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Pictures on a Web Page
Last week, in "Pictures
on a Web Page," I raved so much that I finished a whole article without
answering the question that I began with, basically, why does it take so long to
have a web page appear on your monitor the first time, but when you return to
it, it pops up much more quickly?
I began to answer that question by explaining that each graphic
(illustration, design, or photo) has to load separately, sometimes from
different places on the Internet. I
illustrated by showing the same image twice, once directly from the White House
site, and again from Peanut files, where I had stored a copy.
On a web page, a picture literally is worth a thousand (or more) words,
because it takes a great deal of information to create a picture.
Let's look at a photo of a common household object:
Although you may not recognize it, you are quite likely using one of
these objects now. It is a heat
sink from a computer, used to disperse some of the intense heat generated while
a computer is running. The photo has 28,907 bytes of information, (compared to
6,071 bytes of information for the text of my latest film review).
How is that possible? Look at another view of the heat sink:
That extreme close-up is of the first prong in the upper left corner of
the first photo. It gives you some idea of the amount of information packed into
a tiny area of a photo. That photo,
by the way, has a resolution of 72 dots per inch (dpi), which is standard for
photos for a web page. That answers
another question--why don't photos from web pages print clearly?
Usually, for printing, digital photos have a resolution of 150 dpi.
Let's see what that means. A
photo that is two inches by two inches, at 72 dpi, has 144 dots [72 dots per
inch x 2 inches] x 144 or 20,736 dots.
If a two inch square photo is scanned or created at 150 dots per inch
(which still won't produce a very clear hard copy), it has 300 dots [150 dpi x 2
inches] x 300 or 90,000 dots. So,
with about double the resolution, you have about four times the amount of
information.
Web page designers, of course, want attractive pages, but web surfers
want pages that load quickly. That
is the reason many photos on web pages have such low resolution.
One way to speed up access to the Internet is to save elements of a page
in your computer. Last time, I
referred to accessing the web to sending little imps out from your computer to
claim the elements of a page. Well,
these are rather lazy imps, and so, once they get a page for you, rather than
run back to its source, they simply leave it with you.
Or, consider another way of looking at it: imagine that every time you watch a
television program, your television saves a video tape of it.
Your computer does the same with Internet pages you visit.
You can easily demonstrate this by disconnecting the cable from your
computer to your telephone line. Now,
push the back button on your browser, and although you are no longer connected
to the Internet, you'll see the last page you were on, because your imps are not
getting it from the Internet. They
are just pulling it out of your cache,
where your computer and its imps store the pages, graphics, and sounds, of web
pages you visit. So, the first time
you visit a page, it may take a long time for the pictures to download from the
Internet. The second time, however,
the page and its elements load from your computer (the cache), and that is much
quicker.
Here's a practical hint for you. If you did videotape everything you watch on television, you might soon run out of room to store the tapes. Well, your computer gets similarly clogged up with old web pages, which you should clean out periodically. At the top of the page, click on Tools (for Internet Explorer), then on Internet Options. Then, you can delete Temporary Internet Files. (You may be surprised how long this will take if you don't do it periodically.)
Of course, that means that you just wiped out the photo of Marlene Dietrich in last week's article, so it may take a little longer to load that page next time.
We've roved through a lot of material this time, but we still have one more point to cover, and this week, we've we've had quite a high resolution of points per paragraph. So far this week, we've seen two photos--both of the computer heat sink. But, there is another illustration on this page. Can you identify it? It is the same illustration, by the way, that I asked you about at the end of the last column.
Give up? Remember each illustration (graphic) has a distinct URL, a distinct location on the Internet? Well, here's the URL for that mysterious graphic:
That's right. The background of this page is, itself, a graphic.
With that little bit of new-found knowledge, I'm going to rove on by myself,
leaving you to keep your feet dry, your heart full of noble thoughts, your
photos at a low resolution, and your resolution to get as many points of
knowledge and interest as possible on any web page you create, visit, or just
stash in your cache.
Find more articles about creating your own website.
Rove to the Rovin' and Ravin' opening page.
