Getting the images for free
Pixabay.com has almost 150 000 high quality images that you can download and use for free without any restrictions.
Once you’ve downloaded an image, you can edit it to suite your requirements (resizing, colour correction, adding text, etc.). I use Photoshop but GIMP is just as good and it’s free. You can get GIMP here.
Is the image in a PNG format
Make sure it’s in the PNG format (jpeg does not handle transparency which is necessary for the rounded corners). If it’s not a PNG file then you need to convert it. You can use Microsoft Paint to do the conversion. Microsoft Paint is a free app that is included with the Windows operating system (Start>All Programs>Accessories>Paint). Open the image in Microsoft paint. Then select Save As from the drop-down menu and select PNG (*.png) as the Save as type. Press Save to save the image. I downloaded this great image from Pixabay (the original large size is absolutely stunning!)
Resizing the image
Open up the PNG image in GIMP. The image I have chosen is quite big, 6144 x 4096 pixels. I used GIMP and rescaled it to 320 x 180 (Image>Scale Image and then entered my dimensions for the width and height, completing the resize by selecting Scale).
Rounding the corners
Next, place the cursor over the image and right click. From the drop-down menu select Layer>Transparency>Add Alpha Channel (if this option is greyed out then it means that an Alpha channel already exists). Then (place the cursor over the image and from the menu) select Select>All. Then Select>Rounded Rectangle and set the size of the rounded corner that you want in the dialog window and confirm by pressing OK. I have chosen 30 for mine.Next, select Select>Invert and then Edit>Cut.
Saving the image
Now you are ready to save the image. Go to File and select Save. A pop-up dialog appears, enter a name for the file and PNG image (*.png) as the file type and press Save. A pop-up dialog appears, make sure that Save background color is not selected and press Save. Compare the two images, rounding the corners adds that little something to the image. You could reduce the size of the rounding for a more subtle effect.
Converting the image to jpeg for a smaller file size
You can convert the image to Jpeg and reduce the file size (I achieved 30Kb without much loss of quality) as opposed to the PNG version at 181Kb. Unfortunately the jpg format does not handle transparency so the background will be white, which is okay if the background where you place the image is white. There are ways of accommodating this by ensuring that the background of the image with the rounded corners is the same colour as the background where it will be placed. Maybe I will cover that in another tutorial.