The Basic Principle of Making neagtive image from a normal one involves
complimenting colors.The process of complementing involves representing colors
in a three dimensional cube with the basic colors RGB as the three axis of the cube. When all colors are represented in a cube the opposite corners represent the Complement of the color.
Complement of white is black, complement of blue is yellow. Complementing can be done using the RGB combination.
white rgb(255,255,255)
The complement of white can be obtained by rgb(255-255,255-255,255-255) which
has rgb(0,0,0) which is black.
The same concept as above is used in the program but just converted the integers to hexadecimal for the ease of calculation.
For i = 0 To Picturebox.ScaleHeight - 1
For j = 0 To Picturebox.ScaleWidth - 1
pixvalue = Picturebox.Point(j, i)
hex_pixval = Hex(pixvalue)
red_val = "&h" & Mid$(hex_pixval, 5, 2)
green_val = "&h" & Mid$(hex_pixval, 3, 2)
blue_val = "&h" & Mid$(hex_pixval, 1, 2)
If red_val = "&h" Then red_val = "&h0"
If green_val = "&h" Then green_val = "&h0"
If blue_val = "&h" Then blue_val = "&h0"
red_val = &HFF - red_val
green_val = &HFF - green_val
blue_val = &HFF - blue_val
Picturebox.PSet (j, i), RGB(red_val, green_val, blue_val)
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