Bitmap (AKA Raster images) Pixel based image type which can become jagged or distorted if the image is rescaled or if it hid displayed on a HD screen. Bitmap image files are appropriate for photo editing and/or art works created in painting programmes.  

 A standard bitmap immage

 an enlarged bitmap image

Bitmap images and files use the extensions:

• .Bmp
• .Png
• .Gif
• .Tiff
• .Jpg
• .Psd

Raster image compression Lossless compression

 Lossless compression algorithms reduce file size with no loss in image quality, though they usually do not compress to as small a file as a lossy method does. When image quality is valued above file size, lossless algorithms are typically chosen. 

Lossy compression 

Lossy compression algorithms take advantage of the inherent limitations of the human eye and discard information that cannot be seen. Most lossy compression algorithms allow for variable levels of quality (compression) and as these levels are increased, file size is reduced. At the highest compression levels, image deterioration becomes noticeable. This deterioration is known as compression artifacting. 

Vector images 

Vector graphics are pristine images even with rescaling and high or low resolution monitors they’re well suited for line art, maps and logos. Vector files are also more compressed and take less time to upload/ download from the net and they take less time to open on slower computers or on computers with a low band with. 

 This is an example of a vector work path as used in Adobe Photoshop.  

Points, curves and polygons 

Vector images are made by using points called Vectors to construct the image (sort of like a complex dot to dot) with the ability to turn the lines between each line into a curve or form it into a group of lines to form polygons.  The file extensions used for Vector images  file types are:

• .Eps
• .Ai
• .Fla
• .Pdf
• .Swf
• .Wmf (Windows metafile)

 Bit depth 

Bit depth or colour depth is the term used to describe the number of bits used to colour a single pixel in a bitmap image. The concept is also known as BPP (Bits per Pixel) especially when specified along with how many bits have been used in the image. Higher Bit-depth gives a larger range of distinctive colours. 

Monochrome   

Monochrome in the computer graphical sense technically means Black and White or Greyscale but it can also mean any combination of 2 colours such as Blue and white or Black and red, it may also refer to Sepia or Cyanotype images. 

High colour 

Highcolour graphics (variously spelled Hicolor , Hicolour, and Highcolour, and known as Thousands of colors on a Macintosh) is a method of storing image information in a computer’s memory such that each pixel is represented by two bytes. Usually the color is represented by all 16 bits, but some video chipsets also support 15 bit highcolour. (Definition from Wikipedia)  

True colour 

Truecolour is a method of representing and storing graphical image information (especially in computer processing) such that a very large number of colors, shades, and hues can be displayed at once, such as high quality photographic images or complex graphics. By this definition Truecolour is when an image is colored by at least 256 shades of red, green and blue for a total of 16,777,216 color variations. (Definition from Wikipedia)  

Colour depth RGB 

RGB is a colouring model based on using the colours using Red, Green and Blue to recreate a large array of colours. The term RGBA is also used this isn’t a different colour model the “A” on the end stands for Alpha which is the images transparency. The image to the right is an example of how an image changes if the levels of Red, Green and Blue are changed.