Guilty Gear Image Compression

Hi experts,

I'm trying to look at the BIN Images from the game Guilty Gear. The image structure seems OK, and they look like paletted images of size 640x480, however the file size for each BIN image differs, and is smaller than the size required for 640x480, so I suspect some kind of compression on the pixel data only (the palette indexes). Would anyone be able to take a look please.

The image structure:

+-------------------+
| Guilty Gear *.bin |
+-------------------+

// Image
// Unknown compression on the pixel data

// HEADER
  4 - Header Length? (16)
  12 - Padding (all byte 255)
  2 - Number of Palettes? (1)
  2 - Palette Offset (32)
  2 - Image Format? (8)
  2 - Image Width
  2 - Image Height
  2 - Unknown (10)
  2 - Unknown (9)
  2 - Unknown
  
// COLOR PALETTE
  // for each color (256)
    4 - RGBA Color
  
// IMAGE DATA
  X - Compressed Pixel Data

Thanks for your help!

Guilty Gear Images.zip