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Grokking The Gimp
Previous Page Home Next Page Layer Scaling

As has already been discussed in this section, it is possible to scale an entire image. However, it is also possible to scale a single layer within an image. There are two tools for doing this in the GIMP: the Scale Layer  function, found in the Layers menu, and the Transform  tool in the Toolbox.

As for entire images, a layer can be scaled either smaller or larger. The most typical use of layer scaling is to adjust the relative size of an image on one layer with respect to an image in another. This is needed for almost every compositing project (for examples, see Chapter  7). When it is necessary to scale a layer smaller, either the Scale Layer function or the scaling option of the Transform tool will do the trick. However, the Transform tool might be preferable because it provides interactive control of the scaling process. Scale Layer relies on entering numbers into entry boxes in a dialog. It is difficult to choose the correct dimensions, which leads to repeatedly applying Scale Layer and Undo until the desired effect is achieved.

The problem of finding the right dimensions to scale a layer can sometimes be solved using the Measure  tool, which is discussed in more detail in Section  2.6.5. A good example of using the Measure tool to determine the appropriate amount to rescale a layer is given in Section  7.5. Alternatively, the Transform tool provides interactive visual feedback of the scaling process. In addition, it can be used in conjunction with the Bezier Path  tool and the Transform Lock  icon in the Paths dialog to get very fine, interactive scaling control. The technique for this is discussed in Section  3.4.1, and a relevant example is shown in Section  7.2.

Scaling a layer larger should be avoided if possible, because this operation requires the interpolation  of pixel  values. Interpolation is an approximation process that creates pixels where there were none before and that, consequently, partially degrades the layer's image quality. Thus, when adjusting the relative sizes of several image components on different layers, it is preferable to scale down the larger components to match the size of the smaller ones rather than vice versa.

In the event that it is necessary to scale a layer larger, it is important to know that a layer cannot be scaled to dimensions larger than those of the existing image boundaries. To scale a layer to dimensions greater than these limits, the image window must first be resized larger using the function Canvas Size, previously discussed.

Grokking The Gimp
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