Adobe Photoshop CS2 On Demand [Electronic resources]

Andy Anderson; Steve Johnson

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Changing Image Size and Resolution

You can modify the size and resolution of a document after opening. However, be aware that changing the size and/or the resolution of an image forces Photoshop to add or subtract pixels from the image in a process called

interpolation . For example, when you change the resolution of an image from 72 ppi (pixels per inch) to 144 ppi, Photoshop must add more pixels. Conversely, if you reduce the resolution, Photoshop must remove pixels. The image interpolation method determines how Photoshop completes this process. You can use the Nearest Neighbor method for the fastest way, but it produces the poorest visual image. Or, you can use the Bicubic Sharper method which takes the longest to perform, but produces the best visual results.

Change Image Size

Open an image.

Click the

Image menu, and then click

Image Size .

Select the

Resample Image check box.

Click the

Resample Image list arrow, and then select an option:

  • Nearest Neighbor. Best for quick results with low quality.

  • Bilinear. Best for line art.

  • Bicubic. Default, best for most purposes with high quality.

  • Bicubic Smoother. Best for enlarging an image.

  • Bicubic Sharper. Best for reducing an image.

To maintain image proportions, select the

Constrain Proportions check box.

Enter the desired sizes in the image size boxes.

If you choose to constrain proportions in step 5, when you change a size, the other boxes will adjust automatically.

Click

OK .

For Your Information

Using a Large Canvas Size

Photoshop supports documents up to 300,000 pixels in either dimension, and with up to 56 channels per file. Photoshop offers three file formats for saving documents with file sizes greater than 2 GB: PSD, RAW, and TIFF. It's important to note that most programs, including an older version of Photoshop (before the CS version), support a maximum file size of 2 GB.

Change Image Resolution

Open an image.

Click the

Image menu, and then click

Image Size .

Clear the

Resample Image check box.

Enter a resolution, which automatically adjusts the Height and Width fields.

Click

OK .

Change Image Size Using the Resize Image Wizard

Open an image.

Click the

Help menu, and then click

Resize Image .

The Resize Image Wizard dialog box appears.

Click the

Print or

Online option, and then click

Next .

Specify the image size you want, and then click

Next .

If you selected the Print option, select a halftone screen, click

Next , use the slider to select the image quality you want, and then click

Next .

Click

Finish .

Photoshop makes a copy of the image and leaves the original alone.