Now that we know about the webs default srgb color space and that most browsers don't do much if any color or gamma correction it's time to talk about image creation and editing for the web. You might think that all you need to do is set your system to srgb and go from there but it's not that simple. Well, if your'e creating a new image from scratch it may be. I would recomend that your working space be linear whenever possible.

There has been some argument as to which gamma is best for jpeg compresion. I don't see that it matters. Jpeg ws created to compress real world photos. Those photos could just as easily appear to be gamma 1.0 as gamma 3.0. Jpeg should handle them equaly well. What does matter are the various filters and plugins that we use, even the humble gradient fill. All of these perform linear operations on the colors. A smooth gradient from black to white would have 50% gray in the middle even though it may not appear to be.

PhotoShop 5 and higher has the concept of a working space. This means that the image data and all operations are in one color space while the displayed image is color corected for your monitor. So the image could be linear while your system is set to srgb. Set your working space to linear rgb. Save any source files you create in linear rgb. Save finnal files intended for the web or viewing by others in srgb. Nuff said, go to work.

If your'e using the Gimp this is what you need to know. The Gimp as of version 1.2.3 does no gamma or color correction. Effectively, it assumes that the image data is linear. You should get the best results by calibrating your system to gamma 1 when editing images. In linux you could easily use a script to toggle your systems gama between 1.0 and 2.2. Unfortunately even the png loading plugin doesn't do any correction so you will likely have to alter the image gamma before editing. If the image looks really washed out assume it was srgb and correct it by .4545. As with PhotoShop any xcf files you create should be linear and the files you save for use on the web should be set to the srgb gamma 2.2.

If your using any other program you need to figure out what kind of gamma or color correction it offers. Simple image touchup programs that are meant for cleaning up photos probably won't offer either. If your'e using such a program you should have your system set to srgb so that you get the best web experience. Other programs like PhotoImpact offer both gamma and color correction, but when color correction is enabled the working space becomes srgb.

As you can see image editing for the web can be rather difficult. People with high end editors like PhotoShop that support CMS don't have to wory to much about their system setting, at least not once they have a proper monitor profile. Image editors for normal people should have gamma correction. This would allow them to work on linear data while their system is set for srgb. Just remember to disable gamma correction before saving the final work so you can correct the color. Or you could just apply a .4545 correction without checking.

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