Just curious about those RLE images from old 1997 PC game "My Friend Koo".

 

My Friend Koo RLE samples.zip

1 hour ago, ikskoks said:

Just curious about those RLE images from old 1997 PC game "My Friend Koo".

 

My Friend Koo RLE samples.zip 649.66 kB · 1 download

They don't seem overly complicated - it might be useful to have some uncompressed samples from memory (if possible), from running under DosBox, etc. in order to see exactly what the data should be.

 

14 hours ago, ikskoks said:

Just curious about those RLE images from old 1997 PC game "My Friend Koo".

 

My Friend Koo RLE samples.zip 649.66 kB · 5 downloads

It's similar to PCX/PackBits, where bytes 0xC0–0xFF indicate a repetition and the remaining ones are literal bytes.
PCX-style RLE: bytes >= 0xC0 specify a repetition count (byte & 0x3F) for the following byte.

A 256-color RGB palette is located in the last 768 bytes of the file.

Standard image size is 640x480, with a short prefix/header preceding the pixel data.

Edited May 13May 13 by Rabatini

def pcx_style_rle_decode(data):
    out = bytearray()
    i = 0
    n = len(data)
    while i < n:
        b = data[i]
        i += 1
        if b >= 0xC0:
            count = b & 0x3F
            value = data[i]
            i += 1
            out.extend([value] * count)
        else:
            out.append(b)
    return bytes(out)

def decode_rle_image(filepath, width=640, height=480, offset=None):
    with open(filepath, 'rb') as f:
        raw = f.read()
    palette_size = 768
    if len(raw) <= palette_size:
        raise ValueError("Arquivo muito pequeno, não tem dados de imagem + paleta.")
        
    compressed = raw[:-palette_size]
    palette = raw[-palette_size:]
    
    decoded = pcx_style_rle_decode(compressed)
    expected_pixels = width * height

    # Gambiarra caso o offset não seja informado: pega o final dos dados descompactados
    if offset is None:
        offset = len(decoded) - expected_pixels
        if offset < 0:
            offset = 0

    pixels = decoded[offset: offset + expected_pixels]
    return pixels, palette, offset

Here the essential! 

Let me know if you need the complete tool.

No need. Thank you.

Ah, it was quite simple.  I did wonder if the top 2 bits of the byte had any relevance - for example, to indicate alpha pixels.