ZeScript/ZeGraph

ZeGraph is an open-source freeware designed for scientific data visualization by Dr. Jiye Zeng. It is small, fast, and easy to use. The core library is written in C++ for high performance, using OpenGL as the rendering engine. The developer has embedded ZeGraph in ZeScript to extend its ability of making plots for various types of data. Here are some features of ZeGraph:

Make 2D or 3D scientific plots;
Show or animate an image in a window;
Save an image to various formats;
Send an offscreen image to a web browser for online application;
Render images to a GIF animations;
Use an offscreen image directly as OpenGL texture.

ZeScript is a small and embeddable scripting language. It has a powerful feature allowing redefinition of all operators for any user objects, which makes it possible, for example, to handle matrix naturally. Several library extentions have been added to

Create simple graphic user interfaces;
Manipulate data matrix;
Read and write binary data in various formats, e.g., GRIB, netCDF, and HDF.
Construct databases.