Computer Science - 9210 OxfordAQA

Representing Images

Muhtasari

Hold a phone screen close enough and the photograph on it stops being a photograph. What you see instead is a grid of tiny coloured squares, laid out in rows and columns, each one a flat single colour. Step back and your eye blends them into a face or a landscape. That grid is the entire secret of how a machine that stores nothing but numbers manages to store a picture: the picture is chopped into squares and each square is written down as a number.

This lesson teaches you the two measurements that describe such an image, its size in pixels and its colour depth, and shows you how those two numbers alone determine the file size. You will calculate file sizes in bits and in bytes, turn a pattern of binary digits into a picture and a picture back into binary digits, and be able to say precisely what a photographer is trading away when they choose a smaller file.

Malengo

  1. Understand what a pixel is and be able to describe how pixels relate to an image and the way images are displayed.
  2. Describe the following for bitmaps:
  3. size in pixels
  4. colour depth.
  5. Describe how a bitmap represents an image using pixels and colour depth. Describe using examples how the number of pixels and colour depth can affect the file size of a bitmap image.
  6. Calculate bitmap image file sizes based on the number of pixels and colour depth.
  7. Convert binary data into an image.
  8. Convert an image into binary data.

Ramani ya mawazo

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Maelezo ya Somo

A screen cannot draw a smooth curve. What it can do is switch several million tiny lights on and off independently, and if the lights are small enough and close enough together, a staircase of squares reads to the eye as a curve. Each of those tiny elements is a pixel, a word squeezed out of picture element. A pixel is a single point in a graphical image, and it holds exactly one colour.

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Tathmini ya Somo

Hongera kwa kukamilisha somo la Representing Images. Sasa kwa kuwa umechunguza dhana na mawazo muhimu, ni wakati wa kuweka ujuzi wako kwa mtihani. Sehemu hii inatoa mazoezi mbalimbali maswali yaliyoundwa ili kuimarisha uelewaji wako na kukusaidia kupima ufahamu wako wa nyenzo.

Utakutana na mchanganyiko wa aina mbalimbali za maswali, ikiwemo maswali ya kuchagua jibu sahihi, maswali ya majibu mafupi, na maswali ya insha. Kila swali limebuniwa kwa umakini ili kupima vipengele tofauti vya maarifa yako na ujuzi wa kufikiri kwa makini.

Tumia sehemu hii ya tathmini kama fursa ya kuimarisha uelewa wako wa mada na kubaini maeneo yoyote ambapo unaweza kuhitaji kusoma zaidi. Usikatishwe tamaa na changamoto zozote utakazokutana nazo; badala yake, zitazame kama fursa za kukua na kuboresha.

  1. What does the term pixel stand for? A. Picture element B. Pixel encoding layer C. Point in colour D. Primary index Answer: A
  2. An image has a colour depth of 4 bits. How many different colours can each pixel be? A. 4 B. 8 C. 16 D. 32 Answer: C
  3. A bitmap is 10 pixels by 10 pixels with a colour depth of 8 bits. What is its file size in bytes? A. 80 B. 100 C. 800 D. 8,000 Answer: B
  4. An image is stored at 200 x 100 pixels. It is resaved at 400 x 200 pixels with the same colour depth. How does the file size change? A. It stays the same B. It doubles C. It quadruples D. It halves Answer: C
  5. An image uses exactly 5 different colours. What is the minimum colour depth needed? A. 2 bits B. 3 bits C. 5 bits D. 8 bits Answer: B

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Fanya Mazoezi ya Maswali ya Majaribio

Ungependa kufanya mazoezi ya maswali ya majaribio kuhusu Representing Images? Pakua programu ya Green Bridge CBT ili kupata maswali ya majaribio na tathmini kamili za mazoezi kuhusu mada hii.

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