Study Guide

File extention: used to indicate what is inside the file. (you can't change a file by just changing the extention. This is an important distinction)

example of file extentions.  .jpg, .tif, .psd, .png, .exe, .pdf  *jpeg2000 - uses a different type of algorithm to compress data, has the option of having loss-less compression.  Has not become popular. 


Image size: how do you express the size of an image?  MB, resolution, dpi, blah blah blah.. all of them are acceptable ways of expressing the size.

Resolution: pixels per inch AND pixels per centimetre.  The convention however is to use pixels/inch.

divide by 2.5 to get centimetres.

Bit: Binary Digit... can only be 2 numbers: 1 or 0

8 bits to 1 BYTE.

Can be represented in 2^8 ways.

Photographic Images - Raster
Lines and Shapes - Vector

Vector images can maintain all information.
Raster images deteriorate the more

****Bit Depth: look up bit depth

Three subtractive primary colours: Cyan Magenta Yellow  used for printing
Three additive primary colours: RBG used for monitors that things that emit light.

Complimentary Colours: different sides of a colour wheel are complimentary colours.

In order to compress an image file you must sacrifice information (FALSE!) Tif, Raw, Png, etc....  can all save information.

What results from adding Red and Green (use colour wheel)... R+G = Y

****Bit Map: can only be black or white therefore the bit depth is 1.

Duo tone image: image that is made by using two different colour printing inks. (Andy Warhol Style)

Index Image: each pixel is allocated a number and you look at the look up tables to find out what the number is.  Used for graphic images like Icons or Logos.

Dithering: mingling the colours together to create new tones.

Rasterising: Taking a vector image and convert it to pixels as opposed to lines.  There ARE some programs that can turn a raster image into a vector image... but it's a pointless venture really.


IMAGE SIZE and RESOLUTION CALCULATIONS:

2000 x 2500 pixels
= 5 000 000 pixels
= 5 MP (Megapixels)

Image Size in Inches:

2000 x 2500 with a resolution of 250dpi

2500:250 = 10inches
2000:250 = 8 inches

There you go, basic BASIC equations.... god damn..

****What resolution would require an image size of 12inch by 2.5 inches.?

****Which files are loss-less compression?

If you resize and image from 150 to 250dpi, what happens???  If you go in and start changing the size of the image, you want to know if you are destroying the image.  Resize without resampling, which means the resolution is changing which means that there are a number of pixels lost.

Q21 = A
Q22 = B

Yellow and Magenta Inks combine to make RED!!

THE END!