Trimming the Fat

If you use the Move tool to reposition a layer, and a portion of the layer starts to extend beyond the edge of your document, Photoshop will remember the information beyond the edge (Figure 3.27). Therefore, if you move the layer away from the edge, Photoshop is able to bring back the information that was not visible. You can save a lot of memory by getting Photoshop to clip off all the information beyond the edge of the document (Figure 3.28). Here's a little trick for trimming off that fat. Just choose Select > All and then choose Image > Crop—no more wasted memory.

It also wastes memory when you leave extra white space around the edge of your image (Figure 3.29). Because the paper you print on is white to begin with, that extra white space just makes your file size larger, and has no effect on how the image will look when it's printed. You can choose Image > Trim to have Photoshop remove any unnecessary white space (Figure 3.30). Just adjust the Based On setting so that it will find white information in your image (depending on which corner of your image contains white), and then specify which edge of the document you'd like to trim away—I usually leave all four of the Trim Away check boxes turned on (Figure 3.31).

So far we've talked about how to make your images smaller to save memory and hard drive space, but now let's do the opposite with Photoshop's Image > Reveal All command. When you choose that command, Photoshop will enlarge your document to include any information that extends beyond the bounds of your document (Figures 3.32 and 3.33). That means that all the layers that you've moved beyond the edge of your document will become visible once again.

Use the “trim the fat” technique only if you're absolutely sure you won't need the information beyond the edge of the document, because you cannot get it back once you've cropped it (that is, without resorting to the History palette). The default setting in the Crop tool is to delete the areas that extend beyond the edge of your image. You can prevent it from deleting those areas by clicking the Hide setting in the Crop tool options bar (it will be available only in files that contain layers). That will cause Photoshop to reduce the size of the image based on the cropping rectangle you specify, but it will retain the information that extends beyond the edge of the image.