| |
Preparing Images for the Internet: (aka: Image Optimization or Image Downsizing) (Back)
When preparing images for the Internet, there are two extremely important
factors that effect the viewing experience of your target audience.
They are the image file size (in bytes) and the image size
(width x height in pixels).
- File Size (in bytes): File size directly effects the time required
to download and display images over the Internet. The smaller you make
your image file sizes, the faster they will download and display. Remember, not
all Internet users have high speed connections to the Internet, so
image optimization is very important. If your image files
are large (and therefore slow) you might loose your audience even before your
images are fully displayed. This is especially true when you display
more then one image per page.
(See below for ways to reduce file size.)
- Image Size (width x height in pixels): You must also carefully consider
image size (width x height). Not all Internet users have high resolution
computer monitors. If your images are too large, they will be difficult for
some users to view. Common display screen resolutions are as follows:
VGA 640 x 480 pixels
Super VGA 800 x 600 pixels
XGA 1024 x 768 pixels
For practical purposes, VGA is the lowest standard display resolution still in
use. So to assure that your images are easy to view, you should keep your
image sizes less than 640 x 480 pixels.
How to reduce Image File Size: (image optimization) (The following techniques can be used individually or in combinations.)
- Image Resizing and Cropping:
When you resize and/or crop an image to make its width and/or height smaller,
you reduce the number of pixels it contains. Removing pixels from an image
reduces its file size, and as a consequence it downloads more quickly over
the Internet.
- JPEG Image Compression:
Image compression lets you reduce an image's file size,
without reducing its width or height.
JPEG compression involves a trade-off between image file size and
image quality. JPEG images that are compressed too much display
artifacts (such as fuzzy edges) not visible in the original image.
Most JPEG images however can be highly compressed without any reduction
in quality.
(Shameless Plug) Quick ePics saves
all images in JPEG format.
You can use Quick ePics' WYSIWYG image compression scrollbar to quickly
(and visually) identify the optimal compression level for each image. The
program compresses the image as you drag the scrollbar, and it automatically
shows the file size savings and estimated download time in its statusbar. There is
even a peek button so you can compare to the original image.
- Digital Camera and Scanner Resolution:
Higher resolution is not always better, you should try to match the
resolution of you camera (or scanner) to your intended output. As a
general rule, when creating images solely for the Internet, you should
set your digital camera resolution between 640 x 480 and 1024 x 768 pixels. Using higher
resolutions creates more work and may actually produce lower quality results.
When scanning pictures for the Internet, set your scanner resolution to 96 dpi.
(Click here to learn more.)
|
|
