Round cornered images in Paint.NET

Skyline gondola I’ve been experimenting with doing some simple image post processing for my posts. Rectangular images with sharp right-angled corners look a bit stark. I’m getting most of the images from iStockphoto (referral link), and it seemed a waste if I didn’t fit photos and text together nicely.

The easiest and fastest way to spruce up a stock photo is to create round corners in the image. I’ll be showing you how to do so in the freely available, fantastic and awesome image editor, Paint.NET (did I mention it was free?).

So, suppose here’s the original photo, after loading it into Paint.NET
Original picture

Then you add a new layer by either clicking [Layers] -> [Add New Layer] option
Add new layer by option
or click on the “Add New Layer” button in the “Layers” panel (placed near bottom right by default)
Add new layer by button in layer panel

Next, you want to focus on the 2nd layer for some editing first. On the “Layers” panel, uncheck the “Background” image.
Focus on layer 2

On the 2nd layer, we wash it over with white colour first, because by default it’s in “transparent” colour. We can talk about the difference between white and transparent some other time… We’ll use the paint bucket tool
Paint bucket
By default, if you haven’t changed the colour selection yet, then the primary colour is black and the secondary colour is white.
Primary and secondary colour selection
What this means is if you click and draw with the left mouse button, black is used. If you click and draw with the right mouse button, white is used.

So after selecting the paint bucket tool, go somewhere in the (transparent-coloured) image, and right-click. This will give you a nice clinical white patch.

We want to draw a rounded black rectangle on this white patch. We use the aptly named “Rounded Rectangle” tool
Draw rounded rectangle with filled shape
Some finger nimbleness will be needed here. Our test image is 160 pixels wide and 110 pixels tall. We’ll have to left-click (for black) in the image, at the cursor position of 0,0 and drag-move to cursor position 159,109. You can find out the cursor position by looking somewhere near the bottom of Paint.NET
Cursor position
We’re at cursor position 11,9 in this case.

You should then get this beauty
Black and white rounded corner

After that, go the “Layers” panel, and click on properties for the 2nd layer
Layer properties
and set the blending mode to “Additive”
Set additive blending mode

Check the “Background” layer back (to make it visible again) and you should see this
Skyline gondola

Save and you’re done!

I think a video tutorial would have done a better job. Anyone want to sponsor the Camtasia software for me?

PS. That “Skyline gondola” sign was taken at the halfway point on my practically vertical climb up the hill in Queensland, New Zealand. I was the only one (stupid enough) climbing up. Everyone else was going down… A story for another time perhaps…

[UPDATE: Use this plugin RadiusFillCorners. Much easier if you don’t mind a bit of jaggedness on the corners. But not noticeable on larger images.]

  1. david

    Hi I tried your tutorial following all the steps.
    At the end when I “Check the background layer back (to make it visible again)”. I get my original picture with the sharp corners.
    My picture is a graphics design on a white background.
    Any ideas?

  2. Vincent

    Hi david, the only thing I can think of is that the blending mode should be “Additive”. Was that done? Make sure to select the layer before changing the properties (changing the blending mode). This ensures you are editing the layer, and not the original background.

    If your picture is on a white background, could it be that the rounded corners aren’t so obvious?

    What happens is that a 2nd layer is created, with a black rounded rectangle on white. Because the blending mode on this layer is “Additive”, it “adds” the RGB values onto the 1st layer.

    Since black is (0,0,0), nothing is added onto the 1st layer for the black rounded rectangle. The white part will basically make the corresponding part in the 1st layer white. So in the end, you get the original picture with rounded corners.

  3. david

    Vincent thanks for your quick reply, I tried it again using blue as the primary color and red as the secondary color. I still don’t see any rounded corners, but the black lines (which is all the lines) in the original image are now blue.
    Just so I understand what I’m trying to do, have we just drawn rounded corners on a rectangular image or have we created a new rounded corner image.
    If I understand an image size is defined by its length and width, so its not possible to define anything but a rectangle.


  4. david

    Just continuing the above comment if the image is still rectangular then to see rounded corners the original (sharp) corners should be transparent and not white.

  5. Vincent

    David, I believe I found a way to do it. I’ve privately emailed you the solution. I’ll probably do a tutorial based on it… once I find the motivation to do it…

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