When working on images for
your Web pages you may wonder when to use JPEG and when to use GIF.
For many types of images, GIF is superior in image quality, file size,
or both. One of the first things to learn about the JPEG vs. GIF issue,
is what kinds of images to apply them to. But first, you need to save
your master images in a file format other than GIF or JPEG to maintain
the quality of your original image. For example, you may save it as
the native PSP format (a PaintShop Pro format).
Because Paint Shop Pro requires
that an image have a 24-bit color depth (16 million colors) for many
of its operations, the GIF format would not be ideal as it can only
save with 8-bit color (256 colors). The JPEG format would also be less
than ideal because it each time you save an image in this format, you
will lose some image quality as the JPEG format employs a "lossy"
compression algorithm. In other words, it does a good job of compressing
the image because it loses some of the image quality. If you save a
JPEG over and over, the degradation will quickly become noticeable.
If you keep the compression level under 30% and do not repeatedly save
a JPEG as a JPEG, you will not be able to discern loss of quality under
most circumstances.
JPEG has a tough time with
images that include sharp edges: a row of black pixels next to a row
of white pixels, for example. Sharp edges tend to come out blurred or
"stepped" unless you use a low compression setting. Sharp
edges such as this are rare in photographs, but are fairly common in
GIF files: drawings, text, etc. The blurriness is usually very obvious
with text that is very small in size. If you have a GIF with a lot of
small fonts or text, it's probably best to try to stay away from JPEG.
Black-and-white images should
never be converted to JPEG. You need at least 16 gray levels before
JPEG is useful for gray-scale images. However, GIF is much better for
gray-scale images of up to 256 levels, while JPEG is not.
As a general rule,
save as JPG when saving photographs. Save as GIF when saving line art,
logos, and saving for transparency.
Graphics With Transparency
Both GIF and PNG support
transparent backgrounds, while JPEG does not have the ability to support
transparent backgrounds at all. Save your graphics in GIF rather than
PNG, because GIF is widely supported on the Web, whereas PNG has very
limited support.
To save your image, Choose
FILE>SAVE AS. When the SAVE AS dialogue pops up, under "Save
as type" choose either the JPG or GIF format. You may receive a
warning that layers must be compressed, or that color depth must be
decreased. Click OK to these warnings.
