5. Multimedia Foundation

The two meanings of media

① An entity that stores information , Disk 、 Compact disc 、 Tape, etc .

② The carrier of information , Like numbers 、 written words 、 voice 、 Graphics and images .

Multimedia classification

● Feeling media

It refers to the direct action on human sensory organs , The media that makes people feel directly . Such as ∶ voice 、 graphics 、 Images 、 Animation, etc. .

● Presentation media

For processing 、 Processing and transmitting sensory media for human research 、 A medium constructed , There are various common coding methods .
Such as text encoding 、 Image coding and sound coding, etc .

● Display media

A physical device that represents and obtains information . Such as ∶ Enter display media keyboard 、 Mouse and microphone, etc ; Output display media display 、 Printers, speakers, etc .

● Storage media

A physical device that stores data , Disk 、 Compact disc 、 Memory 、ROM、RAM etc. .

● Transmission media

A physical carrier for transmitting data , Such as cable 、 Optical cable and switching equipment, etc . Three indicators of sound perception

● The volume （ loudness ）

The intensity of the sound , Depends on the amplitude of the sound waveform , That is, it depends on the magnitude and strength of the amplitude .

● tone

The pitch , Depends on the fundamental frequency of the sound wave . The lower the fundamental frequency , The lower you feel , High fundamental frequency makes the sound sharp .· The timbre is blended into the pitch （ Fundamental wave ） Overtone of （ harmonic ） Determined by , Each sound has its own fixed frequency and overtones of different intensities , So that they have a special timbre effect . Three elements of lustre

● brightness

It describes the feeling of brightness caused by light acting on human eyes , It refers to the intensity of the color .

● tonal

It refers to the category of colors , Like red 、 green 、 Different colors such as blue refer to hue .

● Color saturation

It refers to the depth of a certain color （ Or concentration ）. For colors of the same hue , The higher the saturation , The darker the color , The lower the saturation , The lighter the color . Color space
It refers to the color description method used for color images , Also called color model .

●RGB Color space

use R（ red ）、G（ green ）、B（ blue ） The color values of digital image pixels are represented by the components of three primary colors .

●CMY Color space

Color mode based on printing processing , adopt C（ green ）、M（ Purplish red ）、Y（ yellow ）、K（ black ） Four colors combine to create a color image .

●YUV Color space

The TV image of the color a-tv system is adopted in winter Y、U、V The component represents . A luminance component Y And two color differences ⅡJ、V The component represents . Because brightness and chroma are separated , The problem of compatibility between color and black-and-white display systems is solved , If only Y Weight without U、V component , Then the image represented is a black-and-white gray-scale image .

●HIS Color space

It starts from the human visual system , With hues （Hue）、 Color saturation （Saturation or Chroma） And brightness （Intensity or Brightness） To describe color .

Graphic image related concepts

● graphics

It refers to the picture drawn by computer .

● Images

It refers to the actual scene picture captured by the input device or any picture stored in digital form .

● Bitmap

Is an image described in the form of a dot matrix .

Vector graph is an image composed of geometric elements, which is described mathematically .

● The resolution of the

Display separation rate ∶ It refers to the number of pixels that can be displayed on the display screen ∶ Display resolution 1024*768∶ among 768 Indicates that the screen is divided into 768 That's ok , Called vertical resolution ; among 1024 Indicates that each line displays 1024 Pixel , Called horizontal resolution .

Image resolution ∶ Refers to the pixel density of an image ; It is also a horizontal and vertical pixel representation ; That is, how many points per inch （dpi） Represents the size of the digitized image .; use 200dpi To scan a picture 2*2.5 Inch color photos , So get one 400*500 An image of pixels

● Image depth

The number of bits used to store each pixel , It is used to measure the color resolution of an image .

The pixel depth determines the number of colors that each pixel of a color image may have or determines the number of gray levels that each pixel of a gray-scale image may have