Portable Networks Graphics or simply PNG is a file format that uses LZW compression which maintains image quality. It is preferred over most image formats such as GIF, TIFF because of its image quality and size. LZW is a widely used lossless data compression algorithm and PNG utilizes this technique twice to convert longer bit strings of an image to short codes. This keeps the quality of a PNG image intact without any data loss. Another advantage of PNG over JPEG is that it can manage high-contrast and detailed images. This is also one of the reasons for most screenshots to be of PNG file format because there is no compression of pixels. While a majority of images use JPEG format, PNG outshines JPEG when it comes to rendering text or logos clearly over a website’s elements.
One of the distinct features of PNG is that it supports transparency. With both grayscale and color images, PNG files can have transparent pixels. This gives way to image creation so that it can overlay neatly with a website or image’s content. PNG is also great for making logos, especially those with text. However, there are various formats that outshine PNG when it comes to photography because it doesn’t support EXIF data natively. This includes image information like ISO, shutter speed, and aperture. Another disadvantage of PNG is that the file is larger than that of JPEG.
JPEG or Joint Photographic Experts Group is the standard compressed format that is used in online image sharing and digital photography because of the balance it maintains between image quality and file size. The common compression ratio of a JPEG image is 10:1 but it can differ based on the settings and program used. This means that you can have a 1MB file if you export a 10MB image file as JPEG. While there won’t be a significant difference in the quality of image, it also depends on image content. JPEG uses DCT or discrete cosine transform compression for doing this. This compression algorithm basically locates similar pixels groups in an image and merges them together in the form of tiles which are essentially pixels groups having same value.
While this is an efficient method, but it eliminates the possibility of retrieving information which previously present in the image. This makes JPEG images lossy because the lost data cannot be recovered once the image is saved. This is the reasons the quality of a JPEG image declines every time it is opened and saved. This is the reason JPEG file format is avoided for images having illustrations and heavy text with sharp lines because anti-aliasing makes these defined lines blurred. Also, JPEG doesn’t support transparency, which makes it an unlikely candidate for websites. Since most websites contain heavy text and logos, JPEG cannot render these elements effectively because of the lossy compression. This is a major reason why most websites choose PNG file format over JPEG because its image quality much better.