Multimedia on the web: File formats and application Flashcards
How many colours can a pixel display at a time?
One
What are the 3 independent sub-pixels in a pixel?
Red, green and blue
What is the range of the 8-bit red, green, blue number value?
0 (0% intensity), 127(50% intensity), 255( 100% intensity)
What is an image’s colour depth?
The number of bits required to store the colour of each pixel
What is a raster image?
A grid of coloured pixels, with a fixed number of horizontal and vertical pixels
What is a vector image?
Point co-ordinates with maths to draw connecting lines
What was the first image format supported for use in webpages?
X PixMap (XPM)
What was XPM originally used for?
Small icons, where the image data was stored as editable text.
How are modern image formats stored?
Data is stored in binary form, instead of editable text.
Name some challenges of optimising media?
- Bandwidth
- Quality
- Compatibility
- Performance
What is the difference between lossless and lossy compression?
Lossless compression ensures that the decoded data is identical to the original data. Lossy compression means that the decoded data is relatively similar to the original data, and quality lost during encoding
What are JPEG images?
Joint Photographic Experts Group
A type of lossy format designed specifically for photos.
How do JPEG images work?
Its compression uses block based approximation.
Separate brightness and colour components.
Reduce the resolution of the colour portion
Split the image into small blocks
What are GIF images
Graphic Interchange Format images.
Lossless format for images with few colours and repetitive patterns
What are PNG images?
A patent free alternative to GIF images and maintained by the W3C.
Lossless format optimised for artwork with few colours and repetitive patterns
What are WebP images?
Its a format developed by Google that supports both lossy and lossless conversion and most of the time produces better quality than JPEG
SVG images
Scalable Vector Images
Lossless compression. Vector format and its written as markup code in an HTML document or external file
What are some advantages of plug-ins?
- provides 3rd party functionalities
- potentially higher performance
- identical appearance and functionality across different browsers
What are some dis-advantages of plug-ins?
- Requires users to install more software
- Poor support on mobile devices
- potential security issues
What tags did HTML5 introduce for media support?
and
What type of compression do web audio formats usually use?
Lossy compression
