{
* UGraphicUtils.pas
*
* Utility routines used for working with graphics.
*
* $Rev$
* $Date$
*
* ***** BEGIN LICENSE BLOCK *****
*
* Version: MPL 1.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
* the specific language governing rights and limitations under the License.
*
* The Original Code is UGraphicUtils.pas
*
* The Initial Developer of the Original Code is Peter Johnson
* (http://www.delphidabbler.com/).
*
* Portions created by the Initial Developer are Copyright (C) 2006-2009 Peter
* Johnson. All Rights Reserved.
*
* Contributor(s)
* NONE
*
* ***** END LICENSE BLOCK *****
}
unit UGraphicUtils;
interface
uses
// Delphi
Windows, Graphics,
// Project
UStructs;
function CreateDisplayDC: HDC;
{Creates a display device context.
}
type
{
TGradientDirection:
Direction of colour change in a colour gradient.
}
TGradientDirection = (gdHorizontal, gdVertical);
procedure GradientFill(const Canvas: TCanvas; const Rect: TRectEx;
const SecondColour: TColor; const Direction: TGradientDirection);
{Gradient fills an area of a canvas.
@param Canvas [in] Canvas on which to draw. Canvas's brush colour is used
for start of gradient.
@param Rect [in] Area of canvas to be filled.
@param SecondColour [in] 2ndary colour to be used in gradient.
@param Direction [in] Direction of gradient: horizontal or vertical.
}
function StringExtent(const S: string; const Font: TFont;
const MaxWidth: Integer): TSize; overload;
{Calculates the width and height of a string when rendered in a specified
font, word-wrapped within a maximum width.
@param S [in] String for which size is required.
@param Font [in] Font used to render string.
@param MaxWidth [in] Maximum width of rendered string; string word-wraps at
this width.
@return Structure containing width and height of string in pixels.
}
function StringExtent(const S: string; const Font: TFont): TSize; overload;
{Calculates the width and height of a string when rendered in a specified
font.
@param S [in] String for which size is required.
@param Font [in] Font used to render string.
@return Structure containing width and height of string in pixels.
}
function GetTextRect(const Text: string; const Canvas: TCanvas;
const Rect: TRect; const Flags: Longint): TRect;
{Gets rectangle of size required to display text in a specified canvas.
@param Text [in] Text to display.
@param Canvas [in] Canvas on which text to be displayed.
@param Rect [in] Rectangle in which to display text. Bottom field ignored.
@param Flags [in] Flags to use in outputting text.
}
implementation
uses
// Project
SysUtils;
{ Helper routines }
procedure ExtractRGB(const Colour: TColor; out Red, Green, Blue: Byte);
{Extract constituant RGB values from a colour. System colours are converted to
their actual values per current Window display settings.
@param Colour [in] Colour for which RGB values are required.
@param Red [out] Set to red value of colour.
@param Green [out] Set to green value of colour.
@param Blue [out] Set to blue value of colour.
}
var
RGB: TColorRef; // RGB triple equivalent of given colour
begin
RGB := ColorToRGB(Colour); // this ensures system colours are converted
Red := GetRValue(RGB);
Green := GetGValue(RGB);
Blue := GetBValue(RGB);
end;
function CreateDisplayCanvas(const Font: TFont): TCanvas;
{Creates a display canvas that uses a specified font.
@param Font [in] Font to be used by canvas.
@return Required canvas. Should be freed using FreeDisplayCanvas.
}
begin
Assert(Assigned(Font));
Result := TCanvas.Create;
Result.Handle := CreateDisplayDC;
Result.Font := Font;
end;
procedure FreeDisplayCanvas(var Canvas: TCanvas);
{Releases resources and frees a canvas object created by CreateDisplayCanvas.
@param Canvas [in/out] Canvas to be freed. Set to nil once freed.
}
begin
if Assigned(Canvas) then
try
DeleteDC(Canvas.Handle);
Canvas.Handle := 0;
finally
FreeAndNil(Canvas);
end;
end;
{ Public routines }
function CreateDisplayDC: HDC;
{Creates a display device context.
}
begin
Result := CreateDC('DISPLAY', nil, nil, nil);
end;
procedure GradientFill(const Canvas: TCanvas; const Rect: TRectEx;
const SecondColour: TColor; const Direction: TGradientDirection);
{Gradient fills an area of a canvas.
@param Canvas [in] Canvas on which to draw. Canvas's brush colour is used
for start of gradient.
@param Rect [in] Area of canvas to be filled.
@param SecondColour [in] 2ndary colour to be used in gradient.
@param Direction [in] Direction of gradient: horizontal or vertical.
}
var
GradientSize: Integer; // number of pixels gradient changes over
StartR, StartG, StartB: Byte; // R, G & B values of primary gradient colour
EndR, EndG, EndB: Byte; // R, G & B values of 2ndary gradient colour
R, G, B: Byte; // R, G & B values of intermediate colour
I: Integer; // loops thru pixels of gradient
OldPenStyle: TPenStyle; // stores canvas's original pen style
OldPenWidth: Integer; // stores canvas's original pen width
OldPenColor: TColor; // stores canvas's original pen colour
begin
// Record current pen attributes for restoration later
OldPenStyle := Canvas.Pen.Style;
OldPenWidth := Canvas.Pen.Width;
OldPenColor := Canvas.Pen.Color;
try
// Get number of pixels over which gradient extends
if Direction = gdHorizontal then
GradientSize := Rect.Width
else
GradientSize := Rect.Height;
// Record RGB values of primary and secondary gradient colours
ExtractRGB(Canvas.Brush.Color, StartR, StartG, StartB);
ExtractRGB(SecondColour, EndR, EndG, EndB);
// Ensure pen is 1px wide and solid
Canvas.Pen.Width := 1;
Canvas.Pen.Style := psSolid;
// Draw the gradient
// loop thru each pixel across gradient
for I := 0 to Pred(GradientSize) do
begin
// calculate required intermediate colour
R := StartR + I * (EndR - StartR) div GradientSize;
G := StartG + I * (EndG - StartG) div GradientSize;
B := StartB + I * (EndB - StartB) div GradientSize;
Canvas.Pen.Color := TColor(RGB(R, G, B));
// draw line of constant colour in correct direction
if Direction = gdHorizontal then
begin
Canvas.MoveTo(Rect.Left + I, Rect.Top);
Canvas.LineTo(Rect.Left + I, Rect.Bottom);
end
else
begin
Canvas.MoveTo(Rect.Left, Rect.Top + I);
Canvas.LineTo(Rect.Right + I, Rect.Top + I);
end;
end;
finally
// Restore pen's properties
Canvas.Pen.Style := OldPenStyle;
Canvas.Pen.Width := OldPenWidth;
Canvas.Pen.Color := OldPenColor;
end;
end;
function StringExtent(const S: string; const Font: TFont;
const MaxWidth: Integer): TSize; overload;
{Calculates the width and height of a string when rendered in a specified
font, word-wrapped within a maximum width.
@param S [in] String for which size is required.
@param Font [in] Font used to render string.
@param MaxWidth [in] Maximum width of rendered string; string word-wraps at
this width.
@return Structure containing width and height of string in pixels.
}
var
Canvas: TCanvas; // canvas used to measure text extent
Rect: TRectEx; // zero based rectangle required to contain rendered string
begin
Canvas := CreateDisplayCanvas(Font);
try
Rect := GetTextRect(
S, Canvas, TRectEx.Create(0, 0, MaxWidth, 0), DT_WORDBREAK
);
Result.cx := Rect.Width;
Result.cy := Rect.Height;
finally
FreeDisplayCanvas(Canvas);
end;
end;
function StringExtent(const S: string; const Font: TFont): TSize; overload;
{Calculates the width and height of a string when rendered in a specified
font.
@param S [in] String for which size is required.
@param Font [in] Font used to render string.
@return Structure containing width and height of string in pixels.
}
var
Canvas: TCanvas; // canvas used to measure text extent
begin
Canvas := CreateDisplayCanvas(Font);
try
Result := Canvas.TextExtent(S);
finally
FreeDisplayCanvas(Canvas);
end;
end;
function GetTextRect(const Text: string; const Canvas: TCanvas;
const Rect: TRect; const Flags: Longint): TRect;
{Gets rectangle of size required to display text in a specified canvas.
@param Text [in] Text to display.
@param Canvas [in] Canvas on which text to be displayed.
@param Rect [in] Rectangle in which to display text. Bottom field ignored.
@param Flags [in] Flags to use in outputting text.
}
begin
Result := Rect;
Result.Bottom := 0;
DrawText(Canvas.Handle, PChar(Text), -1, Result, Flags or DT_CALCRECT);
end;
end.
