There are many formats in which you can save an image. JPG, GIF and TIF are extensions with compression algorithms to send over the web. Another format is called Portable Network Graphics (PNG), which should be used when you need a transparent layer and little compression is required.
What is PNG?
Portable Network Graphics (PNG, pronounced "PING") is a format that employs lossless data compression. It was developed as the next format to the Graphics Interchange Format (GIF), which was patented by Unisys and Compuserve. PNG supports a 24-bit Red Green Blue palette for the Internet and was approved by the Internet Steering Group in 1996.
It has a transparency level, just like GIF. You can create an image without a background color, which will then overlay another image without blocking it.
Animated PNG files have the extension MNG for Multiple-image Network Graphics.
How to Create PNG files
Since PNG files do not have a patent license, most programs allow saving to PNG of some sort. Adobe Photoshop, Microsoft Paint, Paint Shop Pro, F-Spot and GIMP are some of the photo editors that will save to a PNG format. Older photo editing software might not, if it predates PNG.
For example, in Adobe Photoshop, when you create your image, you simply choose "File" and "Save for Web." You can then choose whether you want the JPG, GIF or PNG format.
In Microsoft Office Picture Manager, choose "File" and "Export" to save in PNG.
When to Use PNG, MNG, GIF or JPG
PNG files are not the best for web pages, as they are larger in size. GIF files have a patent license attached and can show pixelation in an image. The Joint Photographic Experts Group (JPG or JPEG) employes a 10:1 compression ration, which is perfect for images across the web. JPG does not have a transparency layer to it; therefore any image will have a background.
A border with a rounded corner usually is a PNG, while a photo will be a JPG. If a website has an image over another image, the PNG might be in use unless the image has squared corners.
MNG should be used when you want your PNG file to animate. However, MNG files can be fairly large, depending on how many images are included, and therefore should be used sparingly.
PNG is a great format if you need an image with little compression and a transparent layer. For standard web graphics and pictures with squared corners, JPG is still the standard.
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