GIFS TIFFs JPEGs PNGs and More

7 Feb

Guest Site

http://www.wfu.edu/~matthews/misc/graphics/formats/formats.html

So you want to know what these file extentions mean because you didn’t go to school for graphic design…or maybe you’re just a curious (blank). I went to school for graphic design so i’m excited. In the words of eternal Mario…”here we go”…

JPG, GIF, TIFF, PNG, BMP and many other file types are used to encode digital images.

Part of the reason for picture file types is the need for compression. Image files can be quite large, and larger file types mean more computer space usage and slower downloads. Compression is a term used to describe ways of cutting down the size of the file. Compression – to make smaller.

Another reason for the many file types is that images differ in the number of colors they contain. Few colors, reduced file size.

SUMMARY

GIFs and JPGs are the formats used for nearly all web images. PNG is supported by most of the latest generation browsers. TIFF is not widely supported by web browsers, and should be avoided for web use. PNG does everything GIF does, and better. PNG will not replace JPG, since JPG is capable of much greater compression of photographic images, even when set for quite minimal loss of quality

Lossy vs. Lossless compression

A lossless compression algorithm discards no information.

A lossy algorithms accept some degradation in the image in order to achieve smaller file size.

File Types

GIF (pronouced ‘JIF’) Graphics Interchange Format

Compress large pictures to small pictures, this is why GIFs can be used for small animations and low-resolution film clips. It’s not true color and resolution, just a compressed version of it.

GIF achieves compression in two ways. First, it reduces the number of colors of color-rich images, thereby reducing the number of bits needed per pixel,  Second, it replaces commonly occurring patterns with a short/ combined patterns.

GIF creates a table of up to 256 colors from a pool of 16 million. If the image has fewer than 256 colors, GIF can render the image exactly. When the image contains many colors, software that creates the GIF uses any of several algorithms to approximate the colors in the image with the limited palette of 256 colors available. Better algorithms search the image to find an optimum set of 256 colors. GIFs can be still pictures as well. They are usually simple color that compress well

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JPEG/ JPG (pronounced jay peg) Joint Photographic Experts Group

optimized for photographs and similar continuous tone images that contain many, many colors. It can achieve astounding compression ratios even while maintaining very high image quality. JPG works by analyzing images and discarding kinds of information that the eye is least likely to notice. It stores information as 24 bit color. The degree of compression of JPG is adjustable (you can adjust JPEGs compression).

At moderate compression levels of photographic images, it is very difficult for the eye to discern any difference from the original, even at extreme magnification.

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TIFF – Tagged Image File Format

 A very flexible format that can be lossless or lossy. The details of the image storage algorithm are included as part of the file. TIFF is used almost exclusively as a lossless image (exact with all file info/ same as orginal, thus a pain to edit once saved like PNG files and good for non reproducing and altering ) storage format that uses no compression at all. Most graphics programs that use TIFF do not compress. Consequently, file sizes are quite BIG (thus causing other formats and file types like JPEG to be more popular).

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PNG – Portable Network Graphics

A lossless storage format (exact with all file info/ same as orginal). However, in contrast with common TIFF usage, it looks for patterns in the image that it can use to compress file size. The compression is exactly reversible, so the image is recovered exactly.

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RAW

Image output option available on some digital cameras. Though lossless, it is a factor of three of four smaller than TIFF files of the same image. Raw files are so named because they are not yet processed and therefore are not ready to be printed or edited with a bitmap graphics editor. 

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BMP – Bitmap Image File / Device Independent Bitmap (DIB) file

An uncompressed proprietary format invented by Microsoft. (Exclusive to Microsoft, kinda like Apple products can only be used by Apple)

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PSD/  PSP –  Photoshop Document

Proprietary formats used by graphics programs. Photoshop’s files have the PSD extension, while Paint Shop Pro files use PSP. These are the preferred working formats as you edit images in the software, because only the proprietary formats retain all the editing power of the programs. These packages use layers to build complex images, and layer information may be lost in the nonproprietary formats such as TIFF and JPG.

INTERESTED IN LEARNING MORE…READ MORE ON ORIGINAL SITE ABOVE

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