Is it possible to Canvas.Textout and Render is scaled (stretch==true)?
lazarus / 39-Graphics

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Ozz_Nixon · 2023-02-15 17:56

I am working on a project where I need to render 5 to 8 telnet
sessions like little "view screens". I have all of the code ready...
but, it does not work. Could someone help (explain the mistake and
makes a working example?).


Basically, I create a TImage (640x480) scaled down to div 4, click a
toolbar button and mimic a session. In that event, I do:


[/code]Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  var  w, h:
Integer;begin  if ssLeft in Shift then  begin    ReleaseCapture;   
Perform(WM_SysCommand, $F012, 0);  end; 
Image1.Canvas.Brush.Color:=clBlack; 
Image1.Canvas.Font.Color:=clYellow;  Image1.Canvas.Font.Size := 12;  h
:= Image1.Canvas.Font.Height; // in pixels  Image1.Canvas.TextOut(0,
20 + h, 'Superior');  w := Image1.Canvas.TextWidth('Big')+12; 
Image1.Canvas.Font.Color:=clLime;  Image1.Canvas.Font.Size := 6;  h :=
Image1.Canvas.Font.Height; // in pixels  //Image1.Canvas.Font.Style :=
Image1.Canvas.Font.Style + [fsBold];  Image1.Canvas.TextOut(W, 20 + h,
'Bulletin Board Software'); 

The flaw is, it is rendering at 12, and 6 pixels respectively - on the
small TImage. Instead of running the code, and rendering scaled. * Or
am I using the wrong Component/Canvas?


Thanks!
Ozz

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KodeZwerg · 2023-02-15 19:49

I do not fully understand yet what you try to do.
In most cases I do use a TBitmap (or similar) and draw on that what I
want and when done I copy it to a TImage.
If you can show on an Image what you want to have when done, it would
simplify to help you.

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Ozz_Nixon · 2023-02-17 00:48

Okay Screenshot 1 - is what I am getting with the code in my first
post. (I will fix the overlap later)...


Screenshot 2 - is what I am trying to achieve. I was able to produce
screenshot 2, by doing everything in screenshot 1 - at 640x480, then
added a new button that changes the size to "div 4" - to get what I am
trying to produce. (Which makes me think I need to do some type of
Double Buffering, or Offscreen Paint, Copy, Paste to the scaled one? -
And avoid flickering, as this will run all day).

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Thaddy · 2023-02-17 10:10

What you want to achieve needs the font to be scaled in pixels, not
points. That means the font needs to have a negative value (pixels)
instead of points (positive value). That is the ONLY way to be
accurate.
Formula's are like this:
(Given LOGFONT structure on Windows)
Code: [Select]lfHeight := -MulDiv(PointSize, GetDeviceCaps(hDC,
LOGPIXELSY), 72); // pixels
PointSize := MulDiv(-lfHeight, 72, GetDeviceCaps(hDC, LogPixelsY);//
pointsBut note that for high resolution screens you should call
GetDeviceCaps first. The above formulae are for Windows only, but may
be Lazarus supports it cross-platform.

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KodeZwerg · 2023-02-17 10:45

Thats how I calculate the Size field of font.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
Round((Abs(GetFontData(AFont.Handle).Height) * 72 /
AFont.PixelsPerInch));While AFont is a TFont, crossplatform.

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Ozz_Nixon · 2023-02-17 21:43

Thank you both, however, trying negative canvas.font.size - just
resulted in my original output. e.g. Small Image, big Text.


From what I have found via other posts - is to create a
TImage.Visible:=False - Put my text on it, the BitBlt to a visible
TImage2.Stretch:=True, and DoubleBuffers:=True.


If I get this way to work, I will contribute the code for anyone else
to see/use.
Ozz

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KodeZwerg · 2023-02-17 22:36

Since I was not able to watch at your image (all i see is a small
black something at topleft corner) I try to show you how I would do.
Maybe thats a starting point for you.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.Button1Click(Sender: TObject);var  LBmp: TBitmap;  h:
Integer;begin  LBmp := TBitmap.Create;  try    LBmp.Width :=
Image1.Width;    LBmp.Height := Image1.Height;   
LBmp.Canvas.Brush.Color := clBlack;    LBmp.Canvas.FillRect(0, 0,
LBmp.Width, LBmp.Height);    LBmp.Canvas.Font :=
Application.MainForm.Font;    LBmp.Canvas.Font.Size := 12;   
LBmp.Canvas.Font.Color := clYellow;    LBmp.Canvas.TextOut(0, 20,
'Superior');    h := LBmp.Canvas.TextHeight('Superior') + 20;   
LBmp.Canvas.Font.Size := 6;    LBmp.Canvas.Font.Color := clLime;   
LBmp.Canvas.TextOut(0, h, 'Bulletin Board Software');   
Image1.Picture.Assign(LBmp);  finally    LBmp.Free;  end;end;