JPEGsJPEG compression is "lossy" -- information is reduced and in some cases so is image quality. It can sometimes be quite surprising, however, how much compression certain images can tolerate. JPEG is usually best for photographic images and other images with many colors and soft edges. Consider these four versions of a painting of roses:
Even at a compression level of 60, this painting works pretty well. The background is degraded and the edges of the petals are rather fuzzy, but these things don't show up glaringly, given the soft quality of the original image. It's only at very high compression levels -- such as level 90 -- that the image becomes hopelessly degraded. That said, keep in mind that JPEG is not appropriate for images with large blocks of solid colors and sharp-edged color changes, such as you'd find in logos, simple text images, and simple drawings. For these images, even a low compression level will generally provide poor results. GIF is the format of choice for such images. |
