Image File Formats

There are a variety of image formats, and each serve a different purpose, mainly correlated to how is the image is going to be used. There are two main types of graphics file formats, bitmap and vector.

In Compressed Image File Formats it states “Vector graphics formats use a series of drawing commands to represent an image.” Vector formats are easy for editing programs to modify such task as adding, deleting, and resizing.

Bitmaps consists of rows and columns of pixels in a space to create an image. Compressed Image File Formats again states “The greatest advantage of bitmap images is their quality. As the amount of disk space and memory has increased along with the speed of processors, the use of bitmap images has expanded as well. One of the most visible examples of this is in the computer game industry…”

JPEG stands for Joint Photographics Experts group, it is one of the most widely used format for storing photos, it has the most compression ability of any bitmap formats “A photograph that takes 1 MB to store in a Windows BMP file can usually be compressed down to 50 KB with JPEG” This is why most images you see on the web are saved as a JPEG to save space online and physical disk space of the uploader. Its relatively small size also helps with devices with slow bandwidth speeds, as it does not take long to load. However “it is not suitable for some applications. All of the JPEG compression methods in general use are lossy, which makes them unsuitable for an intermediate storage format when you are repeatedly editing an image file.” It is also not as suitable at compressing text and drawings.

Graphics Interchange Format also better known as “GIF” in the early days of computers was the most widely used format, it is capable of up to 256 colours and multiple images per file. GIF has been replaced by JPEG as the most widely used format because of its better compression and colour depth. Despite it’s inferiority GIF is still being used today, its main use is animations because “GIF allows multiple images to be stored in a single file. Web browsers have taken advantage of this capability to store simple animations.”

Portable Network Graphics, otherwise known as PNG is a relatively brand new graphics format, it is now receiving widespread recognition. One of the reasons is because “of the legal issues surrounding the use of GIF, PNG should now be used instead of GIF in those applications where JPEG is not a suitable alternative. In situations where you need lossless compression for 24-bit images, such as the intermediate format for images that are repeatedly edited, PNG is much better suited than JPEG.” Typically when uploading images, where it needs to be in high resolution, PNG is the best format to export to, because of its lossless compression, it will retain all the details that otherwise would have been lost or compressed if exported as a JPEG.

Reference:John Miano, 1999. Compressed Image File Formats: JPEG, PNG, GIF, XBM, BMP. Edition. Addison-Wesley Professional.