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5. Save the resulting image as a new file.

When you make an image smaller, you lose data. That’s perfectly fine for the version you put on the Web, but you should hang on to the original large image in case you want to resize again.

6. Resample, rather than resize.

Resampling is a slower but more accurate technique for changing the image size. This is IrfanView’s default behavior, so leave it alone. It’s still quite fast on a modern computer. The default (Lanczos) filter is fine, although you can experiment with other filters to get a faster conversion, if you want.

Enhancing image colors

Sometimes, you can make improvements to an image by modifying the colors. The Enhance Colors dialog box on the Images menu gives you a wide range of options, as shown in Figure 6-9.

Figure 6-9: You can change several options in the Enhance Colors dialog box.

You can do a surprising number of helpful operations on an image with this tool:

♦ Brightness: When adjusted to a higher value, the image becomes closer to white. When adjusted to a negative value, the image becomes closer to black. This is useful when you want to make an image lighter or darker for use as a background image.

If your image is too dark or too bright, you may be tempted to use the Brightness feature to fix it. The Gamma Correction feature described later in this section is more useful for this task.

♦ Contrast: You usually use the Contrast feature in conjunction with the Brightness feature to adjust an image. Sometimes, an image can be improved with small amounts of contrast adjustments.

♦ Color Balance: Sometimes, an image has poor color balance (for example, indoor lighting sometimes creates a bluish cast). You can adjust the amount of red, green, and blue with a series of sliders. The easiest way to manage color balance is to look at a part of the image that’s supposed to be white and play with the slider until it looks truly white.

♦ Gamma Correction: This is used to correct an image that is too dark or too light. Unlike the Brightness adjustment, Gamma Correction automatically adjusts the contrast. Small adjustments to this slider can sometimes fix images that are a little too dark or too light.

♦ Saturation: When saturation is at its smallest value, the image becomes black and white. At its largest value, the colors are enhanced. Use this control to create a grayscale image or to enhance colors for artistic effect.

Using built-in effects

IrfanView has a few other effects available that can sometimes be extremely useful. These effects can be found individually on the Image menu or with the Image Effects browser on the Image menu. The Image Effects browser (as shown in Figure 6-10) is often a better choice because it gives you a little more control of most effects and provides interactive feedback on what the effect will do. Sometimes, effects are called filters because they pass the original image through a math function, which acts like a filter or processor to create the modified output.

Figure 6-10: The Image Effects browser lets you choose special effects.

Here’s a rundown of some of the effects, including when you would use them:

♦ None: Just for comparison purposes, Figure 6-11 shows the ship image without any filters turned on.

Figure 6-11: Here’s the standard ship image, at full-screen resolution.

I’ve exaggerated the effects for illustration purposes, but it may still be difficult to see the full effect of these filters on the printed page. The grayscale images in this book are a poor representation of the actual color images. Use the images in this chapter as a starting point, but to understand these filters, you really need to experiment with your own images in IrfanView or a similar tool. I’ve also added all these images to my Web site so you can see them there (www.aharrisbooks.net/xfd2ed).

♦ Blur: This filter reduces contrast between adjacent pixels. (Really, we could go over the math, but let’s leave that for