Straighten image with only rounded edges

[pctechtv]

I have a scanned image of something I want to cut out. It has rounded corners. It was not straight on the scanner. I would like to know if there is any method of straightening it in Photoshop? I could also employ Illustrator if that is recommended. Usually, when I have a rectangle-like corner, I use the ruler tool and draw a line. Then I use Image Rotation -> Arbitrary to straighten things. However, I do not have the point to draw my line to and from here. Thanks

[Chuck Uebele]

It looks like there is a square patch on your object that you could use straighten the image.

[Leslie Moak Murray]

Drag guides down even with one corner of the square and the right corner of the object, then Edit>Transform>Rotate.

[Barbara Ash]

This is one of my favorite ways to straighten:

Select the Ruler tool.

Drag the ruler across a horizontal or vertical. You can adjust the angle by moving the end points after dragging.

Then click on Straighten Layer in the Options bar.

[pctechtv]

Thank for the comments so far. I messed this up. When I saw the square I should have scanned the other side. The square is something I stuck there (for something else) and yes I will admit it looks pretty straight. However, I want to know is this possible on a symmetrical rounded side shape. I am doing it for this project now, but I have had other times when I need to do it for other things that did not have a square to reference as straight. Thanks so much.

[pctechtv]

Thanks for the reply. Yes, that is the way I always do with straight edges.

[Barbara Ash · Accepted solution]

With no straight edges, it seems easier to eyeball it.

However, this is one way:

Duplicate the layer. Flip the top layer (the duplicate) horizontally.

Give each layer a different color overlay effect.

Rotate just the top layer until it aligns with the bottom layer.

You could now delete or hide the top layer.

On the bottom layer, rotate it to a negative half that amount.

[pctechtv]

Wow! That's an increadable technique... I understand how eyeballing it can be useful. However, I like the idea of using math as you show. Super help, I appreciate it. 😊