What is this way of representing color in this unknown image format

Question

All right, I have a PS3 image compressed with a variation of the LZ algoritm (magic bytes 43 5A 32 00) (I have successfully decompressed it) and what I get from the decompressed form is a set of ARGB colors/pixels (The number of bytes in the compressed file is 4*width*height thus I know that the decompressed file problably only contain the raw ARGB data).

Here is an image illustrating the result of rendering the ARGB data (transparency omitted to makes thing easier to make out).

Decompressed image:

PS3 edition screenshot:

PSP edition screenshot:

What I want to know is if any of you know what sort of logic this color structure use? To me, it looks like it looks at the last color in terms of the y-axis. Where zero value just gets the value of the last color of the y-axis. It kind of looks like I have to dif/sum colors together.

I have tried varies methods. For example, here I try storing a color array with zero color and for each line, sum the unsigned integer representation of ARGB of x position in the array with the new color' unsigned integer -> A+B = C.

A-B=C, just gives pinkish giberish..

Here are some samples of ARGB values that I use to try and find a solution:

x:0, y:24-27

R   G   B

137 195 255

240 254 000

014 000 255

001 001 001

This should give a blueish color (comparing to Game screenshot) like: 145, 184, 219.

*Please notice that my image for comparison isn't exact. That is to say that I got it from the same game of another platform where another format is used. Since the image sized are different. I can say that the colors aren't 100% the same as the new one.

x:4, y:22-28

R   G   B

137 195 255

118 168 201

255 204 161

This too should give a dark bluerish color like: 020, 068, 096.

*Please notice that the compared color in the game isn't exact, the image has transparency too, so the game has problably messed with the color values of the screenshot.

So if anybody have encountered stuff like this before and could give me a tip of some sort I would be very happy. :)

Answer 1

You asked this a couple of months ago, but I'm going to answer anyway.

First, I fear that your decompression code is buggy. There are several horizontal lines of noise, and I'm pretty sure they're not supposed to be there.

Your A+B=C guess was correct. A tell-tale sign are the visible horizontal edges but hidden vertical edges. I think your mistake was simply to do the addition with the wrong endianness.

I wrote a little Python script:

from PIL import Image
im = Image.open('orig.png')
w, h = im.size
pix = im.load()
def add(p, q):
    # Convert (R,G,B) tuples to RGB integers, add them, and convert back
    pp = (p[0] << 16) + (p[1] << 8) + p[2]
    qq = (q[0] << 16) + (q[1] << 8) + q[2]
    r = pp + qq
    return ((r >> 16) & 0xFF, (r >> 8) & 0xFF, r & 0xFF)
for y in range(1, h):
    for x in range(w):
        pix[x,y] = add(pix[x, y], pix[x, y-1])
im.save('out.png')

The result is this image. You can see that the top third matches the PSP image, but starting from the line of noise in the source image, the picture becomes distorted. Fix your decompression code and the picture will come out right :)

Answer 2

Not sure how i would go about this but there is a tool called cantordust that can help with this, it can visualize binary information into pictograms. The link is down below.

https://sites.google.com/site/xxcantorxdustxx/