Tracing Bitmaps

Image Formats

This tutorial has been brought to you by the numbers 256, 1.6 million and the letter T (for tracing bitmaps). The question of animating and morphing bitmaps has come up a few times on the board recently. Enough so that it inspired this tutorial on the subject.

But first a developer's five on images. JPEGs are 'lossy' image format which means that its compression algorithm converts a spatial image representation into a frequency map. A Discrete Cosine Transform (DCT) then separates the high and low frequency information. When you select a image quality setting, certain high freqency information is discarded and 'lost' never to be found again. In layman's terms JPEGs are good for images involving gradients like photographs.

GIFs on the other hand, are 'lossless' which means its compression algorithm is used to re-code the image into a more compact representation of the same information. Thus no information is lost in the translation.

Solid colours and sharp lines. JPEG = 7k	Solid colours and sharp lines. GIF = 1k Interlaced	Image with Gradients. JPEG = 10k	Image with Gradients. GIF = 19k Interlaced