Hi guys!

I did a very simple program to see what happens with colors between TColor and TFPColor.

The program has just one main form that shows four panels and a TImage object, generates a png image file containing four rectangles with the 'same' color as the panels and load that file to the TImage object with LoadFromFile method.
When I tried to load the file (png) generated, the image appears black. However, the image file is generated correctly because I can open it with other viewers like Explorer, Paint and IrfanViewer. Even at design time I can load other png image files normally but not this one generated by this program.

Am I doing something wrong? Maybe a bug?

And, why r. g. b colors are inverted on TColor objects?

If someone has some free time to see the code and give me a hint I would apreciate a lot!

I am using Lazarus 1.0.10 and FPC 2.6.2, Win 7 32 bits

The program is small so the source folows, contents of .pas, .lfm and .lpr:

unit rgbmain;
{$mode objfpc}{$H+}
interface

uses
Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls, FPimage,
FPImgCanv,

  FPWritePNG;

type
  { TForm1 }
  TForm1 = class(TForm)
    Image1: TImage;
    Panel1: TPanel;
    Panel2: TPanel;
    Panel3: TPanel;
    Panel4: TPanel;
    procedure FormCreate(Sender: TObject);
    procedure GenerateImage(aWidth, aHeight: integer);
  private
    { private declarations }
  public
    { public declarations }
  end;
var
  Form1: TForm1;
const
  FileGenerated = 'rgb.png';
  // TColors used on screen panels
  clLtYellow: TColor = ($FFFF40);
  clLtYellowR: TColor = ($FF0000);
  clLtYellowG: TColor = ($00FF00);
  clLtYellowB: TColor = ($000040);
  // TFPColors used on FileGenerated
  colLtYellow: TFPColor = (Red: $FFFF; Green: $FFFF; Blue: $4000;
    Alpha: alphaOpaque);
  colLtYellowR: TFPColor = (Red: $FFFF; Green: $0000; Blue: $0000;
    Alpha: alphaOpaque);
  colLtYellowG: TFPColor = (Red: $0000; Green: $FFFF; Blue: $0000;
    Alpha: alphaOpaque);
  colLtYellowB: TFPColor = (Red: $0000; Green: $0000; Blue: $4000;
    Alpha: alphaOpaque);
implementation
{$R *.lfm}

{ TForm1 }

procedure TForm1.FormCreate(Sender: TObject);
begin
  Panel1.Color := clLtYellowR;
  Panel1.Caption := 'R: $FF; G: $00; B: $00';
  Panel2.Color := clLtYellowG;
  Panel2.Caption := 'R: $00; G: $FF; B: $00';
  Panel3.Color := clLtYellowB;
  Panel3.Caption := 'R: $00; G: $00; B: $40';
  Panel4.Color:= clLtYellow;
  Panel4.Caption := 'R: $FF; G: $FF; B: $40';
  GenerateImage(image1.Width, image1.Height);
  image1.Picture.LoadFromFile(FileGenerated);
end;
procedure TForm1.GenerateImage(aWidth, aHeight: integer);
var
  Img: TFPMemoryImage;
  Writer: TFPWriterPNG;
  ms: TMemoryStream;
  ImgCanvas: TFPImageCanvas;
  fs: TFileStream;
begin
  Img := nil;
  ImgCanvas := nil;
  Writer := nil;
  ms := nil;
  fs := nil;
  try
    Img := TFPMemoryImage.Create(aWidth, aHeight);
    //Img.UsePalette := False;
    ImgCanvas := TFPImageCanvas.Create(Img);
    // Red
    ImgCanvas.Pen.FPColor := colLtYellowR;
    ImgCanvas.Brush.FPColor := colLtYellowR;
    ImgCanvas.Rectangle(0, 0, aWidth div 3, aHeight div 2);
    // Green
    ImgCanvas.Pen.FPColor := colLtYellowG;
    ImgCanvas.Brush.FPColor := colLtYellowG;
    ImgCanvas.Rectangle(aWidth div 3, 0, (aWidth div 3)*2, aHeight div 2);
    // Blue
    ImgCanvas.Pen.FPColor := colLtYellowB;
    ImgCanvas.Brush.FPColor := colLtYellowB;
    ImgCanvas.Rectangle((aWidth div 3)*2, 0, aWidth, aHeight div 2);
    // RGB
    ImgCanvas.Pen.FPColor := colLtYellow;
    ImgCanvas.Brush.FPColor := colLtYellow;
    ImgCanvas.Rectangle(0, aHeight div 2, aWidth, aHeight);
    // write image as png to memory stream
    Writer := TFPWriterPNG.Create;
    ms := TMemoryStream.Create;
    writer.ImageWrite(ms, Img);
    // write memory stream to file
    ms.Position := 0;
    fs := TFileStream.Create(FileGenerated, fmCreate);
    fs.CopyFrom(ms, ms.Size);
  finally
    ms.Free;
    Writer.Free;
    ImgCanvas.Free;
    Img.Free;
    fs.Free;
  end;
end;
end.

object Form1: TForm1
Left = 325
Height = 277
Top = 145
Width = 492
Caption = 'RGB'
ClientHeight = 277
ClientWidth = 492
OnCreate = FormCreate
LCLVersion = '1.0.10.0'
object Panel1: TPanel
Left = 8
Height = 50
Top = 8
Width = 150
Caption = 'R'
TabOrder = 0

  end
  object Panel2: TPanel
    Left = 168
    Height = 50
    Top = 8
    Width = 150
    Caption = 'G'
    TabOrder = 1
  end
  object Panel3: TPanel
    Left = 336
    Height = 50
    Top = 8
    Width = 150
    Caption = 'B'
    Font.Color = clWhite
    ParentFont = False
    TabOrder = 2
  end
  object Panel4: TPanel
    Left = 8
    Height = 50
    Top = 64
    Width = 478
    Caption = 'RGB'
    TabOrder = 3
  end
  object Image1: TImage
    Left = 8
    Height = 138
    Top = 128
    Width = 480
    Stretch = True
  end

end

program rgb;
{$mode objfpc}{$H+}

uses

  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Interfaces, // this includes the LCL widgetset
  Forms, rgbmain
  { you can add units after this };

{$R *.res}
begin
  RequireDerivedFormResource := True;
  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.
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Lazarus 1.1 r42508M FPC 2.6.2 i386-linux-gtk 2

see image down....

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Edilson Vieira wrote

And, why r. g. b colors are inverted on TColor objects?

1. TColor is not an object, but a ordinal value
2. Delphi compatibility

Regards,
Sven

2013/8/28 Sven Barth

Thanks Sven.
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I have just tried the sample with another Lazarus instalation (1.0.8), also Win7.

Same problem!

2013/8/28 Edilson Vieira

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