Image-Based Formats

Image-based formats come in all shapes and sizes, and can vary quite widely in how they can be used. For example, a special image-based format called a geoTIFF is used in GIS systems to create useful maps. The most common image-based formats are used simply to show a single thing in a graphical way without other intended use, and this use is how SCERA defines a image-based format.

The most common types of image based formats are:

• .tif/.tiff
• .jpg/jpg 2000
• .bmp
• .png
• .gif

.tif/.tiff

.tif/.tiff stands for Tagged Image File Format (.tif is a shortening of .tiff). Images in TIFFs are divided into individual pixels with an assigned color. Pixels are measured by how many exist per square inch. The number of pixels that can fit into a single square inch varies based on the preference of the person creating the file, but the more pixels per inch the higher the clarity. Each individual pixel is given a tag to give a tiff-rendering program exact pixel coordinates for the image reconstruction. Because of this level of detail and description, a tiff file can have a very large file size. A tiff file can either be compressed (the size is made smaller using a computer trick) or uncompressed.

.jpg

.jpg, sometimes called a .jpeg, is a compressed type of image file format. Images in JPGs are divided into individual pixels with an assigned color just like in TIFFs. Pixels are measured in quantity per square inch and can vary widely in frequency. The difference between a JPG and a TIFF is how it stores an image. A JPG uses a special reference method to tell a jpg-rendering program the coordinates of pixels in the image (based on what color the pixel is) without repeating the pixel information every single time. This makes a much smaller file size, but often means the picture is less clear. JPG 2000 is the least “lossy” of the JPG file formats.

.bmp

.bmp is an abbreviation for Bitmap. BMP files are one of the oldest types of image files. It renders “bits” of color information onto a rectangular area or “map” of a particular size that results in a image. While in some areas of practice it is common, and tends to be stable, in SCERA public versions of BMP files are migrated to jpg or tiff format.

.gif

.gif stands for Graphics Interchange Format. GIF images use a limited number of colors, and are uncommon for pictures and other large images. However, it is often used for logos and basic art presented on the internet. It also support short animations that automatically repeat. It uses a lossless compression to make the file size smaller. The default computer program for most systems to view a GIF is a web-browser.

.png

.png stands for Portable Network Graphics. PNG files are very similar to GIF files and were invented about the same time as the GIF. They are commonly used on internet webpages for graphics and logos, although they do not support animations. Also like a GIF, PNG files use a lossless compression to make the file size smaller.