How to Do Everything With Your Scanner- P25 potx

How To… ■ Recognize line art, grayscale, and different types of color images ■ Clearly scan line art ■ Capture a grayscale image to its best advantage ■ Scan vibrant color images Human beings have an instinctive desire to produce images. Only a couple hundred thousand years after our ancestors first began scrawling on cave walls, our species has evolved the ability to reproduce digital images with scanners and PCs. Images captured in digital form fall into five general categories: line art, black and white, color, half-tone, and text. This chapter tells you how to recognize and differentiate different types of images, and how to adapt your scanning techniques to best capture them. Overview of the Different Types of Images If you’re serious about scanning, you need to know about the different kinds of originals. There are five types of images you can expect to be working with: Line art Line art is an image consisting of a single color (such as black) against a single-color background (such as white), or vice versa. The term is a little mis- leading because the image doesn’t necessarily need to be lines. For example, a solid black circle on a uniform white background is considered line art. Figure 6-1 is an example of line art. Grayscale A black-and-white photo (like most of the figures in this book) is an example of a grayscale image. A grayscale image appears to have smooth, continuous shading gradations ranging from black to white, with all the shades of gray in between. Color When graphic artists refer to a color image, they usually mean an image such as a photograph or transparency that’s made up of a continuous range of color tones. Half-tones When you scan a photograph that’s been printed in a color magazine or newspaper you’re actually scanning a type of image called a half-tone. Color photographs are reproduced on a printing press using a process called half-toning, in which continuous tones are translated either manually or digitally into a matrix of dots that emulate the tones in the original. The technique allows a printing press 104 How to Do Everything with Your Scanner Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. to produce the continuous tones of a color photo using black, yellow, cyan, and magenta dots. Figures 6-2 and 6-3 show an original image, and the same image reproduced using a particular half-toning technique and resolution that make the normally indiscernible dots visible to the naked eye. Text Scanning text requires the use of optical character recognition (OCR) software, discussed in Chapter 13. All the foregoing images require you to take a slightly different approach to scanning to get the optimum result. FIGURE 6-1 This blue jay is an example of line art. CHAPTER 6: Scanning Techniques for Different Types of Images 105 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. FIGURES 6-2 AND 6-3 An original color image (left) and a scanned half-tone showing the dots that compose the image (right) Scan Clear, Clean, Line-Art Images When you’re working with line art, the operative words are sharpness and clarity. The goal is to produce clean lines that lend a professional quality to your line art–scanning project. You can achieve this by scanning at the right resolution and choosing the correct color setting on your scanner. Scan Line Art at a High Resolution The rule of thumb for resolution when scanning line art is quite simple: the higher the better. The higher the resolution setting, the clearer and sharper your final image will be. Increasing resolution increases the density of the pixels that make up an image. Denser pixels along the edges of each line of an image make the image appear sharp and clear. Too low a resolution, and the lines of the image have a fuzzy, jagged effect. Line-art images are particularly prone to this effect when enlarged, as illustrated in Figure 6-4, which shows a portion of an enlarged line-art image. Enlarging has the effect of reducing the resolution of the image and decreasing the density of the pixels. 106 How to Do Everything with Your Scanner Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. FIGURE 6-4 The lines of the blue jay (shown in Figure 6-1) when the photo is enlarged When you scan line art, start by scanning at a resolution that matches the dpi (dots per inch) setting on your printer. For example, if you’re working with a 600 dpi printer, try scanning at 600 ppi (which stands for pixels per inch). Test your results by printing a copy of the image, then compare the result by scanning at a slightly higher or lower resolution. You might find that scanning at 1,200 ppi makes your file very large, but doesn’t improve the quality of your image very much. It’s very important to print a test copy of your image at the size you’ll actually be producing. When you view an image on screen, the tendency is to zoom in and blow up the image to a much larger size than you actually need for your printed copy. When you enlarge any image three or four times, you can get it to appear fuzzy and jagged. CHAPTER 6: Scanning Techniques for Different Types of Images 107 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. How to Capture Black-and-White Bitmaps and Vectors The lines that make up a line-art image might be thick or thin, and placed at different intervals; however, all the lines have one color of dots, usually black. Availability of Black-and-White Settings Since the only color you need to capture is black, it makes sense to set your scanner to capture as few colors as possible. Scanners capture the line art as something called single-bit or binary images. Some old scanners don’t have settings for less than 16 different shades, while virtually all new scanners have specific black-and-white settings for capturing two-shade binary images. Many scanners offer you a choice between two types of black-and-white settings. They allow you to select either a bitmap or vector for your black-and-white image. Figure 6-5 shows the drop-down menu for the Hewlett-Packard Precision Scan Pro, which offers such a choice. FIGURE 6-5 Some scanners offer you both bitmap and vector options for black-and- white scans. 108 How to Do Everything with Your Scanner Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. . emulate the tones in the original. The technique allows a printing press 104 How to Do Everything with Your Scanner Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. to produce. pixels. 106 How to Do Everything with Your Scanner Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. FIGURE 6-4 The lines of the blue jay (shown in Figure 6-1) when the photo. offer you both bitmap and vector options for black-and- white scans. 108 How to Do Everything with Your Scanner Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.