The Free Transform Tool is one of the most essential tools in Photoshop. We have been free transforming our layers since the very first version and as a result the shortcut Cmd + T is burnt into our muscle memory like riding a bike.
In Photoshop CS6 a new feature has been introduced to this well-known essential namely the image interpolation dropdown. In PS CS6 when transforming a normal layer you can change the interpolation method with each transformation you do.
The interpolation methods include the same settings as with changing the image size from the Image -> Image size menu. These are:
Nearest Neighbor – The simplest method of scaling images. It replaces every pixel with four pixels of the same color.
Bilinear – Or two-dimensional interpolation performs linear interpolation first in one direction, and then again in the other direction. It considers the closest 2×2 neighborhood of known pixel values so the four nearest pixel values located in diagonal directions from a given pixel to calculate color values for non-defined color pixels resulting from the scaling of the image. It takes a weighted average of these 4 pixels to arrive at its final, interpolated value. The weight on each of the 4 pixel values is based on the computed pixel’s distance from each of the known points.
Bicubic – Similar to bilinear interpolation but instead of only considering the 2×2 neighborhood the bicubic interpolation method considers a 4×4 pixel area. Therefore the results are smoother and have fewer interpolation artifacts. In Photoshop Bicubic interpolation has four settings:
Bicubic – Due to the complexity of the calculation Bicubic produces smoother tonal gradations than Nearest Neighbor or Bilinear.
Bicubic Smoother – Designed to produce smoother results than the normal bicubic interpolation. That is why it is considered to be best for enlargement.
Bicubic Sharper – It incorporates advanced sharpening and can be used well for reducing the size of our images. It case it over sharpens the image use bicubic instead.
Bicubic Automatic – With this option Photoshop will try to select the best interpolation method automatically. It basically sets smother when scaling up and sharper when scaling down.
Last year Adobe released an interpolation extension for Photoshop. This extension introduces Interpolate and Match Edges methods. You can download the extension and read more about the new interpolation methods at the Adobe Labs website:
This all great, but those of us who use the Free Transform Tool extensively might have noticed a small inconsistency whit this new feature. When free transforming smart objects the method selection dropdown is missing and committing to the transformation might not bring a satisfying result. We have seen some users rasterizing their smart objects in order to maintain control over their transformations but this is defeating the whole purpose of using smart objects.
When free transforming Smart Objects Photoshop will use the default interpolation method. You can set this default method in the Preferences under the General tab using the Image Interpolation dropdown.
It might be a bit tedious to change this every time you transform a smart object but it is still better than converting them to normal layers and until Adobe adds the dropdown to the transformation of smart objects it will be the only way to ensure that resizing your smart objects gives the best results.