Rotate part of an image?

I have a .tiff file that I read into matlab as a .mat file and plot. When I plot the matrix, the image I am actually interested in (part no including purple triangle edges around the image) is rotated. How do I first remove the purple border around the image (highlighted in light blue in the attached jpeg file) and then take the image and rotate it by 30 degrees counterclockwise to make the image flat? The outside purple part of the image I to remove from the image has a value of 0 and color purple according to the colorbar.

Answer 1

[madhan ravi]

https://www.mathworks.com/help/images/ref/imrotate.html

[Andrew Poissant]

Thank you I was able to rotate the image without issue but I still have the purple border around the actual image, which I do not want. I need to remove that portion.

[madhan ravi]

Chop off the the points from extracting the points from the rotated image using imread