Today's tutorial we will learn to use "RULER" Tool in Photoshop to rotate a Canvas/Layer. The scanned photograph below has a certain degree of rotation, we can simply use transform/rotate canvas option to rotate the image and adjust the orientation but to get accurate result it will take some adjustment time and skill. Here is an easy method to get accurate result.
First Select the RULER tool from the Tool Bar, this tool is mainly used as a measuring tool.
To adjust the orientation of the image we need to mark a reference line using the RULER. In this case we will use the brick wall in front as the reference and draw a line(RULER Tool).
Once the reference line is set, Select the ARBITRARY option from the IMAGE menu (Image>>Rotate Canvas>>Arbitrary...). this will popup a Angle Value.
The Angle Field automatically takes the Value from the RULER reference line drawn earlier. Click OK and your canvas will adjust according to the reference line.
The same method can be used to rotate a layer, only change will be after clicking on Arbitrary(Image>>Rotate canvas>>Arbitrary), Copy(Ctrl+C) the angle Value and then click CANCEL.
This is because Arbitrary option in Rotate canvas will rotate the entire file not just a layer.
Once the Value is copied, Select the layer and Transform (Ctrl + T), Paste the Value to the rotate field and Press Enter. The orientation of the Layer is adjusted to your reference RULER marker.
DONE.
