Wikipedia:Image use policy

Rules of thumb

Here's a quick checklist of rules for use of images. After the list, a more detailed discussion explains the reasoning behind them.

Always describe the image and where it came from on the description page. Images without descriptions may be summarily deleted!
Don't use tiny thumbnails; make small but viewable images 150-250 pixels across.
Crop the images to show just the relevant subject.
If you think having a larger image is necessary, include an ":image:..." link to the larger version on the description page of the smaller.
Don't put rendered images on the description pages; they are for text.
Don't put photo credits in articles or on the images themselves; put them on the description page.
Use JPEG format for photographic images, with moderate quality settings.
Use PNG format for icons, drawings, maps, flags, and such; but...
Never convert a JPEG original to PNG; if JPEG is all you have, go ahead and use it.
Do convert GIF images to PNG, except for "animated" GIFs.
Encode sounds as 64K-bitrate mono Ogg Vorbis files.

Details

The primary and most important policy is this: the purpose of the upload facilities of Wikipedia is to allow authors to upload illustrations to accompany articles. Don't upload images just because they're interesting, or because they might be useful in an article. Just upload ones that will actually be used.

Just like the articles, it is important that images follow the same guidelines about copyrights. Make sure you own the image, or that it is in the public domain, or that the copyright holder has agreed to license it under the GFDL.

Also like articles, they may be edited or deleted by others if they think that serves the purpose of making a better encyclopedia.

Add good descriptions

Each uploaded file has as associated image description page into which you can put text, and which shows the image's history and usage. You should at least always include a brief description here, and especially mention where the image came from (perhaps with a link to the original source), and what its copyright status is.

Do not put images themselves on the description page. It often makes the text and history hard to find, and marks the image as being "used" when it would otherwise show up in the orphan list. Especially avoid putting a large version on the description page of a smaller one--that forces users to download a large image just to find information about the smaller one. You can include a link like this to the larger image's description page, giving the user a choice whether to download it. The description page already has links to the image: one at the top of the page, and one or more in the history list.

Descriptive titles are also useful. Uploading a file named, for example, "Africa.png" is likely to collide with one already present, and doesn't give any clue about its contents. A more descriptive name like "Africa_map_2002.png" is better. Avoid special characters in filenames or excessively long filenames, though, as that might make it difficult for some users to download the files onto their machines.

Do not put image credits in the articles using the image. The image might be used from more than one place, and so such glosses might go out of sync. Also, the article might be edited, and we could lose information about the image itself. Finally, it puts irrelevant information in the article anyway. That information belongs on the image description page, which also enables you to make much longer descriptions without affecting any of the articles that use the image.

Images themselves should not contain any rendered text such as credits, subject identification, and so on. Information about the image should go onto the image description page where it will be readable by users with non-visual browsers, and where it can become verbose without becoming distracting. The image file may contain embedded comments, as is common in PNG and JPEG images, but preferably not so much as to increase download time. For example, a copyright notice and statement of license under the GFDL would be good to include.

Use appropriate format and size

This scalebar is red from 0 to 100 pixels, yellow from 100 to 150, green from 150 to 250, yellow again from 250 to 300 and red again from 300 to 400 pixels.

There are many technical hints in this section that some people may not have the tools or expertise to deal with themselves. If, for example, you find a great image that needs to be cropped, resized, or recoded and you don't know how to do that, ask someone on the Wikipedia-L list to do it for you.

Scale and crop images to a size appropriate for the article. Keep in mind that many readers are using 800x600 displays, and so images wider than 300-400 pixels may overwhelm the article. Larger images also take more time to download over slow links. Likewise, images smaller than 100 pixels wide may be difficult for users of larger displays to see. An optimum size for images with text flowing around them would be 150-250 pixels. Images without text on the side can be wider.

Of course image complexity is an important factor to consider when sizing images. Don't use tiny "thumbnail" images linked to a large image--use an image of the appropriate size; adding a link to a larger version (perhaps the original source) is fine as well, but don't upload the larger one unless it is really needed. A good way to do this is to put a link to the larger image (or to its description page) on the description page of the smaller one.

Drawings, icons, political maps, flags and other such images with limited colors should be in PNG format, preferably grayscale or indexed color with fewer than 200 colors. GIF images should be converted to PNG before upload unless they are "animated" GIFs. Do not use PNG for "photographic" images, unless that (or GIF) is the only format available.

Photographic images should be in JPEG format, with quality settings set to make a reasonably sized file. Do not use JPEG for iconic images or maps (except possibly for photo-like maps that show terrain and such).

If you find an original of a map or flag in JPEG format, only convert it to PNG if this has a positive effect on the file size. You may want to check and see if areas of the same color are not in fact areas of slightly differing colors: PNG compresses same-color areas much better. Your image editors fill tool may be of help here.

Five steps to make an image that was incorrectly save as JPEG, fit for saving as PNG

Suppose you have got a map for an island that was inadvertently saved as JPEG. Looks OK, does it not?	1. In your bitmap graphics editor, set your fuzzy selection (magic wand) tool so that it only will select pixels of exactly the same color. (Here: Threshold = 0)	2. Click on the main land mass: see how it does not select every pixel of the land mass?
		5. Now choose an appropriate color for the land mass, and make sure the entire selected area is filled. How to do this may differ between applications.
3. Go back to the fuzzy select tool, and make it be less uptight.	4. As you can see, more of the land mass will be selected. Experiment to get all of the land, but none of the edge surrounding the island.

In particular, most of the maps from the CIA World Factbook website are incorrectly coded as JPEG. If you have the tools and knowledge to do so, render the original PDF maps at high resolution, then rescale them and convert to indexed PNG. The result will be both a higher quality image and a smaller file than the JPEGs from their site. If you can't find the original PDFs, but have the knowledge and skill to convert them to indexed PNGs, do so. The difference in file size can be tremendous.

However, if you don't know what you are doing, then go ahead and use the original JPEG.

Try to avoid cropping or otherwise editing JPEGs too frequently--each edit creates more loss of quality. If you can find an original of a photograph in 24-bit PNG or TIFF, edit that, and save as JPEG before you upload.

Avoid images that mix photographic and iconic content; the quality of one or the other will always suffer. In particular, do not use photographs with text captions on the image itself. Upload the image and add the caption in plain text to the article or to the description page.

Sounds

Sounds should be encoded in Ogg Vorbis format with at most a 64K bitrate. Speech samples should be in mono and perhaps at even smaller bitrate; music samples can be in stereo if necessary. Use only short samples, and try to keep them under 100K. If they are large, include the size of the file in the link so that users are warned that they may have a long download, like this: SAMPLE (202K).