Hosting Images On Your Web Site
Providing images for any kind of download is very different from hosting a standard web site. Images take up considerably more space than text files or HTML files, and there are some serious things to consider when you plan to host images on your web site. How Images Are Saved Images can be saved in a variety of different formats. The most web-friendly formats are GIFs and JPEGs; the least web-friendly are bitmaps (BMPs) and TIFs (sometimes spelled "TIFFs"). Here's why: Images are really saved as a gridwork of squares, each square having very specific information associated with that square. In the case of BMPs and TIFs, a LOT of information is stored: the specific location of that square in relation to the other squares, the number associating a color value (which is often very long), and sometimes things like dark/light value or RTF values. It's not much information when it's just a few squares - but if you have a regular 3x5 photograph that you're storing with pretty good resolution (which is at least 600 dpi, or dots per inch - 600 squares to the inch), you're looking at 3 times 5 times 600 - 9000 squares with information in each of them. This can translate to a megabyte-sized file or better. (And that's just for a standard small photo image!) What Happens To Your Server A megabyte is not that much - it'll fit on an old-fashioned floppy disk - but if you're hosting images, you're going to have hundreds, maybe thousands, of images. And for each one of those being downloaded, it will put a strain on your server. You say, so what? The people coming to my site are paying for the pictures anyway, so I can pay for the bandwidth. But if you're hosting full-size images, each and every VIEWING of the image counts as a download. If you have ten images on a page, that's ten simultaneous downloads of 1 megabyte each, not counting whatever you have on your page besides the images. This adds up. And if you're hosting a popular site, you may have several people at the same time viewing these images. If you don't have enough bandwidth to support this, you will have slow downloads (just the viewing downloads), customers unable to access your site, and sometimes even crashed servers. Ways To Host Images Now that I have your attention, there are things you can do about this. If you're selling photographic images, you really do want to use BMPs and TIFs; they have by far the best print quality. In addition, you probably want to increase the resolution to 1200 dpi if you're not selling poster prints; that way, your customers can safely increase the size of their images without sacrificing quality. But how do you display that without crashing your server? Simple: images hosted on your site that customers can browse should be limited to GIF and JPEG thumbnails - images reduced in size to maybe 1 inch by 1 inch, at 300 dpi. That will be large enough for your customers to determine whether they're interested in seeing the whole thing. When customers click on the image, instead of associating the full image, use a JPEG version with your watermark, and, again, less resolution than you use for the full size image you're selling. This means your customers can see ten or twenty images at a time in thumbnail view (not enough to crash you, unless you're just way too limited in bandwidth); one image at a time in preview (with watermark and reduced resolution so they still have impetus to purchase your full image); and one downloaded full image at a time. You can even zip the download to decrease bandwidth used; the customer doesn't need to see the full image until it's downloaded to their hard drive. Before hosting images, discuss your plans with your web service provider; he or she will have a very good idea about how much bandwidth you need.
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