Following up the thread by Jerzy, Eugene and Michael, I would like to comment that both GIF and PNG have some deficiencies when it comes to capturing chemical formulas. Although the GIF and PNG formats do have "invisible" fields which could be made to contain a connection table, there is very little software which can easily either detect or read this information. If either the raster component, or the connection table were to be edited, the two would certainly no longer correspond. Additionally, the raster component cannot be scaled, indexed or transformed in any useful way. About 18 months ago, we suggested an alternative display format called SVG (http://www.ch.ic.ac.uk/svg/ ) is based on XML and vector graphics. We expect that more and more chemical programs will have an SVG (and CML) export filter. The advantage of SVG is that, being an XML language, transforms to and from it from other XML languages such as eg CML (http://www.xml-cml.org/ ) are possible. Indeed, such transforms are often done on the fly For example, JUMBO3-JS (see http://www.xml-cml.org/jumbo3/jumbo3-JS/ ) is a collection of JavaScripts and XML/XSLT which takes an XML file containing eg the CML namespace and converts it to SVG for display. This example is rather nice in illustrating that the primary purpose of any chemical file should be to carry well structured "self-identifying" data, and that the decision on how to display it should be managed elsewhere, ie in this case an SVG transform. The resulting SVG can be displayed as high quality using eg Adobe's SVG viewer, or directly in an SVG aware browser (i.e. http://www.croczilla.com/svg, or Amaya, http://www.w3.org/Amaya/ ). These browsers have not yet reached the stage of being usable on a daily basis, and we have not quite reached the stage where capturing chemical structures into CML for SVG-based display can immediately display the use of PNG images, but the day cannot be too far off. Google claims that 1.3 billion web pages exist. These probably reference 10 billion GIF/JPG/PNG images. If even only 1% of these images relate to chemistry, that is 100 million chemical images out there which carry no easily retrievable chemical information such as connection tables, or 2D/3D coordinates. That is a terrible loss to the community. Imagine however the situation if eg 100 million SVG/CML files existed (SVG can contain CML and vice versa, ie you can have BOTH in a file). That would be three times the known number of molecules, and a fantastic resource! Dream on you may say, but we have to plan for this day, which may come sooner than you think! -- Henry Rzepa. +44 (0)20 7594 5774 (Office) +44 (0870) 132-3747 (eFax) Dept. Chemistry, Imperial College, London, SW7 2AY, UK. http://www.ch.ic.ac.uk/rzepa/ chemweb: A list for Chemical Applications of the Internet. To post to list: mailto:chemweb@ic.ac.uk Archived as: http://www.lists.ic.ac.uk/hypermail/chemweb/ To (un)subscribe, mailto:majordomo@ic.ac.uk the following message; (un)subscribe chemweb List coordinator, Henry Rzepa (mailto:rzepa@ic.ac.uk)