PNG is an acronym for Portable Network Graphic. The PNG file format is an extensible file format for graphic bitmap images. PNG files are very similar to GIF files and maintain the original image quality corresponding to smaller file size after compression. It contains bitmap of indexed colors under a lossless compression however has no copyright limitations (i.e. patent-free). PNG extension is normally used to store graphics for Web images.

PNG is an extensible file format for the lossless, portable, well-compressed storage of raster images in which there is no loss of data. The image attributes that can be stored in PNG files include background color, gamma values, and textual information. The standard allows up to 16 bits per channel, however 8 bits per channel is sufficient. PNG file format actually allows three different styles of transparency: one for indexed color images and two for greyscale or truecolor images in addition provide an optional alpha channel for transparency.

File Extension: .png
MIME type: image/png

Features of PNG Format:

  • PNG files not only allows you to make the image one color transparent but even permits the users to control the degree of transparency (referred as Opacity)
  • Provides support for interlacing of the image, which is much faster than the GIF format
  • PNG has a feature called Gamma correction that allows the user to “tune” the image in terms of color brightness
  • It facilitates your to save the images using true color as well as in the palette and gray-scale format
  • PNG lets the image to be filtered before compressing it this improves the compressibility of the data

Applications that open PNG files:

For Windows: Microsoft Windows Photos, Windows Photo Viewer, Adobe Photoshop CS6, Other picture viewer, Adobe Photoshop Elements 11,

For Mac OS: Apple Preview, Apple Safari, Adobe Photoshop CS6, Other picture viewer, Adobe Illustrator CS6 and other Web Browser 

PNG supports the following image types:

  • Line-art : pure black-and-white, that is 1-bit grayscale
  • Grayscale: Supports with up to 65536 shades of gray (16-bit)
  • Indexed color: Ranges from 1-bit to 8-bit (also referred as palette-based color or pseudo color)
  • RGB: Supports up to 48-bit (16 million colors)

Advantages of PNG:

Lossless Compression: PNG employs lossless compression technique, in which no  rmation of the image will be lost even after compression. It preserves the originality of the image even before and after compression.

True-color depth (48-bit): Higher bit depths (more colors) PNG allows for 1, 2, 4, 8, 16, 24 and 32 bit images, smashing the 8-bit barrier

Varying levels of transparency: PNG supports alpha channels; with this you can easily tune the degree of transparency according to the need. This is referred as opacity and PNG allows users to specify the opacity of any pixel from 0–255, in which case 0 is fully transparent and 255 is fully opaque.

Gamma Correction: One other advantage of PNG images is this Gamma correction, which is the ability of adjusting the gamma value based on monitor settings. It is the process of fine-tuning the color of images on your Macintosh and Windows systems. Normally (where there is no Gamma value), the same image viewed on a Macintosh will look much lighter than on a Windows PC. But by storing gamma information in an image then the original image can be viewed on both systems, until your application that reads the PNG takes note of the gamma.

Limitations of PNG:

  • PNG images do not support multiple images on the same file hence, they cannot include animations
  • Since, PNG files has alpha channels, some browsers like IE6 does not provide support alpha channels and hence your PNG files cannot be opened on these browsers
  • PNG images do not support CMYK color as they are not used for professional graphics

NOTE: Many times PNG files gets deleted or lost from storage devices like memory card, external hard drive, USB drive etc; in order to perform PNG recovery and get back those files, read here in detail.

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