Having a transparent background is often important for images used on a Tableau dashboard.
PNG is the correct image format for transparent images.
Sometimes an image needs editing to make it suitable for use. Often a simple “Save As PNG” doesn’t suffice. This is where PowerPoint can help.
Use PowerPoint to create transparent images for Tableau
For those like me, who aren’t natural picture editors, PowerPoint is a wonderful thing.
PowerPoint has evolved significantly in this area, with some tools to make editing pictures quite straightforward. Images are often a challenge for the website.
While working on images I found some of the new (I think) PowerPoint features to make picture editing far simpler.
Remove Background in Powerpoint
Searching for an image for my post about sending an email from Tableau, I found a suitable, but very colourful, image.

To begin, copy the image into a PowerPoint slide.
The first thing I wanted to do was remove the bright yellow.
Powerpoint has an option Remove Background in the Format Picture menu.

When clicking Remove Background, the purple colour is how Powerpoint indicates the background for removal. The default selection for this image cuts off the top of the envelope.

In the Background Removal menu, it has tools to Mark Areas to Keep and Mark Areas to Remove.

I can use these and keep the top of the envelope, simply by clicking the purple triangle at the top of the envelope.
Once the parts are marked to keep / remove, click Keep Changes.
The result, with a few clicks, is:

Other background removal free alternatives
You can also try online alternatives, such as:
Gimp.org (far more powerful than only background removal, but also more complex)
Re-colour in PowerPoint
Now the bright background colour is gone it’s hard to see the letter on the white background.
Again, PowerPoint to the rescue.
Another option on the Format Picture menu is Color (yes, deliberate American spelling to match PowerPoint).
Click Color and PowerPoint will change the colour of this, with many suggested alternatives.

I like blue so choose one of the blue options. That gives this:

With PowerPoint, it’s easy to save this as a PNG, which means transparency in Tableau.
Right-click on the image in the PowerPoint slide and Save as Picture.
PowerPoint Design Ideas are also great
I also needed images for the website. I thought it would be interesting to show some Tableau work as an image.
In the end the collages didn’t make it on to the website, but below is an example of what the Design Ideas suggested.

Thinking this would be complicated, I started to snip some charts from various Tableau dashboards and pasting them into a PowerPoint slide.
Then I discovered PowerPoint Design Ideas. Fortunately it self-activated after I pasted the second image into a slide, otherwise I still wouldn’t know it exists.
If you need to switch it on it’s under the Design menu. It offered a large number of different designs using the images on the slide.
All I needed to do was copy and paste the images, no need to manually rearrange anything.

This saves so much time and design pain.
PowerPoint is great for image tweaking.
Wrapping up, PowerPoint massively simplifies the creating and editing of images. If you need to alter images for your Tableau dashboards this is the first place I suggest turning to.