Session 3: How to Resize your Picture Files
File size in regards to picture files means how many K or MB the
file is, not whether the picture is an 8 x 10 or a wallet size!
Keep in mind that at school, you have access to very fast
internet connections. I have high speed internet at home as well, so
larger picture files are no longer a problem for me. But less than a year
ago, I could only connect to the internet at 28.8 bps (bytes per second) and it
took me about 10 minutes to download a 1 MB file. If you had sent me a 3
MB file, it wouldn't taken half an hour to download it to my computer. Ten
such pictures would've taken 5 hours!! Now it would take just a couple of
minutes for me to download that much data. But just because we can
download quickly, doesn't mean we shouldn't keep our file sizes down to
manageable levels! Not everyone has high speed available to them.
What is a manageable size? A 1 MB picture file is fine for
me. Files bigger than that should be scaled down if possible. When emailing
pictures to friends and family, a 1MB picture would be considered a large
file. They might not have high speed internet. Ideally, a picture
file for emailing should be under 200 K. Under 100 K, even better.
Regardless of what size file you send to me, I will resize it to 506 x 378 and I
will optimize it as well--- more on that in a minute. If you file is to
small, I will have to use it as it is. I cannot make small files larger,
it will pixelate.
To check your image file size, you need to check the image file
properties while the image is closed. Close the photo editing program. On a PC,
find your image file, right click and choose properties. On a Mac, find your
image file and click "get info" on the finder tool bar. Both
Properties and Get Info will give your the image file size in KB or MBs.
There are 3 ways to change a picture's "size".
1. Shrink it.
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 When you shrink a picture, you do not change its
file size, just the dimensions of the picture.
Open your picture
in your photo editing program or word processing program. ( I am using Adobe PhotoDeluxe for my photo editing.)
When
you click on the picture, you see little boxes at the corners.
By dragging the boxes inward, you can shrink the picture to a new
size. Likewise, by dragging the little boxes outward, you can
enlarge the photo. Notice the file size at the bottom of the
picture. It does not change after shrinking the picture.
Shrinking is commonly used in word processing programs
when inserting pictures or clip art. The file size doesn't really
matter as word document files are meant to be printed on paper. |
2. Reduce a picture's resolution.
This has been discussed previously. The smaller the resolution, the
smaller the file size. If you use a scanner to digitalize a photograph,
you can choose to scan in a smaller resolution. For many scanners, the default is 300
ppi, but you can change this. Look for a "web" or
"email" setting. If possible, choose 72 for the resolution
setting if you are going to use the photograph for a web page. I change
all photographs to a resolution of 72 before I use them for the web page.
Some digital cameras also have a resolution choice, or a "web"
setting.
3. Actually "Resize" the
Photographs
True resizing changes both the file size and the dimension sizes.
4. Optimize the Photo
Optimizing is something webmasters should do to reduce file sizes--I will do
this for you. By using a photo editing program (I could never do it
myself!) to optimize a photograph, some of the pixels are removed throughout the
photograph. Where there is a solid block of color, for example a solid
blue sky, or a black shirt, many pixels are removed from that section. In
the picture below, you can see which pixels have been removed. Your eye
does not notice the missing pixels because the remaining pixels blend together
to trick your brain!! Where pixels of many different colors are adjacent,
as in skin tones or if there is a "busy" pattern in a shirt or
background, few or no pixels are removed. Two different photographs that
start out the same size may be very different sizes after optimization. The end
result is that the size of the photograph can be greatly reduced, but it will
look the same!
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click for enlargement
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