Setting the Image Size and Resolution

Before we talked about changing the view size of the image, it had already been rotated. So the image should be upright now. Next, you'll want to set the size and resolution.

Let's say you want your image to be the size of a photo print, 13.5 cm x 18 cm, about 5 in x 7 in, so it can easily fit on one print page. The target resolution of the image is 300 dpi.

Options for setting the size and resolution are located in the image window; just choose Image > Scale Image.

When the Scale Image window pops up, you can set the measurement for Xresolution to 300 pixels/in (= dpi). In the text field, just overwrite the default value and press Enter to accept your changes. Both resolution values should now be 300 pixels/in.

2.3 EDITING IMAGES IN GIMP

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Make sure the chain icon near the resolution settings is closed and that the X and Y resolutions are equal (see Figure 2.24).

The next step is to set the image size (measured in pixels, inches, millimeters, etc.). In the upper part of the window, you will see two values: Width and Height. You want to use inches as your size unit. To set inches as the measurement unit, click the arrow next to the Pixel/in field (to the right of the Height field) and select inches. Then type the number 7 for the value in the Height field. Press Enter to accept your changes. The value for the width should now be 5.25.

Figure 2.24

The Scale Image window

Figure 2.24

The Scale Image window

Now choose the interpolation quality (pixel recalculation). Set Interpolation to Sinc (Lanczos3) in the Quality section of the Scale Image window. Confirm the settings by clicking the Scale button. The program now computes the new image size; this also may change the size of the image in the display. To see the entire image in the display, you have a variety of tools to choose from. But first I would like to give you some more information on the relation of resolution and size.

Try it out if you are not sure what you should choose. The results can vary from image to image.

GIMP can be a bit fussy when you're making a selection in the Scale Image window. Sometimes it doesn't accept an entry the first time you press Enter. Simply repeat the procedure again. I admit I might be imagining this, but pressing the Enter key harder seems to help in this case. Since the pixels are being recalculated with this method, it has an effect on the quality of the image. You must apply this function if you want to enlarge the image or when you want to scale down the image for use on a website or for sending via email. When setting up the image for printing, you may want to have a look at the function described in the next section, which doesn't need any recalculating. The original numbers of pixels as well as the quality remain the same.

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Responses

  • anja
    What should the x and y resolution be on an image?
    6 years ago

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