How do I edit the pixel size?

To edit the pixel size of an image, you typically use image editing software like Adobe Photoshop. Here's a step-by-step guide:

Steps to Change Pixel Size in Photoshop

Open the Image: In Photoshop, go to File > Open and select the image you want to edit.
Access Image Size Dialog: Go to Image > Image Size. This will open the Image Size dialog box.
Enter New Pixel Dimensions: In the Image Size dialog box, you'll see fields for Width and Height under "Pixel Dimensions." Enter your desired pixel dimensions. Make sure the "Resample" option is checked if you are changing the actual number of pixels. If unchecked, only the document size (print size) will change, but the pixel dimensions will remain the same.
Select Resampling Method (If Resampling): If you are changing the actual number of pixels, choose a resampling method from the dropdown menu. Common options include:
- Automatic: Photoshop chooses the best method based on the image.
- Preserve Details (enlargement): Best for increasing the image size while preserving details.
- Bicubic Smoother (enlargement): Good for enlarging images, producing smoother results.
- Bicubic Sharper (reduction): Best for reducing the image size while maintaining sharpness.
- Bicubic: A balanced option for general use.
- Nearest Neighbor (hard edges): Good for images with hard edges and distinct color changes, such as pixel art.
Click OK: Once you've entered your desired pixel dimensions and chosen a resampling method (if needed), click OK to apply the changes.

Resampling: When you change the pixel dimensions, Photoshop has to either add new pixels (upsampling) or remove existing pixels (downsampling). This process is called resampling and can affect the image quality. Upsampling can lead to a loss of sharpness and the introduction of artifacts. Downsampling can also result in a loss of detail.
Constrain Proportions: Make sure the "Constrain Proportions" option is checked (indicated by a chain icon) if you want to maintain the image's aspect ratio while changing the size. If it's unchecked, you can change the width and height independently, which might distort the image.
Resolution vs. Pixel Dimensions: Be aware of the difference between resolution (pixels per inch/centimeter) and pixel dimensions (total number of pixels). Changing the resolution without resampling will affect the printed size of the image but not the number of pixels. Changing pixel dimensions changes the number of pixels in the image.
Non-Destructive Editing: For greater flexibility, consider using Smart Objects. Convert the image layer into a Smart Object before resizing. This allows you to resize multiple times without losing quality.