Combine two colors

[bigeno]

I've some selection on spreadsheet and some cell colors. How to combine selection color with colored cells ? example below. I simply using canvas.brush.color for cell background.

[wp]

Is this an fpspreadsheet question? The screenshot looks like that.

In fpspreadsheet the color of the selected cells is determined by this function from the color c of the cell:

Code: Pascal  [Select][+][-]

1. function CalcSelectionColor(c: TColor; ADelta: Byte) : TColor;
2. type
3.   TRGBA = record R,G,B,A: Byte end;
4. begin
5.   c := ColorToRGB(c);
6.   TRGBA(Result).A := 0;
7.   if TRGBA(c).R < 128
8.     then TRGBA(Result).R := TRGBA(c).R + ADelta
9.     else TRGBA(Result).R := TRGBA(c).R - ADelta;
10.   if TRGBA(c).G < 128
11.     then TRGBA(Result).G := TRGBA(c).G + ADelta
12.     else TRGBA(Result).G := TRGBA(c).G - ADelta;
13.   if TRGBA(c).B < 128
14.     then TRGBA(Result).B := TRGBA(c).B + ADelta
15.     else TRGBA(Result).B := TRGBA(c).B - ADelta;
16. end;

This function adds ADelta to each dark color component (i.e. makes it brigher) and subtracts ADelta from a bright color component (i.e. makes it darker). ADelta should not be too large, definitely less than 128; in the worksheet grid the value is 16.

[bigeno]

No, thats screenshot from MS Excel, I work with TStringGrid.
Thank you, you right, I don't need mix two colors, darker will be ok in that case

[Blaazen]

I use this in ECControls:

Code: Pascal  [Select][+][-]

1. function GetMergedColor(AColor, BColor: TColor; AProportion: Single): TColor;
2. var aR, bR, aG, bG, aB, bB: Integer;
3. begin
4.   GetRGBIntValues(ColorToRGB(AColor), aR, aG, aB);
5.   GetRGBIntValues(ColorToRGB(BColor), bR, bG, bB);
6.   aR := bR + trunc((aR - bR)*AProportion);
7.   aG := bG + trunc((aG - bG)*AProportion);
8.   aB := bB + trunc((aB - bB)*AProportion);
9.   Result := RGBToColor(aR, aG, aB);
10. end;

Parameter AProportion should be between 0..1, where 1 means AColor, 0 means BColor.