Mega Code Archive
Gradientfill
<![CDATA[
Richard E:
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my code to do a gradient fill in a given rectangle (from StartColour to EndColor)...
procedure TDrawObj.GradientFillRectangle(thisCanvas: TCanvas; fRect: TRect;
StartColor, EndColor: TColor);
var
y: Integer;
GradientDistance: Integer;
tempIntOne: Integer;
tempIntTwo: Integer;
tempColor: TColor;
NewRed, NewGreen, NewBlue: Byte;
StartRed, StartGreen, StartBlue: Byte;
EndRed, EndGreen, EndBlue: Byte;
RedIncrement, GreenIncrement, BlueIncrement: Byte;
IncRed, IncGreen, IncBlue: Boolean;
begin
IncRed := True;
IncGreen := True;
IncBlue := True;
//calculate the total gradient distance (height)
GradientDistance := Round(fRect.Bottom - fRect.Top);
//find the initial red, green, and blue values
StartRed := GetRValue(StartColor);
StartGreen := GetGValue(StartColor);
StartBlue := GetBValue(StartColor);
//find the final red, green, and blue values
EndRed := GetRValue(EndColor);
EndGreen := GetGValue(EndColor);
EndBlue := GetBValue(EndColor);
//find the proper increment (for one loop iteration, below)
//for each of the three red, green and blue values...
tempIntOne := (EndRed - StartRed);
tempIntOne := abs(tempIntOne);
tempIntTwo := Round(tempIntOne / GradientDistance);
RedIncrement := byte(tempIntTwo);
tempIntOne := (EndGreen - StartGreen);
tempIntOne := abs(tempIntOne);
tempIntTwo := Round(tempIntOne / GradientDistance);
GreenIncrement := byte(tempIntTwo);
tempIntOne := (EndBlue - StartBlue);
tempIntOne := abs(tempIntOne);
tempIntTwo := Round(tempIntOne / GradientDistance); //iterate through GradientDistance
BlueIncrement := byte(tempIntTwo); //drawing a line on each iteration
NewRed := StartRed;
NewGreen := StartGreen;
NewBlue := StartBlue;
for y := 0 to GradientDistance do
begin
//set new colour according to changed
//red, green, and blue values...
tempColor := RGB(NewRed, NewGreen, NewBlue);
//set the new pen color
thisCanvas.Pen.Color := tempColor;
//and finally draw a line in the new color
thisCanvas.MoveTo(fRect.Left, (fRect.Top + y));
thisCanvas.LineTo(fRect.Right, (fRect.Top + y));
//increment the red, green and blue values...
//BUT take into account the fact that if we
//go over 255, values become meaningless -this
//we do by decrementing instead of incrementing
//(so then we need to check for going below 0
//as well)...
if ((IncRed = True) and ((NewRed + RedIncrement) > 255)) then IncRed := False;
if ((IncRed = False) and ((NewRed - RedIncrement) < 0)) then IncRed := True;
if ((IncGreen = True) and ((NewGreen + GreenIncrement) > 255)) then IncGreen := False;
if ((IncGreen = False) and ((NewGreen - GreenIncrement) < 0)) then IncGreen := True;
if ((IncBlue = True) and ((NewBlue + BlueIncrement) > 255)) then IncBlue := False;
if ((IncBlue = False) and ((NewBlue - BlueIncrement) < 0)) then IncBlue := True;
if (IncRed = True) then NewRed := (NewRed + RedIncrement)
else NewRed := (NewRed - RedIncrement);
if (IncGreen = True) then NewGreen := (NewGreen + GreenIncrement)
else NewGreen := (NewGreen - GreenIncrement);
if (IncBlue = True) then NewBlue := (NewBlue + BlueIncrement)
else NewBlue := (NewBlue - BlueIncrement);
end;
end;
*******************************************************************************************
my code to do a gradient fill in a given rectangle (from BLACK to EndColor)...
procedure TDrawObj.GradientFillRectangle(thisCanvas: TCanvas; fRect: TRect;
EndColor: TColor);
var
y: Integer;
GradientDistance: Integer;
GradientWidth: Integer;
tmpColor: TColor;
NewRed, NewGreen, NewBlue: Byte;
EndRed, EndGreen, EndBlue: Byte;
begin
//initialize tmpcolor
tmpColor := EndColor;
//set our gradient distance
GradientDistance := Round(fRect.Bottom - fRect.Top);
//set our gradient width
GradientWidth := Round(fRect.Right - fRect.Left);
//get initial red, green, and blue
EndRed := GetRValue(EndColor);
EndBlue := GetBValue(EndColor);
EndGreen := GetGValue(EndColor);
//go from start to finish of our gradient
for y := 0 to GradientDistance do
begin
//offset our red, green, and blue according
//to the distance into our gradient against
//the total distance to go
NewRed := (y * EndRed) div GradientDistance;
NewBlue := (y * EndBlue) div GradientDistance;
NewGreen := (y * EndGreen) div GradientDistance;
//set our new color according to our changed
//red, green, and blue values
tmpColor := RGB(NewRed, NewGreen, NewBlue);
//set the new pen color
thisCanvas.Pen.Color := tmpColor;
//draw our line according to the new color
thisCanvas.MoveTo(fRect.Left, (fRect.Top + y));
thisCanvas.LineTo(fRect.Right, (fRect.Top + y));
end;
end;
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