1.2 InfoRepr&Multimedia.multimedia Flashcards
What is a bit-map image?
A system that uses pixels to make up an image, stored as a two-dimensional matrix of pixels.
What is a pixel?
The smallest picture element that makes up an image.
What is colour depth?
The number of bits used to represent colours in a pixel; for example, 8-bit colour depth can represent 256 colours.
What is bit depth in images?
The number of bits used to represent the smallest unit in an image; a higher bit depth improves colour quality.
What is image resolution?
The number of pixels that make up an image; for example, 4096 × 3192 pixels (12,738,656 pixels in total).
What is screen resolution?
The number of horizontal and vertical pixels making up a screen display; lower screen resolution than image resolution reduces quality.
What is pixel density?
The number of pixels per square centimetre
What are vector graphics?
Images that use 2D points to describe lines, curves, and shapes rather than pixels.
What is sampling resolution in sound?
The number of bits used to represent sound amplitude (also known as bit depth).
What is the sampling rate?
The number of sound samples taken per second.
What is frame rate in video?
The number of video frames per second.
How does bit depth affect colour representation in bit-map images?
A higher bit depth allows for more colours; for example, 8-bit depth enables 256 colours, while 32-bit depth enables over 4 billion colours.
What happens when a pixel-generated image is scaled up?
The number of pixels remains the same, but they cover a larger area, which can reduce sharpness.
What is pixel density?
The number of pixels per unit area; key when scaling up images to maintain quality.
What is the main drawback of using high-resolution images?
Increased file size, which affects storage capacity, download time, and transfer speed.
How do bit-map images take advantage of human vision?
The human eye can tolerate some resolution reduction before the quality loss becomes significant.
How is the file size of a bit-map image calculated?
File size = Image resolution × Bit depth (in bits), then divided by 8 to convert to bytes.
Calculate the file size of a 1920 × 1080 image with a 24-bit depth.
1920 × 1080 × 24 = 49,766,400 bits (≈6.222 MB in SI units or 5.933 MiB in IEC units).
What additional data is stored in a bit-map image file header?
File type, file size, image resolution, bit depth, and compression type (if any).
What are vector graphics?
Images that use 2D points to describe lines, curves, and their properties, forming geometric shapes.
How are vector graphics created?
Using CAD software or drawing applications with a digital canvas.
What is a drawing list in a vector graphic file?
A list containing commands, attributes, object positions, and relationships between objects.
Why do vector graphics not lose quality when scaled up?
They store relative positions and properties mathematically rather than using pixels.
Why do vector graphics need to be converted to bit-map images for printing?
Most printers work with bit-map formats rather than vector-based formats.
How do vector graphics compare to bit-map images in terms of file size?
Vector graphics have smaller file sizes since they store geometric shapes instead of individual pixels.
Why are vector graphics less realistic than bit-map images?
They use geometric shapes with limited detail rather than tiny pixels for precise colour and shading.
What file formats are commonly used for vector and bit-map images?
Vector: .svg, .cgm, .odg | Bit-map: .jpeg, .bmp, .png
When should vector graphics be used instead of bit-map images?
- When the image needs resizing or scaling
- When the image must be drawn to scale
- When file size must be minimised
When are bit-map images better than vector graphics?
- When the image must look realistic
- When modifying photographs
- When pixel-level editing is required
What are some applications of vector graphics?
Logo design, CAD drawings, and technical diagrams like exploded views of machines.
Why do bit-map images require larger file sizes?
They store information pixel by pixel, capturing more detail and colour variations.
How does sound travel?
Sound requires a medium (such as air or water) to travel through as it moves by causing oscillations of particles.
Why can’t sound travel in a vacuum?
Sound relies on particle oscillations to propagate, and a vacuum lacks particles to transmit the waves.
What characteristics define a sound wave?
Frequency, wavelength, and amplitude (which determines loudness).
How is sound stored in a computer?
It is converted from analogue to digital using an analogue-to-digital converter (ADC).
Why is sound filtered before digitisation?
To remove frequencies outside the range of human hearing, making storage more efficient.
What is sound sampling?
Measuring the amplitude of a sound wave at set time intervals and encoding it in binary.
What is sampling resolution (bit depth)?
The number of possible values used to represent sound amplitude, affecting accuracy.
What is sampling rate?
The number of sound samples taken per second.
How does increasing sampling rate and bit depth affect sound quality?
It improves accuracy and sound quality but increases file size.
What is the standard bit depth used for CDs?
16-bit sampling resolution
What are the advantages of higher sampling rate and resolution?
- Larger dynamic range
- Better sound quality
- Less sound distortion
What are the disadvantages of higher sampling rate and resolution?
- Larger file sizes
- Longer transmission/download times
- Requires greater processing power
What are some common sound editing features?
- Edit start/stop times and duration
- Extract, save, or delete parts of a sample
- Alter frequency and amplitude
- Fade in/fade out
- Mix and merge multiple tracks
- Remove noise and enhance specific sounds
- Convert between different audio formats
How do digital cameras, smartphones, and tablets capture moving images?
By ‘stitching’ a series of still frames together to create motion.
What does DV stand for in video recording?
Digital Video
What is motion JPEG?
A video format where compressed photo frames are stored at a speed of 25 MB per second.
How do cameras capture light from an image?
Using light-sensitive sensors that convert light into an electronic signal.
How is video data stored in DV cameras?
The electronic signals are automatically converted into a compressed digital file format.
What is frame rate in video recording?
The number of frames recorded per second.
