Fast pixel access

[user5]

    In the code below lines 1 and 2 together do the same thing as line 3 except of course line 3 would be much slower if I used it in the code instead of lines 1 and 2. Line 1 uses a raw image fast pixel access method that is similar to BGRABitmap.
    Line 5 accesses pixels next to x and y and I was wondering if anyone knows how I could use the fast pixel method to accomplish the same thing but at a faster speed.
    Thanks and happy Thanksgiving morning!

   

Code: Pascal  [Select][+][-]

1. for y := starty to (mybitmap.height - 1) do
2.   begin
3.    PixelPtr := PixelRowPtr;
4.    for x := startx to (mybitmap.width - 1) do
5.     begin
6.      tempcolor := PixelPtr^; //line 1
7.      tempcolor := SwapRedBlue(tempcolor); //line 2
8.  
9.      tempcolor := mybitmap.canvas.pixels[x,y]; //line 3
10.  
11.      newcolor := mybitmap.canvas.pixels[x + 1,y + 1]; //line 5
12.     end;
13.   end;

[user5]

    Oops. Line 5 should have been: newcolor := mybitmap.canvas.pixels[x + 1,y]; //to access the pixel next to x

[winni]

Hi!

There is a page about fast direct pixel access in Lazarus with a lot of examples:

https://wiki.freepascal.org/Fast_direct_pixel_access

No thanksgiving here tomorrow - just another Friday for Future.

Winni

[user5]

    I checked out the page you mentioned and it led me to some other sites but it seems like not enough information is provided. For example, I found the following code but I can't get it to work. "colGreen" from what I understand is supposed to be a TFPColor but the compiler wouldn't let me define something like var newcolor:TFPColor. I put in all the correct headers.

 

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button4Click(Sender: TObject);
2. var
3.   b: TBitmap;
4.   t: TLazIntfImage;
5. begin
6.   b := TBitmap.Create;
7.   try
8.     b.LoadFromFile('test.bmp');
9.     t := b.CreateIntfImage;
10.  
11.     // Read and/or write to the pixels
12.     t.Colors[10,20] := colGreen; //This won't compile.
13.  
14.     b.LoadFromIntfImage(t);
15.   finally
16.     t.Free;
17.     b.Free;
18.   end;
19. end;

[wp]

Just missing the "uses":

Code: Pascal  [Select][+][-]

1. uses
2.   fpImage,        // colGreen, TFPColor
3.   IntfGraphics;   // TLazIntfImage

 

[user5]

    You are absolutely correct. I was missing FPImage in the "uses" clause. It's working now. The old slow pixel method took 7 seconds to fill a 1053x655 image with the color red but the TLazIntfImage method did it almost instantaneously. Wow! I wonder if there's anything even faster. Thanks a lot.

[user5]

    Does the TFPColor "colRed" equal "clRed" or do I need a conversion of some kind?

[user5]

    Okay... I found the conversion function which converts a TColor to a TFPColor so that: newcolor := TColorToFPColor(tempcolor); newcolor is a TFPColor and tempcolor is a TColor. I also found the function which converts a TFPColor to a TColor. Thanks again for taking the time to help me. I really appreciate it. This seems to be what I need.

[Soner]

Don't forget, TBitmap has Scanline property now. As someone the wikipage wrote, then tbitmap has not this property.
NOw, you can manipulate Tbitmap without TLazIntfImage faster.