[SOLVED] Projective transformation and the poor image quality

[furious programming]

Coordinates were the same as in the windowed application (which work correctly to this day), and even the source image was the same (exactly the same file). But instead of got the same output, I got what you see in the attachment. Same shape (correct coordinates), same background (white), same antialiased edges but instead of the transformed texture, only a black polygon (no colored content).

If I have some time, I will try to prepare a test program and reproduce this bug. Though I'm not saying it's a bug — maybe I made a mistake somewhere porting the code. The test program should answer.

[paweld]

Code: Pascal  [Select][+][-]

1. program project1;
2.  
3. {$R *.res}
4.  
5. uses
6.   BGRABitmap, BGRABitmapTypes;
7.  
8. var
9.   ImageSource, ImageDest: TBGRABitmap;
10.  
11. begin
12.   //load
13.   ImageSource := TBGRAbitmap.Create('data\source.png');
14.   //apply
15.   ImageDest := TBGRABitmap.Create(ImageSource.Width, ImageSource.Height, BGRAWhite);
16.   ImageDest.FillQuadPerspectiveMappingAntialias(
17.     PointF(0, 176),
18.     PointF(1088, -24),
19.     PointF(1024, 768),
20.     PointF(192, 652),
21.     ImageSource,
22.     PointF(0, 0),
23.     PointF(ImageSource.Width, 0),
24.     PointF(ImageSource.Width, ImageSource.Height),
25.     PointF(0, ImageSource.Height)
26.   );
27.   //save
28.   ImageDest.SaveToFile('data\dest.png');
29.   ImageDest.Free;
30.   ImageSource.Free;
31. end.                  

[furious programming]

Thank you @paweld — looks like I did something wrong earlier, that's why the “kicked” image was entirely black. But still I don't know why it happened — why the transformation produced a black shape. Never mind.

Finally, I made a small console application that searches for an image in its directory, does a transformation and crop on it, and finally saves the snip to a new file (without showing a console window). The final code is below, and the project files in the attachment (with source image to test its operation).

Code: Pascal  [Select][+][-]

1. program thumbnail;
2.  
3. {$MODE OBJFPC}{$LONGSTRINGS ON}
4.  
5. uses
6.   SysUtils, Types, BGRABitmap, BGRABitmapTypes;
7. var
8.   InputFile: TSearchRec;
9.   ImageSource, ImageKicked, ImageOutput: TBGRABitmap;
10. begin
11.   if FindFirst('*.png', faAnyFile, InputFile) = 0 then
12.   try
13.     try
14.       ImageSource := TBGRABitmap.Create(InputFile.Name);
15.       ImageKicked := TBGRABitmap.Create(ImageSource.Width, ImageSource.Height, BGRAWhite);
16.       ImageKicked.FillQuadPerspectiveMappingAntialias(
17.         PointF(0, 176),
18.         PointF(1088, -24),
19.         PointF(1024, 768),
20.         PointF(192, 652),
21.         ImageSource,
22.         PointF(0, 0),
23.         PointF(ImageSource.Width, 0),
24.         PointF(ImageSource.Width, ImageSource.Height),
25.         PointF(0, ImageSource.Height)
26.       );
27.       ImageOutput := TBGRABitmap.Create(680, 382, BGRAWhite);
28.       ImageOutput.CanvasBGRA.CopyRect(0, 0, ImageKicked, Bounds(202, 240, 680, 382));
29.       ImageOutput.SaveToFile('thumbnail.png');
30.     finally
31.       ImageSource.Free();
32.       ImageKicked.Free();
33.       ImageOutput.Free();
34.     end;
35.   finally
36.     FindClose(InputFile);
37.   end;
38. end.

Before anyone asks — the name of the output file is hardcoded because in my environment there will never be a collision with another file. Just in the executable directory, there will always be one source image file whose name is in a specific format.

Thanks again for your help.