相关资料：
http://blog.csdn.net/tokimemo/article/details/18702689
http://www.myexception.cn/delphi/215402.html
http://bbs.csdn.net/topics/390627275
结果总结：
1.生成的环中间会少一部分颜色，颜色会小于16581375。
2.手动选择颜色不准，手容易抖，要支持用户输入准确的数值。
代码实例：
1 unit Unit1; 2 3 interface 4 5 uses 6 Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, 7 Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls; 8 9 type 10 TForm1 = class(TForm) 11 Button1: TButton; 12 Image1: TImage; 13 CheckBox1: TCheckBox; 14 Label1: TLabel; 15 Label2: TLabel; 16 Label3: TLabel; 17 Label4: TLabel; 18 Label5: TLabel; 19 Label6: TLabel; 20 procedure Button1Click(Sender: TObject); 21 procedure Image1MouseMove(Sender: TObject; Shift: TShiftState; X, 22 Y: Integer); 23 private 24 { Private declarations } 25 public 26 { Public declarations } 27 end; 28 29 var 30 Form1: TForm1; 31 32 implementation 33 34 {$R *.dfm} 35 36 //生成RGB色环的代码绘制 37 //传入图片的大小 38 function CreateColorCircle(const size: integer): TBitmap; 39 var 40 i,j,x,y: Integer; 41 radius: integer; 42 perimeter,arc,degree,step: double; 43 R,G,B: byte; 44 color: TColor; 45 begin 46 radius := round(size / 2); 47 RESULT := TBitmap.Create; 48 R:=255; 49 G:=0; 50 B:=0; 51 with RESULT do 52 begin 53 width := size; 54 height:= size; 55 pixelFormat := pf24bit; 56 Canvas.Brush.Color := RGB(R,G,B); 57 x := size + 1; 58 y := round(radius) + 1; 59 Canvas.FillRect(Rect(size,round(radius),x,y)); 60 for j := 0 to size do 61 begin 62 perimeter := (size - j) * PI + 1; 63 arc := perimeter / 6; 64 step := ( 255 * 6 ) / perimeter ; //颜色渐变步长 65 for i := 0 to round(perimeter) - 1 do 66 begin 67 degree := 360 / perimeter * i; 68 x := round(cos(degree * PI / 180) * (size - j + 1) / 2) + radius;//数学公式，最后加上的是圆心点 69 y := round(sin(degree * PI / 180) * (size - j + 1) / 2) + radius; 70 71 if (degree > 0) and (degree <= 60) then 72 begin 73 R := 255; 74 G := 0; 75 B := round(step * i); 76 end; 77 if (degree > 60) and (degree <= 120) then 78 begin 79 if perimeter / 3 / 120 * (degree - 60) > 1.0 then 80 R := 255 - round(step * (i - arc)) 81 else 82 R := 255 - round(step * ABS(i - arc)); 83 G := 0; 84 B := 255; 85 end; 86 if (degree > 120) and (degree <= 180) then 87 begin 88 R := 0; 89 if perimeter / 3 / 120 * (degree - 120) > 1.0 then 90 G := round(step * (i - 2 * arc)) 91 else 92 G := round(step * ABS(i - 2 * arc)); 93 B := 255; 94 end; 95 if (degree > 180) and (degree <= 240) then 96 begin 97 R := 0; 98 G := 255; 99 if perimeter / 3 / 120 * (degree - 120) > 1.0 then100 B := 255 - round(step * (i - perimeter / 2))101 else102 B := 255 - round(step * ABS(i - perimeter / 2));103 end;104 if (degree > 240) and (degree <= 300) then105 begin106 if perimeter / 3 / 120 * (degree - 240) > 1.0 then107 R := round(step * (i - 4 * arc))108 else109 R := round(step * ABS(i - 4 * arc)) ;110 G := 255;111 B := 0;112 end;113 if (degree > 300) and (degree <= 360) then114 begin115 R := 255;116 if perimeter / 3 / 120 * (degree - 300) > 1.0 then117 G := 255 - round(step * (i - 5 * arc))118 else119 G := 255 - round(step * ABS(i - 5 * arc));120 B := 0;121 end;122 color := RGB( ROUND(R + (255 - R)/size * j),ROUND(G + (255 - G) / size * j),ROUND(B + (255 - B) / size * j));123 Canvas.Brush.Color := color;124 //为了绘制出来的圆好看，分成四个部分进行绘制125 if (degree >= 0) and (degree <= 45) then126 Canvas.FillRect(Rect(x,y,x-2,y-1));127 if (degree > 45) and (degree <= 135) then128 Canvas.FillRect(Rect(x,y,x-1,y-2));129 if (degree > 135) and (degree <= 225) then130 Canvas.FillRect(Rect(x,y,x+2,y+1));131 if (degree > 215) and (degree <= 315) then132 Canvas.FillRect(Rect(x,y,x+1,y+2));133 if (degree > 315) and (degree <= 360) then134 Canvas.FillRect(Rect(x,y,x-2,y-1));135 end;136 end;137 end;138 end;139 140 //扣出中心的黑色圆141 //输入图片与中心圆的半径142 procedure BuckleHole(ABitmap: TBitmap; ARadius: Integer);143 var144 oBmp :TBitmap;145 oRgn :HRGN;146 begin147 // oBmp := TBitmap.Create; //为了代码整齐就不写try了148 // oBmp.PixelFormat := ABitmap.PixelFormat;149 // oBmp.Width := ABitmap.Width;150 // oBmp.Height := ABitmap.Height;151 // BitBlt(oBmp.Canvas.Handle, 0, 0, oBmp.Width, oBmp.Height, ABitmap.Canvas.Handle, 80, 80, SRCCOPY); //要拷贝的位图152 // oRgn := CreateEllipticRgn(0, 0, 100, 100); //创建圆形区域153 // SelectClipRgn(ABitmap.Canvas.Handle, oRgn); //选择剪切区域154 // ABitmap.Canvas.Draw(0, 0, oBmp); //位图位于区域内的部分加载155 // oBmp.Free;156 // DeleteObject(oRgn);157 ABitmap.Canvas.Pen.Color := clBlack;158 ABitmap.Canvas.Brush.Style := bsClear;159 ABitmap.Canvas.Brush.Color := clBlack;160 ABitmap.Canvas.Ellipse(Trunc(ABitmap.Width/2)-ARadius, Trunc(ABitmap.Height/2)-ARadius,161 Trunc(ABitmap.Width/2)+ARadius, Trunc(ABitmap.Height/2)+ARadius);162 end;163 164 //把中心圆做成透明的165 procedure MyDraw(ABitmap: TBitmap; ARadius: Integer);166 var167 bf: BLENDFUNCTION;168 desBmp, srcBmp: TBitmap;169 rgn: HRGN;170 begin171 with bf do172 begin173 BlendOp := AC_SRC_OVER;174 BlendFlags := 0;175 AlphaFormat := 0;176 SourceConstantAlpha := 0; // 透明度，0~255177 end;178 179 desBmp := TBitmap.Create;180 srcBmp := TBitmap.Create;181 182 try183 srcBmp.Assign(ABitmap);184 185 desBmp.Width := srcBmp.Width;186 desBmp.Height := srcBmp.Height;187 188 Winapi.Windows.AlphaBlend(desBmp.Canvas.Handle, 0, 0,189 desBmp.Width, desBmp.Height, srcBmp.Canvas.Handle,190 0, 0, srcBmp.Width, srcBmp.Height, bf);191 192 rgn := CreateEllipticRgn(Trunc(ABitmap.Width/2)-ARadius, Trunc(ABitmap.Height/2)-ARadius,193 Trunc(ABitmap.Width/2)+ARadius, Trunc(ABitmap.Height/2)+ARadius); // 创建一个圆形区域194 SelectClipRgn(srcBmp.Canvas.Handle, rgn);195 srcBmp.Canvas.Draw(0, 0, desBmp);196 197 ABitmap.Assign(nil);198 ABitmap.Assign(srcBmp);199 finally200 desBmp.Free;201 srcBmp.Free;202 end203 end;204 205 procedure TForm1.Button1Click(Sender: TObject);206 var207 oBitmap: TBitmap;208 rgn: HRGN;209 begin210 oBitmap := CreateColorCircle(Image1.Width);211 if CheckBox1.Checked then //要不要代中心圆选项212 // BuckleHole(oBitmap, 100);213 MyDraw(oBitmap, 100);214 Image1.Picture.Graphic := oBitmap;215 oBitmap.Free;216 end;217 218 procedure TForm1.Image1MouseMove(Sender: TObject; Shift: TShiftState; X,219 Y: Integer);220 var221 oColor: TColor;222 begin223 //鼠标移动时提取颜色RGB的值224 with Image1 do225 oColor := GetPixel(GetDC(Parent.Handle), X + left,Y + Top);226 Label4.Caption := IntToStr(oColor and $FF);227 Label5.Caption := IntToStr((oColor and $FF00) shr 8);228 Label6.Caption := IntToStr((oColor and $FF0000) shr 16);229 end;230 231 end. 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