From wiki-JPEG, we could see a baseline/progressive JPEG have byte marker mapping differently as following:
|SOF0||0xFF, 0xC0||variable size||Start Of Frame (baseline DCT)|
|SOF2||0xFF, 0xC2||variable size||Start Of Frame (progressive DCT)|
So to tell the image is progressive JPEG, we need to check if it contains
0xFF, 0xC0 which is
Two-byte hexadecimal display.