Here are some basic truths about pixels that you really need to know. Although reading this next section probably won't improve your love life, let you speak to the dead, or give you the winning lottery number, it will help you understand what's happening to your image as you work with it in Photoshop.
i Each pixel can be exactly one color. That color can change as you edit or alter the image, but each pixel consists entirely of a single color — there's no such thing as a two-tone pixel. Figure 2-2, at 1600% zoom, shows each pixel distinctly.
i Each pixel is independent. You might think that you see a car or a circle or a tree or Uncle Bob in an image, but the image is actually only a bunch of little colored squares. Although you can read about various ways to work with groups of pixels throughout this book, each pixel exists unto itself.
i Each pixel is square (except on TV).
Really! Each pixel in a digital image is square except when creating images for television, which uses nonsquare pixels. (That's a rather specialized field, which I very briefly address in Chapter 3.) It's important that you understand the squareness (totally, like L7, Daddy-O) of pixels because you sometimes have to deal with those pointy little corners.
i Smaller is better (generally speaking). The smaller each pixel, the better the detail in an image. (However, when preparing images for the Web, you need smaller images that invariably have less detail.) If you capture an image of a dog in a park with two million pixels and capture the same shot with only 30,000 pixels, it's pretty obvious which image will better show the individual blades of grass and the fur. Take a look at Figure 2-3 for an example of this critical concept.
Smaller pixels also help hide those nasty corners of pixels that are sometimes visible along curves and diagonal lines. When the corners of pixels are noticeable and degrade the image, you call it a bad case of the jaggies.
l Pixels are aligned in a raster. The term raster appears regularly when you discuss images created from pixels. Raster, in this case, refers to the nice orderly rows and columns in which pixels appear. Each image has a certain number of rows of pixels, and each row is a certain number of pixels wide — the columns. Within the raster, the pixels perfectly align side-to-side and top-to-bottom.
l Every picture created with pixels is rectangular. Some images might appear to be round, or star-shaped, or have a hole cut from the middle, but they don't unless you print them out and grab your scissors. The image file itself is rectangular, even if it appears round. There are actually pixels in those seemingly empty areas; the pixels are, however, transparent.
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