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EECS > W6 (presenting Images) > Flashcards

W6 (presenting Images) Flashcards

1
Q

What is the another name of the pixel?

A

picture element

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2
Q

how many type of light-sensitive exist in human retina?

A

4.

1 for low-light “night” vision: rods, ignored here
* 3 for “regular” vision
short/medium/long
Most birds: 4
Dogs, cows…: 2

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3
Q
A

most of the important perceptible colors can be formed by combining these RGB components

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4
Q

RGB color model

A

Three integers (usually in the range 0..255*) describe the amount
of Red, Green, and Blue required to reproduce the colour

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5
Q
A

Other colour models
* Cyan, Magenta, Yellow, and blacK (CMYK) − e.g., colour printers
* Start with white [paper], then subtract individual components
* Hue, Saturation, Luminance (HSL); Luminance, Blue, Red (YUV)
* Similar to colour wheel principle
* Map better to how human brain interprets colours

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6
Q

what is the range for each R,G andB?

A

0..255 (1 byte)

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7
Q

Color values and HTML color picker

A
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8
Q

What is resolution mean in digitized images and graohics?

A
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9
Q
A
  • Resolution
  • Number of pixels in an image (or on a display)
  • Size of an image, measured in pixels
  • Sometimes refers to the pixel density, the number of pixels per
    unit of distance (e.g., pixels per inch or ppi
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10
Q

what is vector graphics?

A

An image that is defined using mathematical equations

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11
Q

what does resolution in Digitized Images and Graphics

A

In practical terms, resolution describes the sharpness, or clarity, of an image or picture. It is expressed in terms of the number of pixels that can be displayed both horizontally and vertically. Resolution is an important factor to measure the visual quality of digital images, photos and videos.

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12
Q

what is the example of resolution in Digitized Images and Graphics

A

For example, an image that has a resolution of 600 ppi will contain 600 pixels within each in of the image. 600 is a lot of pixels to live in just one inch, which is why 600ppi images will look very crisp and detailed. Now, compare that to an image with 72ppi, which has a lot fewer pixels per inch.

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13
Q

what is the unit for measuring the size of an image?

A

pixels

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14
Q

what does pixels per inch or ppi mean?

A

sometimes refers to the pixel density, the number of pixels per unit of distance

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15
Q

what is vector graphics? what kind of format it has?

A
  • An image that is defined using mathematical equations
    representing lines, curves, and polygons
  • Can be enlarged without loss of detail, or change in file size
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16
Q

what kind of changes we have for enlarging the vector graphics?

A

Nothinggggggggggggg

  • Can be enlarged without loss of detail, or change in file size
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17
Q

how image created in vector graphics

A

using 1) drawing application
2) text editors

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18
Q

what kind of vector graphics format is text- base and can be compressed accordingly?

A

SVG ( scalable vector graphics )

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19
Q

What is SVG ( scalable vector graphics)

A

1) Popular vector graphics format
2) SVG files are text-based and can be
compressed accordingly

20
Q

computer typeface (fonts) and geometric shapes are example of ?

A

vector graphics

21
Q

what are the example of vector graphics?

A

1) computer typefaces (fonts)
2) geometric shapes in various apps

22
Q

what is raster graphics?

A
  • An image that is comprised of a matrix of pixels
23
Q

how does image create and edit in rater graphics?

A

by using painting applications

24
Q

what is the advantage and disadvantage of raster graphics?

A

1) very good for photographs
2) suffers from pixelation

25
Q

What happens to an image in raster graphics when enlarging happens?

A

When enlarged, the rectangular shape of pixels becomes apparent

26
Q

what is the popular technique for compressing image?

A

indexed colour

27
Q

what is indexed colour ?

A

Popular technique for compressing images
* Instead of representing all colours, save only those used (or
those that are most useful to keep)

28
Q

what is indexed colour similar to?

A

similar to compressing text with keyword encoding, but the colours instead, and with some colours possibly removed

29
Q

what is keyword encoding?

A

Keyword Encoding. Frequently used words are replaced with a single character. For example… Note, that the characters used to encode cannot be part of the original text.

30
Q

what kind of image format we have?

A

1) GIF (Graphics Interchange Format, pron. “Jiff” or “ghif”)
2) PNG (Portable Network Graphics)
3) JPEG (Joint Photographic Experts Group)

31
Q

which of the image formats are lossless?

A

GIF and PNG

32
Q

Which of the image formats are lossy?

A

JPEG

33
Q

how much is the compression ratios of GIF?

A

10%

34
Q

how much is the compression ratios of PNG?

A

7%

35
Q

what is the maximum of indexed colour in GIF?

A

max of 256

36
Q

What is coding in GIF related to?

A

related to huffman’s

37
Q

which image formats allows transparency and animation?

A

GIF

38
Q

what kind of encoding does PNG have?

A

run- length encoding

39
Q

GIF?

A
  • Lossless, indexed colours (maximum of 256), coding related to
    Huffman’s
  • Compression ratios of 10 % [reference]
  • Allows transparency and animation
40
Q

PNG

A
  • Lossless compression using indexed colours, run-length encoding
  • Compression ratios of 7 % [reference]
  • Allows transparency
  • More modern
41
Q

how does lossless compression occur in PNG?

A

by using indexed colour

42
Q

which of the image formats are more modern?

A

PNG

43
Q

which of the image format allows transparency?

A

PNG and GIF

44
Q

Does PNG allow animation?

A

noooooooooooooooooo
Just onlyyyyyyyyy transparency

45
Q

what are PNG and GIF use for?

A

-best use for line drawing, logos, or diagrams
-Photos: PNG – too large (lossless); GIF – low quality (256 colours)

46
Q

JPEG

A

(Joint Photographic Experts Group)
* Great for photos, bad for images with text or sharp lines
* Compression ratios of 1–10 %, depending on quality [reference]
* Lossy; compression technique
* Reduce colour resolution (sharp colour transitions less
noticeable than to sharp brightness transitions)
Divide the entire image into blocks of 8 × 8 pixels
For each block perform a frequency transform (called DCT)
* Store the average intensity
* Relative to that average, save only the most important
spatial frequencies
* Similar to how stronger sound frequencies (notes) might
dominate in a music passage
* Faint consistent noise might disappear (small details too)
* How much info to keep depends on quality setting chosen
by the user
* Sharp transitions (e.g., letter outlines) have a wide range
of spatial frequencies around edges: nothing to remove

47
Q

what is the compression ratio depends on in JPEG?

A

Compression ratios of 1–10 %, depending on quality

EECS (6 decks)

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