copying a jpeg image of a chart to the clipboard

[mtanner]

I have found some posts about saving a jpeg image of a chart to a file, but I cannot figure out how to copy a chart image to the clipboard. How do you do that?

[wp]

Borrowed and adapted from TChart.CopyToClipboardBitmap:

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button1Click(Sender: TObject);
2. begin
3.   with Chart1.SaveToImage(TJpegImage) do
4.     try
5.       SaveToClipboardFormat(RegisterClipboardFormat(MimeType));
6.     finally
7.       Free;
8.     end;
9. end;

But I just added a new method TChart.CopyToClipboard(AClass: TRasterImageClass) which gets the desired image type as a parameter. So, if you are using trunk you can also call

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button1Click(Sender: TObject);
2. begin
3.   Chart1.CopyToClipboard(TJpegImage);
4. end;

[mtanner]

Thanks for that. I'm using FPC 3.2 on Win7. I found RegisterClipboardFormat in the unit jwawinuser, but than I get a compiler error of thre MimeType parameter, sayinh "got ansistring expected pchar".  Not sure how to proceed?

[mtanner]

My basic probem is that I don't know what a"mimetype" is. Ob googling I find referebces to getting a mimetype from a file extension, but that doesn't tell me what a mimetype is. I imaging it's something that says jpeg or text or whatever, but I see no examples of actual instances of a mimetype.

[mtanner]

I have tried varous things fro mimetype, most likely seems to be "image/jpeg", but although the code compiles and runs, there seems to be nothing on the clipboard afterwards.

[wp]

Bad "with" instruction...

Chart.SaveToImage(TJpegImage) creates a TRasterImage instance of the specified type and draws the chart on it. Because of the "with" the MimeType is not meant to be a separate variable but a property of the TRasterImage. And because the TJpegImage knows how to handle this there is nothing to do for you.

Here is the code without the "with", and I hope you understand:

Code: Pascal  [Select][+][-]

1.    
2. procedure TForm1.Button1Click(Sender: TObject);
3. var
4.   jpg: TRasterImage;
5. begin
6.   jpg := Chart1.SaveToImage(TJpegImage);
7.   try
8.     jpg.SaveToClipboardFormat(RegisterClipboarFormat(jpg.MimeType));
9.   finally
10.     jpg.Free;
11.   end;
12. end;

[mtanner]

Thanks, just trried that, but still gte compiler error "got ansistring expected pchar" of jpg.mimetype. If I put "image/jpeg" uin explicitly thebn it runs but nothing on the clipboard. Maybe its's something to be with FPC bersion of being on Win7.

[wp]

What are your Laz/FP versions and operating system so that I can test with correct machine?

[mtanner]

Using Lazarus version 2.0.10, FPC version 3.2.0, SVN revision 63526, on Win 7 64 bit.

[mtanner]

Just to extend the question a bit, is it also possible to capture a jpeg of a form, rather than just the chart? ( Mainly I want to do charts, but have an occcasional wish to capture a form).

[wp]

The form has a method GetFormImage which renders the form into a TBitmap. If you need a jpeg you must convert the bitmap to jpeg before copying to the clipboard:

Code: Pascal  [Select][+][-]

1. uses
2.   clipbrd;
3.  
4. var
5.   CF_JPEG: Integer = -1;
6.  
7. procedure TForm1.Button1Click(Sender: TObject);
8. var
9.   bmp: TBitmap;
10.   jpeg: TJpegImage;
11. begin
12.   bmp := GetFormImage;
13.   try
14.     jpeg := TJpegImage.Create;
15.     try
16.       jpeg.Assign(bmp);
17.       if CF_JPEG = -1 then
18.         CF_JPEG := RegisterClipboardFormat('image/jpeg');
19.       jpeg.SaveToClipboardFormat(CF_JPEG);
20.     finally
21.       jpeg.Free;
22.     end;
23.   finally
24.     bmp.Free;
25.   end;
26. end;  

I tested this on Win 10, Laz 2.0.10/FPC 3.2.0 / 64 bit, and it works (there was an error initially because I had forgotten to add "clipbrd" to "uses").

GetFormImage renders the form WITHOUT the non-client areas such as title bar and border. I don't know how this can be handled (except for taking a screenshot of the entire screen and cropping to form size). If everything breaks you can still press ALT+PRINT which copies the current form to the clipboard, but as a TBitmap only.

[lucamar]

Alternatively, though a little more convoluted, you can use the form's PaintTo() method to paint it to any canvas like, for example, a TBitmap's:

Code: Pascal  [Select][+][-]

1. procedure TForm1.SaveImageTo(const AFilename: String);
2. var
3.   ABitmap: TBitmap;
4. begin
5.   ABitmap := TBitmap.Create;
6.   try
7.     ABitmap.SetSize(Width, Height);
8.     PaintTo(ABitmap.Canvas, 0, 0);
9.     ABitmap.SaveToFile(AFilename);
10.     {or CopyToClipboard or whatever}
11.   finally
12.     ABitmap.Free;
13.   end;
14. end;

Though, IIRC, it has the same drawback: it paints only the client area, not the non-client one drawn by the system.

[wp]

This is (almost) what Form.GetFormImage is doing:

Code: Pascal  [Select][+][-]

1. function TCustomForm.GetFormImage: TBitmap;
2. var
3.   ARect: TRect;
4. begin
5.   Result := TBitmap.Create;
6.   try
7.     Result.SetSize(ClientWidth, ClientHeight);
8.     LCLIntf.GetWindowRect(Handle, ARect);
9.     with GetClientOrigin do
10.       PaintTo(Result.Canvas, ARect.Left - X, ARect.Top - Y);
11.   except
12.     Result.Free;
13.     raise;
14.   end;
15. end;  

Except for the image size and origin so that part of title bar and border is include. Combining them and some calculation for the window border size may solve it.