Images handeling

[Snaples]

Hi there,
i have this regular VCL form application with a JPG image,
How do i Resize, Rotate, etc... ?
(As code, not initial values).

Thanks in advance!

 

[AP81]

What you need to do is:

1. Create a bitmap
2. use a rectangle (TRect) to assign set the size of the new image (Left & Top = 0, right = new width, bottom = new height)
3. use the StretchDraw bitmap procedure to draw the jpeg on the bitmap canvas
4. Save the JPEG

Here is a basic example:

uses JPEG;
....

procedure ResampleJPEG(AJPG : TJPEGImage; AWidth, AHeight : Integer; AFileName : String);
var
  bmp : Tbitmap;
  rect : TRect;
begin
  rect.Left    := 0;       //left corner
  rect.Top     := 0;       //top
  rect.Right   := AWidth;  //width
  rect.Bottom  := AHeight; //height

  
  bmp         := TBitmap.Create;
  bmp.Width   := rect.Right;
  bmp.Height  := rect.Bottom;

  bmp.Canvas.StretchDraw(rect,AJPG);
  
  AJPG.Assign(bmp);
  AJPG.CompressionQuality := 100;
  AJPG.SaveToFile(AFileName);

  bmp.Free;
end;

This is rough example, so you should add a try-finally statement to free the bitmap (unless you do it on form.destroy). You should also free the jpeg (AJPG.Free) in the procedure that you create it.

I can't think of how to rotate off the top of my head.

Also try googling:

Delphi resample OR resize image
Delphi rotate image

 

[DelphiAaron]

Resize (dispwidth is the width to make the jpg)

function ResizeImg(Image : TJPegImage) : TJPegImage;
var bitmap: TBitmap;
const Dispwidth = 309;
begin
  Try
   bitmap := TBitmap.create;
   result := TJPegImage.create;
   bitmap.width := Dispwidth;
   bitmap.height := round(Image.Height/(Image.Width/Dispwidth));
   bitmap.canvas.stretchDraw(rect( 0,0, Dispwidth, round(Image.Height/(Image.Width/Dispwidth))), Image);
   result.Assign(bitmap);
   result.JpegNeeded;
  Finally
   bitmap.free;
 end;
end;

Rotate 90deg

function RotateImg(Bitmap : TBitmap): TBitmap;
var
  x,y : Integer;
  H,W : Integer;
begin
  W:=Bitmap.Width;
  H:=Bitmap.Height;
  Result := TBitmap.Create;
  try
    with Result do
    begin
      Width:=H;
      Height:=W;
      for x:=0 to W-1 do
        for y:=0 to H-1 do Canvas.Pixels[H-y-1,x]:=Bitmap.Canvas.Pixels[x,y];
    end;
  except
    Result.Free;
    raise;
  end;
end;

you will need to tweak these because the result isnt freed.

Aaron