Adobe Photoshop CS5 for Photographers - Martin Evening [166]
Disable edge snapping
The edge snapping behavior can be distracting when you are working with the crop tool. This can easily be disabled in the View Snap To submenu (or by using the shortcut).
Image rotation
If an image needs to be rotated you can use the Image Rotate controls to orientate a photo the correct way up or flip it horizontally or vertically even. More likely you will want to make a precise image rotation, especially if the horizon line appears to be at an angle. You can correct for this by applying a rotated crop with the crop tool, or you can now use the ruler tool to measure the rotation error and then use the Straighten button in the ruler tool Options bar to correct the image, as described in Figure 5.66 below.
Figure 5.66 When an image is opened up in Photoshop, you may discover that it is not perfectly aligned. Although the crop tool will allow you to both crop and rotate at the same time, there is another more accurate way you can correct the alignment. Select the ruler tool from the Tools panel and drag along what should be a vertical or horizontal edge in the photo. After doing this, go to the tool Options bar and click on the Straighten button. The image will be accurately rotated so that it appears to be perfectly level.
Canvas size
The Image Canvas size menu item allows you to enlarge the image canvas area, extending it in any direction. This is useful if you want to extend the image dimensions in order to place new elements. If you check the Relative box you can enter the unit dimensions you want to see added to the current image size. The pixels that are added are then filled using the current background color, but you can also choose other fill options from the Canvas Size dialog (see Figure 5.67). It is also possible to add to the canvas area without using Canvas Size. You can use the crop tool as an ‘add canvas tool’ by dragging beyond the document boundaries (see Figure 5.68 below).
Figure 5.67 To add extra pixels beyond thecurrent document bounds, use the Canvas Size from the Image menu. In the example shown here, the image is anchored so that pixels are added equally left and right and to the bottom of the image only. When the Relative box is checked this allows you to enter the number of units of measurement you wish to add ‘relative’ to the current image size.
Figure 5.68 To use the crop tool as a canvas size tool, first make a full frame crop, release the mouse and then drag any one of the bounding box handles outside of the image and into the canvas area. Double-click inside the bounding box area or hit to add to the canvas size, filling with the background color.
Content-aware scaling
The content-aware scale feature first appeared in Photoshop CS4. It was also the most controversial new feature since it invited Photoshop users to tamper with photographs in ways that were likely to raise the hackles of photography purists. Would this spell the ‘death of real photography’ (DORP)? That I don't know, but over the next few pages I have outlined some of the ways you can work with this tool and have suggested some practical uses. Advertising and design photographers may certainly appreciate the benefits of being able to adapt a single image to multiple layout designs.
Edge detection success rate
The content-aware scale feature is very clever at detecting which edges you would like to keep and those you would like to stretch or squash, but it won't work perfectly on every image. You can't expect miracles, but if you follow the suggestions on these pages, you will pick up some of the basic tips for content-aware scaling. What I have noticed though is that it does appear to do a very good job of recognizing circular objects and can preserve these without distorting them. Russell Brown has done