Using the Image Size Command in Photoshop

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, or you may simply need to make sure that the resolution is appropriate for printing or some other paper output. Or you need to adjust the dimensions so that they’re just right for viewing on-screen. And sometimes — only sometimes — you may need to add or delete pixels.

Or you need to change the width, height, and/or resolution of your image for printing or some other kind of output. Photoshop, being the powerhouse that it is, certainly allows you to do so with the Image Size command found on the Image menu. Follow these steps to resize your image:

1. Open the image and then choose Image➪Image Size.
The Image Size dialog box opens. This is where the magic happens.

2. Note the current pixel dimensions of your image and the resulting file size.
Mine shows 1536 pixels in width and 1024 pixels in height for a file size of 4.5M.

3. Also note your current document size.
This is the size of your image when it prints on paper. Mine shows a width of 21.333 inches and a height of 14.222 inches with a resolution of 72 ppi. A resolution of 72 ppi isn’t adequate for printing purposes. I will be able to see some pixelation (visible little squares) on my printout. Therefore, I need to reduce the size of the image so that my total pixels are spread out over a smaller area, making them more densely packed.

3. Make sure that the Resample Image check box is deselected and then enter a new value for the width in the Document Size area.
Don’t worry about the definition of resample; I explain it in the next section. I entered a value of 5.12 inches. Note how my height value automatically changed to 3.413. That’s because the Constrain Proportions check box is selected, as indicated by the chain and bracket icon. Notice that the check box is also grayed out. If the Resample Image option is deselected, the Constrain Proportions option is unavailable. Nine times out of ten, you’re probably going to want your image to stay proportional. You can also change your units of measurement by choosing from the pop-up menu.

4. Note how the resolution automatically changed based on what you entered in Steps 3 and 4.
In my example, my resolution went from 72 ppi to 300 ppi. When you do not have Resample Image selected, your pixel dimensions remain unchangeable (note how there is no text box for you to enter new pixel dimension values). Therefore, when you enter a smaller width or height value, the resolution must increase in order to accommodate all the pixels in the image. Similarly, if you enter a new resolution value (rather than a width value as I did), Photoshop then adjusts the width and height values in order to accomplish the same thing.

Before you close this dialog box, I would be remiss in not telling you about the Auto button. This is Photoshop’s way of giving you a suggested resolution setting based on your screen frequency. Don’t worry about it for now. But if you feel the burning need to know about screen frequencies.

Again, before you click OK, I want to fill you in one new option. The Scale Styles option allows you to scale or not scale any effects or styles that you have applied to your layer(s). Note that this option is available only if you have checked Constrain Proportions.

6. Click OK.
You won’t notice any difference in the way your image appears on-screen because you haven’t added or deleted any pixels; you’ve merely compacted them into a smaller space. Congratulations! You have just safely resized your image. You can proudly say, “No pixels were harmed in the making of this image.”