Thu Jun 15 21:51:40 EDT 2006 Paul Stenquist wrote: > Jpeg is a compressed file. Tiff is an uncompressed file. When you open > a jpeg in PhotoShop, the software decompresses the file, restoring it > to original size.
A few "academic" corrections (aka "nit-picking") which I hope might help somebody people to obtain a better understanding of what is happening. Strictly speaking, when a jpeg is read and displayed, it is the image, and not the file that is decompressed. I.e. "jpeg" format assumes a special format of encoding the image pixels into a smaller data volume, resulting in smaller file size. This algorithm is not applicable to any other type of data. Other compression algorithms (e.g. zip, which is lossless ) can be used on both data and images (e.g. in a compressed TIFF or PDF). When used on images, zip-compression essentially compresses image-data part of the file, rather similarly to how any file is compressed with zip. In either case, the number of pixels in the image is unchanged (unless you resize the image), which results in the same file size if you save the image as uncompressed TIFF (or any other uncompressed bitmap format, i.e. where each the value of each pixel is stored as is,- what I would call a "pixelmap"). If you use compression in the TIFF, the size may very depending on the type of compression and type of the image. Igor -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
