How to Use the Image Size Command in Photoshop CS6
One of the main reasons people use Adobe Photoshop Creative Suite 6 is to manipulate images to what you need them to be, sometimes changing the size of the image. A time will come when you need to mess with the resolution or dimensions of an image. You may want to
Change the file size.
Make sure the resolution is appropriate for print.
Adjust the dimensions so that they’re just right for viewing onscreen.
Change the width, height, and/or resolution of your image for printing or some other kind of output.
Photoshop — powerhouse that it is — allows you to size an image in all these ways with the Image Size command on the Image menu. Follow these steps to resize your image:
Open the image and then choose Image→Image Size.
The Image Size dialog box opens. This is where the magic happens.
Note the current state of your image and decide whether any of the following values need to change in order to get a nice-looking image for the desired output (print or the web):
The current pixel dimensions and the resulting file size: the example shows 720 pixels in width and 960 pixels in height for a file size of 1.98MB (megabytes).
The current document size: The size of your image when it prints on media, such as paper.
The resolution: the example is 72 ppi, which is good for displaying onscreen or on the web, but inadequate for printing. You’ll see some pixelation (visible little squares) on your printout. Therefore, to print, you need to reduce the size of the image so that your total pixels are packed into a smaller area, to give the image cleaner lines.
Make sure the Constrain Proportions check box is selected.
The chain-and-bracket icon in the Document Size area indicates that the Constrain Proportions check box is selected. Nine times out of ten, you want your image to stay proportional. With the option selected, changing one value in the Document Size area makes the other values change automatically so that the proportions stay intact.
You can also select the Scale Styles check box, which allows you to scale or not scale any effects or styles that you’ve applied to your layer(s). This option is available only if you select Constrain Proportions.
Make sure that the Resample Image check box is deselected.
When you resample, you add or delete pixels in the image. Although you sometimes need to resample, doing so isn’t good for your image.
Enter any new values in the dialog box.
For example, because you may want to print your image, you need to enter a new value of 300 pixels per inch for resolution in the Document Size area. The other values automatically change.
You won’t notice any difference in the way your image appears onscreen because you haven’t added or deleted any pixels; you’ve merely compacted them into a smaller space.
Congratulations! You’ve just safely resized your image. You can proudly say, No pixels were harmed in the making of this image.