Using Content-Aware Scale
Did you ever need to change the aspect ratio of an image, such as to recompose it for a widescreen video frame or square social media frame, but you didn’t want to crop it because doing so would cut out important details? Content-Aware Scale can help in this situation. It allows you to exclude certain areas of your image from the transformation, leaving them untouched while you scale the rest.
The key to getting the best results with Content-Aware Scale is selecting what you want to prevent from scaling and saving that selection as an alpha channel that Photoshop can use during the transformation. Technically, you don’t have to do this, but it helps so much that we consider it an essential step.
Note that Content-Aware Scale works on individual pixel layers and selections only. You can’t apply it to multiple layers, Smart Objects, or masks unless you rasterize them first.
To use Content-Aware Scale:
Start by making a selection of the area you want to protect from being distorted when the image is scaled (FIGURE 15.22).
FIGURE 15.22 Use any selection method to isolate the part of the image you want to keep unscaled.
On the Channels panel, click the button to save the selection as a new channel () (FIGURE 15.23).
FIGURE 15.23 This alpha channel can be used to prevent the torii gate in the image (and its reflection in the water) from being affected when Content-Aware Scale is applied.
Deselect the selcted area.
(Optional) If you’re working on the Background layer, Select All (Ctrl/Command+A).
Choose Edit > Content-Aware Scale.
In the Options bar, choose the channel you saved from your selection in the Protect menu.
Drag a handle on the bounding box. Hold Shift as you drag for non-proportional scaling (FIGURE 15.24). Alternatively, you can change the values in the Width and Height fields in the Options bar.
FIGURE 15.24 Dragging the bounding box scales the trees, sky, and water, but not the gate or its reflection.
To accept the result, Press Enter/Return or click the Commit Transform button.