efficient way to compare 2 images?

[bplus]

TestData:
' -1 means no alpha channel, -2 means end of data
Data 255,0,0,-1
Data 0,0,255,-1
Data 128,128,128,-1
Data 64,64,64,-1
Data 0,255,255,-1
Data 0,254,254,-1

Data 255,0,0,255
Data 255,0,0,-1
Data 255,0,0,254
Data 255,0,0,-1
Data 255,0,0,253
Data 255,0,0,-1
Data 255,0,0,255
Data 255,0,0,254
Data 255,0,0,255
Data 255,0,0,253
Data 255,0,0,254
Data 255,0,0,253
Data 255,0,0,254
Data 255,0,0,252
Data 255,0,0,253
Data 255,0,0,252
Data 255,0,0,253
Data 255,0,0,251
Data -2,-2,-2,-2
Data -2,-2,-2,-2
Data -2,-2,-2,-2
Data -2,-2,-2,-2


I think 255 = no alpha for _RGB32 color which meaqns it's a solid color

No something else is wrong.