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tvdien
11 Posts |
 Posted - Jan 06 2012 : 18:15:46
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Hello,
With 4.0.2, no matter what I do, DrawTo never gets ImageEnView2 to show anything:
ImageEnView1.IO.LoadFromFile('c:\pic\prod.jpg');
ImageEnView1.LayersAdd;
ImageEnView1.IO.LoadFromFile('c:\pic\clos.jpg');
ImageEnView1.DrawTo(ImageEnView2.Bitmap.Canvas);
ImageEnView2.Update;
It doesn't work with TImage either; then it paints all white. What am I doing wrong? |
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fab
1310 Posts |
Posted - Jan 07 2012 : 03:20:37
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Hello,
DrawTo doesn't work because nothing has been still painted in TImageEnView canvas. Painting of loaded images occurs when Paint messages are processed. For example, you could write:
ImageEnView1.IO.LoadFromFile('c:\pic\prod.jpg');
ImageEnView1.LayersAdd;
ImageEnView1.IO.LoadFromFile('c:\pic\clos.jpg');
Application.ProcessMessages(); // <<<<<<<<<<<
ImageEnView1.DrawTo(ImageEnView2.Bitmap.Canvas);
ImageEnView2.Update; |
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tvdien
11 Posts |
Posted - Jan 07 2012 : 05:35:05
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| I see, but I'm afraid that there are some risks to calling ProcessMessages(). Is there another way to copy just what the ImageEnView1 looks like now (like DrawTo() does)? |
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fab
1310 Posts |
Posted - Jan 07 2012 : 05:53:45
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Yes, just replace ProcessMessages with:
ImageEnView1.Paint();
Anyway there are several ways to do this task. |
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tvdien
11 Posts |
Posted - Jan 07 2012 : 06:22:35
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I'll give you some background information.
I need to create a composite image; let's say it will be a photo and two logos on top of it. The composite image always has to be 640x640 and the logos have a fixed place. The only thing that can vary, is how the photo is placed within this frame; it can be both scaled and moved.
Perhaps I might be able to do this by only putting a TImageEnView on a form, adding fixed layers for the logos. However, there are more other methods that I would like to add related to these logos, and encapsulation into one TBrandedImage (or so) would be nice.
For that, I could inherit from TImageEnView, but I would have a lot of behavior to take care of, and some separation between GUI and business logic would be nice. Therefore I'm thinking of making a simple TBrandedImage that encapsulates a TImageEnView, and can be shown on another one that I will drop on my form. The TBrandedImage has no parent (Nil), which seems to spoil the Paint() option.
Simply put, I'm looking for the best way to create a new image of what TBrandedImage.TImageEnView would look like on a form, which I can then show on the form. Zooming in on TBrandedImage.TImageEnView, for example, should cause a change in output of TBrandedImage's copy/draw method.
Am I trying do something weird or is this quite simple to do? |
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fab
1310 Posts |
Posted - Jan 07 2012 : 12:20:28
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quote:
Therefore I'm thinking of making a simple TBrandedImage that encapsulates a TImageEnView, and can be shown on another one that I will drop on my form.
Encapsulation is my preferred way (rather than inheritance), especially if you don't want to expose all TImageEnView methods/properties. However, this is your choice.
I can only suggest to look at TImageEnView.BackBuffer (a TBitmap) property, that contains the result of the rendering.
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tvdien
11 Posts |
Posted - Jan 08 2012 : 14:51:06
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Thanks for your suggestions.
In the end I decided to make it a component, inherited from TCustomControl, which embeds a TImageEnView. In its constructor I initialize it as follows:
FImageEnView := TImageEnView.Create(Self);
FImageEnView.Parent := Self;
FImageEnView.Align := alClient;
In this way, I never need to do any copying between canvases and so on. However, double buffering doesn't work properly now. I set FImageEnView.DoubleBuffer to True and also on the inherited DoubleBuffered property of my own component. Still, when I put TMyComponent on a form and set anchors, resizing the window looks all but smooth. Why is this happening? I haven't done anything with the Paint procedure; should I implement some other layer of my own double buffering, unlikely of doing a better job than you guys did with TImageEnView? |
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tvdien
11 Posts |
Posted - Jan 09 2012 : 17:11:40
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| Ignoring WM_ERASEBKGND seems to do a good job of solving this. Other thoughts are still welcome, though. |
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fab
1310 Posts |
Posted - Jan 11 2012 : 14:21:08
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Here is my thoughts (I don't know if these suggestions can actually help):
- TImageEnView inherits from TCustomControl, so maybe you could do the same.
- in the constructor ControlStyle is changed with:
ControlStyle := ControlStyle + [csOpaque, csAcceptsControls, csReplicatable, csNeedsBorderPaint];
- In CreateParams overload WindowsClass.Style is set as:
WindowClass.style := WindowClass.style and not (CS_HREDRAW or CS_VREDRAW);
- WM_ERASEBKGND is handled with:
procedure TImageEnView.WMEraseBkgnd(var Message: TMessage);
begin
Message.Result := 0;
end;
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DrawTo never works
