How to Straighten a Horizon With Paint.NET

Correct skewed perspectives and crooked pictures in Paint.NET

Taking a perfectly horizontal image is practically impossible. Fortunately, it is possible to straighten horizons in Paint.NET.

Instructions in this article apply to version 4.2 of the Paint.NET image editing software for Windows, not to be confused with the website of the same name.

How to Straighten Images in Paint.NET

Unlike other image editors for Windows such as Adobe Photoshop or GIMP, Paint.NET doesn't offer the ability to add guiding lines to an image. To make it easier to adjust the horizon, you can add a semi-transparent layer and use that as a guide. You can skip steps 1-7 if you trust your eye, but performing these steps ensures that your image with be perfectly horizontal.

  1. Go to File > Open and select the image you want to straighten.

    Go to File > Open and select the desired image.
  2. Go to Layers > Add New Layer.

    A screenshot of Paint.NET with the Add New Layer command highlighted
  3. Select the Rectangle Select tool from the toolbox, and then click-and-draw a wide rectangle across the top half of the image so that the bottom of the selection crosses the horizon at the middle.

    A screenshot of Paint.NET with the Rectangle tool highlighted
  4. Change the Primary color if necessary. If the image is very dark, use a very light color. If the image is light, use black.

    If you don't see the Colors palette, select the icon in the top-right corner to open it.

    A screenshot of Paint.NET with the Primary color highlighted
  5. Move the Opacity - Alpha slider to the halfway position.

    If you don't see the Opacity - Alpha slider, select More on the Colors palette to make it visible, then select Less to hide it.

    

    A screenshot of Paint.NET with the Opacity-Alpha slider highlighted
  6. Go to Edit > Fill Selection to fill the selection with the semi-transparent color. This gives a straight horizontal line across the image that can be used to align the horizon.

    A screenshot of Paint.NET with the Fill Selection command highlighted
  7. Go to Edit > Deselect to remove the selection as it is no longer needed.

    A screenshot of Paint.NET with the Deselect command highlighted
  8. Select the Background layer in the Layers palette, then go to Layers > Rotate/Zoom.

    To select a layer, you must click on it. Checking the box beside the layer simply shows or hides the layer.

    A screenshot of Paint.NET with the Rotate/Zoom command highlighted
  9. Move the first slider under Roll/Rotate to rotate the image so that the horizon aligns with the semi-transparent layer, then select OK.

    You can use the left and right keys to adjust the image, or you can adjust the value beside the slider.

    A screenshot of Paint.NET's Rotate/Zoom window with the top slider and OK button highlighted
  10. Select the transparent layer and go to Layers > Delete Layer.

    A screenshot of Paint.NET with the Delete Layer command highlighted
  11. Rotating the image leads to transparent areas at the edges, so it needs to be cropped. Select the Rectangle Select tool and draw a selection over the image that doesn't contain any of the transparent areas, then go to Image > Crop to Selection.

    A screenshot of Paint.NET with the Crop to Selection command highlighted
  12. Save your new image.

    Go to File > Save As to save your new image.