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[quote author=davem link=msg=799 date=1271749683]
  I got very interesting problem. I manipulate an image using TImageData however then I need to add a text and modify a few pixels manually. So I do this:

ImgBitmap:=TImagingBitmap.Create;
        ImgBitmap.AssignFromImageData(MainImage);

// add text (just an example)
        ImgBitmap.Canvas.TextOut(x,y,'some text');

// set some colors (just an example)
        ImgBitmap.Canvas.Pixels[x,y]:=col;

// save the changes back to ImageData
        ImgBitmap.AssignToImageData(MainImage);
        ImgBitmap.Free;

However, my problem is that in some cases (let's say every fifth case) the changes of colors are not visible on the picture when I save it. It seems to me that the Canvas/Handle hasn't been updated yet at the moment I assign the bitmap back to ImageData. Sometimes the part of the image is even partially black. Does anyone have any idea what can be done? I tried to put sleep behind, I tried to use a CriticalSection (it is multithreading appl), I tried to Lock the canvas (although the ImgBitmap is not shared) however nothing works. I also tried to run only one thread but it was the same. Does anyone have any idea?
[/quote]

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Posted by davem

- 20 April 2010, 16:10:02

Quote from: Galfar on 20 April 2010, 15:33:20
What about calling Canvas.Release or Canvas.Refresh after the pixels are set?

Canvas.Refresh did not help. I haven't tried Canvas.Release.

Posted by Galfar

- 20 April 2010, 15:33:20

What about calling Canvas.Release or Canvas.Refresh after the pixels are set?

Posted by davem

- 20 April 2010, 10:12:50

Hmm, Synchronize seems to solve the issue. But I don't know why. :-\

Posted by davem

- 20 April 2010, 09:48:03

I got very interesting problem. I manipulate an image using TImageData however then I need to add a text and modify a few pixels manually. So I do this:

ImgBitmap:=TImagingBitmap.Create;
ImgBitmap.AssignFromImageData(MainImage);

// add text (just an example)
ImgBitmap.Canvas.TextOut(x,y,'some text');

// set some colors (just an example)
ImgBitmap.Canvas.Pixels[x,y]:=col;

// save the changes back to ImageData
ImgBitmap.AssignToImageData(MainImage);
ImgBitmap.Free;

However, my problem is that in some cases (let's say every fifth case) the changes of colors are not visible on the picture when I save it. It seems to me that the Canvas/Handle hasn't been updated yet at the moment I assign the bitmap back to ImageData. Sometimes the part of the image is even partially black. Does anyone have any idea what can be done? I tried to put sleep behind, I tried to use a CriticalSection (it is multithreading appl), I tried to Lock the canvas (although the ImgBitmap is not shared) however nothing works. I also tried to run only one thread but it was the same. Does anyone have any idea?

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