Hi Ullrich and Jose -- GIL has something similar to promotion traits in the numeric extension. Moreover, it is designed so that users can easily override the default behaviors without sacrificing performance. More specificly, the algorithms in the numeric extension allow users to specify types for holding intermediate results. The intermediate types are then passed into a set of pre-defined structs for doing fundamental numerical operations such as addition, subtraction, etc (see extension/numeric/pixel_numeric_operations.hpp). All the structs are templated over input types (one, two or more) and output types, which are often the intermediate types, and these structs are consistently used throughout the numeric extension. As a result, the user can specify either "float" or "double" as the intermediate type for convoluting a "unsigned char" image with a "float" kernel. Hailin Ullrich Koethe wrote:
Lubomir Bourdev wrote:
The fact that GIL doesn't provide campling makes me argue it is not a mature library. It's such a basic need (I get this
from reading the book!)
To clamp a channel in GIL you can just say:
T channel; T clamped = std::min(channel, channel_max_value<T>());
But that's not how things work in practice. When the data are already stored as type T, overflow has already occured. Moreover, the possibility of overflow typically arises deep inside some algorithm, where you cannot simply call std::min(), but need another mechanism (e.g. promotion traits).
Ulli