Being a technical writer who takes many, many (many) screenshots, one of my favorite features of Photoshop is its ability to automatically create new documents of exactly the size I need.
When you take a screenshot on your computer using the PrintScreen button on Windows or CTRL+CMD+SHIFT+3 on Mac, you take a snapshot of your monitor(s) contents, at the size of your monitor display(s). For example, when I take a screen capture on my dual monitor system, I grab an image that’s 2560 pixels wide by 1024 pixels deep. That screenshot is captured as a raster image on my system clipboard.
[Click image to zoom] Figure 1: The New Document dialog automatically picks up the size of the clipboard data and sets the new document dimensions to match.
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Switching to Photoshop CS, CS2, or CS3, I can press CTRL+N/CMD+N to bring up the New document dialog (see Figure 1). Photoshop reads my clipboard and automatically fills in the Width and Height fields for me. The key is the “Clipboard” new document preset. After clicking OK to create the new, blank Photoshop document, I only have to paste (CTRL+V/CMD+V); my screenshot will come in as Layer 1, fitting perfectly within the document dimensions.
Of course, the same trick works in other situations, too. Many Web browsers, for instance, offer the option to copy an image directly from a Web page. Right-click (or Control-click using single-button Mac mice) on an image and select Copy from the context sensitive menu to copy the image to the clipboard. Switch back to Photoshop, press CTRL+N/CMD+N, and note that Photoshop sizes the new document to fit the dimensions of the Web image. Click OK and paste. Ta da!