I have rectagular photos of different sizes and i need to know how to resize them all to 1080x1080 without distorting the image - its ok for them to end up with a white border (similar to instagram photo sizing) - (ive done it before but cant recall how - these are 3024x4032 converted to 1080x1080 with white border)
I'd make a new file 1080x1080 and then drag the photo over into it and move it around till it looks good. I looked at the shoes image, and I can see right away you have room at the top and the bottom that can be cropped off. You can't just resize a rectangle into a square without some distortion,
You would use menu File>Automate>Fit Image... set 1080 PX is width and Height. to resize the image to fit within 1080x1080 canvas size then use menu Image>Canvas Size... Un-check relative and set wirth and height 1080 px to add any missing canvas boarders will be added if required.
I agree with @JJMack 's suggestion and want to add that this way you can automate process using Photoshop actions and built-in scripts because from what I understand you have multiple/lots of images to process.
Use the Crop Tool.
Set crop height and width to 1080 x 1080. See screenshot.
If you crop you discard image content. The image has different aspect ratio the image's composition is changed.
It sounds like JJMack’s solution is the one you want. Below is what the steps would look like. If you want white borders, then while you are in the Canvas Size dialog box, choose White as the Canvas Extension Color as shown below. Using the Fit Image command means it will work regardless of the dimensions, proportions, or orientation of the original, so it works great for batch automation.