Rendering large pdf

Sorry for post under post,
but there is hope, my workaround idea,
After some experiments on this (and another) sample, I got one of the idea:
QPL has functions for separate bitmap from pdf file (in my example this image is only one graphical object in pdf file)
My idea is functions GetPageImageList, SaveImageListItemDataToFile use, works ok).
This function extract image (jpg) from this pdf file, but this jpg also big image for pixel analyse.
I have to deal with large format scan and print (A0+ 300dpi)

Does anyone have experience with the analyse of large jpg files in Delphi (scan jpg format and analyze pixels?)

Only what I want, its detect "inked area" (for crop white margins on pdf file).

Im sorry for my poor english,

Regards,
Adam

Edited by ADev - 09 Mar 12 at 7:34PM

Thanks Werner,
yes, the right direction :)

After further experiments, I came to satisfactory results:
pseudocode:

if RenderPageToFile=False then
if (pdf_page has only one img) and (img.size=pdf_page.size [points]) then
begin
    extract img (SaveImageListItemDataToFile)
    LoadBigImg to TBitmap with resize to 72 dpi (without resizing is memory problem)
    Analyze TBitmap
end

To load jpg with resize I'm found function:

function ResizeImage(sInImage, sOutImage: string; iHeight, iWidth: integer): boolean;
var JpgImg : TJpegImage;
   BmpImg : TBitmap;
   Rectangle: TRect;
begin
   try
    JpgImg := TJpegImage.Create;
    BmpImg := TBitmap.Create;
   
    JpgImg.LoadFromFile(sInImage);
    Rectangle := Rect(0, 0, iWidth, iHeight);
    with BmpImg do
    begin
    Width := iWidth;
    Height := iHeight;
    Canvas.StretchDraw(Rectangle, JpgImg);
    >> Analyze TBitmap here or BmpImg.SaveToFile <<
    end;
    finally
    
//    JpgImg.Assign(BmpImg);
//    JpgImg.SaveToFile(sOutImage);
    JpgImg.Free;
    BmpImg.Free;
    end;
   Result := True;
   end;

Yes, I used scanline method to analyze TBitmap.
If extracted image is jpeg image, for scanline important is also TBitmap.PixelFormat:=pf24bit; (oryginally assigned jpg has 32bit and white color has (255,0,255) r,g,b values )

I think that the problem is already solved, a little round,
partially pdf page rendering/rasterizing would be better.
Thank you for your interest, Werner

Regards,
Adam