Quick MasksWhen you select a portion of your image, you see the flashing dotted linesthey're fondly known as marching ants to most Photoshop folks. But what are these ants really showing you? In a typical selection, the marching ants outline the boundary of pixels that are selected 50 percent or more. There are often loads of other pixels that are selected 49 percent or less that you can't see at all from the marching ants display. Very frustrating.Tip: Hide the Marching AntsThe human eye is a marvelous thing. Scientists have shown us that one of the things the eye (and the optical cortex in the brain) is great at is detecting motion (probably developed through centuries of hunting and gathering in the forests). However, evolution sometimes works against us. In Photoshop, the motion of a selection's marching ants is so annoying and distracting that it can bring production to a halt.Fortunately, you can hide those little ants by turning off Extras from the Select menu (or pressing Command-H). We do this constantly. In fact, we almost never apply a filter or do much of anything in Photoshop while the ants are marching.The only problem is that you actually have to use your short-term memory to remember where the selection is on screen. With complex operations, you also have to remember that you have a selectionwe've lost count of the number of times we've wondered why our filter or curve was having no visible effect on the image, only to remember belatedly that we had a 6-pixel area selected, usually one that currently wasn't visible.However, seeing a cut-and-dried marching ant boundary is often not helpful. So Photoshop includes a Quick Mask mode to show you exactly what's selected and how much each pixel is selected. When you enter Quick Mask mode (select the Quick Mask icon in the Tool palette or type Q), you see the underlying selection channel in all its glory. However, because the quick mask is overlaying the image, the black areas of the mask are 50-percent-opaque red and the white (selected) areas are even more transparent than that (see Figure 8-7). The red is supposed to remind you of rubylith, for those of you who remember rubylith. Figure 8-7. Quick Mask mode[View full size image] Figure 8-8. Quick Mask Options dialog boxEditing Quick MasksThe powerful thing about quick masks isn't just that you can see a selection you've made, but rather that you can edit that selection with precision. When you're working in Quick Mask mode, you can paint using any of Photoshop's painting or editing tools, though you're limited to painting in grayscale. Painting with black is like adding "digital masking tape" (it subtracts from your selection), and painting with white (which appears transparent in this mode) adds to the selection.If the element in your image is any more complicated than a rectangle, you can use Quick Mask to select it quickly and precisely. (We do this for almost every selection we make.)
Note that if you switch to Quick Mask mode with nothing selected, the quick mask will be empty (fully transparent). This would imply that the whole document is selected, but it doesn't work that way.Tip: Filtering Quick MasksThe Quick Mask mode is also a great place to apply filters or special effects. Any filter you run affects only the selection, not the entire image (see Figure 8-10). For instance, you could make a rectangular selection, switch to Quick Mask mode, and then run the Twirl filter. When you leave Quick Mask mode, you can fill, paint, or adjust the altered selection. Figure 8-10. Filtering quick masks |