I had to flip the z-coordinates on the x axis. Hopefully, that isn't a mistake that happens to be correct, too. haha. I believe a plane terrain would need to be adjusted since the center is 0,0.
zworldcoordinate = (y * (sizez#/height))-(((y * (sizez#/height))-sizez#/2)*2) This could probably be better written but I am not a math guy.
tempmb = CreateMemblockFromImage(splatmap)
width = GetMemblockInt(tempmb, 0)
height = GetMemblockInt(tempmb, 4)
size = GetMemblockSize(tempmb)
for x = 0 to width-1
for y = 0 to height-1
n = 12+(x*4)+((y*width)*4)
r = Round(GetMemblockByte(tempmb, n+0))
g = Round(GetMemblockByte(tempmb, n+1))
b = Round(GetMemblockByte(tempmb, n+2))
a = Round(GetMemblockByte(tempmb, n+3))
xw = x*(sizex#/width)
zw = (y*(sizez#/height))-(((y*(sizez#/height))-sizez#/2)*2)
next y
next x
Thank you Bengismo. Man, I love having you around. Need to start paying you tutor fees.