PHPLOT is a PHP graphics class for creating charts and plots. It works with PHP5 (but older versions can use PHP4). PHPlot uses the PHP GD extension to produce PNG, GIF, or JPEG images. TrueType fonts (TTF) are optional, or built-in GD fonts can be used. The available plot types are: area, bars, line/points, lines, pie, points, squared, stacked-bars, and thin bar-line. Labels, tick marks, plot legend, X/Y axes, and more are all configurable. Images can be imported as a background, multiple graphs can be drawn on one image, and images can be saved to disk or returned to a browser.
Open Tool Kit (Otk) is a portable widget library for making graphical user interfaces for C programs. It emphasizes simplicity for the application programmer without eliminating capability. Based on OpenGL, Otk supports Linux, Unix, and other OSs neutrally and efficiently. It is simple and compact, and it strives for easy compilation and linking to other applications. In seeking to address several issues associated with earlier graphics APIs, Otk explores some interesting methods, such as window-relative layout instead of pixel-based layout.
Mapnik is a toolkit for developing GIS applications. At the core is a C++ shared library providing algorithms/patterns for spatial data access and visualization. Essentially a collection of geographic objects (map, layer, datasource, feature, and geometry), the library doesn't rely on "windowing systems" and can be deployed in any server environment. It is intended to play fair in a multi-threaded environment and is aimed primarily, but not exclusively, at Web-based development. High-level Python bindings (boost.python) facilitate rapid application development, targeting zope3, django, etc.
Qanava is a C++ library designed to display graphs on a Qt canvas. Qanava provide classes to generate various layouts of directed graphs and visualize their nodes with custom styles on a graphic canvas. Qanava is designed for applications with basic graph visualization needs such as Gantt charts, social networks, and document or network modelling applications. It is not meant for a complex interactive visualization of very large data sets.