check50 fails my pset 5 resize.c even though output is identical to staff's implementation

Question

I ran diff with the bmp file outputted by my resize program and the same bmp file outputted by the staff's implementation, and it says that the two files are identical; but check50 says it doesn't resize correctly.

here is the check50: https://sandbox.cs50.net/checks/5ebeff094fea4ca6bc959ffa39b6e379