2. So what is Digital Imaging?
Images are objects that can communicate a
meaning or information. Now, if an image is
transferred into a computer or a digital device, it
must be in a digital form.
Digital Image – an image that can communicate
meaning or information digitally.
There are two types of Digital images these of
which are Vector Images and Raster Images.
3. Raster Images
Raster Images are made of
individual pixels on the screen
Can also be referred to as Bitmap
images
Dependant on resolution - very
difficult to resize without altering
the quality of the image
IDEAL for natural and
photographic images that have a
high level of detail with complex
colours and tones.
4. Raster Images
Advantages:
- Ideal for natural and photographic images with high level
of detail
- Maintains image quality with a reduced file size
- Easy to edit which is a plus for users that digitally
manipulate images
- Easy to alter the colour of the image
Disadvantages:
- Resolution dependant, which means that pixels are visible
as the quality is reduced
- File size is determined how the image is altered
5. Vector Images
Created on the computer using
mathematical calculations to
make a line or a curve.
Are NOT resolution dependant –
resizing the image will not affect
the quality of the it.
IDEAL for simple geometric
shapes and logos and
typefaces
6. Vector Images
Advantages:
- Much more flexible than raster images
- NOT resolution dependant – quality does not change when
image is resized
- File size is smaller than Raster images since they produce
less information
Disadvantages:
- In order to be viewed on a monitor, they must be converted
to become a raster image.
- Since computer monitors can only show pixels
- The computer has to recalculate the vector images every
time it is refreshed.
7. Image file formats
Image file formats are images that have been stored
using a specific file format. This allows the computer
to tell what type/kind of data is stored within the
image file.
IMAGE FILE FORMATS
- .jpg
- .tif - TIFF
- .bmp - bitmap
- .gif
- .png
8. Image file formats - JPEG
JPEG – Joint Photographic Expert Group
- Developed specifically to provide a suitable format for the storage of
photographic and photo-realistic images
- For photographic and image files
Advantages:
- Gives very high compression ratios
- Used for highly detailed, natural, art or photographic images
- Acceptable in most websites
- Great for transmitting across different Media
Disadvantages:
Compression is cumulative – this means that everytime it is
compressed over and over again, the quality is lost as data keeps on
being removed
Mainly designed for websites and emails.
9. Image file formats - GIF
GIF – Graphic Interchange Format
Developed specifically for online use
Ideal use for webpages since it GIF’s are cross platform and compressed
Advantages:
- Best for images with a large area of solid colours. E.g shapes, logos and
text
- Designed to produce small files. Hence, the best file format for
transmit over the net
- Can be interlaced and animated
- Can be set to be transparent
Disadvantages:
- Has a limited colour depth of 8 bits (only 256 colours)
- Not suitable for natural or photographic images.
10. Image file formats - TIFF
Tagged Image File Format
Leading professional image standard.
Used to archive important images because of its high
quality and flexibility for an image
Advantages:
- Lossless – image resolution does not change after being
modified
- Quality of the image is very high
- Good for photo-realistic images
Disadvantages:
- File size is very large
- Not a suitable format for the web
11. Image file formats - PNG
PNG – Portable Network Graphic
For displaying colour images on the web
Advantages:
- Supports transparency
- Has a colour depth of 32 bits
- Improved image compression
- Lossless compression scheme
Disadvantages:
Has not been widely accepted and supported by viewing
browsers and the public
Lossless compression scheme will make it have a larger file
size
12. Image file formats - BMP
BMP – Bitmap
Used as a simple graphics format for platforms
Advantages:
- Free of patents
- Pixel values can be modified individually or as large groups.
Disadvantages:
- Can’t be used to transfer files over the net
- Very large file size
- Can’t be compressed (typically)
