Essential revision

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1. ASCII

2. Features of Unicode (4) • Can represent characters from all languages • Tries to represent every possible character, and covers all major languages. • Comes in 16-bit and 32-bit binary codes. • Is recognised by all major hardware and software manufacturers

3. Why humans use HEX (3) • Much shorter than binary • Easier to work with • Less prone to error

4. Examples of metadata (7) • File format • Width • Height • Colour depth • Resolution • Time/date the image was created/edited • Author

5. Factors affecting image size and quality (6) Colour depth is the number of bits used for each pixel. • To work out how many colours can be represented is 2d where d is the number of bits used per pixel (e.g. 4-bit image is 24 = 16 colours). • Human eye can see around 10 million colours so 24-bits tend to be popular (16.7 million colours). • Increasing colour depth means more bits in the image which improves image quality but increases file size. Resolution is the density of pixels in the image (e.g. how many pixels in a given area like an inch - dpi). • The higher the resolution, the greater the density of pixels in a given area increasing quality. Increasing resolution means more bits in the image which increases the file size.

6. Factors affecting image size and quality (6) Colour depth is the number of bits used for each pixel. • To work out how many colours can be represented is 2d where d is the number of bits used per pixel (e.g. 4-bit image is 24 = 16 colours). • Human eye can see around 10 million colours so 24-bits tend to be popular (16.7 million colours). • Increasing colour depth means more bits in the image which improves image quality but increases file size. Resolution is the density of pixels in the image (e.g. how many pixels in a given area like an inch - dpi). • The higher the resolution, the greater the density of pixels in a given area increasing quality. Increasing resolution means more bits in the image which increases the file size.