I’d like to rejuvenate a feature that made it’s debut in Photoshop CS4. Content Aware Scale was Adobe’s intro into the work of Content Aware Technology and it is still a great feature. Content Aware Scale is designed to support the re-size of an image whilst protecting important parts of it from the re-size operation.
In the example I am using today i would like to re-size the image, however, I want to protect the hikers in the scene.
If a regular transform operation is performed on the image, everything will be re-sized.
To use the Content Aware Scale feature, Photoshop needs to know which areas to protect, in this case the hikers. Content aware scale won’t use the physical selection, but will use an Alpha channel, the selection is just a route to create the alpha channel (otherwise know as a mask).
There are many ways to select the hikers in the scene, but today will use a Quick Mask. To apply the quick mask, make sure that the Brush (B key) is enabled, then press Q (for quick mask). I tend to use a Wacom tablet for my painting however you can just about get away with a mouse, once painting starts a red mask will start to be formed. Continue to paint until all of the walkers are painted red.
Once the mask painting is complete, the image looks like the following
Pressing the Q key will turn off Quick mask and create the selection (quick mask can be enabled at any time using the Q key and the mask can be easily modified). The quick mask in this case will exclude the hikers from the scene, i.e. the rest of the image will be selected, therefore we need to invert the selection. To invert the selection use the short cut key SHIFT+CMD+I (on a PC replace CMD with CTRL). Once the selection has been inverted, save the selection using the menu item Select / Save Selection and give the selection a name (i.e. in this case hikers).
The selection/mask will be saved in the Channels panel (menu item Window / Channels), marked Red in the following screen shot.
Once the alpha channel has been created you will need to de-select the selection using CMD+D (mac) or CTRL+D (PC).
If you are going to re-size a locked background layer, you will need to unlock it (the background layer is typically locked and is denoted using a padlock on the layer itself). To remove the lock, press the ALT key and double click the lock on the background layer in the layers palette. Then to perform the re-size using Content Aware Scale, select menu item Edit / Content Aware Scale.
The image will have a bounding box surrounding it, this is used to re-size the content. By default resizing at this point will resize everything including the hikers. Let us drill down on the tool menu bar
Red – Defines the part of the image that the scale will be driven from
Yellow – Reference point placement on the x axis for the scale
Green – User defined location to start the scale from
Light Blue – Reference point placement on the y axis for the scale
Dark Blue – New width and height of the image, the icon between the W and H is used to keep the original aspect ration of the image during the re-size.
Purple – The amount is a percentage of how much to protect the original size of the alpha mask. i.e. 100% means that the alpha mask will not be sized, if 50% is chosen, the alpha mask will be reduced to a maximum of half the original size. If 25% is chosen, the alpha mask will be resized to a maximum of 25% of the original size.
White – This is the important choice. this defines the alpha mask that will be protected in accordance with the amount value.
Brown – selecting the person icon will chose to preserve skin tones during the scale operation.
Once you have selected the “Hikers” channel to protect, then you can re-size away and create you new image.
I have recorded a short video of this in action
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