Does TPaintBox work with other than *.BMP?

[OC DelGuy]

When I import a BMP file into a TPaintBox, it works fine.  But If I import a .JPG or PNG, it balks.  I get a runtime error says File Format is bad.  Is there something I need to do to be able to import JPG's and PNG's (or other image formats)?

[wp]

If you need access to any registered image file format use a TPicture rather than a TBitmap. It can automatically detect the file format and then read the image into uncompressed memory. From there you can access the image via the generic property Graphic or, reformatted, via Bitmap, PNG, JPEG, or ICO properties (https://wiki.freepascal.org/Developing_with_Graphics#Working_with_TBitmap_and_other_TGraphic_descendents):

Code: Pascal  [Select][+][-]

1. type
2.   TForm1 = class(TForm)
3.     PaintBox1: TPaintBox;
4.     procedure FormCreate(Sender: TObject);
5.     procedure FormDestroy(Sender: TObject);
6.     procedure PaintBox1Paint(Sender: TObject);
7.   private
8.     pic: TPicture;
9.   end;
10.  
11. procedure TForm1.FormCreate(Sender: TObject);
12. begin
13.   pic := TPicture.Create;
14.   pic.LoadFromFile('project1.ico');  // or any other registered graphic file format such as .jpg, .png, .bmp, ...
15. end;
16.  
17. procedure TForm1.FormDestroy(Sender: TObject);
18. begin
19.   pic.Free;
20. end;
21.  
22. procedure TForm1.PaintBox1Paint(Sender: TObject);
23. begin
24.   Paintbox1.Canvas.Draw(10, 10, pic.Graphic);
25. end;

[Remy Lebeau]

When I import a BMP file into a TPaintBox, it works fine.  But If I import a .JPG or PNG, it balks.  I get a runtime error says File Format is bad.  Is there something I need to do to be able to import JPG's and PNG's (or other image formats)?

TPaintBox is just a Canvas that you draw on. It has no concept of BMPs or other images. What are you importing, exactly? Can you show the code you are having trouble with?

[Boleeman]

Use a TbgraBmp in conjunction with a TPaintbox to load jpg.
Also if the quality of the jpg is poor then expect the loaded picture to be pixelated/poor.

Loading png to a TPaintbox should work OK.
Below is a working example:

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls, StdCtrls, ExtDlgs, LCLType;
9.  
10. type
11.  
12.   { TForm1 }
13.  
14.   TForm1 = class(TForm)
15.     btnLoadPng: TButton;
16.     OpenDialog1: TOpenDialog;
17.     PaintBox1: TPaintBox;
18.     procedure btnLoadPngClick(Sender: TObject);
19.     procedure FormCreate(Sender: TObject);
20.     procedure PaintBox1Paint(Sender: TObject);
21.   private
22.        FBitmap: TBitmap;
23.   public
24.  
25.   end;
26.  
27. var
28.   Form1: TForm1;
29.  
30. implementation
31.  
32. {$R *.lfm}
33.  
34. { TForm1 }
35.  
36.  
37. procedure TForm1.btnLoadPngClick(Sender: TObject);
38. var
39.   Png: TPortableNetworkGraphic;
40.  
41. begin
42.   if OpenDialog1.Execute then
43.   begin
44.     FBitmap := TBitmap.Create;
45.     Png := TPortableNetworkGraphic.Create;
46.     try
47.       Png.LoadFromFile(OpenDialog1.FileName);
48.       FBitmap.SetSize(Png.Width, Png.Height);
49.       FBitmap.Canvas.Draw(0, 0, Png);
50.       PaintBox1.Width := Png.Width;
51.       PaintBox1.Height := Png.Height;
52.       PaintBox1.Invalidate;
53.     finally
54.       Png.Free;
55.     end;
56.   end;
57. end;
58.  
59. procedure TForm1.PaintBox1Paint(Sender: TObject);
60. begin
61.  if (FBitmap <> nil) and (FBitmap.Width > 0) and (FBitmap.Height > 0) then
62.     PaintBox1.Canvas.Draw(0, 0, FBitmap);
63. end;
64.  
65. end.