Creating a Selection with the Polygon Lasso Following a Contour

Figure 3.61

The arrow indicates the starting point of the tool.

Figure 3.61

The arrow indicates the starting point of the tool.

First, determine the starting point of your selection by clicking onto one point on the contour of the image object you want to select. Now let the mouse-button go and shift the mouse cursor along the object's contour: you are pulling on the "rubber band" of the lasso tool. Apply the "rubber band" to the contour and set another point on the contour by clicking. By additional clicking and dragging, set further control points along the contour. You must know on which side of the mouse pointer the tool is applied.

In figure 3.61, you can see an enlarged depiction of the mouse pointer when the polygon lasso is selected. The point of the arrow is where the tool places its anchor point. The same applies to the the Free Select tool as a freehand lasso.

The polygon lasso is definitely the tool of choice if you want to follow a straight contour. You select a corner as an anchor point, click on it, and drag the tool to the next corner, thereby applying the rubber band to the contour. You follow the contour until you reach your starting point again. This is where you close your selection. The form is selected.

Double-clicking the mouse closes the selection at any time. The tool returns in a straight line from the point where you double-clicked to the starting point, thus closing the selection. If you accidentally double-click, you will have to undo the entire selection and start again from the beginning. You can keep on working if you switch to the mode Add to the current selection. Then you continue by applying the tool to where you previously left off and close your selection as you had intended to.

Next, select the rounded form of the wine glass with the polygon lasso. Take your time, zoom in on your image, and break up the selection of the contour into several stages; you may have to click several times. Panning is a great feature when you have zoomed in on your image: When you move your cursor close to the edge of the image, it scrolls in the direction you are going. This works with the Free Select tool and other similar tools. However, don't make any hasty movements because otherwise you might land in the middle of nowhere of your image. With GIMP 2.6, it is also possible to move the picture detail beyond the edge of the monitor. Try it with the little navigation window that can be opened by clicking the icon of the crossed arrows (Navigate the image display) at the bottom right of the image window. The auto-panning feature in GIMP 2.6.8 didn't work on my computer with Windows Vista. However, holding down the spacebar, you can easily (and safely) pan around by moving the mouse.

3.10 EXTRACTING IMAGE OBJECTS WITH SELECT AND MASKING TOOLS

Figure 3.62

Zoom into your image, enlarging the picture. Follow the contour of the curved glass by breaking it up in stages when setting the control points. The dark outline is the contour that has been applied to the glass so far. The selection has not been closed yet.

Figure 3.62

Zoom into your image, enlarging the picture. Follow the contour of the curved glass by breaking it up in stages when setting the control points. The dark outline is the contour that has been applied to the glass so far. The selection has not been closed yet.

Next, start at a distinctive spot on the image and set the first control point with a left mouse click. In the end, you must return to the first control point. Follow the contour of the wine glass with the tool, applying the rubber band to the contour. Then click again to set another control point. A line now connects the control points that you have set. If your image has a curve, you must set several control points, splitting up the curve in a polygon. If there is less of a curve, you can reduce the amount of control points, drawing out the length of the line between the points. Continue the procedure until you have circumnavigated the entire figure. At the end, connect the selection with the first control point to extract your figure.

Basically that's it. You can continue editing the extracted selection as you would any other selection in the Select menu.

Now you will continue editing the image. First you should save the extracted figure by choosing Select > Save to Channel.Then you should feather your selection (Select > Feather) with a gradient of 3 pixels.

U SI NG MASKS AN D LAYERS—PAI N TI NG, FI LLI N G, AND COLOR TOOLS

Figure 3.63

The finished image, wineglass.xcf

Figure 3.63

The finished image, wineglass.xcf

Copy the wine glass (Edit > Copy) and make sure the layer from which you want to copy is selected in the Layers dialog. Then paste the extracted image (Edit >Paste) as a new layer back into the image. Place the new inserted layer (Floating Selection) in the Layers dialog as a new layer (right-click on the Floating Selection layer and choose New Layer). Label the new layer wine glass.

You can check the quality of your work by making the background layer invisible via a click onto the eye symbol.

Create a new layer, background. Now delete the selection (Select > None). Fill the background layer with a color. Make the the wine glass semi-opaque by using a large and soft eraser (Eraser tool) with an opacity of 10% to depict the transparency of the glass.

The image is finished thus far. With a little practice, the polygon lasso is rather easy to use. However, the result for figures having rounded contours is not entirely exact, because the contour had to be split up into a polygon. Now let us have a look at a tool that lets you work precisely with curved contours. This is the Paths tool.

3.11 USING THE PATHS TOOL AS A MASKING TOOL —USING FILTERS FOR LIGHT EFFECTS

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