Bitmaps

Description:

• A bitmap is a represntation of an image where each square represnts a pixel (picture elements).
• The colour of each pixel is represented by a binary code
• The number of colours available in an image depends on the number of bits each pixel has.

For example, a black and white image only uses 2 colours therefore, only needs 1 bit to represnt each pixel.

For Example:

Images with 4 colours for example, will have 2 bits per pixel where each pixel can be one of 4 values:

• 00
• 01
• 10
• 11

For Example:

You can increase the range of colours and shades by increasing the number of bits per pixel.

Colours

Colour Depth:

• The colour depth is the number of bits used for each pixel.
• Given the colour depth, you can calculate how many colours are used in an image using the formula:

Total number of colours = 2^n Where n = number of bits per pixel.

• Most devices use 24-bit colour depth, this ensures that the device will cover all of the colours humans can possibly see.
• This is because humans can see around 10,000,000 colours and 24-bit colour depth covers around 16,000,000 colours.

24-bit colour depth:

Image Resolution:

• Image resolution is the number of pixels in an image.
• To calculate image resolution: width X height of a bitmap.
• The higher the image reolution indicates the that the image has more pixels so is better quality.

File Size

• To calculate file size/ the number of bits an image will take up, the following formula is used:

File size = Image reolution (width X height) X Colour Depth.

• Using a greater image resolution or colour depth will increase the file size but will increase the quality of the image.