Photoshop Crib Sheet

Am just learning Photoshop (real Photoshop - CS 8.0, to be precise ). I still fear it, but am getting the hang. This page is a kind of aide-memoire for things i like to do.

• The key insight is that Photoshop's domain model is not a grid of pixels, it's a stack of layers, each layer being a grid of pixels with an offset. This makes it a sort of hybrid of a paint and a draw program, since you can manipulate whole semantically defined chunks of the image at once. Note that PS thinks of layers as finite grids - if you paste a 100 x 100 image into a 500 x 500 image, you have a layer which is 100 x 100, smaller than the total image, and PS knows where its edges are. Layers and the pixels in the total image are somewhat orthogonal concepts; i'm going to talk about 'selecting' areas of the image, but 'activating' layers.
• To set the resolution of an image (eg something you've just pulled in from your microscope software ), do Image > Image Size ..., then uncheck Resample Image and put your resolution in the resolution box (300 ppi seems to be what journals want) and hit OK.
• If an image comes out too large or small, do as above, but leave the Resample Image box checked, and set the size in pixels; the resolution will stay the same, so the physical dimensions will change accordingly. Note that the best resampling PS will do is bicubic; this is perceptibly worse than the Lanczos resampling that ImageMagick does, so it's best to do this step offline.
• Select > All selects an entire image, suitable for copy-and-pasting onto your canvas image. Weirdly, control-clicking on the layer in the Layers palette doesn't seem to work here.
• Guides are handy - View > New Guide .... Layers will snap their edges to align with guides; this is neat, although it doesn't seem to work if you're moving a bunch of linked layers. Note that you can move guides with the move tool; this doesn't move any snapped layers. There's a way to lock layers to guides in CS2, but apparently not in CS.
• PS doesn't do margins, so throw down some guides instead.
• You can group layers - PS calls it 'linking': activate one layer, then, in the Layers palette, click the checkbox to the left of the other layer; moving one will now move the other. There's also a thing called 'layer sets', but this appears to be a bit pointless; you can link a whole set to another layer (or vice versa, etc), which is kind of handy, though.
• You can align layers, like graphics objects in a draw program: select the area corresponding to one layer by control-clicking it in the Layers palette, activate the other by clicking it (in the palette or in the image), then do Layer > Align To Selection > whatever kind of alignment you want to do. Alternatively, link the two layers, then do Layer > Align Linked.
• To distribute layers, link them, then do Layer > Distribute Linked.
• Doesn't seem to be a way to get at the properties of shapes (rectangles etc) explicitly, ie to say 'make this box 1.355 cm wide'.
• Photoshop's ideas about shapes, paths, etc are most unhelpful. No, it's not a draw program, but it's hard to see why this is the right way to do things.
• Select > Deselect clears the selection. As, indeed, does clicking anywhere with the marquee tool.
• If you've got a shape and you want it filled with transparent, select the later, and set the Fill spinner/slider near the top of the Layers palette to 0%. If you want a line round the edge, bring up the Layer Style dialogue (i just sort of randomly click things until this happens), go to the Stroke tab, tick the box (actually, it should tick itself), and set the appropriate settings.
• Note that if you've drawn a line, the above won't work, since a line is not a path you can stroke, it's a shape in its own right (a long, thin box at an arbitrary orientation - there is a path, but it's the outline of the line). Instead, set its width, and fill it. Set the width using the tool options toolbar at the top of the window, with the line tool selected and the chainlink toggle set, so the toolbar applies to the active layer; just put something in the Weight box. To fill it (in the Layer Style dialogue, go to Color Overlay (obviously!) and pick a colour.
• I don't know a way to get the Layer Style dialogue up per se, but if you go to Layers > Layer Style, you get a submenu of the various things you can do. This also pops up from the little f-in-a-circle button (isn't that the Flash logo?) at the bottom of the Layers palette.
• The order of layers in the Layers palette is the z-order of the layers. You can drag to rearrange - provided you drag one of the blank bits of the layer panel, that is; try dragging the little icon and you're fucked.
• Oh, turns out you can get the Layer Styles dialogue by double-clicking on the f-in-a-circle icon at the right end of the layer's panel in the Layers palette, or indeed anywhere quite near it. OF COURSE HOW COME I DIDN'T REALISE THAT STRAIGHT AWAY?

It is my increasingly firmly held conclusion that Photoshop is a mistake. A program that's about editing bitmaps is fine, but as soon as you start talking about composing bitmaps, as Photoshop does, you're in the realm of a draw program, and the correct way to do this is to be object-oriented from the ground up. Photoshop tries to tack this sort of functionality onto a bitmap editor, and so fails.