DelphiX 實戰：TDIB.Darker 與 Lighter 亮度調整

TDIB.Darker 與 Lighter 以指定幅度調整影像整體亮度，分別對應變暗與變亮操作。本文提供載入圖片後按鈕觸發雙向亮度調整的完整範例。

效果預覽

核心程式碼

unit Unit1;
interface
uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, DIB, StdCtrls;
type
  TForm1 = class(TForm)
    DXPaintBox1: TDXPaintBox;
    Button1: TButton; // 載入圖片
    Button2: TButton; // 變暗
    Button3: TButton; // 變亮
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  end;
var Form1: TForm1;
implementation {$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
const ImgPath1 = 'C:\Temp\DX.jpg';
begin
  DXPaintBox1.DIB.LoadFromFile(ImgPath1);
  DXPaintBox1.Width := DXPaintBox1.DIB.Width;
  DXPaintBox1.Height := DXPaintBox1.DIB.Height;
  DXPaintBox1.Repaint;
end;

procedure TForm1.Button2Click(Sender: TObject); // Darker
begin
  // Darker(Amount: Integer)
  DXPaintBox1.DIB.Darker(130);
  DXPaintBox1.Repaint;
end;

procedure TForm1.Button3Click(Sender: TObject); // Lighter
begin
  // Lighter(Amount: Integer)
  DXPaintBox1.DIB.Lighter(110);
  DXPaintBox1.Repaint;
end;
end.

參數說明

Darker(Amount: Integer)   // Amount: 0~255，建議 0~200
Lighter(Amount: Integer)  // Amount: 0~255，建議 0~200

• Darker：每像素 RGB 分量減去 Amount（飽和至 0）
• Lighter：每像素 RGB 分量加上 Amount（飽和至 255）
• 範例值 130/110 為明顯但不過曝的調整
• 就地修改，不可逆（除非保存原圖副本）

效果對比

動畫化：呼吸燈/閃爍效果

var Phase: Integer = 0; Dir: Integer = 1;
procedure TForm1.Timer1Timer(Sender: TObject);
begin
  DXPaintBox1.DIB.Assign(OriginalDIB);
  Phase := Phase + Dir * 5;
  if Phase > 100 then begin Phase := 100; Dir := -1; end;
  if Phase < -100 then begin Phase := -100; Dir := 1; end;
  if Phase >= 0 then DXPaintBox1.DIB.Lighter(Phase)
  else DXPaintBox1.DIB.Darker(-Phase);
  DXPaintBox1.Repaint;
end;

進階：Gamma 校正 vs 線性亮度調整

Darker/Lighter 為**線性位移**，不符合人眼感知（Gamma 2.2）。專業影像處理應使用 Gamma 校正：

procedure GammaCorrect(DIB: TDIB; Gamma: Single);
var x, y: Integer; c: TRGBQuad; inv: Single;
begin
  inv := 1 / Gamma;
  for y := 0 to DIB.Height - 1 do
    for x := 0 to DIB.Width - 1 do begin
      c := DIB.Pixels[x, y];
      c.rgbRed := Round(255 * Power(c.rgbRed / 255, inv));
      c.rgbGreen := Round(255 * Power(c.rgbGreen / 255, inv));
      c.rgbBlue := Round(255 * Power(c.rgbBlue / 255, inv));
      DIB.Pixels[x, y] := c;
    end;
end;