With image-editing software you can create cool graphics for your web site, fix photographs, or work with scanned images. Image editing software is easier to use than it used to be as more companies have noticed that with the prevalence of digital cameras, a lot of non-artists need image editing software too.
Even with easier software, you can still make a big mess when you work with images. So before you attempt your next great photo retouching project, it helps to know something about how image editing works. A little common sense goes a long way when dealing with image files. If you consider what you are going to use the file for and think about who will view your files and where, you can avoid cluttering your hard disk with loads of gigantic and unwieldy files.
When you work with images, you need to understand the term resolution. You run across this term in relation to your monitor, scanner, printer, and the image itself. Resolution is measured in dots per inch (dpi) and indicates how many dots (or pixels) is in one lineal inch. Most monitors display 72-96 dpi and laser printers range from 300-1200 dpi. Imagesetters print at 1270-2540 dpi. The higher the dpi, the more detail there is and the sharper the image appears.
When you create an image in an image editing program, you need to consider where the image will be viewed. If it will be printed on an imagesetter, the resolution needs to be higher than if you are going to put it on your web site. And vice versa.
If you don't plan to do anything with that cool photo of your cat, except put it on your website, scan Fluffy at 72 or 96 dpi. Image files get very large very quickly, so resist the temptation to scan photographs at high resolutions. Just because your scanner or digital camera can support high resolutions, doesn't mean you should create images at the highest resolution possible.
More is not better in this case because the higher the resolution, the larger the file size. If you plan to print your image at a commercial print shop, talk to the printer and find out what resolution they need before you hand over the image files.
When you create images, wasted pixels mean wasted space on your hard disk. It's best to know the final dimensions of the image you plan to use and then scan the image at the correct size. When you resize an image, the software either adds or deletes pixels. When you decrease the number of pixels to make an image smaller, the software has to delete information from the image.
Obviously this process of resizing can have an effect on your image. What's
less obvious is that making an image larger also affects the image. When you
increase the number of pixels the software adds information about the new pixels
based on color values of neighboring pixels. So basically the software has to
"make up" this new information, and the results can be hideous. In
general, in terms of image quality, it is better to make a large picture smaller
than to make a small picture larger.
Understand File Formats
When you start using image editing software, you will be confronted with a dizzying array of file formats in the Save As dialog box. Not everyone uses the same image editing software, so saving your art in one of the standard formats makes it easier to share files with others. The format you select depends on what you want to do with the file.
Tagged Image Format (TIF) has been popular among artists for years. If you are going to print your image or share it with someone using a Macintosh, TIF is a good choice. This format uses a "lossless" form of compression, which means it reduces the file size without sacrificing image quality.
If you plan to put your files on the Internet, GIF and JPG are the formats supported by most Internet browsers. However, they compress images differently, so the choice between GIF and JPG depends on the type of image you are saving. The GIF format can display a maximum of 256 colors, so it is best used for line drawings, clip art, and other images with large blocks of solid colors. GIF files also are used for animations and support transparency, so a Web pages' background shows through when the image is displayed in a browser.
Unlike GIF, the JPG format can display more than 256 colors. So it's most often
used for photographs and scanned pictures or images with color gradients. Unlike
TIF or GIF, JPG uses a "lossy" form of compression, which means it
discards information when the picture is resaved. Unlike GIF, the JPG format
does not support animation or transparency. When you save a picture as a JPG
file, the transparent parts of the image are converted to a solid color.
Learn About Color
When you create an image, you also need to think about how many colors it will use and which color model you should use. If the image is going to be printed using four-color process printing technology, be sure that the image mode is set to CMYK. Conversely, if you are going to use your image on the Internet, the image should be set to the RGB color model or a web-safe palette, so you can select browser-safe colors. Browser-safe colors are one of the 216 common colors that are shared across browsers, operating systems, and computer platforms. The 216 colors are combinations of RGB values 0, 51, 102, 153, 205, and 255. Many people have put color palettes on the Web that give you the RGB values for browser-safe colors.
Additionally, in many programs commands may be grayed out depending on which color model you are using and/or how many colors are being displayed (called the color depth). For example, in Paint Shop Pro your image must have a 24-bit color depth (16 million colors) before you can apply many of the programs effects and functions. You can make the commands available by increasing the color depth of your image. However, remember that the more colors an image has, the larger the file size will be.
Blend Two Images
A popular effect is to blend two images together, often to create a ghosted effect. It's easy to do in most software, but it helps to understand feathering and antialiasing to make it look good. Feathering makes the edges of the pasted image less noticeable. When you are trying to merge together images you want a smooth transition, not a "cut and paste" look. You use feathering and antialiasing to smooth out the hard edges of a selection so the transition isn't as noticeable.
The feathering value you enter is the width of the transition in pixels. Higher values create a softer edge.
So to blend your images, open the two images. In the second image select the
area you want to paste into the main image. Once you have the second image selected,
press Ctrl+C to copy the selection to the clipboard. In the main image, paste
the selection as a new layer. Then adjust the opacity of the layer to get the
effect you want.
Image files are large and one rule of computing is that the larger the file
size, the more likely the file is to crash your computer. So save your files
frequently. Editing an image can be painstaking work and few things rival the
despair you feel when your computer expires with a blue screen of death right
after you've just spent 45 minutes outlining a complex selection perfectly.