HTML, XHTML and CSS All-In-One for Dummies - Andy Harris [353]
You can see the Tool Options dialog for any tool by double-clicking the tool in the Toolbox. Generally, I dock the Tool Options dialog to the main Toolbox tabs because it’s so frequently used.
Utilities
Gimp also comes with a number of handy utilities. The tools highlighted in Figure 4-6 have a variety of uses:
✦ Color Selector: The two overlapping rectangles show the current foreground and background color. Click one of the rectangles to pick a new color to work with. You can choose colors in a number of ways, using RGB and HSV schemes, as well as prefilled color palettes and a very cool watercolor tool.
✦ Color Picker: Allows you to determine the RGB value of any pixel on the image and pick that color as the current drawing color. It’s very handy when you want to match colors precisely.
Figure 4-6: These tools often come in handy.
✦ Zoom: Allows you to quickly zoom in and out of your image. Drag around an area, and the selected area will fill the entire window. Hold down the Ctrl key while dragging to zoom out. Hold the center mouse button (often also the scroll wheel) to pan your zoomed-in view in any direction. It’s very helpful to zoom in close when you’re doing detail work.
✦ Measure: Drag the mouse on an image, and you can find the distance and angle between any two points. The Move tool is useful for precise placement.
✦ Move: Allows you to move a selection or layer.
✦ Align: The Align tool simplifies lining up various elements with each other.
✦ Crop: Used to crop unwanted border areas from an image.
✦ Text: Adds editable text to the image. The Text tool works with layers, so check the upcoming “Understanding Layers” section for more detail.
♦ Perspective Clone: This tool combines the Perspective tool and the Clone tool. Although it’s cool, the applications are a bit rare, so I don’t use it often in Web development.
Understanding Layers
Gimp has an astonishing variety of tools, but most of the interesting things you can do with a raster graphics tool involve a concept called layers. Layers are really pretty simple: Imagine the old animated movies (before digital animation was possible). Painters would create a large background, but the characters were drawn on transparent sheets (called cels in animation). A single frame of an animation might contain a single opaque background with a large number of mainly transparent layers on top. Each layer could be manipulated individually, providing a great deal of flexibility.
Any high-end graphics editor will support some form of layer mechanism. (In fact, support for layers is a primary differentiator between basic and advanced graphics tools.) Figure 4-7 shows the Layers panel in Gimp.
The primary area of the Layers panel is the window, showing a stack of layers. The background is on the bottom of the stack, and any other layers are on top. Anything on an upper layer obscures a lower layer. Imagine a camera at the top of the stack pointing down at the stack of layers. If a higher layer has transparency (as it usually does) the lower layer will show through any transparent pixels.
The Opacity slider in the Layers panel allows you to adjust the overall transparency of the layer. This can be useful for quickly lightening or darkening a layer, and for other effects, such as shadows.
Only one layer is active at a time. The current layer is highlighted in the window at the bottom of the Layers panel. Most operations will occur on the active layer only. Click a layer in the layers window to make that layer active.
Figure 4-7: The Layers panel allows you to manipulate layers.
Be sure you know what layer is active. Many times I try to draw on a layer and nothing happens. I then typically scribble harder, thinking that will help. Almost always when this happens, I’ve selected the wrong layer and made a big mess somewhere. It’s possible (and common) to have a layer