some particular tone mapping library 
without a framework for flexible and language independent pluging in of 
new operators. The Oyranos CMS is designed toward providing the later.

kind regards
Kai-Uwe Behrmann
-- 
developing for colour management 
www.behrmann.name + www.oyranos.org


Am 23.04.08, 11:02 +0800 schrieb xie guofu:

> instead of gamma compressed 8-bit integers. It allows values outside of the
> [0..1] range, creating a much larger effective gamut. It also has greater
> precision because the half-precision format has a 10-bit significand.
> In my solution, the 16-bit floating-point data type is implemented as a C
> struct, half, which is designed to behave as much as possible like the
> standard floating-point data types built into the C language. half numbers
> have 1 sign bit, 5 exponent bits, and 10 mantissa bits. The interpretation
> of the sign, exponent and mantissa is analogous to IEEE-754 floating-point
> numbers. half supports normalized and denormalized numbers, infinities and
> NANs (Not A Number). The range of representable numbers is roughly 6.0×10-8
> - 6.5×104; numbers smaller than 6.1×10-5 are denormalized. Conversions from
> float to half round the mantissa to 10 bits; the 13 least significant bits
> are lost. Conversions from half to float are lossless; all half numbers are
> exactly representable as float values.

> One problem with HDR has always been in viewing the images. Mundane CRTs,
> LCDs, prints, and other methods of displaying images only have a limited
> dynamic range. Thus various methods of converting HDR images into a viewable
> format have been developed, generally called "tone mapping". In the project,
> I will research on how the human eye and visual cortex perceive a scene,
> trying to show the whole dynamic range while retaining realistic color and
> contrast. In the project, I will present an adaptive logarithmic mapping
> approach, which was introduced in Drago et al. [2]. Of course, if there is
> enough time, I will implement other tone mapping algorithms, for example,
> Fattal et al. [3] and Mantiuk et al. [4].
 
> [2] Adaptive Logarithmic Mapping For Displaying High Contrast Scenes
> http://www.mpi-inf.mpg.de/resources/tmo/logmap/
> [3] Gradient domain high dynamic range compression
> http://www.cs.huji.ac.il/~danix/hdr/
> [4] A Perceptual Framework for Contrast Processing of High Dynamic Range
> Images
> http://www.mpi-inf.mpg.de/~mantiuk/contrast_domain/