% of color
lazarus / 39-Graphics

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xinyiman · 2016-01-27 08:40

Hello guys, who explained to me how to know the percentage of the
presence of an image of a specific color. For example I want to know
what red is a percentage of an image. How can I do? Thank you

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balazsszekely · 2016-01-27 09:16

I would use BGRABitmap because it's fast:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses
BGRABitmap, BGRABitmapTypes; procedure TForm1.Button1Click(Sender:
TObject);var  X, Y: Integer;  P: PBGRAPixel;  BGRABitmap:
TBGRABitmap;begin  BGRABitmap :=
TBGRABitmap.Create(Image1.Picture.Bitmap);  try    for Y := 0 to
BGRABitmap.Height - 1 do    begin      P := BGRABitmap.Scanline[Y];  
  for X := 0 to BGRABitmap.Width - 1 do      begin        //acces
pixel here  P^.Red; P^.Green; P^.Blue then calculate percentage      
Inc(P);      end;    end;  finally    BGRABitmap.Free;  end;end;

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wp · 2016-01-27 09:31

Your question is not clear: You want the perentage of "red"? What is
"red"? Full red, ie. R=255, G=B=0? Or all shades of red, R = 1..255,
G=0, B = 0, or maybe R=1..255, G=B? Or the red component of every
color?

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xinyiman · 2016-01-27 10:34

Thanks, my actual solution is:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  function
ColorInPerc(MyColor: TColor; MyCanvas: TCanvas; MyLarg: integer;
MyAlt: integer): single;var   ret: single;   numColor, numTot:
integer;   i,j: LongInt;begin     ret:=0;     numColor:=0;   
 numTot:=0;     for i:=0 to MyLarg-1 do         for j:=0 to MyAlt-1
do         begin              if MyCanvas.Pixels[i,j]=MyColor then   
            Inc(numColor);              Inc(numTot);         end;    
 ret:=(numColor*100)/numTot;     Result:=ret;end;   
But I do not know how to tell him that I want to take all kinds of
orange.

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balazsszekely · 2016-01-27 10:53

First of all you can convert between TColor and RGB. Secondly,
according to the net:
RGB(Orange)      -> (255, 165, 0)
RGB(Dark Orange) -> (255, 140, 0)
RGB(Red Orange)  -> (255,  69, 0)

so:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
IsOrange(R, G, B: Byte): Boolean;begin  Result := (R = 255) and (G >=
69 and G <= 165) and (B = 0);end;
You can add more shades if you like.

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xinyiman · 2016-01-27 11:02

Thank you

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xinyiman · 2016-01-27 11:14

And how can I convert my TColor in 3-byte RGB

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rvk · 2016-01-27 11:21

I also would call this orangy:
http://www.color-hex.com/color/e59400
which is #E59400 (229,148,0)

Color-determination is a really tricky subject.
You need to determine how far you want to go with each value of Red,
Green and Blue.

For your TColor question:
Look at the Graphics unit:
http://wiki.freepascal.org/Colors

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
Blue(rgb: TColor): BYTE; // does not work on system colorfunction
Green(rgb: TColor): BYTE; // does not work on system colorfunction
Red(rgb: TColor): BYTE; // does not work on system colorfunction
RGBToColor(R, G, B: Byte): TColor;procedure RedGreenBlue(rgb: TColor;
out Red, Green, Blue: Byte); // does not work on system colorfunction
FPColorToTColor(const FPColor: TFPColor): TColor;function
TColorToFPColor(const c: TColor): TFPColor; // does not work on system
colorfunction IsSysColor(AColor: TColorRef): Boolean;

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circular · 2016-01-27 19:24

To determine the hue of the color, you can call BGRAToHSLA or BGRADiff
(using BGRABitmap).

BGRAToHSLA returns the hue/saturation/lightness components. So you
could check if the values are within a specified range. For example,
you can get the values from a test color, and then compare the values.
The function HueDiff helps to compute the value of two hues.

Otherwise you can call BGRADiff with two colors, and it returns a
value that expresses the difference. So if the difference is less than
a certain value, you could count it as "orange", or "red"...

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wp · 2016-01-27 19:33

But just for calculation of the hue of a color it is not necessary to
add a requirement for a third-party library. Use ColorToHLS or
RGBToHLS from GraphUtil, instead.

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avra · 2016-01-28 10:58

Quote from: xinyiman on January 27, 2016, 09:40:54 amHello guys, who
explained to me how to know the percentage of the presence of an image
of a specific color. For example I want to know what red is a
percentage of an image. How can I do?If you are serious about human
like ways to determine color in an image, the best way would be to use
fuzzy logic. Dark orange or light brown is a little different color
for different people, but a general rule can be written in words, and
if descriptive rules can be created, accurate color detection can be
implemented in fuzzy logic. It is a lot of reading and study if you
are new to this area. There are many fuzzy logic tutorials and ways to
implement it in a programming language. You might want to look at
following link to read about solving your specific problem:
http://www.google.rs/search?q=fuzzylogic+color+detection