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Re: DougM, I'm a little slow on computers,, Posted by Justin VanAbrahams [Email]  (#32) [Profile/Gallery]
(more from Justin VanAbrahams) on Mon, 20 May 2002 04:05:20
In Reply to: DougM, I'm a little slow on computers,,, KeithR, Sun, 19 May 2002 20:49:02 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Without going into too much detail, there are three basic ways to store an image (or any data, for that matter):
1. Uncompressed. One pixel equals one "chunk" of data, which varies based on how many colors that image has. It could be one bit (black & white) or 24 bits (16.7 million colors) or more, or anywhere in the middle. This is the least efficient method of image storage. TIFF is a common uncompressed file format.
2. Compressed. A piece of software goes through and finds indentical colors in a row, and represents them. Rather than storing five blue pixels in a row, the compression software makes a note saying "the next five pixels are blue" so it doesn't have to store each pixel individually. GIFs and PCXs are common compressed file formats.
3. Lossy Compressed. Lossy compression works much the way regular compression (also "non lossy compression") works, except rather than combining only identical colors it's smart enough to combine similar colors within a certain range, often specified by the user. For example, everything from periwinkle to navy blue might end up getting combined into a single unit. You get much smaller images, but you also end up with images that aren't necessarily true to the original, and can look "pixelated" or blotchy. Normally, you can set how much less you're willing to tolerate when compressing in this fashion, from zero loss to "get it as small as you can and damn the quality" loss. JPGs are an example of a lossy compression format.
This is grossly oversimplified, but should give an idea of what you're dealing with. In general, you don't wanna ever save anything uncompressed, though as always there are exceptions, especially if you're in the art or photography business. GIF is a good choice if you don't want to lose any detail but don't want a raw or uncompressed image. JPG is a good choice if you don't mind losing some detail. Remember also that some types of images compress better in certain ways than others - in general cartoons and line art (with vast areas of identical colors) do better with GIFs, and complex images like photographs and artwork (with lots of minute detail and rapid color changes) do better with JPGs.
Hope this helps some... don't be afraid to experiment saving scans in different formats to see what ultimately ends up being smaller... save the original as a TIFF (for backup) then save in other formats and compare sizes & qualities.
-Justin
posted by 64.166.4...
, Sun, 19 May 2002 12:03:21
, Mon, 20 May 2002 09:15:06
, Sun, 19 May 2002 22:59:51, Mon, 20 May 2002 12:12:49, Mon, 20 May 2002 04:05:20 <-- Viewing This Message, Sun, 19 May 2002 19:34:36
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