JPEG stands for "Joint Photographic Experts Group" and is a means of compressing a digital image. It is also commonly used to refer to files that have been compressed in this way. Like all digital images, JPEGs are made up of pixels. A pixel is the smallest controllable element of a picture on a screen. Increasing the number of pixels in an image increases sharpness and allows you to make a larger print without losing picture quality. Images can be resized using an image editing program like Adobe Photoshop.
Resize an image with the same number of pixels
Launch Adobe Photoshop. Click the "File" option in the top-left corner. Click "Open" from the drop-down menu. A new "Open" window will appear.
Locate the JPEG you wish to resize from wherever it is stored on your computer. Click to select the JPEG then click the "Open" button in the "Open" window. The image will appear in the Photoshop workspace.
Click "Image" then select "Image Size." Deselect the "Resample Image" option. Increase the number in the "Resolution" box. This will increase the number of pixels per inch (PI) in the image. This will actually decrease the size of the image because the same number of pixels are used but they are more tightly packed together.
Decrease the number in the "Resolution" box to decrease the number or pixels per inch. This will result in a larger image but there will be a corresponding loss of sharpness.
Add extra pixels with Resampling
Follow Steps 1 and 2 in Section 1 to select and open your image. Click "Image" then select "Image Size."
Click to select the "Resample Image" option. Select "Bicubic Smoother (best for enlargement)" from the pop-up menu. Resampling is a function that adds more pixels based on the colours and qualities of the existing pixels around them
Increase the number in the "Resolution" box. This will increase the number of pixels per inch and therefore the overall number of pixels without changing the size of the image.
Increasing the number of pixels with Resampling will increase the file size of the JPEG.