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GIF vs. PNG vs. JPG vs. TIFF - which image file format to use?

When you create your Business Website, you will undoubtedly use images.
Their use is discussed in A Picture is worth 1000 Words and various sources for your images discussed in Where Can I Get Professional Looking Images for my Website.

However there is another important decision you will need to make for your Business Internet Website - which image file format to use?

Image file formats are various widely accepted standards to store and display digital images. There are hundreds of image file formats and the first criteria of which to choose is to identify the use of the image. There are specific image file formats for printing such as TIFF, others record the image in vector format (these are described geometrically and not pixel by pixel which allows smooth rendering of the image at any desired display size), or even ones for storing and displaying images side by side for a 3D effect such as JPS or PNS (stereo versions of JPEG and PNG).

The 3 most commonly used image file formats for displaying images on the Internet are GIF, PNG and JPG. These are all pixel formats where the pixels are ordered in columns and rows. Each pixel is a number that represents the colour and brightness of what to display and which when placed side by side with the other pixels displays the required image.

 

GIF (Graphic Interchange Format) images

These use a lossless compression technique, supporting up to 256 colours.

The data values for the colour and brightness of each pixel is stored in a way that no data is lost during the opening, changing and saving of the image. However, this compression works best when large areas of the image have a single colour and it inefficient for detailed images or photos. GIFs are most suitable for images with relatively few colours such as logos, shapes or cartoon line drawings.

GIFs support transparency, where the background colour of the image can be set to transparent and whatever is behind the GIF will show through.

GIFs also support animation where several GIF images are put together in a sequence to obtain an animated image.

The algorithm that performs the compression and stores the pixel values of the image was patented by Unisys. In 1995 Unisys announced that any programs that output GIF images would have to pay a license fee, although anyone who wants to create and use GIF images on their Internet website could do so for free. The disagreement over the licensing was a large factor leading to the development of a new image file format (PNG standard) however the patent expired in June 2003.

 

JPEG/JPG (Joint Photographic Experts Group) images

These use a lossy compression, supporting up to 16 million colours.

The data values for the colour and brightness of each pixel is compressed and some data is lost. Each time the image is opened and then saved, a deterioration in the quality occurs, although the algorithm is designed to discard information the human-eye cannot detect. JPGs are best suited to photos but are generally not the best image format for logos or cartoon line drawings where there is not much of the image that can be discarded and compressed.

JPGs do not support transparency - a background colour is always defined and displayed within the image format. Although if you select a background colour of your JPG to be the same as the background colour of your Internet website, it will appear that your image is overlaid on the web page.

JPGs do not support animation. The algorithm to hold the data is too complex to support multi images side by side.

The level of compression can be adjusted giving a 'tradeoff' between filesize and quality of the image. This has made it an ideal image format for the Internet where filesize is important. Normally filesize compressions of between 50% and 80% reduction can be achieved with acceptable image quality.

In 2002, Forgent Networks announced it owned the patent on the JPG technology and that it would charge a license fee to use the JPG image compression. Between 2002 and 2004 it charged licensing revenue to about 30 companies, although this has since been overturned by the courts. The Joint Photographic Experts Group committee had a written goal that their image format standard would be available to everyone without any payment of licensing fees. And this has now been upheld.

 

PNG (Portable Network Graphics) images

These use a lossless data compression and can store as many colours as a JPG image.

PNGs are a little like choosing the best of both worlds and are seen as a successor to GIFs as they offer a free and open-source image format. PNGs provide the lossless data compression and transparency of GIFs and the true colour option of JPGs. PNGs are best suited to photos like JPGs but will not achieve the same compression due to the lossless data format.

There was initial slow support of the PNG image format, but now all major browsers will display PNG images correctly.

 

Conclusion

When you create your own Business Website, you will want to use images. The Website Creation system at AB Publish allows full integration of all 3 of the major image file formats detailed above (although to ensure the maximum compatibility GIFs are converted to JPGs). The final choice of which to use is not based on technical limitation but rather the use of the image on your Business Website:

GIFs are best for logos or images with a limited number of colours. They support transparency, animation and store the image in a lossless format.

JPGs are best for photos where filesize is the most important criteria. No transparency or animation can be performed and the image is stored in a lossy format.

PNGs are best for photos were effects such as halos, glows or drop shadows are required. Full transparency is supported but no animation and store the image in a lossless format.

Mon 6 June 2011 15:13:19

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