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Author Topic: [Solved] Change background color of a BMP  (Read 2502 times)

bobonwhidbey

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[Solved] Change background color of a BMP
« on: June 19, 2017, 11:59:29 pm »
My goal is to change all the pixels of a BMP that are "kinda" white to a new HiliteColor. I tried to adapt some code that worked in Delphi but it didn't convert well. The following is my "labor intensive" approach, but it's not working. I'd like to think that there's a better way. If not I'd like to get this code working in Laz.

Code: Pascal  [Select]
  1. const
  2.   delta = 50;  // from trial and error
  3.   maxd = 255 - delta;
  4. var
  5.   Row: PRGBQUAD;
  6.   x, y: integer;
  7.   R, G, B: cardinal;
  8. begin
  9.   BMP.Assign(CardBMP); // copy original to a BMP component
  10.   R := GetRValue(HiliteColor);
  11.   G := GetGValue(HiliteColor);
  12.   B := GetBValue(HiliteColor);
  13.   for y := 0 to BMP.Height - 1 do
  14.   begin
  15.     Row := BMP.Scanline[y]; // process one line at a time
  16.     for x := 0 to BMP.Width - 1 do
  17.       with Row[x] do // process one pixel at a time in each line
  18.         if (rgbRed > maxd) and (rgbGreen > maxd) and (rgbBlue > maxd) then
  19.         begin
  20.           Row[x].rgbRed := R; //
  21.           Row[x].rgbGreen := G;
  22.           Row[x].rgbBlue := b;
  23.         end;
  24.   end;
  25.   CardBMP.Assign(BMP);
  26. end; // ColorHilite
  27.  
  28.  

it would seem that I need to overwrite the old row with this new changed Row.
 something like the opposite of Scanline 
« Last Edit: June 21, 2017, 04:05:01 pm by bobonwhidbey »
Win10 64-bit
Lazarus 1.7
FPC 3.0.0

PatBayford

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Re: Change background color of a BMP
« Reply #1 on: June 20, 2017, 02:36:08 am »
In Delphi you would use the Pixels property of the BMP objects canvas to do this - not sure if this is available in Lazarus!
(property is : property Pixels[X, Y: Integer]: TColor;)

Lazarus 1.6.4 FPC 3.0.2 SVN 54278 Windows 10 64bit

Mr.Madguy

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Re: Change background color of a BMP
« Reply #2 on: June 20, 2017, 08:40:01 am »
Why do you need to do it at runtime? Can you use pre-baked bitmaps? If you really need to do it at runtime (for example if you need to change background color many times), then fastest way - to prepare mask bitmap first and then use it as mask, when filling background with desired color. GDI isn't good for per-pixel operations, so this thing is a little bit tricky. I'm busy now, but I'll show you example later, if you will be interested in this approach.

Ñuño_Martínez

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Re: Change background color of a BMP
« Reply #3 on: June 20, 2017, 09:52:24 am »
As Mr.Madguy this would be a bit tricky using GDI and FCL.  Better use a graphics library.  Here you have the list of available grahpics libraries at the wiki, including game libraries and game engines.  If you only need to do color changes, BGRABitmap may be your best choice.

Handoko

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Re: Change background color of a BMP
« Reply #4 on: June 20, 2017, 01:14:22 pm »
@bobonwhidbey

I have not tried your code but because I recently posted an answer to a thread asking how to get bitmap color data, I improved that code, which I think it is maybe is what you want. Here is the previous thread:
http://forum.lazarus.freepascal.org/index.php/topic,37242.0.html

I have found, which I think a bug or maybe the documentation's bug. Using assign to copy bitmap data won't create a separate copy, but they will share same data location. I think it is the culprit that causing the issue.

Try my code, it works. After open the image, move your mouse pointer on the image and press 'C'. The target color is clGreen, it was harcoded, change it if you want. You can download the test.zip to try.

Code: Pascal  [Select]
  1. unit Unit1;
  2.  
  3. {$mode objfpc}{$H+}
  4.  
  5. interface
  6.  
  7. uses
  8.   Classes, SysUtils, Forms, Graphics, Dialogs, StdCtrls, ExtCtrls, LCLType,
  9.   Spin;
  10.  
  11. type
  12.  
  13.   { TForm1 }
  14.  
  15.   TForm1 = class(TForm)
  16.     Button1: TButton;
  17.     Image1: TImage;
  18.     Image2: TImage;
  19.     Label1: TLabel;
  20.     Label2: TLabel;
  21.     Label3: TLabel;
  22.     OpenDialog1: TOpenDialog;
  23.     Shape1: TShape;
  24.     SpinEdit1: TSpinEdit;
  25.     procedure Button1Click(Sender: TObject);
  26.     procedure Button1KeyPress(Sender: TObject; var Key: char);
  27.     procedure Image1MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer
  28.       );
  29.   public
  30.     procedure ChangeColor(oldColor, newColor: TColor; Tolerance: Byte);
  31.   end;
  32.  
  33. var
  34.   Form1: TForm1;
  35.  
  36. implementation
  37.  
  38. const
  39.   SelectedColor: TColor = clWhite;
  40.   TargetColor = clGreen; // Change target color here
  41.  
  42. {$R *.lfm}
  43.  
  44. { TForm1 }
  45.  
  46. procedure TForm1.Button1Click(Sender: TObject);
  47. var
  48.   AJpg:  TJPEGImage;
  49. begin
  50.   if not(OpenDialog1.Execute) then Exit;
  51.   AJpg := TJpegImage.Create;
  52.   AJpg.LoadFromFile(OpenDialog1.FileName);
  53.   Image1.Picture.Bitmap.Assign(AJpg);
  54.   AJpg.Free;
  55.   Image1.Enabled := True;
  56.   Image2.Enabled := True;
  57. end;
  58.  
  59. procedure TForm1.Button1KeyPress(Sender: TObject; var Key: char);
  60. begin
  61.   if (Key = 'c') or (Key = 'C') then
  62.     ChangeColor(SelectedColor, TargetColor, SpinEdit1.Value);
  63. end;
  64.  
  65. procedure TForm1.Image1MouseMove(Sender: TObject; Shift: TShiftState; X,
  66.   Y: Integer);
  67. var
  68.   ScanData: PRGBQuad;
  69.   ValR, ValG, ValB: Byte;
  70. begin
  71.  
  72.   // Point to the pixel's data location
  73.   ScanData := Image1.Picture.Bitmap.ScanLine[Y];
  74.   Inc(ScanData, X);
  75.  
  76.   // Get RGB values of the pixel
  77.   ValR := ScanData^.rgbRed;
  78.   ValG := ScanData^.rgbGreen;
  79.   ValB := ScanData^.rgbBlue;
  80.   SelectedColor := RGBToColor(ValR, ValG, ValB);
  81.  
  82.   // Show information of the pixel
  83.   Shape1.Brush.Color := RGBToColor(ValR, ValG, ValB);
  84.   Label1.Caption := 'x'+IntToStr(X)+':y'+IntToStr(Y)+' = r'+
  85.     IntToStr(ValR)+', g'+IntToStr(ValG)+', b'+IntToStr(ValB);
  86.  
  87. end;
  88.  
  89. procedure TForm1.ChangeColor(oldColor, newColor: TColor; Tolerance: Byte);
  90. var
  91.   ScanData, ResultData: PRGBQuad;
  92.   CurR, CurG, CurB: Byte; // Current pixels' RGB
  93.   ReqR, ReqG, ReqB: Byte; // Required RGB
  94.   TarR, TarG, TarB: Byte; // Target RGB
  95.   X, Y: Integer;
  96. begin
  97.  
  98.   ReqR := Red(oldColor);
  99.   ReqG := Green(oldColor);
  100.   ReqB := Blue(oldColor);
  101.   TarR := Red(newColor);
  102.   TarG := Green(newColor);
  103.   TarB := Blue(newColor);
  104.  
  105.   // Don't use assign to avoid sharing same data location
  106.   Image2.Picture.Bitmap := TBitmap.Create;
  107.   Image2.Picture.Bitmap.Height := Image1.Picture.Bitmap.Height;
  108.   Image2.Picture.Bitmap.Width := Image1.Picture.Bitmap.Width;
  109.  
  110.   for Y := 0 to (Image1.Picture.Bitmap.Height-1) do
  111.   begin
  112.     ScanData := Image1.Picture.Bitmap.ScanLine[Y];
  113.     ResultData := Image2.Picture.Bitmap.ScanLine[Y];
  114.     for X:= 0 to (Image1.Picture.Bitmap.Width-1) do
  115.     begin
  116.       ResultData^ := ScanData^;
  117.       CurR := ScanData^.rgbRed;
  118.       CurG := ScanData^.rgbGreen;
  119.       CurB := ScanData^.rgbBlue;
  120.       if (abs(CurR-ReqR) < Tolerance) and
  121.         (abs(CurG-ReqG) < Tolerance) and
  122.         (abs(CurB-ReqB) < Tolerance) then
  123.         begin
  124.           ResultData^.rgbRed := TarR;
  125.           ResultData^.rgbGreen := TarG;
  126.           ResultData^.rgbBlue := TarB;
  127.         end;
  128.       Inc(ScanData);
  129.       Inc(ResultData);
  130.     end;
  131.   end;
  132.  
  133. end;
  134.  
  135. end.

---edit---
Line #83 should use SelectedColor.
« Last Edit: June 20, 2017, 01:38:12 pm by Handoko »

Mr.Madguy

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Re: Change background color of a BMP
« Reply #5 on: June 20, 2017, 02:29:23 pm »
I've written my example, but unfortunately it doesn't work. Main idea: to make mask, that would make background transparent. Then, all we would need - to fill background with any arbitrary color and then draw our transparent bitmap over it.

I have two variants:
1) First create default mask bitmap and then modify it
2) Create mask bitmap and then set it to bitmap

Both don't work. Once I touch mask bitmap - card stops being displayed, despite of all code being properly executed (according to debugging).  :'(

Currently I have no time to solve this problem, but I'll try to do it later.

Variant 1:
Code: Pascal  [Select]
  1. unit TestMain;
  2.  
  3. {$mode objfpc}{$H+}
  4.  
  5. interface
  6.  
  7. uses
  8.   Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls;
  9.  
  10. type
  11.  
  12.   { TCardTestForm }
  13.  
  14.   TCardTestForm = class(TForm)
  15.     Image1: TImage;
  16.     procedure FormCreate(Sender: TObject);
  17.     procedure FormDestroy(Sender: TObject);
  18.     procedure Image1Click(Sender: TObject);
  19.   private
  20.     { private declarations }
  21.   public
  22.     { public declarations }
  23.     CardBitmap:TBitmap;
  24.     procedure DrawBitmap;
  25.   end;
  26.  
  27. var
  28.   CardTestForm: TCardTestForm;
  29.  
  30. implementation
  31.  
  32. {$R *.lfm}
  33.  
  34. { TCardTestForm }
  35.  
  36. type
  37.   TABGR = packed record
  38.     R, G, B, A: Byte;
  39.   end;
  40.  
  41.   TABGRColor = record
  42.     case Boolean of
  43.       False:(Color:TColor);
  44.       True:(ABGR:TABGR);
  45.   end;
  46.  
  47. const
  48.   Delta = 60;
  49.   MaxColor = 255 - Delta;
  50.  
  51. procedure TCardTestForm.FormCreate(Sender: TObject);
  52.   var MaskBitmap:TBitmap;
  53.   I, J:Integer;C:TABGRColor;
  54. begin
  55.   Randomize;
  56.   with Image1.Picture do begin
  57.     Bitmap.Assign(TBitmap.Create);
  58.     Bitmap.Width := 640;
  59.     Bitmap.Height := 640;
  60.     Bitmap.Canvas.FillRect(0, 0, Bitmap.Width, Bitmap.Height);
  61.   end;
  62.   CardBitmap := TBitmap.Create;
  63.   CardBitmap.LoadFromFile('Card.bmp');
  64.   CardBitmap.Transparent := True;
  65.   {Can be loaded from file too}
  66.   MaskBitmap := TBitmap.Create;
  67.   MaskBitmap.Handle := CardBitmap.MaskHandle;
  68.   for I := 0 to CardBitmap.Width - 1 do begin
  69.     for J := 0 to CardBitmap.Height - 1 do begin
  70.       C.Color := CardBitmap.Canvas.Pixels[I, J];
  71.       if (C.ABGR.R > MaxColor) and (C.ABGR.G > MaxColor) and (C.ABGR.B > MaxColor) then begin
  72.         MaskBitmap.Canvas.Pixels[I, J] := clWhite;
  73.       end
  74.       else begin
  75.         MaskBitmap.Canvas.Pixels[I, J] := clBlack;
  76.       end;
  77.     end;
  78.   end;
  79.   MaskBitmap.Free;
  80.   DrawBitmap;
  81. end;
  82.  
  83. procedure TCardTestForm.FormDestroy(Sender: TObject);
  84. begin
  85.   CardBitmap.Free;
  86. end;
  87.  
  88. procedure TCardTestForm.Image1Click(Sender: TObject);
  89. begin
  90.   DrawBitmap;
  91. end;
  92.  
  93. procedure TCardTestForm.DrawBitmap;
  94. begin
  95.   with Image1.Picture do begin
  96.     {Random background color}
  97.     Bitmap.Canvas.Brush.Color := Random(clWhite);
  98.     Bitmap.Canvas.FillRect(0, 0, CardBitmap.Width, CardBitmap.Height);
  99.     Bitmap.Canvas.Draw(0, 0, CardBitmap);
  100.   end;
  101. end;
  102.  
  103. end.
  104.  

Variant 2:
Code: Pascal  [Select]
  1. unit TestMain;
  2.  
  3. {$mode objfpc}{$H+}
  4.  
  5. interface
  6.  
  7. uses
  8.   Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls;
  9.  
  10. type
  11.  
  12.   { TCardTestForm }
  13.  
  14.   TCardTestForm = class(TForm)
  15.     Image1: TImage;
  16.     procedure FormCreate(Sender: TObject);
  17.     procedure FormDestroy(Sender: TObject);
  18.     procedure Image1Click(Sender: TObject);
  19.   private
  20.     { private declarations }
  21.   public
  22.     { public declarations }
  23.     CardBitmap, MaskBitmap:TBitmap;
  24.     procedure DrawBitmap;
  25.   end;
  26.  
  27. var
  28.   CardTestForm: TCardTestForm;
  29.  
  30. implementation
  31.  
  32. {$R *.lfm}
  33.  
  34. { TCardTestForm }
  35.  
  36. type
  37.   TABGR = packed record
  38.     R, G, B, A: Byte;
  39.   end;
  40.  
  41.   TABGRColor = record
  42.     case Boolean of
  43.       False:(Color:TColor);
  44.       True:(ABGR:TABGR);
  45.   end;
  46.  
  47. const
  48.   Delta = 60;
  49.   MaxColor = 255 - Delta;
  50.  
  51. procedure TCardTestForm.FormCreate(Sender: TObject);
  52.   var I, J:Integer;C:TABGRColor;
  53. begin
  54.   Randomize;
  55.   with Image1.Picture do begin
  56.     Bitmap.Assign(TBitmap.Create);
  57.     Bitmap.Width := 640;
  58.     Bitmap.Height := 640;
  59.     Bitmap.Canvas.FillRect(0, 0, Bitmap.Width, Bitmap.Height);
  60.   end;
  61.   CardBitmap := TBitmap.Create;
  62.   CardBitmap.LoadFromFile('Card.bmp');
  63.   {Can be loaded from file too}
  64.   MaskBitmap := TBitmap.Create;
  65.   MaskBitmap.Width := CardBitmap.Width;
  66.   MaskBitmap.Height := CardBitmap.Height;
  67.   for I := 0 to CardBitmap.Width - 1 do begin
  68.     for J := 0 to CardBitmap.Height - 1 do begin
  69.       C.Color := CardBitmap.Canvas.Pixels[I, J];
  70.       if (C.ABGR.R > MaxColor) and (C.ABGR.G > MaxColor) and (C.ABGR.B > MaxColor) then begin
  71.         MaskBitmap.Canvas.Pixels[I, J] := clWhite;
  72.       end
  73.       else begin
  74.         MaskBitmap.Canvas.Pixels[I, J] := clBlack;
  75.       end;
  76.     end;
  77.   end;
  78.   CardBitmap.MaskHandle := MaskBitmap.Handle;
  79.   CardBitmap.Masked := True;
  80.   DrawBitmap;
  81. end;
  82.  
  83. procedure TCardTestForm.FormDestroy(Sender: TObject);
  84. begin
  85.   CardBitmap.Free;
  86.   MaskBitmap.Free;
  87. end;
  88.  
  89. procedure TCardTestForm.Image1Click(Sender: TObject);
  90. begin
  91.   DrawBitmap;
  92. end;
  93.  
  94. procedure TCardTestForm.DrawBitmap;
  95. begin
  96.   with Image1.Picture do begin
  97.     {Random background color}
  98.     Bitmap.Canvas.Brush.Color := Random(clWhite);
  99.     Bitmap.Canvas.FillRect(0, 0, CardBitmap.Width, CardBitmap.Height);
  100.     Bitmap.Canvas.Draw(0, 0, CardBitmap);
  101.   end;
  102. end;
  103.  
  104. end.
  105.  

When either MaskBitmap.Handle := CardBitmap.MaskHandle; or  CardBitmap.MaskHandle := MaskBitmap.Handle; is commented - program works this way (mask bitmap is ok, as you can see):
« Last Edit: June 20, 2017, 03:01:20 pm by Mr.Madguy »

Handoko

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Re: Change background color of a BMP
« Reply #6 on: June 20, 2017, 02:40:39 pm »
I'm not sure the cause of your issue. But I did some inspections why OP's code didn't work. I found the missing thing. Before changing the bitmap data (directly), we have to use TBitmap.BeginUpdate:

http://lazarus-ccr.sourceforge.net/docs/lcl/graphics/trasterimage.html
http://lazarus-ccr.sourceforge.net/docs/lcl/graphics/trasterimage.beginupdate.html

Perhaps it can solve your puzzle too.

The strange is, in my example I didn't use TBitmap.BeginUpdate. Instead I created a new TBitmap and it worked.
« Last Edit: June 20, 2017, 02:46:09 pm by Handoko »

Mr.Madguy

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Re: Change background color of a BMP
« Reply #7 on: June 20, 2017, 02:57:25 pm »
I'm not sure the cause of your issue. But I did some inspections why OP's code didn't work. I found the missing thing. Before changing the bitmap data (directly), we have to use TBitmap.BeginUpdate:

http://lazarus-ccr.sourceforge.net/docs/lcl/graphics/trasterimage.html
http://lazarus-ccr.sourceforge.net/docs/lcl/graphics/trasterimage.beginupdate.html

Perhaps it can solve your puzzle too.

The strange is, in my example I didn't use TBitmap.BeginUpdate. Instead I created a new TBitmap and it worked.
It doesn't help. First variant works the same way (no card - just background) and in second variant mask bitmap becomes black (i.e. opaque card), but card is being displayed this time.

Handoko

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  • My goal: build my own game engine using Lazarus
Re: Change background color of a BMP
« Reply #8 on: June 20, 2017, 04:48:08 pm »
I managed to fix your first variant. I haven't tested your second variant.

To make it work, you have to remove (or comment) line #79.
That's all.

Because:
MaskBitmap.Handle := CardBitmap.MaskHandle;

then it means MaskBitmap is linked to CardBitmap, so you should not free MaskBitmap. If you really want to free MaskBitmap, I guess you may need to set the handle to nil before calling MaskBitmap.Free.

Try it, it works on my tests!

edit:
Pixels[x, y] is slow, you should consider to use ScanLine.
« Last Edit: June 20, 2017, 04:56:14 pm by Handoko »

bobonwhidbey

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Re: Change background color of a BMP
« Reply #9 on: June 20, 2017, 05:01:20 pm »
Here's a view of what I'm trying to accomplish. This picture is taken from my Delphi program that I'm trying to reproduce in Laz. In the example, I've made the background of the 8D red. It's not possible to rely on changing just one color (eg. clWhite) because there are many pixels that are almost white, especially in the face cards.
Win10 64-bit
Lazarus 1.7
FPC 3.0.0

Handoko

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Re: Change background color of a BMP
« Reply #10 on: June 20, 2017, 05:07:20 pm »
You can increase the red, perhaps something like this:

Code: Pascal  [Select]
  1. var
  2.   Z: Integer;
  3.  
  4. // Increase Red
  5. Z := OriginalRed + 10;
  6. if (Z > 255) then Z := 255;
  7. OriginalRed := Z;
  8.  
  9. // Reduce Green
  10. Z := OriginalGreen - 10;
  11. if (Z < 0) then Z := 0;
  12. OriginalGreen := Z;
  13.  
  14. // Reduce Blue
  15. Z := OriginalBlue - 10;
  16. if (Z < 0) then Z := 0;
  17. OriginalBlue := Z;

You need the Z (as Integer) because the original values are Byte, increasing it over 255 may cause overflow error.

Handoko

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Re: Change background color of a BMP
« Reply #11 on: June 20, 2017, 05:10:18 pm »
Your original code should work correctly if you use
TBitmap.BeginUpdate

http://lazarus-ccr.sourceforge.net/docs/lcl/graphics/trasterimage.beginupdate.html

Mr.Madguy

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Re: Change background color of a BMP
« Reply #12 on: June 20, 2017, 05:57:28 pm »
I managed to fix your first variant. I haven't tested your second variant.

To make it work, you have to remove (or comment) line #79.
That's all.

Because:
MaskBitmap.Handle := CardBitmap.MaskHandle;

then it means MaskBitmap is linked to CardBitmap, so you should not free MaskBitmap. If you really want to free MaskBitmap, I guess you may need to set the handle to nil before calling MaskBitmap.Free.

Try it, it works on my tests!

edit:
Pixels[x, y] is slow, you should consider to use ScanLine.
Strange, but I actually suspected it and tried to either comment this line or to use global MaskBitmap, that was destroyed in OnDestroy (like in second variant) - and it didn't help. I'll try it next time.

P. S. Nope, isn't working.
« Last Edit: June 20, 2017, 06:05:43 pm by Mr.Madguy »

Handoko

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Re: Change background color of a BMP
« Reply #13 on: June 20, 2017, 06:13:06 pm »
I didn't remember what I have changed. But this is the code that works. Tested on Linux64 Lazarus 1.6.4.

Mr.Madguy

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Re: Change background color of a BMP
« Reply #14 on: June 20, 2017, 06:21:05 pm »
Here's a view of what I'm trying to accomplish. This picture is taken from my Delphi program that I'm trying to reproduce in Laz. In the example, I've made the background of the 8D red. It's not possible to rely on changing just one color (eg. clWhite) because there are many pixels that are almost white, especially in the face cards.
I think, such result is usually accomplished via Alpha-blending. It's something like this:
Code: Pascal  [Select]
  1. type
  2.   TABGR = packed record
  3.     A, B, G, R: Byte;
  4.   end;
  5.  
  6. function MyAlphaBlend(Color1, Color2:TColor;Alpha:Byte):TColor;  //Alpha of Color2!!!
  7. begin
  8.   TABGR(Result).R := (Integer(TABGR(Color2).R) * Integer(Alpha) + Integer(TABGR(Color1).R) * Integer(not Alpha)) shr 8;
  9.   TABGR(Result).G := (Integer(TABGR(Color2).G) * Integer(Alpha) + Integer(TABGR(Color1).G) * Integer(not Alpha)) shr 8;
  10.   TABGR(Result).B := (Integer(TABGR(Color2).B) * Integer(Alpha) + Integer(TABGR(Color1).B) * Integer(not Alpha)) shr 8;
  11. end;
  12.  
  13. //Example!!!
  14.  
  15. DestBitmap.Canvas.Pixel[I, J] := MyAlphaBlend(SrcBitmap.Canvas.Pixel[I, J], clRed, 64);
  16.  

I didn't remember what I have changed. But this is the code that works. Tested on Linux64 Lazarus 1.6.4.
Lazarus 1.6.4 too, but Windows is completely different beast. :'(
« Last Edit: June 20, 2017, 06:37:31 pm by Mr.Madguy »

 

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