Save Timage picture as png

[Lainkes 0]

Hello,

I have a TImage that contains a picture.

Now I want to save this as a PNG file.

I found this code :

 

var PNG: TPNGImage; 

...
   
  // save image to file
  PNG := TPNGImage.Create;
  try
    PNG.Assign(imgPerson.Picture.Graphic); // ImgPerson is TImage component
    PNG.SaveToFile(image_path + file_name + '.PNG');
  finally
    PNG.Free;
  end;

When I open the png-file, I just see a grey square. 

Any idea what is going wrong?

 

Thanks

 

Lainkes

[Uwe Raabe 2057]

What graphic class is image? You can retrieve that from imgPerson.Picture.Graphic.Classname

[PeterBelow 238]

Whether this works or not depends on the source image format. TPngImage does not support direct assignment from a TJpegImage, for example. In such a case you have to go through a TBitmap as intermediate.

procedure TForm1.Button1Click(Sender: TObject);
var
  png: TPngImage;
  bmp: TBitmap;
begin
  image1.Picture.LoadFromFile('C:\Users\Peter_2\Pictures\7.5. Stadtführung.jpg');
  bmp:= TBitmap.Create;
  try
    bmp.Assign(Image1.Picture.Graphic);
    png:= TPngImage.Create;
    try
      png.Assign(bmp);
      png.SaveToFile('C:\Users\Peter_2\Pictures\test.png');
      bmp.SaveToFile('C:\Users\Peter_2\Pictures\test.bmp');
    finally
      png.Free;
    end;
  finally
    bmp.Free;
  end;
  ShowMessage('Done');
end;

 

[Remy Lebeau 1393]

5 hours ago, PeterBelow said:

Whether this works or not depends on the source image format. TPngImage does not support direct assignment from a TJpegImage, for example.

In which case, you should be getting an EConvertError exception raised, not a corrupted/empty file created.

[George Birbilis 1]

Is there any chance the output file is locked (or not locked but the filesystem eventually fails to write to it)? I think I had seen OneDrive cause issues when trying to save too often onto the same filename (replace a file it was trying to sync to the cloud)

 

There is a free tool from SysInternals (now Microsoft) called ProcMon that may be helpful to see what is happening