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Paul Nicholls
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 Posted: Tue Aug 23, 2005 5:59 am Post subject: Re: detecting pixels of certain color |
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"SupportX" <SupportX (AT) SupportX (DOT) com> wrote
| Quote: | Subject: detecting pixels of certain color
Hi,
I have a small bitmap. I wish to scan one horizontal line in it (the
middle one) from left to right, and determine which points on this line
are black.
How to?
TIA,
SupportX
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you have two options:
1) use TBitmap.Canvas.Pixels[x,y] - easiest by far, but slow!
2) use TBitmap.Scanline[] - more difficult to code, but much faster!
cheers,
Paul
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Charles Hacker
Guest
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| Posted: Tue Aug 23, 2005 6:06 am Post subject: Re: detecting pixels of certain color |
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SupportX wrote:
| Quote: |
I have a small bitmap. I wish to scan one horizontal line in it (the middle one) from left to right, and determine which points on this line are black.
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How close to black?
Lets assume black is colour (0-255) less than '4' intensity!
var Line: PByteArray;
X,Y,col: Integer;
Bitmap.Pixelformat:= pf24bit;
{note this code only works with 24 bit RGB color images}
col:= 0;
Y:= Bitmap.Height DIV 2;
Line:= Bitmap.Scanline[Y];
for X := 0 to Bitmap.Width-1 do
begin
// Red is Line[X*3 ]
// Green Line[X*3+1]
// Blue Line[X*3+2]
if (Line[X*3]<4 and Line[X*3+1]<4 and Line[X*3+2]<4) then
begin
// Color is black
INC(col);
end;
end;
ShowMessage(IntToStr(col)+' Pixels were black');
--
Charles Hacker
Lecturer in Electronics and Computing
School of Engineering
Griffith University - Gold Coast
Australia
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SupportX
Guest
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| Posted: Tue Aug 23, 2005 6:49 am Post subject: detecting pixels of certain color |
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Subject: detecting pixels of certain color
Hi,
I have a small bitmap. I wish to scan one horizontal line in it (the middle one) from left to right, and determine which points on this line are black.
How to?
TIA,
SupportX
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SupportX
Guest
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| Posted: Tue Aug 23, 2005 7:34 pm Post subject: Re: detecting pixels of certain color |
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Subject: Re: detecting pixels of certain color
Thanks, worked like a charm!
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Francesco Savastano
Guest
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| Posted: Wed Aug 31, 2005 2:36 pm Post subject: Re: detecting pixels of certain color |
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| Quote: | // Red is Line[X*3 ]
// Green Line[X*3+1]
// Blue Line[X*3+2]
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Actually Red is Line[X*3+2] and Blue is Line[X*3 ]
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