[SOLVED] drawing a grid on a TImage

[petevick]

I'm attempting to import a project written in RapidQ to Lazarus. Part of the project draws different sized grids on a TImage. In RapidQ the QImage accepts Double variables so if the QImage size is 350x350 and a grid of 55x55 is drawn on it, then the space between the grid lines is 350 / 55 which equals 6.3636 etc, but in Lazarus the TImage.Canvas.Line() only accepts LongInt variables. I really can't see any way around it.

[balazsszekely]

I'm attempting to import a project written in RapidQ to Lazarus. Part of the project draws different sized grids on a TImage. In RapidQ the QImage accepts Double variables so if the QImage size is 350x350 and a grid of 55x55 is drawn on it, then the space between the grid lines is 350 / 55 which equals 6.3636 etc, but in Lazarus the TImage.Canvas.Line() only accepts LongInt variables. I really can't see any way around it.

I would create a transparent 3500x3500 bgrabitmap, draw the grid at 64(close enough), resize the image back to 350x350, then draw the grid to the original image with transparency. You can also play with the tickness of the pen.
IIRC bgrabitmap supports anti-aliasing lines too.

[Eugene Loza]

Or if you don't want to do the resizing you can just

Code: Pascal  [Select][+][-]

1. const
2.   Lines = 55;
3. for I := 1 to Lines-1 do
4.   Image1.Canvas.Line(Round(Single(I) * Image1.Width / Lines), 0, Round(Single(I) * Image1.Width / Lines), Image.Height);

[petevick]

Or if you don't want to do the resizing you can just

Code: Pascal  [Select][+][-]

1. const
2.   Lines = 55;
3. for I := 1 to Lines-1 do
4.   Image1.Canvas.Line(Round(Single(I) * Image1.Width / Lines), 0, Round(Single(I) * Image1.Width / Lines), Image.Height);

Well I'll be damned, that's spot on, I would never have got that. Thanks for posting Eugene, and GetMem