Pixels and image data

A three-pixel row uses 0 for white and 1 for black, read left to right. Under that rule, what does 101 describe?

Interpret each bit as one pixel code, not as an integer place weight

A bitmap stores a grid of pixels

A bitmap represents an image as a rectangular grid of picture elements called pixels

A colour code gives a stored value to each pixel. In the two-colour model used first, white is 0 and black is 1

Storage order matters. These tasks explicitly read a row from left to right; changing the order may change the represented image

The tables describe pixel colours or their stored codes, not a full image-file format

Encode the colours in order

A bitmap row has three pixels. For this supplied two-colour code, white is 0 and black is 1

Store the pixels from left to right, one bit per pixel

Write the three stored bits in order, with no spaces

The codes from left to right are 1, 0, 1

The stored row is 101; each bit describes one pixel, not a place-weight contribution to one integer

Keep a white starting pixel

The table is a three-column, two-row pixel-code grid, with 0 for white and 1 for black. Change only row 1, column 2. Predict which count changes and which remains fixed, then compare both states

When the selected pixel changes from white to black, what happens in this one-bit-per-pixel model?

Count pixels, then bits per pixel

The number of pixels is width in pixels multiplied by height in pixels

For an uncompressed model with a fixed number of bits per pixel, multiply the pixel count by that number of bits

These calculations exclude headers, metadata, padding and compression. They do not predict the complete size of a PNG or JPEG file

Count a two-colour payload

An uncompressed classroom bitmap model is 3 pixels wide and 2 pixels high

Each pixel uses exactly 1 bit. Count pixel data only: no header, metadata, row padding or compression is included

How many bits of pixel data does this model store?

Number of pixels = 3 × 2 = 6

Pixel data = 6 × 1 = 6 bits

This counts only the explicitly stated pixel payload, not the size of a real image file

Use both dimensions

RGB stores three channel values

An RGB colour model gives separate red, green and blue channel values for each pixel

In the model used here, each channel is an eight-bit unsigned value from 0 through 255. Its code is stored separately from the other two channels

Three eight-bit channels use 3 × 8 = 24 bits per pixel. This model has no alpha channel or compression

To encode one requested channel, find that channel's value and use the earlier eight-bit construction method; do not add the red, green and blue numbers together

A zero channel still occupies eight bits

In this RGB model, one pixel stores three separate unsigned channels in order: red, green, blue. Each channel uses eight bits and can range from 0 through 255

Encode only the green channel

Use an unsigned 8-bit binary representation: each position contains 0 or 1, and there is no sign bit

Write exactly 8 binary digits, keeping leading zeros when needed, with no spaces or base label

The green channel has value 0; the other two channel values are stored separately

Start with 0 and consider the weights from largest to smallest

Use 1 when the weight fits the amount left, then subtract it; otherwise use 0

The 8 digits are 00000000; check their weighted sum: \(0 = 0\)

Encode only the requested channel

Three channels for each pixel

An uncompressed classroom bitmap model is 3 pixels wide and 2 pixels high

Each pixel uses exactly 24 bits. Count pixel data only: no header, metadata, row padding or compression is included

How many bits of pixel data does this model store?

Number of pixels = 3 × 2 = 6

Pixel data = 6 × 24 = 144 bits

This counts only the explicitly stated pixel payload, not the size of a real image file

Apply the stated bits per pixel

A pixel grid is not the only description

A bitmap description stores colour data for a grid of pixels

A shape-based vector description can instead store geometry such as a line's endpoints or a circle's centre and radius, together with appearance properties

SVG can contain shapes, text and embedded images, so a filename alone does not establish that every object is vector geometry

Enlarging a pixel display does not automatically recover details that were never recorded. Producing or editing an image is a separate practical task

Description A stores a colour for every cell in a 20-by-10 grid. Description B stores a circle's centre, radius and fill colour. Which comparison follows?

Compare the stored data, not the filename or whether both can be displayed on a screen

Use the representation and its assumptions

Apply the given pixel-colour code in the specified order

Keep red, green and blue channel values separate when encoding an RGB pixel

Count raw payload as width × height × bits per pixel, only under the stated exclusions

Distinguish a pixel grid from stored shape geometry, without assuming that file size or recovered detail follows from appearance alone