Disabling anti-aliasing in Image Canvas,
lazarus / 39-Graphics

----------------------------------------------------------------------
cov · 2026-01-08 16:26

I'm trying to transfer text rendered onto a Tbitmap canvas onto
another image canvas, but I cannot get rid of the anti aliasing.

This is the image file created (attached), which is unusable:

Reducing the image.PixelFormat:=pf1bit and specifying Image.Monochrome
as True gives me an error message.

Runerror (204), invalid pointer operation in the file dynarr.inc at
line 129.

Is there a way to disable text antialiasing?

----------------------------------------------------------------------
wp · 2026-01-09 17:13

You mean you want to remove the extra anti-aliasing pixels from an
existing bitmap? I think that's not possible (at least not easily).

----------------------------------------------------------------------
cov · 2026-01-09 20:34

No.

The image is just to show the anti aliasing.

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       bmp:=
TBitmap.Create;      bmp.Canvas.TextOut(0,2,'1.789 m³/Hr WATER');    
  
I want to transfer the image onto the screen pixel by pixel. This is
so that I can add additional information related to the text behind
each pixel. I hope this makes sense. I'm aware that I could simply
Bitblock copy the canvas to the screen, but I'm planning to map each
pixel to an array with more information.

The image was simply generated by using
bmp.SaveToFile('/tmp/image.bmp') to illustrate what I meant.

----------------------------------------------------------------------
jamie · 2026-01-09 22:18

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
bmp.Canvas.Font.quality := fqnonAntialiased 
jamie

----------------------------------------------------------------------
cov · 2026-01-10 13:05

Thanks.

Unfortunately it doesn't work.

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
bmp.Canvas.Font.Quality:=fqNonAntialiased; bmp.Canvas.Brush.Style :=
bsSolid;bmp.Canvas.Brush.Color := clWhite;bmp.Canvas.FillRect(0,0,txtW
idth,txtHgt);bmp.Canvas.TextOut(0,2,'1.789 m³/Hr WATER');

----------------------------------------------------------------------
cov · 2026-01-10 16:43

OK, thanks everyone.

According to this, GTK2 does not support fqNonAntialiased.

An alternative work around is suggested.

----------------------------------------------------------------------
wp · 2026-01-10 17:14

Mentioning nonAntialiased font quality gives the impression that you
want to draw text in a non-antialiased way? In this case, simply paint
to a monochrome bitmap like in the attached demo project.