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> I am hoping someone can explain this mystery to me: I've discovered
> Word 10 does a way better job of resizing jpgs than Gimp. My target
> jpgs are
> illustrations of an instrument with some fairly fine detail, but they
> too big-I need to reduce them from 18 inches wide to 5 inches wide.
Understanding the mystery begins with understanding this: A JPEG image (any bitmap, actually) isn't X inches by Y inches, it's X pixels by Y pixels. The width in inches at which it appears depends on the resolution at which it's displayed. For instance, an image that's 1200 pixels wide is over 12" wide displayed at 96 dpi (dots per inch). But displayed at 300 dpi, a good setting for PDFs and laser printers, it's 4" wide.
A bitmap image generally has a default resolution associated with it, and it's often 96 dpi, the screen resolution for most Windows PCs, or 72 dpi, the Mac default.
> If I insert the original image into a Word file, it comes in at 6
> (35% of its size) and with all the detail preserved. If I grab a
> of it with Hypersnap, the screenshot looks great.
> If I open the image in Gimp and scale it to 6 inches, then open the
> image in Word, it's fuzzy.
I think two things are happening. First, JPEG is a lossy format. So every time you resave the image, you're reducing the quality. Second, when you scale the image in the Gimp, I believe you're discarding pixels. If you're starting with an image that's 18" wide at 96 dpi (1728 pixels) and you scale it so it's 5" at 96 dpi, the resulting image contains only 345 horizontal pixels, and you've lost a lot of detail.
I'm not an expert in Word, but I'm pretty sure that it doesn't discard pixels. That means that when it makes a 1728-pixel-wide image fit within your 5" text column, it retains all 1728 pixels and just "squeezes" them together to a resolution of 345 dpi. Of course, your monitor can't display 345 dpi, but all the data is there in the file. It shows up when you print to a laser printer or zoom in on the image.
I'm not familiar with the Gimp, but I assume you could accomplish the same thing in it by changing the dpi setting. But you'd still introduce the degradation associated with resaving a JPEG file. If your source files are JPEGs (as images from non-pro digital cameras all are), your best bet is to edit and resave only if absolutely necessary, and always start from the original, not from a second, third, or fourth generation copy.
Richard G. Combs
Senior Technical Writer
richardDOTcombs AT polycomDOTcom
rgcombs AT gmailDOTcom
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