The dimensions are different you see.

For JEE Main it is

Photograph of Candidate JPEG format 4KB to 40KB 3.5cm x 4.5cm

Signature of Candidate JPEG format 1KB to 30KB 3.5cm x 1.5cm

Signature of Father/Mother/Guardian JPEG format 1KB to 30KB 3.5cm x 1.5cm

For WBJEE it is

Photograph JPG/JPEG 3 kb to 100 kb. 4 cm x 3 cm

Signature JPG/JPEG 3 kb to 30 kb. 4 cm x 1.5 cm

Us an online tool, resize it accordingly and you are good to go. all the best!