JPEGs: problems with web textures

JPEGs have the advantages of being an almost universally recognisable format. They can be stored in full 24-bit colour, and they can be compressed to any degree.

However, because they are designed to represent any photographic image, and the vast majority of textures used as backgrounds to web pages form a tiny subset of this, their representation is almost certainly inefficient.

When compared with algorithmic texture formats, JPEGs have the following disadvantages:

They are too large.
They cannot be rendered at different scales, and so exhibit tesselation patterns which depend on their size.
They cannot be easily resized without generating pixellation artefacts.
When compressed, they exhibit JPEG artefacts which reduce their image quality.
They cannot be conveniently embedded within HTML.

The disadvantage of the last point is that the texture cannot easily be loaded before the page is displayed. This is because it is a separate fetch (which may fail) from the one that loaded the HTML document.

Some of these points it is possible to address without recourse to proposals as extreme as those put forward by the author. The points concerning size and artefacts are partly addressed by the PNG format; this also offers partial transparency, amongst a number of other interesting features.

Some of Xara Ltd's proposals for web graphics formats address the inability of textures to resize without generating images that rapidly degrade.

However, there remain some desirable features which can only be addressed by using algorithmic textures.