restyling image

[jscheuer1]

See:

http://en.wikipedia.org/wiki/Graphics_file_format

for information on file formats.

The basic idea though is to save anything important in a lossless format first, then work only on copies of that. Often you will need several lossless versions of an image to make sure you can go back to one or the other of them as the need may arise. Once you have settled on the version of the image that you want to use on the web, then it is time to compress and/or resize down a copy of it into either a lossy JPG or a palette reduced GIF or PNG to save space and bandwidth on the web. Images for the web should also be optimized, this basically is a process of finding the maximum amount of compression for a JPG or the minimum amount of colors for a GIF or PNG that will still look good. There are techniques to get higher compression with a JPG with less loss or an illusion of less loss than other techniques used with JPG. Similarly with GIF and PNG, you can try different combinations of color reduction and dithering to get the optimal look at the smallest size. There are programs devoted to this that make the process easier. But any decent image editor can do these things if you know how to use it for that purpose.

Generally GIF and PNG are good for graphics, and JPG for photos.

[chechu]

Generally GIF and PNG are good for graphics, and JPG for photos.

maximum amount of compression for a JPG or the minimum amount of colors for a GIF or PNG

If gif gives the best colors, shouldn't gif be used for foto's then ?

[jscheuer1]

If gif gives the best colors, shouldn't gif be used for foto's then ?

If it did, it doesn't.

GIF (Graphics Interchange Format) is limited to an 8-bit palette, or 256 colors.

But it might be good for certain photos. If you want the best result for an image, you need to be willing to play around with it. Experience in doing this will tend to make you think what might be best in any given case, but this will not always be accurate. Then again, as long as what you come up with looks good and carries a small byte load, it doesn't matter too much if you have arrived at the absolute best optimization for that particular image or not.

[chechu]

In my case, using pictures of portraits, the result needs be to be as close to the reality as possible. So I take a picture, resize it with Photoshop, and save it as a gif.
Is that the best way ?

[djr33]

Gif is best for graphics because it uses relatively little space to save data when there are only a few colors. So, a logo would work well. However, on any photo, even something like a portrait which doesn't have as many colors as a photo, but certainly more than 256, you'll see a noticable loss in using gif. However, in this case, it doesn't look that bad, but you might in fact be happier with a jpg.

gif-- simple graphics, ends up in a small file size. (also currently the only supported animated format)

jpeg-- good for pictures

png-- no real use for this, unless you want to have a significantly larger file that is nearly lossless. You can save a basically lossless photo with png, and though it will be a large filesize, it'll be small compared to other lossless formats, and it is compatible with all browsers. (png can also double as 8bit, basically copying how a gif works-- sorta replacing it. However, I don't use it for that because there's some small chance that png wouldn't be supported (if they were using ie 4 or something, perhaps), and it doesn't do any better than gif as far as I can tell in 8bit mode. note: default for png is now 24bit... lossless, many more colors.)

[jscheuer1]

I think after having worked with you on a few things for Ceci's site I am familiar with the kind of photo that you are talking about chechu. Since you are taking a picture of a drawing or of a painting that looks a lot like a drawing, it sort of qualifies as 'line art', the sort of thing that works better as a .gif or .png on the web. However, if you start with the file that the camera produces, and work with it in an editor (making sure to keep a copy of the original), you might be surprised how small a bytes size you may be able to get as a .jpg, and still have it looking good. GIF or PNG might still be best for this though, as they are both lossless when it comes to lines and their precision, and if the number of colors is low can produce fairly small, sometimes even very small byte sizes for the image files.

In general though, a photo is not of a two dimensional object of art, rather of the real world. In that case JPG is usually the best for the web.

[techno_race]

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