Cannot apply Resize image and Canvas size in Troubleshooting & Bug Reports Posted March 4, 2016 · Edited March 4, 2016 by jim100361 First, the interface is an "either or" situation. You select one method or the other. Since you're not changing the size by percentage, then you are specifying the size you want it to be. The "OK" button is greyed out because you did not modify any of the original dimensions to specify what you want it to be now. It logically cannot say OK I'll change your image to this size if you never indicated what size to change it to. The 800/600 values are the existing dimensions of the image. It is Paint.net's starting point. It says, OK, here is what we have: 800 x 600. How do you want to resize it (because resizing can be reducing or enlarging it) and it doesn't know your intentions until you tell it. Also, be aware that this action applies to all layers on the canvas. You are not resizing a layer, you are resizing everything (everything that will inherently make up the complete image). If you desire to resize a layer independently/separately, then you must do so manually.