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Why do I need to resize an
image?
The majority of this section will deal with photographs, as that tends to be
where most of the problems occur for beginners (and because most .gif images
will have been "acquired" from elsewhere on the Internet and will have been
properly sized by their creator - the only exception I can think of is where you
want to use an existing gif as your avatar which will be covered later.)
Photographs for Internet display should always be saved in .jpg format, giving
the best balance between file-size and quality. The bigger the file, the slower
it is to load on the viewer's screen - but on the other hand, you don't want
something that instantaneously appears but looks dreadful. You can
upload photos in .bmp or .tif format but they won't display (in our forums) as a
picture, only as a link which the viewer will then have to click to see the
picture. They are also much bigger files than .jpgs and will therefore take
you longer to upload and the viewer longer to download.
Image file size is dependent on only three things - the format, the physical
dimensions of a picture measured in pixels
and the amount of compression applied to it.
You may have heard things about image resolution - that has nothing to do with
the file size (but a heck of a lot to do with the quality of a printout! That's
another topic altogether!).
Physical Dimensions
We prefer photographs to be no bigger than 600 x 450 pixels. There are
2 reasons for this:
- It fits onto most people's screens and avoids that most detested of
actions - horizontal scrolling
- When correctly compressed the file size will be around 35-40KB whilst
allowing a decent-sized, good quality image to view.
The file size, and hence loading speed, is not usually a problem for
broadband users (if you have to wait for a noticeable period of time for a
picture to load over a broadband connection, then it's a fair bet that it is
far too big and that the author has not prepared it correctly!). However, many
www.southport.gb.com users are still
on a dial-up connection and it is important for them that pictures are
correctly optimised for the web.
So how DO I resize an image?
If you are scanning a photo in, then there is usually either a button on the
scanner, or an option within the scanning software, something like "Prepare for
Web" or "Ready for E-mail" - you will have to check the documentation and help
files that came with your own software.
If you are going to upload the pictures from a Digital Camera, then you will
almost certainly need to make the picture smaller; again, there should be
instructions with the camera itself or associated software on how to prepare
images for the web. Look in the help files for "Resample" or "Resize" or
"Web-ready" for example.
There are far too many different image-editing applications out there for us to
be able to give you instructions on every one, but some common ones are detailed
below.
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As more and more people
get digital cameras or start to experiment with sharing pictures with
us, we think a collection of "How to" for different image editing
software might be useful.
It's easy enough
for us to say "Reduce to 600x450 pixels and keep the file size
to 30-70KB" but many people who are new (and some who aren't!)
to digital image handling simply don't know how to get through their
software to achieve the result.
However, your first
port of call should be to check if your software has a "Prepare for web"
or "Publish to web" option. If it does, it simplifies the task
considerably. Check your Help files.
If you use different image-editing software to the ones listed below,
then please send in your own "How to", to
webmaster@southport.gb.com
We will assume the starting point for everyone is "Open the picture you
wish to edit in your chosen software"!
Corel Photopaint
- Click Image
- Click Resample
- In the dialogue window that appears, make sure that the top right box
reads pixels and that Anti alias and Maintain aspect
ratio are both ticked.
- If neither the Width
nor the Height box exceeds 600 then go to step 6
- Make the bigger
of the Width and Height boxes read 600 - the other will
auto adjust
- You can leave the resolution as it is for screen and web display as
it has no bearing on the file size.
- Click OK
- Click on File
- Click on Export
- In the dialogue window that appears, make sure that the Files of
Type box reads JPG
- Click Save
- Set the Compression to about 50% - with many photos you can go as
high as 75, even 80% before there is a sudden marked loss of quality.
Click Preview to see the effect of the different compression
setting on the file size.
You can zoom and pan on the Original image in the left pane to see what
the quality looks like.
The smaller the file, the faster it will load in the forum - but don't
sacrifice quality for speed.
- When happy, Click OK. Your file is now ready to be attached to your
posting.
Back to the top
Microsoft Photo
Editor
- Click Image pull down then
Resize
- Change Units to Pixels (if cm)
- Make the largest
(width or height) 600
- File Save As - Usually select a new name as you can then keep the
original photo in full resolution. Have the file type as JPEG (JPG).
Click MORE to set compression at 50%
Back to the top
ACDsee Image Editor
- Click on TOOLS, then
RE-SIZE
- Check the SELECT PIXELS option.
- From the Drop Down Box, select
REDUCE TO.
- Enter 600 in
either PIXELS WIDE or PIXELS HIGH box and make sure the PRESERVE
ORIGINAL ASPECT RATIO box is checked.
NB If you want to keep the original sized image too, make sure the
REMOVE/REPLACE ORIGINAL FILES box is unchecked.
- Then SAVE FILE AS - choose name and select .JPG format
Eztouch
- Open Edit menu - select Image Size - box opens giving
'Current
Image Size' and below that 'New Image Size'.
- Change New Image Size to 600 x 450 (or 450 x 600)
- Click execute
- Then Save as giving the smaller image a new name (If you wish to
keep the larger sized image).
Remember though, your first
port of call should be to check if your software has a "Prepare for web"
or "Publish to web" option. If it does, it simplifies the task
considerably. Check your Help files.
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Back to the top
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The same picture
as a thumbnail (160 x 120 pixels) which has a file size of about 4KB - loads
up in less than 1 second but shows sufficient detail for the viewer to
decide if they want to view a larger version.