delphi - Getting surrounding pixels color and change them -

i want make application first checks image pixelcolor. when has found pixel correct pixelcolor 'highlight' pixel.

but here comes tricky part, after want check color of 8 surrounding pixels of 'highlighted' pixel. if 1 of these surrounding pixel black, color of pixel should change.

i have managed ' highlight' pixels have pixelcolor (see code below), i'm stuck @ finding out how check surrounding pixels...

i hope question clear.

procedure tform_main.analyzepixels (bitmapanalyse : tbitmap); var c: tcolor; x, y:integer; pixels : prgbtriplearray  begin   bitmapanalyse := tbitmap.create;   try   bitmapanalyse.assign(fbitmap);    form_memo.memo1.lines.beginupdate;   try   y := 0 bitmapanalyse.height - 1   begin     pixels := bitmapanalyse.scanline[y];     progressbar2.stepit;     progressbar2.update;     application.processmessages;     x := 0 bitmapanalyse.width - 1     begin       if (pixels[x].rgbtred >= pixelcolor) ,           (pixels[x].rgbtgreen >= pixelcolor) ,              (pixels[x].rgbtblue >= pixelcolor)             begin         c := rgb(           pixels[x].rgbtred,           pixels[x].rgbtgreen,           pixels[x].rgbtblue         );             form_memo.memo1.lines.add(           '===============' + slinebreak +           'pixel[' + inttostr(x) + '; ' + inttostr(y) + ']' + slinebreak +           'color: ' + colortostring(c))          ;         pixels[x].rgbtred := 255;         pixels[x].rgbtgreen := 255;         pixels[x].rgbtblue := 0;       end;     end;   end;   form_memo.memo1.lines.endupdate; end; 

i'm missing something, since have (x, y) can obtain surrounding pixels using

[x - 1, y - 1][x  , y - 1][x + 1, y - 1] [x - 1, y    ][x  , y    ][x + 1, y    ] [x - 1, y + 1][x  , y + 1][x + 1, y + 1] 

you have logic specific pixel. i'll refactor have for

function getrgbat(abitmap: tbitmap; const x, y: integer) : prgbtriple; begin     result := nil; // don't remember if necessary     if (y >= 0) , (x >= 0)     begin         result := abitmap.scanline[y];         inc(result, x);     end; end;  function isrgbblack(abitmap: tbitmap; const x, y: integer) : boolean; var     p: prgbtriple; begin     p := getrgbat(abitmap, x, y);     result := (p <> nil) ,              (p^.rgbtblue + p^.rgbtgreen + p^.rgbtblue = 0); end; 

then need add check code. since delphi short-circuits on or boolean expressions, following should suffice:

if    isrgbblack(bitmapanalyse, x - 1, y-1)     or isrgbblack(bitmapanalyse, x,     y-1)     or isrgbblack(bitmapanalyse, x + 1, y-1)      or isrgbblack(bitmapanalyse, x - 1, y)     // x, y not needed    or isrgbblack(bitmapanalyse, x + 1, y)      or isrgbblack(bitmapanalyse, x - 1, y + 1)     or isrgbblack(bitmapanalyse, x,     y + 1)     or isrgbblack(bitmapanalyse, x + 1, y + 1)   // logic here (x, y) 

this extremely simplistic approach, haven't state want in case of adjacent eligible pixels, example, may need add logic those.