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Using Gimp - Partie 3
In the previous article, I showed how to alter the colors of an entire image. Now, I'll describe how to alter selected parts of an image, while leaving the rest untouched. This is done using the selection tools (below). From left to right, the first two buttons select a rectangle or an oval, respectively (hold Shift for a perfect circle). The third button opens a free-selection tool for outlining selected portions on an image. Try it. Click the icon, then left click your mouse, hold it, and draw around an item. When you release the mouse button, you'll see a region selected for manipulation (right). Now, all modifications will affect only the selected region. This helpful method is, however, not very good for precise selections. Next is a fuzzy selection. When a dot is clicked, this selection enlarges until it encounters a different color. The enlargement can be fine-tuned by editing the Threshold number in the tool options (below the icons). By holding down Shift, more colors can be selected to widen the selection. Once a selection has been made, further modifications apply to it alone (right). Next is the color-selection tool. It is similar to the fuzzy selection, so lets move on to the last (for now): the scissor selection tool. This is more precise than the freehand tool discussed above, but it only works well on items with definite outlines. The method is this: click to start selecting, and put a point on the outline; click again to put another point further along the item's outline; the scissor tool then tries to determine the item's perimeter (above); continue clicking on the image's outline; more added clicks (and points) increase the selection's precision; the last click should be back at the starting point. Before committing to a selection, any of the points can be clicked and dragged to fine-tune the outline. To create the actual selection, click inside the completed loop (shown below). To remove a selection, go to the menu and click Select > None. But how do you make a precise selection? Pen tool (icon shown left). The pen tool permits more precise curve creation than does the scissor tool. First, click the pen tool to open it. Then, click around the outline of the desired selection, as was done with the scissor tool. But unlike the scissor tool, the first point can not be re-clicked as the last of the points to close the selection – so just click near it. Don't worry if a point is slightly out of place. After inserting all the points, any point can be clicked and moved into place (below). Now, the points can be edited to produce nice curves between them. Hold down the Ctrl key, click on a point (keep the mouse button down) and move your mouse. A line will then come out from that point and a curve will begin forming between the chosen point and one of the points on either side of it (below left). Each point can have two lines coming from it to form a curve (above right). So, click on the point, hold down Ctrl, and drag out the second line. Now you will have a curve. The initial point can still be moved, but clicking and dragging a box at the end of a line can fine tune a curve, or create a curve leading in (or out) from a point, or form a straight line on the other side – this latter was useful in the present example where the steps meet the doorway. When all the points are in place, and the curves are satisfactory, tell GIMP to select the area. To do this, click the Paths tab (beside your Layers tab). If it's not there, display it by clicking Dialogues > Paths. The just-created path is shown in miniature in the Paths tab. Right click on its name and select Path to Selection. To hide the path to work on the selection, or to show it again, click the eye icon. Combining the selection tools with the color-correction items can be amazingly powerful, especially if all that is needed is to color-correct family photos or holiday snaps. Zoom Sometimes, even more precision is needed when creating selections. The zoom tools are very handy for this. At the bottom of the image window is a drop-down menu (above) that gives quick access to a variety of settings for zooming in or out of images. The Zoom tool (left) is also accessible from the toolbox on the left. With the Zoom tool, clicking on an image will zoom in (holding Ctrl and clicking will zoom out). In addition, holding a click permits drawing a box around just a portion of an image (below) for zooming (above right). Don't forget to combine tools. For instance, to select a piece of an image, zoom in first, then go for the tool of your choice. Next month, we will discuss probably the most important part of GIMP: layers. Creating an image using layers allows you to create non-destructive additions to an image which, when saved in GIMP format, can be edited at a later date.