User:Pandoraxero/Making GOOD Images

Reaction to my somewhat sarcastic post on how to make a BAD image wasn't all that great, so here's a more positive version:

I'll start by mentioning a list of good software, some of this stuff relates specifically to PNG, as that's the image format i support for most purposes:
 * Adobe Photoshop - If you got the cash or the connections, use it
 * GIMP - if you have neither the cash nor the connections, or are lazy, OR don't run a compatible system, this will work just as well for all practical purposes
 * Taksi - I use this for capturing screenshots, windower is also acceptable, but i recommend setting windower up to take screenshots in either bmp or png (preferrably png, they take up less space)
 * AdvanceCOMP - this one's PNG-specific, i use it frequently to recompress PNG images. it makes enough of a difference to warrant mention.
 * PNGrewrite - this one is also PNG-specific. its used to optimize palettes in indexed-color PNG images.

And now for the meat of the guide

Images are NOT an easy thing to deal with. the presence of several different image formats often makes it difficult to tell what format you should use. Thankfully, this wiki only supports 3 different image formats: JPEG, GIF, and PNG.

each of these formats have their limitations, advantages, and disadvantages: JPEG - is a "lossy" image format. it is capable of obtaining exceedingly high levels of compression, at the expense of image quality. if quality is not exactly an issue, as is the case with screenshots of characters, mobs, etc, JPEG is the image format you'll want to use. JPEG is also used by most (if not all) digital cameras. this is because quality is less of an issue for photographic issues, as well.

GIF - is an image format created in 1987 by CompuServe (an old ISP, absorbed by AOL some years ago.) It is a partially-lossless format. an image in the GIF format is limited to 256 colors, so if amount of colors is an issue, i would advise against using GIF. However, GIF offers animation capabilities, and so is suitable for creating limited-color animations. also, grayscale images work well with GIF. Aside from color, the only disadvantage GIF has is its use of an outdated compression method. In the general sense, this makes animation the only real use for gif.

PNG - is a relatively new image format that was developed in 1995 once patent concerns arose over the compression method used in the GIF format. these patents have expired, but PNG is still slowly gaining influence. PNG's most redeeming factors are its compression, and its support for a range of color formats, including indexed color similar to that used by gif, grayscale, 24-bit color, and 24-bit color with alpha transparency. alpha allows parts (or all) of an image to be partially transparent. PNG's compression allows it to, if put in indexed color mode, produce an image that is SMALLER in file size than a GIF equivalent.

The things you need to keep in mind when deciding which format to use are: 1. what is the size (dimensions) of the image 2. what is the content of the image 3. how much does quality matter 4. how much does size (file size) matter 5. how many colors are actually in the image.

these 5 factors will invariably affect what image format you choose.

Size - a larger image might mean the data in the image is less important, in which case, JPEG would be an excellent option, whereas PNG would waste space, and GIF would cause undesirable color loss, especially in images with many colors. in the real world, nothing can be simplified down to 256 colors.

Content - what is actually IN the image. is there an icon or text in the image with which detail might be important? small text is not well compressed by jpeg, and may end up badly blurred at lower jpeg qualities. in this case, you may have to play around with the quality for jpeg. for smaller images that don't have photo-like elements in them, png usually gets reasonably good compression, so you might also want to try that if you can't get a size/quality balance to your liking in jpeg. and this sort of bleeds into...

Quality - image quality is very important. depending on what kind of image you're posting, the format could make a big difference. the biggest things to remember when creating an image are how many people are likely to look at it, whether or not people might want to edit it, and how important the image is to you or might be to someone else. in my case, if i ever DO upload a JPEG image, i make sure i have a png version over here as backup.

Size - Size is an issue if you're running a server. the amount of stuff downloaded PER DAY is enough to drive admins INSANE. and bandwidth costs a pretty penny, so in order to save as much of it as possible, you sometimes have to use an image format you wouldn't use otherwise or perhaps lower the quality below what you normally would. jpeg is actually VERY good at holding image data. at normal zoom, its not obvious its a jpeg most of the time, but if you zoom in, you can see the jpeg artifacting. another thing that'll cost you with size is converting a jpeg to a png. this is a VERY bad idea, since it doesn't compress well at all, if you're going to do this, you should just do a total recapture of the image, it'll compress better.

Colors - this is an issue especially with icons. most of the item icons used in ffxi are in 256-color, and can be compressed as such. BUT, there ARE some cases where using indexed-color isn't necessarily the BEST option. i've ran into some cases myself where a png icon compressed better in rgb than it did in indexed color. the reason WHY is unknown to me, but i would suspect it has something to do with the fact that the Palette table is either compressed separately from the image itself, or not compressed at all. in either case, its clear that indexed color is NOT the way to go for an image with 162 colors and only 32x32 pixels.

This last one is sort of common sense, and not following it is against the image policy here, but its worth mentioning that the naming of an image is important. i ran into one case while i was doing some image replacement where i had a new image BronzeKnife.png and another new image BronzeKnifePlus1.png there were already images on for each of the bronze knife qualities, but i put BronzeKnife.png up, then realized the one for the +1 version was titled bronzeknife.png ... very ambiguous name, not to mention if the server were running Windows, it might be horribly confused.