How to crop batch multiple images?

Provided all files are set up the same way (if not, batch save out as png first);
Set up an action that performs a CTRL+Left Click on the layer,
Then ALT+i
Then P to crop flush.
Then CTRL+SHIFT+ALT+S to save for web as a png.
Test it on a control group, once confirmed as working, batch run this action on your folder.

If you have glow effects and such, there may be empty space that seems useless, but it still contains a pixel somewhere at the outermost edge.

Photoshop has a facility to record a set of repetitive actions which you can run in the future.

Canvas Size is a means to change the canvas size (not to be confused with resampling the image).  So if you had a canvas of (say) 200px x 200px.  If you set canvas size to 180px x 180px, you would reduce the canvas size by 10px on each side. (crop).

What do you mean by 'blank page'?  Why have images got blank page?   

Do they all need exactly the same amount of crop and same positioning of crop?

If so, create a 'canvas size' action.  Then go to File > Automate > Batch.  Select your images and apply your Canvas Size action.

If each image needs a unique input, I can't think of a way to batch that.