One of the oldest graphic formats which is still very common today is that of the BMP file or bitmap. Its popularity has grown since it’s conception thanks to the use and support of the file in both Windows as well as the OS/2 operating systems. Today, many graphical programs such as Photoshop and Fireworks actively support bitmaps and even use them in their subsystems.
The image itself is stored in a bit depth format and in the case of BMP files, this is based on the colour depth albeit 1, 4, 8, 16, 24 or even 32 bits per pixel. The images which are 8 bits per pixel or less can be either colour indexed or greyscale; however the colour choices are very slim in 8 bits. Today, the use of 32 bits is common, but in bitmap files, this can mean a very large sized file. This is why many people have begun turning to the use of PNG files for larger colour depth since they are compressed.
Because of the ability to interchange and view bitmapped images on a wide variety of applications, a need for a device-independent form of the BMP file was needed. This was so that the differences between the programs would be able to still render the image properly no matter which application or device for that matter were to open them. These are also known as DIB files or device-independent bitmaps. They are bitmaps in all simplicity, but they are more readily interchanged.
Much like any image format, there are blocks used in the development of the file which helps with the proper rendering of the image. Without these blocks and the rules that go along with them, an image created on one computer would not be accessible from another. In the case of the BMP, the typical block layout of the file is the header which stores metadata abut the image, the bitmap information which is more in-depth information about the image, the colour palette so that a program knows what colours to render as well as the bitmap data which allows the program to know where to render the image’s pixels and in what colours.
In most cases today though, the bitmap is generally losing its flair as people have been moving away from them due to size. Much like the TIFF image file, while the format is still in use by some who are in need of an uncompressed and lossless format, most people will rather deal with a compressed format such as a JPG or PNG since in many cases the compression is not really noticeable.
Original Authors: Nick
Edit Update Authors: M.A.Harris
Updated On: 09/02/2009