design basics elements colour pre-press production finishing 12­25 image types file types working with images image manipulation type 28­31 resizing images channels layers and combining images adjustment layers working with clipping paths masks 36­37 26­71 72­111 112­139 140­163 164­183 32­35 36­51 52­55 56­71 38­39 40­41 42­43 44­45 46­51 adjustment layers Adjustment layers allow a designer to alter an image, while preserving the original at the same time. For example, a designer could make alterations to the colour levels of a photograph, but if a client subsequently decided that they did not want this alteration, the levels adjustment could easily be turned off to restore the image to its original form. If the levels of the image were changed without an adjustment layer, the designer would have to find the original image file and other alterations such as cleaning the image or colour balancing would have to be done again. original image # 1 original image # 2 combined images Channels Normal Lock: Paths Layers Opacity: 100% Fill: 100% Layer 1 Layer 0 Starting with two original images, a mask can be applied to the top layer (the girl) to combine them (see pages 46­47). When a mask is applied, the black areas of the mask allow the image below to show through, while the white areas block image show-through. Solid Color... Gradient... Pattern... Levels... Curves... Color Balance... Brightness/Contrast... Hue/Saturation... Selective Color... Channel Mixer... Gradient Map... Photo Filter... Invert Threshold... Posterize... Adjustment layers can then be added to alter each image layer, or the resulting composite image.