Colors/zh CN

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概述

在LCL，TColor是标准颜色类型。它和Delphi的TColor兼容。TColor 可以表示要么一个RGB (3x8比特)值，要么一个system颜色，像clDefault。LCL也可以和fpImage系统一起工作，使用TFPColor类型(它是RGBA(4x16比特)，非 RGB(3x8比特)，像TColor)。

在TColor 和RGB值之间转换

Graphics单元提供提供下面的函数：

function Blue(rgb: TColor): BYTE; // does not work on system color
function Green(rgb: TColor): BYTE; // does not work on system color
function Red(rgb: TColor): BYTE; // does not work on system color
function RGBToColor(R, G, B: Byte): TColor;
procedure RedGreenBlue(rgb: TColor; out Red, Green, Blue: Byte); // does not work on system color
function FPColorToTColor(const FPColor: TFPColor): TColor;
function TColorToFPColor(const c: TColor): TFPColor; // does not work on system color
function IsSysColor(AColor: TColorRef): Boolean;

转换TColor到/来自字符串

函数来转换字符串像"25500"或"$AA0088"或"clNavy"到TColor：

• StringToColor
• StringToColorDef

转换TColor到一个友好的字符串像"clNavy"或"$AA0002"：

• ColorToString

转换TColor到/来自HTML字符串 #rrggbb

查看代码在转换颜色到/来自HTML。

标准颜色表

大约20种预定义颜色常量被提供，它们是与Delphi-兼容的：

颜色常量	意思	TColor使用十六进制值	示例
clBlack	黑色	TColor($000000);
clMaroon	褐红色	TColor($000080);
clGreen	绿色	TColor($008000);
clOlive	橄榄绿	TColor($008080);
clNavy	深蓝色	TColor($800000);
clPurple	紫色	TColor($800080);
clTeal	蓝绿色	TColor($808000);
clGray	灰色	TColor($808080);
clSilver	银色	TColor($C0C0C0);
clRed	红色	TColor($0000FF);
clLime	酸橙绿	TColor($00FF00);
clYellow	黄色	TColor($00FFFF);
clBlue	蓝色	TColor($FF0000);
clFuchsia	紫红色	TColor($FF00FF);
clAqua	湖绿色	TColor($FFFF00);
clLtGray	浅灰色	TColor($C0C0C0);	clSilver别名
clDkGray	深灰色	TColor($808080);	clGray别名
clWhite	白色	TColor($FFFFFF);
clCream	奶油色	TColor($F0FBFF);	Lazarus 1.2和较新的
clMedGray	中灰色	TColor($A4A0A0);	Lazarus 1.2和较新的
clMoneyGreen	薄荷绿	TColor($C0DCC0);	Lazarus 1.2和较新的
clSkyBlue	天蓝色	TColor($F0CAA6);	LLazarus 1.2和较新的

System colors

Example: clInfoBk, clInfoText

System colors are color constants with a special meaning. Their real value depends on the context and theme. They are not simple colors. For example clInfoBk:

Form1.Canvas.Brush.Color:=clInfoBk;  // use the default background brush of a hint window
Form1.Canvas.FillRect(10,10,50,50);

A hint window on MS Windows might have a white background so the above will draw white. On Linux/gtk2 it might be a metallic texture, so the above will draw the texture. If you want to put some text onto this you need a corresponding color like clInfoText, otherwise your text might be unreadable for the user. For example:

Form1.Canvas.Brush.Color:=clInfoBk;  // use the default background brush of a hint window
Form1.Canvas.FillRect(10,10,50,50);
Form1.Canvas.Font.Color:=clInfoText;  // use the default text color of a hint window
Form1.Canvas.TextOut(10,10,'Hint');

The system color clInfoBk can not be used for Pen.Color and not for Font.Color. If you do so the result is undefined and depends on the widgetset and user theme. The same for clInfoText: It can only be used as a Font.Color. Using it as Brush.Color may not work. At the moment all widgetsets allow to use it as Pen.Color too.

Theme changes

When the user switches the theme the system colors changes. A clInfoBk might change from white to blue or from a color to a texture. This change will happen when you allocate a new Brush handle. Keep in mind that a simple assignment Brush.Color:=clInfoBk does not allocate a Brush Handle. The Brush Handle is allocated on use. For example:

Form1.Canvas.Brush.Color:=clInfoBk; // this will not create a new brush handle
Form1.Canvas.FillRect(10,10,50,50); // this will create the brush handle with the currently active theme brush for hint windows
...
// if the theme changes in this moment the Brush.Handle is still allocated with the old values
...
Form1.Canvas.FillRect(10,10,50,50); // this will paint with the old theme brush
Form1.Canvas.Brush.Color:=clInfoBk; // assigning the old value will not create a new brush handle
Form1.Canvas.FillRect(10,10,50,50); // this will paint with the old theme brush
Form1.Canvas.Brush.Color:=clRed;    // assigning a new color, old Handle invalid
Form1.Canvas.Brush.Color:=clInfoBk; // assigning a new color, old Handle invalid
Form1.Canvas.FillRect(10,10,50,50); // this will create a new handle and paint with the new theme

Table of system colors

The following table lists the system colors and their meaning. Using them outside the scope of the definition is undefined and the result depends on the widgetset and theme. For example clDefault is the normal background brush of the used device context. If you want to paint button elements on your own custom controls use the drawing functions of the unit Themes.

Constant	LCL definition	Delphi notes	Supported Widgetsets
clNone	Indicates "do not paint". Using it as Control's color is undefined. The control will not get transparent.	-	all
clDefault	Using it for Brush will use the normal background brush of the target DC (device context). On a Form's canvas a FillRect will paint a rectangular area filled with the normal background of a standard window. This is whatever the widgetset and theme defines. This might be the color gray or a gradient or a picture. Using clDefault on the Canvas of a TListBox will paint with the normal background, which is normally white on Windows. So in a TListBox clDefault is the same as clWindow. Using it as Pen color will use the default line color for the device context. Using it as Font color will use the normal text color of the device context.	-	all
clScrollBar	Scrollbar body	-	all
clBackground	Desktop background color	-	all
clActiveCaption	Active window titlebar	-	none
clInactiveCaption	Inactive window titlebar	-	none
clMenu	Regular menu item background color	-	none
clWindow	The normal background brush of unselected text. Defined for controls like TEdit, TComboBox, TMemo, TListBox, TTreeView.	-	none
clWindowFrame	Color of frame around the window	-	none
clMenuText	The font color to use together with clMenu	-	none
clWindowText	Font color to use together with clWindow	-	none
clCaptionText	Active window titlebar text color	-	none
clActiveBorder	?	-	none
clInactiveBorder	?	-	none
clAppWorkspace	MDIMain form background	-	none
clHighlight	The brush color of selected element	-	none
clHighlightText	Font color of selected text (to use together with clHighligh).	-	none
clBtnFace	Button background	-	none
clBtnShadow	Button shadow color (bottom right) used to achieve 3D effect	-	none
clGrayText	The font color of disabled element	-	none
clBtnText	Button font color to use together with clBtnFace	-	none
clInactiveCaptionText	Inactive window titlebar text color	-	none
clBtnHighlight	Button highlight color (top left) used to achieve 3D effect	-	none
cl3DDkShadow	?	-	none
cl3DLight	?	-	none
clInfoText	Font color for hints. Use together with clInfoBk	-	all
clInfoBk	Brush color for hints. Use together with clInfoText	-	all
clHotLight	?	-	none
clGradientActiveCaption	The second color used to make gradient of active window titlebar	-	none
clGradientInactiveCaption	The second color used to make gradient for inactive window titlebar	-	none
clMenuHighlight	The background color of selected menu item	-	none
clMenuBar	The Backround color of menu bar	-	none
clForm	?	-	none
clColorDesktop	?	-	none
cl3DFace	?	-	none
cl3DShadow	?	-	none
cl3DHiLight	?	-	none
clBtnHiLight	Same as clBtnHighlight	-	none

Finding the rgb values of a system color

Use the function ColorToRGB (in unit Graphics to determine the rgb components of a system color. This functions detects whether a color is a system color and, if this is true, looks up the system color in the themes color. The returned Longint can be understood as a normal color:

// This example has a TColorBox on a form and uses this OnChange handler for the TColorbox:
procedure TForm1.ColorBox1Change(Sender: TObject);
var
  c: TColor;
begin
  c := ColorToRGB(ColorBox1.Selected);
  Caption := Format('R%d G%d B%d', [Red(c), Green(c), Blue(c)]);
end;

Drawing theme elements on your custom controls

The unit Themes provides functions to draw single elements of standard controls. For example to draw an expand sign like a TTreeView use the following code:

uses Themes;

...

procedure TYourCustomControl.Paint;
const
  PlusMinusDetail: array[Boolean {Hot}, Boolean {Expanded}] of TThemedTreeview =
  (
    (ttGlyphClosed, ttGlyphOpened),
    (ttHotGlyphClosed, ttHotGlyphOpened)
  );
var
  Details: TThemedElementDetails;
  R: TRect;
  Collapse: boolean;
begin
  ...
  //draw a themed expand sign.
  Details := ThemeServices.GetElementDetails(PlusMinusDetail[False, Collapse]);
  R := Rect(ALeft, ATop, ARight + 1, ABottom + 1);
  ThemeServices.DrawElement(Canvas.Handle, Details, R, nil);
  ...
end;

贡献者和更改

• 简体中文版本由 robsean 于 2019-07-17 创建。