Mega Code Archive
How to convert a color image to grayscale
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Title: How to convert a color image to grayscale
uses
Windows, Graphics;
function ConvertBitmapToGrayscale1(const Bitmap: TBitmap): TBitmap;
var
i, j: Integer;
Grayshade, Red, Green, Blue: Byte;
PixelColor: Longint;
begin
with Bitmap do
for i := 0 to Width - 1 do
for j := 0 to Height - 1 do
begin
PixelColor := ColorToRGB(Canvas.Pixels[i, j]);
Red := PixelColor;
Green := PixelColor shr 8;
Blue := PixelColor shr 16;
Grayshade := Round(0.3 * Red + 0.6 * Green + 0.1 * Blue);
Canvas.Pixels[i, j] := RGB(Grayshade, Grayshade, Grayshade);
end;
Result := Bitmap;
end;
procedure ConvertBitmapToGrayscale2(const Bmp: TBitmap);
{From: Pascal Enz, pascal.enz@datacomm.ch }
type
TRGBArray = array[0..32767] of TRGBTriple;
PRGBArray = ^TRGBArray;
var
x, y, Gray: Integer;
Row: PRGBArray;
begin
Bmp.PixelFormat := pf24Bit;
for y := 0 to Bmp.Height - 1 do
begin
Row := Bmp.ScanLine[y];
for x := 0 to Bmp.Width - 1 do
begin
Gray := (Row[x].rgbtRed + Row[x].rgbtGreen + Row[x].rgbtBlue) div 3;
Row[x].rgbtRed := Gray;
Row[x].rgbtGreen := Gray;
Row[x].rgbtBlue := Gray;
end;
end;
end;
procedure ConvertBitmapToGrayscale3(const Bitmap: TBitmap);
type
PPixelRec = ^TPixelRec;
TPixelRec = packed record
B: Byte;
G: Byte;
R: Byte;
Reserved: Byte;
end;
var
X: Integer;
Y: Integer;
P: PPixelRec;
Gray: Byte;
begin
Assert(Bitmap.PixelFormat = pf32Bit);
for Y := 0 to (Bitmap.Height - 1) do
begin
P := Bitmap.ScanLine[Y];
for X := 0 to (Bitmap.Width - 1) do
begin
Gray := Round(0.30 * P.R + 0.59 * P.G + 0.11 * P.B);
// Gray := (P.R shr 2) + (P.R shr 4) + (P.G shr 1) + (P.G shr 4) + (P.B shr 3);
P.R := Gray;
P.G := Gray;
P.B := Gray;
Inc(P);
end;
end;
end;
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