How to Adjust Size, Color, and Contrast in Photoshop CS6
You’d think the Image menu in Photoshop CS6 might have something to do with making changes to an entire image document, wouldn’t you? In practice, some of the entries you find here do apply to the whole document, but others can apply to only particular layers or selections.
For example, the Mode menu item allows you to change an entire image from color to grayscale. The Image Size, Canvas Size, Image Rotation, Crop, and Trim selections all change the whole document in some way.
On the other hand, you can only apply the changes wrought from the Adjustments submenu to an entire image if the document consists of only a background and has no layers. If the document has more than one layer, then adjustments such as Color Balance, Hue/Saturation, or Levels work only with a single layer or a selection on that layer.
The Variables and Apply Data Set commands work with data-driven graphics. Briefly, data-driven graphics make it possible to quickly produce multiple versions of an image for print and web projects. Multiple versions allow for target audience customization for projects such as direct mail pieces.
For example, you can base hundreds of versions of a brochure or web banner on a single template. The Variables define which elements change within a template. A Data Set is a collection of variables and associated data.
You’ll find yourself turning to the Image menu more often than many of the other menus, partially because it’s so useful and partially because, for some reason, many of the options don’t have keyboard shortcuts that let you bypass the menu.