54 lines
1.7 KiB
Markdown
54 lines
1.7 KiB
Markdown
---
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categories:
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- Computer Architecture
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tags: [binary, binary-encoding]
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---
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# Binary encoding of colours
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The approach to encoding binary representations of colour is very similar to the
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approach we explored when looking at the encoding of
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[alphanumeric values](/Electronics_and_Hardware/Binary/Text_encoding.md).
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We begin by determining the total number of colours and colour shades we want to
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represent. With this value established we then decide on the bit-length required
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that will accomodate this number of variations. Finally, we assign a binary
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number to each representation.
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### Greyscale
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We can start with a limited palette: greyscale. Here there is black and white
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and number of interim shades of grey. The convention is to use an 8-bit number
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which, given $2^8 = 256$ provides 256 shade variations.
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In decimal, 0 is equal to black (zero light intensity) and 255 is equal to white
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(full light intensity). Some examples of this (including binary and hex
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representations are below):
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### Colour encoding
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A single 8-bit number is sufficient for 256 greyscale combinations but with
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colour, the convention is to use three 8-bit numbers where each byte corresponds
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to a value for red, green and blue (RGB). Thus the overall bit-length is 24
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($2^3 + 2^3 + 2^3$). Each value corresponds to a light intensity for the given
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colour. Combined they are capable of representing all colours.
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Some examples below
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#### Red
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Red is represented in RGB with all 8 red bits to set to 1 and the remaining 16
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bits for the other two colours set to 0.
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#### Yellow
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Yellow is represented in RGB with both red and blue set to 1 and the remaining 8
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green bits set to ):
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## Binary encoding of images
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