videobear
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Oct 20, 2005, 11:11 PM
Post #2 of 2
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Re: [eeha] formating an image....
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If you specify the dimensions in pixels, then dpi only tells you how large the image will look when printed out; it has no effect on the actual file size.
Uncompressed file size is determined by number of pixels X the number of bits used to specify the color of each pixel. So, for a 240x360 image, 24 bit color would give you 240x360x24 = 2,073,600 bits or 259,200 bytes. That's too big to fit into our 65,000 byte limit, so let's try 16 bit color. 240x360x16 = 1,382,400 bits or 172,800 bytes. Still too big. 8 bit color will cut that in half again, to 86,400 bytes. Darn, still too big. But wait! This is all for uncompressed bitmap files, like .bmp or .tga. But .jpg is a compressed file format! We can vary the file size when we convert from our original to a .jpg file.
If you have Photoshop CS, you also have Image Ready, an application to prepare images for the web. It has lots of handy tools to let you achieve a specified file size. Or try Photoshop's "Save for the Web" command.
Regards,
Doug Graham
Panda Productions
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