Transcript sourcing images

A computer display is made up of small squares, called pixels.
Digital images are also made up of pixels and have a resolution (measured in
pixels) indicating the width and height. The higher the resolution, the larger the
image appears on the screen.
As the resolution increases, so does the file size (in bytes) because the image
contains more information.
The display has a screen resolution, measured in pixels, indicating the width
and height:
e.g. 1024 x 768 pixels denotes a display consisting of 1024 rows of 768
pixels.
Displays are often capable of using different screen resolutions:
e.g. 800 x 600 pixels or 1024 x 768 pixels, 1280 x 1024.
The higher the resolution, the more detail is displayed on the screen.
At a screen resolution of 1280 x 1024 pixels, a 518 x 255 image appears quite small on
the screen. At a screen resolution of 800 x 600 pixels, the image appears much larger.
The image's actual size has not been altered, it simply takes up more of the screen
pixels, as there are less screen pixels available.
1280 x 1024
800 x 600
Compression
• File formats are used to encode digital images.
• Part of the reason for different file types is the need for compression.
• Image files can be quite large, and larger file types mean more disk usage
and slower downloads.
Compression is a term used to describe ways of cutting the size of the file. This
can be achieved by removing colour information (e.g. From 16 million colours
to 256) or by removing detail that would be unnoticeable to the eye.
Compression schemes can be described as lossy or lossless. This indicates
whether compression affects the quality of the image on successive saves.
Digital Images: Output
Choice of image format depends on the
type of output.
If you are using images for publications,
desktop publishing or a final print
output, choose lossless formats and high
resolutions (larger file sizes)
For the internet, speed and accessibility
are the most important aspects, so
formats which give a decent image but
have a relatively low file size are ideal.
Therefore, we might use ‘lossy’ formats
like JPEG.
WEB PRODUCTION FORMATS
JPEG (Joint Picture Experts Group)
JPEG is popular image format for web use due to its
retention of image quality with relatively small file sizes.
Beneficial effects of compression are best seen on
photographs with smooth gradations of colour.
JPEG is the most commonly used format for saving Digital
Photographs.
JPEG is a ‘lossy’ format.
Not as effective for line drawing, text objects or icons where
contrasts are sharp.
WEB PRODUCTION FORMATS
GIF
(GRAPHIC INTERCHANGE FORMAT)
GIFs are used to display limited (indexed) colour graphics
on the web.
More appropriate for logos and artwork than
photographs.
GIF files support transparency.
GIF is a compressed format that reduces the file size of images.
It only supports a limited number of colours.
WEB PRODUCTION FORMATS
PNG
(Portable Network Graphics)
PNG was developed as an alternative to GIF for displaying
images on the web.
It uses lossless compression and supports transparency.
Some browsers do not support PNG.
PRINT PRODUCTION FORMATS
TIFF
(TAGGED IMAGE FILE FORMAT)
TIFF is a common bitmap image format, so most imageediting software and page-layout applications support TIFF
images up to 2GB in size.
TIFF supports most colour modes and can save images
with alpha channels.
While Photoshop can also include layers in a TIFF file, most other
Applications cannot use these extended features and see only the
Flattened image.
SOURCING IMAGES
From the Internet
From a Digital Camera
SOURCING IMAGES
From the Internet
USING SEARCH ENGINES
VIDEO HERE
SOURCING IMAGES
From a Digital Camera
TAKING PICTURES AND TRANSFERRING THEM TO A PC
VIDEO HERE
PREVIEWING IMAGES
Viewing and Organising Digital Images with Windows