Picture.CompareBrightnessMBS(other as picture, mode as Integer, threshold as Integer) as Double

dim p as picture = New Picture(100,100,32)
dim q as Picture = New Picture(100,100,32)

dim diff as Double = p.CompareBrightnessMBS(q, 0, 0)

MsgBox str(Diff) // shows 0 = equal

Returns the percent of difference: Number of pixels where the squared color difference is bigger than the threshold divided by the total number of pixels.
If width and height are not equal, the result is 1.0.
If you need to check the mask also, please call this method a second time for the masks.

Modes:

0	y = 0.33 * R + 0.5 * G + 0.16 * B	Faster version of 3
1	y = 0.375 * R + 0.5 * G + 0.125 * B	Faster version of 3
2	y = 0.2126 * R + 0.7152 * G + 0.0722 * B	Photometric/digital ITU-R
3	y = 0.299 * R + 0.587 * G + 0.114 * B	Digital CCIR601

Mode 2 and 3 uses doubles and mode 0 and 1 use integers so they should be faster.
Still Mode 0 and 1 are just approximation formulas which trade accuracy for perfomance.

Only compares raw pixels without checking mask or alpha channel.