Pixelation in digital images refers to the rough or jagged edges around objects in photographs. Pixelation can be introduced a number of ways, including through artefacts induced by digital scanning, upsizing an image to be larger than the resolution of the input image or a noisy sensor in a digital camera. While it is very difficult to completely eliminate pixelation from an image, Photoshop has a variety of tools that to minimise or even partially remove pixelation. While each of the techniques can be used in harmony, experiment with each to determine which works best.
Open the image you want to correct in Photoshop by opening the "File" menu and choosing "Open." Find the image file you wish to open in the explorer window, highlight it and then click "Open."
Duplicate the Background layer by dragging the layer from the Layer pane to the "Create new layer" button. The new layer appears on top of the old one and is automatically named "Background copy."
Open the drop-down Blending Options menu in the layer pane and select the option "Luminosity." This softens the effects of the blurring you perform on the top layer so that sharpness is retained while the pixelation is removed.
Open the Filter menu, and then select "Noise" and "Despeckle." Photoshop automatically applies despeckle algorithm to the image, which detect the edge of an image and blurs all but the edge of the image. If you find that the blurring effect is too great, go to the Edit menu and select the option "Fade Despeckle." Choose the amount of despeckle to remove by entering a value in the Opacity box. The higher the number in the box, the more of the image reverts to its original state.
Highlight the original background layer and open the Filter menu and choose "Blur," and then "Gaussian Blur." The amount of blur you use depends on the amount of pixelation, but keep the Radius number below 2.0 for best results. Keep the Preview box checked to see the edits you make in real time on your image.
Open the Image menu. Select "Adjustments," and then "Brightness/Contrast." Move the Contrast slider to the left to increase the contrast of the bottom layer and enhance any sharpness that may have been lost in your blurring. The value depends on your image and your preference, but values between +10 and +20 are most effective.
Some pixelated images cannot be rescued without needing a significant blur that will distract from the image more than the pixelation would have. For these types of pictures, resizing the image is the best way to hide pixelation. From the Image menu, choose "Image Size" and enter values that cause your image to shrink.
Each of these manipulation techniques is destructive, meaning it permanently alters the pixels of your original image. Never overwrite your original file or it will be impossible to later return to your image and undo the changes you make.