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.Well, sure enough, the time has come to do exactly that.When selected, thischeck box prevents you from painting inside the transparent portions of the layer.And although that may sound like a small thing, it is in fact the most useful Lockoption of them all.Chapter 12 &' Working with Layers599Figure 12-32: The Lock Transparency check box enables you to paint insidethe layer s transparency mask without harming the transparent pixels.Suppose I want to paint inside the girl shown in Figure 12-32.If this were a flat, non-layered image, I d have to draw a selection outline carefully around her hair andarms, as I did back in Chapter 9.But there s no need to do this when using layers.Because the girl lies on a different layer than her background, a permanent selec-tion outline tells Photoshop which pixels are transparent and which are opaque.This is the transparency mask.The first example in Figure 12-33 shows the girl on her own with the background hid-den.The transparent areas outside the mask appear in the checkerboard pattern.When the Lock Transparency check box is turned off, you can paint anywhere youwant inside the layer.Selecting Lock Transparency activates the transparency maskand places the checkerboard area off limits.Part IV &' Layers, Objects, and Text600Figure 12-33: The layered girl as she appears on her own (left) and whenairbrushed with the Lock Transparency check box turned on (right).The right image in Figure 12-33 shows what happens after I select Lock Transparencyand paint around the girl with the airbrush.The foreground color is set to white.Notice that no matter how much paint I might apply, none of it leaks out ontothe background.Although this enlightening discussion pretty well covers it, I feel compelled to sharea few additional words about Lock Transparency:Tip&' You can turn Lock Transparency on and off from the keyboard by pressing thestandard slash character, /, right there on the same key with the question mark.&' Remember, you can only fill the opaque pixels in a layer, whether LockTransparency is on or off.Use Ctrl+Shift+Backspace to fill with the back-ground color and Shift+Alt+Backspace to fill with the foreground color.&' The Lock Transparency check box is dimmed when the background layer isactive because this layer is entirely opaque.There s no transparency to lock,eh? (That s my impression of a Canadian explaining layer theory.It needs alittle work, but I think I m getting close.)Chapter 12 &' Working with Layers601And finally, here s a question for all you folks who think you may have Photoshopmastered.Which of the brush modes (explained in Chapter 5) is the exact oppositeof Lock Transparency? The answer is Behind.To see what I mean, turn off LockTransparency.Then select the paintbrush tool and choose the Behind brush modein the Options bar.Now paint.Photoshop applies the foreground color exclusivelyoutside the transparency mask, thus protecting the opaque pixels.So it follows,when Lock Transparency is turned on, the Behind brush mode is dimmed.The moral? Behind is not a true brush mode and should not be grouped with thelikes of Multiply and Screen in the Options bar.If you ask me, the better solutionwould be a Lock Opacity check box in the Layers palette.Alas, Adobe s engineersseem to have better things to do, such as add three other Lock check boxes, noneof which have the slightest thing to do with locking opacity.But just because I vebeen complaining about the Behind  brush mode for the last, oh gosh, seven yearsdoesn t mean that I m bitter or anything.Heavens no.I like to be ignored! It robsmy life of meaning, which is precisely what I m looking for.In fact, I think I ll goand end it all right now.And for what? A check box.That s all I want.A small andunobtrusive check box, possibly with a picture of my face next to it and a littlecaption reading,  Yes, Deke, you were right.Can you ever forgive us for beingsuch knot-heads? I mean, really, am I asking too much?So, in conclusion, Lock Transparency is your friend; Behind is the tool of Satan.Too bad so few things in the world are this black and white.Creating layer-specific masksIn addition to the transparency mask that accompanies every layer (except thebackground), you can add a mask to a layer to make certain pixels in the layertransparent.Now, you might ask,  Won t simply erasing portions of a layer makethose portions transparent? The answer, of course, is yes.And I hasten to add,that was a keen insight on your part.But when you erase, you delete pixels perma-nently.By creating a layer mask, you instead make pixels temporarily transparent.You can return several months later and bring those pixels back to life again simplyby adjusting the mask.So layer masks add yet another level of flexibility to a pro-gram that s already a veritable image-editing contortionist.To create a layer mask, select the layer you want to mask and choose Layer ª' AddLayer Mask ª' Reveal All.Or more simply, click the layer mask icon at the bottom ofthe Layers palette, as labeled in Figure 12-34.A second thumbnail preview appearsto the left of the layer name, also labeled in the figure.A second outline around thepreview shows the layer mask is active.TipIf the second outline is hard to see, keep your eye on the icon directly to the left ofthe layer name.If the icon is a paintbrush, the layer and not the mask is active.Ifthe icon is a little dotted circle, the mask is active.Part IV &' Layers, Objects, and Text602Indicates layer mask is activeLink iconLayer mask thumbnailLayer mask iconFigure 12-34: The black area in the layer mask (which you can see in thethumbnail view, top right) translates to transparent pixels in the layer.To edit the mask, simply paint in the image window.Paint with black to make pixelstransparent.Because black represents deselected pixels in an image, it makes thesepixels transparent in a layer.Paint with white to make pixels opaque.Thankfully, Photoshop is smart enough to make the default foreground color in alayer mask white and the default background color black.This ensures that paint-ing with the paintbrush or airbrush makes pixels opaque, whereas painting withthe eraser makes them transparent, just as you would expect.In Figure 12-34, I created a feathered oval, inversed it, and filled it with black bypressing Ctrl+Backspace.This results in a soft vignette around the layer.If I decideChapter 12 &' Working with Layers603I eliminated too much of the hair, not to worry.I merely paint with white to bring itback again.Photoshop goes nuts in the layer mask department, adding lots of bells and whis-tles to make the function both convenient and powerful.Here s everything youneed to know:&' Reveal Selection: If you select some portion of your layer, Photoshop auto-matically converts the selection to a layer mask when you click the layermask icon at the bottom of the palette.The area outside the selectionbecomes transparent.(The corresponding command is Layer ª' AddLayer Mask ª' Reveal Selection.)Tip&' Hide Selection: You can also choose to reverse the prospective mask, makingthe area inside the selection transparent and the area outside opaque.To dothis, choose Layer ª' Add Layer Mask ª' Hide Selection.Or better yet, Alt-clickthe layer mask icon in the Layers palette.&' Hide everything: To begin with a black mask that hides everything, chooseLayer ª' Add Layer Mask ª' Hide All.Or press Ctrl+D to deselect everythingand then Alt-click the layer mask icon.Tip&' View the mask: Photoshop regards a layer mask as a layer-specific channel.You can actually see it listed in italics in the Channels palette [ Pobierz caÅ‚ość w formacie PDF ]