| We live in a world filled with pixels. Although we may not think about it very often, we see innumerable images made up of tiny little squares throughout the day. Adobe Photoshop and the other CS2 applications work with bitmapped (otherwise known as raster) images. The easiest way to think of a bitmapped image is as a grid of pixels (see Figure 4-1). A pixel is a "picture element," and it's the basic building block of a bitmapped graphic. When pixels are stored, they are saved into a raster file format. Figure 4-1. A bitmapped graphic is made up of a grid of pixels. 
In Chapter 5, "Getting to the Point of Vector Graphics," we discuss the differences between working with vectors and working with pixels, so we won't repeat that discussion here. We'll just point out some of the main reasons pixels (and the images that are made from them) are so important: Pixels are created by scanners and digital cameras, or can be easily acquired by buying stock photography. While not everyone can learn the Pen tool (though we hope you will try!), almost everyone has access to a scanner or digital camera that can produce pixels. Pixels are your choice if you want to retain the naturally soft edges found in drop shadows, glows, feathered edges, and so on. Bitmapped images, composed of pixels, are generally simpler than vector graphics. They're simpler to comprehend, and it's generally easier for software to convert from one raster format to another than to convert vector formats.
In this chapter, we'll focus on the world of pixels and raster file formats. We'll talk about how we get pixels not only from the obvious places like scanners and digital cameras, but from less well-known sources. We'll show how you can create pixels in InDesign and Illustrator, and cover the essentials of how pixels work, including three key concepts of dimensions, resolution, and bit depth. We'll discuss all the different ways you can work with pixels. Sometimes you interact with pixels directly, as you do in Adobe Photoshop when you paint with brushes or use the retouching tools. Other times, you manipulate all the pixels within the raster file (the stored pixels), particularly when you apply effects and commands to placed images in InDesign and Illustrator. Finally, to use the pixels in another application, they must be saved in the proper format. We'll explain what raster file formats will work for your particular workflow. As big as this chapter is, we can't cover everything about pixels here: Pixels can also have color and transparency. We discuss those concepts in Chapter 10, "Colors and Color Management," and Chapter 11, "Transparency." Pixels must be selected to apply a tonal or color adjustment, or to run a filter. We talk about this in the "Selecting and Moving Pixels in Photoshop" section in Chapter 7, "Managing and Customizing the Interface." You can create layered compositions with pixels in Photoshop. We discuss this throughout Chapter 12, "The Flexibility of Layers." Photoshop works in a color modeusually Bitmap, Grayscale, RGB Color, CMYK Color, or Duotoneand includes three more specialized modes Indexed Color, Lab Color, and Multichannel. To learn about color modes, read "Color Modes in Photoshop" in Chapter 10, "Colors and Color Management."
Behind the Scenes: Photoshop Revolutionizes Image Editing The first pixel editor developed for desktop computers was MacPaint. Bill Atkinson developed it for Apple's introduction of the Macintosh computer in 1984. Although MacPaint only worked with black-and-white pixels at screen resolution, it was a revelation to those who saw it, and it was one of the first desktop publishing applications that drove the Macintosh's success. At about the same time, Adobe Systems developed PostScriptthe page description language that controlled laser printers and imagesettersand this was also critical to the development of computer publishing. While PostScript supported printing bitmapped images, as well as vector type and graphics, the language itself provided no way to edit the images. Within a few years, other desktop computer pixel-editing applications like PixelPaint and ImageStudio were developed. They focused on painting, and they worked only with black-and-white and grayscale images before desktop color computers were available. But soon two brothers developed an application that did much moreit included routines which operated on pixels mathematically, like the high-end photoretouching stations that at the time cost $300,000and it soon revolutionized the world of bitmapped graphics. In 1987, Thomas Knoll was a doctoral candidate in computer vision at the University of Michigan. For his own use, he developed an application he called Display, as a way to display grayscale images. His brother John was a filmmaker at Industrial Light and Magic, an outgrowth of George Lucas' Star Wars film empire, where he worked with the software that created the movie magic. He urged his brother to develop the software further. When Thomas acquired a color Macintosh from his brother, he added color support. Together they built in features that they thought were important, which are the core features of the application we now know as Adobe Photoshop: image-processing routines that would become filters; soft-edged selections; Levels for adjusting tones; and controls for adjusting color. They also supported many raster file formats. John Knoll pushed his brother to develop the application commercially. They first licensed Photoshop version 0.87 as a software utility distributed with the Barneyscan scanner. But Adobe was interested in licensing Photoshop as soon as John Knoll demoed the product. Russell Brown, Adobe's art director, and John Warnock, Adobe's co-founder, saw that it was far ahead of the competition. Adobe Photoshop 1.0 was developed and released in February 1990 as a Macintosh application. (The first Windows version was 2.5.) The application's release was well-timed. More and more people were using desktop computers for publishing, the computers were becoming more powerful, and most users were buying scanners. Sales of Photoshop took off quickly, much to Adobe's surprise, and soon surpassed those of Illustrator, Adobe's vector graphics application. |
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