Graphics And Compression

Question 1

Bit Mapped Graphics

Answer 1

Resolution of VDU screen = no. of pixels per row X no. pixels per column

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Resolution = Dpi

Question 2

Colour Depth

Answer 2

• number of bits per pixel

Monochrome - 1 bit each for black and white ,
12 bit colour - 4096 colours

True colour - 8 bits for each R G and B
16777216 colours

32 bit colour
Extra 8 bits used for alpha channel - transparency

Question 3

Image size

Answer 3

Bits per colour * number of pixels

Question 4

Metadata

Answer 4

Data about data

• date it was created
• width and height in pixels
• colour depth
• gps co ords where photo taken

Question 5

Data compression

Answer 5

Reducing number of bits required to represent data to reduce storage requirements or to transmit files more quickly

Question 6

Lossless

Answer 6

File can be uncompressed , original quality of image can be restored

Question 7

Lossy

Answer 7

Some of original image lost forever , smaller file size

Question 8

Run Length Encoding

Answer 8

If 3 or more consecutive cells contain same colour , run of cells can be encoded into 2 bytes
First byte stores number of contiguous cells in run and second store the colour code