Bitmap Basics Review Refresher from Year 8 Multimedia

Bitmap Basics Review Refresher from Year 8 Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

Review of Year 8 We’ll actually start this new unit by reviewing what we did last year. That will remind us about some basic ideas and some continuing themes… Multimedia Memes - Year 9, Unit 1 Hello, I’m Herman Did you Forget me? ! QES Computing 2016 - 17

Review of Year 8 • Last year’s focus was ‘theory’ with bitmap images and how they’re stored in files as binary data • So we’ll quickly review the key points because they’ll help our practical work making memes… Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

Review Page Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

Review – Range of Images Our digital world is filled with all kinds of imagery, from photos & clip art through to animated films Bitmap Image Vector Image 3 D Animation e. g. photos e. g. clip art e. g. movies We focused on photos because we all use them LOTS! Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

Review – Bitmaps & Pixels Bitmaps are a grid of tiny squares or pixels Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

Review – Counting Pixels How many pixels in this tiny sample? 15 pixels 10 pixels 15 x 10 = 150 ? pixels Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

2, 345 pixels Review – Counting Pixels 3, 519 pixels How many pixels in the whole photo? 2, 345 x 3, 519 = 8, 252, 055 ? pixels Imagine you took 8 million this photo & clicked ‘share’. How big would the exported photo be? 8 megapixels Multimedia Memes - Year 9, Unit 1 But many colours are there in our bitmap images? QES Computing 2016 - 17

Review – Counting Colours For example, think about the colour ‘blue’ That’s 29 ‘colours’ – just for ‘blue’ ! Each needs a unique binary colour code So the more binary bits you have… …the more colour codes you can use! Let’s recall why more bits is better… Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

0 0 0 0 00 bit byte 8 bits = 1 byte So how many colour codes can you have with one or more bytes…? Unit 1 – Exploring Digital Data

0 1 2 3 = = 128 64 32 16 8 4 2 1 0 0 0 0 0 1 1 0 1 0 0 0 0 8 bits = 1 byte 256 values 255 = Unit 1 – Exploring Digital Data 128 64 32 16 8 4 2 1 1 1 1 1

18 byte bits 9 bits 10 bits 11 bits 12 bits 13 bits 14 bits 15 bits 216 bytes 256 x 2 values 512 65, 536 values x 2 32, 768 x 2 1, 024 2, 048 16, 384 4, 096 x 2 Unit 1 – Exploring Digital Data x 2 8, 196 x 2

1 byte 2 bytes 17 bits 18 bits 19 bits 20 bits 21 bits 22 bits 23 bits 3 bytes 256 values 65, 536 values ? 16. 7 million x 2 131, 072 values x 2 262, 144 8, 388, 608 x 2 524, 288 x 2 2, 097, 152 1, 048, 576 Unit 1 – Exploring Digital Data 4, 194, 304 x 2 x 2

Images, Pixels & Colours GIF JPEG 8 bits = 1 byte 24 bits = 3 bytes 256 rs Colou Multimedia Memes - Year 9, Unit 1 16 m Colours QES Computing 2016 - 17

GIF & One Byte GIFs 8 bits = 1 byte JPEG 24 bits = 3 bytes Sky & sea not ‘smooth’ More bits GIF can’t do all colours So more colours ‘Posterised’ ‘True colour’ But can do animation! Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

Review Page Multimedia Memes - Year 9, Unit 1 QES Computing 2016 - 17

JPEGs & Three Bytes • So each of the three primary colours can have a value from 0 to 255 • You can write these colour codes in binary (eg 111100000000) • Or you can use those hex codes like you can in Fireworks (eg FF 0000) • But it’s easiest to use decimal RGB codes… codes Unit 1 – Exploring Digital Data