Well, there are some pretty compelling commonalities. Here’s the same document being edited in Photoshop 7, Photoshop 3, and The Gimp.
As you can see, all three environments work from the idea that a document can have many layers, which can be stacked in a specific order and given a degree of opacity with regards to layers beneath, can be rendered visible or invisible, and one of them is active at any given time. All three have a primary palette of tools which includes a selection marquee (oval or rectangle), a lasso selector tool, and a “magic wand” selector tool; a paintbrush tool along with a separate palette from which to select brush size and shape, a pencil tool, an eyedropper tool for picking up color, a “rubber stamp” area-cloning tool (which also utilizes the brushes palette), an airbrush tool (likewise), a finger-smudging tool, an eraser (uses the brushes palette for eraser size), a pen tool, a dodge/burn tool (in the screen shots I’ve got dodge selected in 3 and burn in 7 and Gimp), a text tool*, a cropping tool†, and a paint-dump can tool. All three also have a Channels (red, green, blue, w/others possible) palette and a Paths palette, although in the Gimp you can’t separate them from the Layers/Channels/Path window as you can in Photoshop. All three have an Options palette which is context-specific, providing options relevant to the currently selected tool.
- works differently in Photoshop 7, more on this below
† looks like a cutting blade in Gimp, but works the same as the cropping tool in Photoshop.
Finally, there are menu commands. In Photoshop, the menus are in the normal Macintosh (or Windows, if you’re on a PC) overhead position, with menu headings such as File, Edit, Select, Image, Filters, and so on. Within each menu are relevant commands (Rotate and Resize and stuff like that under Image, Deselect and Inverse and Load Selection in the Select menu, the normal Undo Cut Copy and Paste in Edit, and so on. The Gimp has the same stuff but in a different place —the menus pop out of the side of the active window when you click on a > shaped button at upper left. Contents are pretty much comparable. Maybe that’s the part that throws some folks?
OK, major differences. The biggest ones are between Photoshop 7 and everything else.
• In Photoshop 7, every damn time you paste something, it creates a different layer. In Photoshop 3 and the Gimp, what you paste gets pasted into the currently active layer, where it sits as a floating selection which you can drag around, delete, or apply commands and filters to. When you deselect it, it merges with the layer you pasted it into. In Photoshop 3 and the Gimp, you can create a new layer if you want it, or choose Paste as Layer instead of Paste, but it’s not the default behavior.
• In Photoshop 7, text is handled as text rather than as bitmapped representations of text. This enables you to go back and edit text you created earlier — edit it as text, I mean, not editing the image of text as image. In Photoshop 3 and the Gimp, the world is a bitmapped world and text, once entered, exists as pixels, not as text. This would be a more powerfully compelling “pro” feature of PS7 were it not for the fact that when you WANT the text to behave like any other set of pixels, the way you’re used to dealing with text from earlier versions of Photoshop, it’s downright cumbersome. And, as with pasting, every bit of text you create wants to go into its own layer.
• To continue the trend, every time you go to draw something with the brush tools you’ll find yourself in another new unintended layer. In the Gimp and Photoshop 3 you can draw in a new layer if you want to, by creating one deliberately, but by default you’re working in the layer you’re working in; tools that put new shapes and colors onscreen do so in the layer you’re working in, they don’t blop them into new layers that you then have to merge down if you insist on them being in the same layer as the previous swatch of color you painted or sprayed.
• Photoshop 7 has a History palette, which lets you undo backwards in time, step by step, hopping over a dozen steps to get back to where you were 8 hours ago if you want. This is a powerful feature, although it sure plays hell with the available disk space on your scratch disk. In Photoshop 3 or the Gimp, if you’re going to do some work that you’re speculative about, you make a backup copy first or you could find it very difficult to undo what you’re about to do. (They do have regular single-step Undo functions like most programs, though).
• Photoshop 3 is obsolete; Photoshop 7 is too, I guess, having just been supplanted by Photoshop CS which is mildly different and costs quite a few hundreds of dollars. The Gimp is up to date and free.
Aside from that, there are ten zillion little nuances that take some getting used to in any of the three, but mostly they are no big deal.