Changing Image Size in GIMP | Spring Into Linux

You can change image size in one of three ways:

Crop: Keep part of an image and discard the rest.
Scale: Change the size of an image, keeping all the content of the image. For instance, if you scale the image smaller, all parts of the image shrink to fit the new image size.
Resize: Change the size of the window, while keeping the image the same size. This is generally used to make the window larger, thereby making room to add new elements to the image.

To crop an image, you select the section you want to keep and throw away the rest. Use a select tool from the toolbox to select the part of the image to keep. For instance, click the first tool to use the tool that selects a rectangular section of the image. Then, move your mouse to the image window. The mouse pointer now shows a rectangle beside the pointer, so you know which tool is active. Click and drag the mouse to enclose the image section that you want to keep. To remove the selection and select again, right-click and select Selection->None.

Click Image on the image window menu bar and select Crop to Selection. The image outside of your selection disappears. You can undo a crop to return the cropped part of the image.

To scale an image, click Image and select Scale Image. A dialog window opens that allows you to specify the width and height wanted for the new size. Or, in the ratio fields, you can specify the percentage to scale by, such as .60 (60%) or 1.5 (150%). By default, the ratio of width to height remains the same. If you want to change the shape of the image, click the link icon to the right of the ratio fields. It separates into two links. Then you can set the height and width independently.

To resize an image, click Image and select Canvas Size. A dialog window opens, similar to the scale image dialog window. You can set the width and height of the window. If you resize the window smaller, you can only see part of the image in the window. If you resize the window larger, extra space is added to the window where you can add elements to the image.