stack overflow when press button delphi - delphi

Question

I'm build an application that reducing the pixels width.
When I'm pressing the button of that application two or three times, Message will appear and say stack overflow.
Here's the Message :
Error Line on my application
Here's my code :
procedure TForm1.cariThin();
var
baris_gbr, kolom_gbr, x, y, a, b, i, j, p1, p2, n : integer;
imgval : array [0..500,0..500] of integer;
mark : array [0..500,0..500] of integer;
nb : array [1..9] of integer;
hasdelete: boolean;
R, G, BL, AB : integer;
begin
Image3.Width := Image1.Width;
Image3.Height := Image1.Height;
baris_gbr := Image1.Picture.Height;
kolom_gbr := Image1.Picture.Width;
For kolom_gbr:= 0 To image1.Width - 1 Do
Begin
For baris_gbr:= 0 To image1.Height - 1 Do
Begin
R:= GetRValue(image1.Canvas.Pixels[kolom_gbr, baris_gbr]);
G:= GetGValue(image1.Canvas.Pixels[kolom_gbr, baris_gbr]);
BL:= GetBValue(image1.Canvas.Pixels[kolom_gbr, baris_gbr]);
AB:= (R + G + BL) Div 3;
if (AB > 200) then
begin
Image1.Canvas.Pixels[kolom_gbr, baris_gbr] := rgb(255,255,255);
end
else
begin
Image1.Canvas.Pixels[kolom_gbr, baris_gbr] := rgb(0,0,0);
end;
End;
End;
for y := 0 to baris_gbr-1 do
begin
for x := 0 to kolom_gbr-1 do
begin
if (Image1.canvas.pixels[x,y] = clBlack) then
begin
imgval[x,y] := 1;
end
else
begin
imgval[x,y] := 0;
end;
end;
end;
hasdelete := True;
while (hasdelete) do
begin
hasdelete := False;
for y := 0 to baris_gbr-1 do
begin
for x := 0 to kolom_gbr-1 do
begin
if (imgval[x,y] = 1) then
begin
for n:=1 to 8 do
begin
nb[n] := 0;
nb[1] := imgval[x,y];
nb[2] := imgval[x,y-1];
nb[3] := imgval[x+1,y-1];
nb[4] := imgval[x+1,y];
nb[5] := imgval[x+1,y+1];
nb[6] := imgval[x,y+1];
nb[7] := imgval[x-1,y+1];
nb[8] := imgval[x-1,y];
nb[9] := imgval[x-1,y-1];
a := 0;
end;
for i:= 2 to 8 do
begin
if ((nb[i] = 0) AND (nb[i+1] = 1)) then
begin
inc(a);
end;
end;
if ((nb[9] = 0) AND (nb[2] = 1)) then
begin
inc(a);
end;
b := nb[2] + nb[3] + nb[4] + nb[5] + nb[6] + nb[7] + nb[8] + nb[9];
p1 := nb[2] * nb[4] * nb[6];
p2 := nb[4] * nb[6] * nb[8];
if ((a = 1) AND ((b>=2) AND (b <= 6)) AND (p1 = 0) AND (p2 = 0)) then
begin
mark[x,y] := 0;
hasdelete := true;
end
else
begin
mark[x,y] := 1;
end
end
else
begin
mark[x,y] := 0;
end;
end;
end;
for y:=0 to baris_gbr-1 do
begin
for x:=0 to kolom_gbr-1 do
begin
imgval[x,y] := mark[x,y];
end;
end;
end;
end;
Why my application keep says overflow? is there any solution to fix it? or can we can exception handler? thanks
EDIT
Now my pplication says access violation.
It raised error in this line : nb[7] := imgval[x-1,y+1];
why it exactly happened?

Answer 1

var
imgval : array [0..500,0..500] of integer;
mark : array [0..500,0..500] of integer;
These variables are located on the stack and are huge. They have size 501*501*4 = 1,004,004. The default stack size is 1MB. These large arrays are the reason for your stack overflow.
You will need to use dynamically allocated arrays instead. Or avoid the need to store 2D arrays that contain information for each pixel and instead process the image in smaller sub-blocks. I've no idea whether or not that is possible because I've no idea what the code is trying to do. That's for you to work out.
Of course, one advantage of using dynamically allocated arrays is that you don't need to run the gauntlet of a buffer overrun, as you currently do. If either dimension of the image exceeds 501 then you have overrun the buffer. I do hope that you have enabled range checking in the compiler options.
for y := 0 to baris_gbr-1 do
and
for x := 0 to kolom_gbr-1 do
cannot be correct. The baris_gbr and kolom_gbr variables are not initialised since they were most recently used as loop variables. So, as well as turning on range checking, you'll want to turn on hints and warnings, and then heed them.