Hi, I am trying to write a fast edge detection function using LockedPixels. It is all working fine except certain colours are being filled in! It seems that when some colours are Poked it changes surrounding colours to yellow, making the code think there is an edge.
Here is the code and the test image, any help would be great.
http://www.avds12.dsl.pipex.com/Test.bmp
Graphics 800,600,32,2
image=LoadImage("Test.bmp")
Width=ImageWidth(image)
Height=ImageHeight(image)
LockBuffer(ImageBuffer(image))
LBank=LockedPixels(ImageBuffer(image))
LPitch=LockedPitch(ImageBuffer(image))
LFormat=LockedFormat(ImageBuffer(image))
Select LFormat
Case 1
Case 2
Case 3,4
For y=0 To Height-1
YPos=y*LPitch
For x=0 To Width-1
RGB=PeekInt(LBank,YPos+(x*LFormat))
SrcR=(RGB And $FF0000) Shr 16
SrcG=(RGB And $FF00) Shr 8
SrcB=RGB And $FF
If x<(Width-1)
RGB=PeekInt(LBank,YPos+((x+1)*LFormat))
x1R=(RGB And $FF0000) Shr 16
x1G=(RGB And $FF00) Shr 8
x1B=RGB And $FF
EndIf
If x>0
RGB=PeekInt(LBank,YPos+((x-1)*LFormat))
x2R=(RGB And $FF0000) Shr 16
x2G=(RGB And $FF00) Shr 8
x2B=RGB And $FF
EndIf
If y<(Height-1)
RGB=PeekInt(LBank,(y+1)*LPitch+(x*LFormat))
y1R=(RGB And $FF0000) Shr 16
y1G=(RGB And $FF00) Shr 8
y1B=RGB And $FF
EndIf
If y>0
RGB=PeekInt(LBank,(y-1)*LPitch+(x*LFormat))
y2R=(RGB And $FF0000) Shr 16
y2G=(RGB And $FF00) Shr 8
y2B=RGB And $FF
EndIf
SrcBright=SrcR+SrcG+SrcB
SrcBright=SrcBright/3
x1Bright=x1R+x1G+x1B
x1Bright=x1Bright/3
x2Bright=x2R+x2G+x2B
x2Bright=x2Bright/3
y1Bright=y1R+y1G+y1B
y1Bright=y1Bright/3
y2Bright=y2R+y2G+y2B
y2Bright=y2Bright/3
If SrcBright>x1Bright And x<(Width-1)
PokeInt LBank,YPos+((x+1)*LFormat),ConvertRGB(0,0,0,LFormat)
EndIf
If SrcBright>x2Bright And x>0
PokeInt LBank,YPos+((x-1)*LFormat),ConvertRGB(0,0,0,LFormat)
EndIf
If SrcBright>y1Bright And y<(Height-1)
PokeInt LBank,((y+1)*LPitch)+(x*LFormat),ConvertRGB(0,0,0,LFormat)
EndIf
If SrcBright>y2Bright And y>0
PokeInt LBank,((y-1)*LPitch)+(x*LFormat),ConvertRGB(0,0,0,LFormat)
EndIf
Next
Next
End Select
UnlockBuffer(ImageBuffer(image))
DrawImage image,0,0
Flip
WaitKey
End
Function ConvertRGB(r,g,b,Mode=0)
Select Mode
Case 1
Col=((r/8) Shl 11) Or ((g/4) Shl 5) Or (b/8)
Return Col
Case 2
Col=((r/8) Shl 10) Or ((g/8) Shl 5) Or (b/8)
Return Col
Default
Col=(r Shl 16) Or (g Shl 8) Or b
Return Col
End Select
End Function
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