In Gens (tested on version 2.1x, but it should work also in almost all Gens branches), make sure the render filter is set to "normal" (Graphic -> Render -> Normal) and press shift+backspace. Keep in mind that Gens uses two different render filters when windowed and fullscreen, so make sure that the you set the correct one on "normal" otherwise the screenshot will come out with the wrong render filter. Once you pressed shift+backspace, Gens will place a BMP file in your Gens folder.
In Fusion (tested on version 3.6x, I think 3.5x didn't have one of the options I'm going to mention), make sure that the configuration is correct by going to Options -> Set Config -> Extras and set "File Format: BMP unc", "Output Stage: Raw". Once that is done, just press shift+F12 to catch a screenshot in BMP format, which will be placed in the folder you specified in the dialog above.
Once you have that BMP file, check that its width is either 256 or 320, and that its height is either 224 (if taken in Gens) or 240 (if taken in Fusion). If not, then you did something wrong. REDO FROM START.
You should now convert that BMP to 8-bit PNG, which is the best format when it comes to screenshots. The problem is that many cheap graphic editors (read: MS Paint) suck when it comes to save pictures to PNG, so if you don't have some decent tool you should just upload the BMP on Imageshack which will automatically perform the conversion to PNG for you. It won't optimise the PNG to the max, but the conversion will be flawless and you didn't have to do anything complex, so if you're lazy this is the easiest thing you can do.
Another option is just to get the command-line version of PNGOUT (mirrored here for your convenience), and just drop your BMP files over it. PNGOUT will create a PNG right next to your source file, and it will have a fairly high level of optimisation. Again, this doesn't require ANY graphic editing software like Photoshop or Paint Shop Pro. You just take the BMP outputted by your emulator and drop it on PNGOUT's program icon. Once you have that PNG you just upload it on Imageshack as above.
Now, if you DO have a decent graphic editor, you should consider removing the colored canvas from Fusion screenshots, giving them an height of 224. But this is something advanced and a very minor issue, so don't do that if you don't feel like to.
Someone may ask why PNG and not JPG (yes, I've seen screenshots in JPG). The answer is simple.
This is a screenshot in PNG format:
file size: 8865 bytes.
This is the same screenshot in JPG format with quality 100:
file size: 74533 bytes.
Now, look at the small details such as Sonic's shoe. There is a quality loss even if you set the JPG quality to the maximum. And the file size is 8.4 times bigger. JPG is the worst choice ever when it comes to pixel art and small details.
GIF is a more acceptable option than JPG, but once again, since you're converting from BMP to a format of your choice anyway, let's choose the best format and not a "not so bad" one. Especially because you're likely to use MS Paint to save to GIF, and Paint sucks at picking palettes as mentioned above.
Note that I discourage the use of alt+printscreen to take screenshots, especially when windowed. If you do so, you'll be forced to use an external graphic editor, at least to crop the pic (which requires skills) and/or resize it (which will make it look gay especially if you took the screenshot while running the emulator windowed and maximized, I can't even realise why people do that ;_; ). If you think you're smart and you're saving time by using printscreen rather than using the built-in functions then open your eyes: you're not. As mentioned above, with the built-in functions and Imageshack (and possibly PNGOUT), a good graphic editor is not needed at all. So that's a double victory: lazyness and optimisation.
The next time I see a distorted or dithered screenshit (not a typo) I will come personally to your house and burn it.
Finally, when you copy the link from Imageshack, use the DIRECT LINK, as all the other links will carry spyware and adware with them once clicked. And some people (shame on them) still use Internet Explorer so they're vulnerable. So yeah, take the Direct Link and slap it between two IMG tags on any forum of your choice.
Thanks for your time.
Edited by nineko, 29 December 2011 - 06:24 PM.